UNCLASSIFIED

AD NUMBER

AD909379

NEW LIMITATION CHANGE

TOApproved for public release, distributionunlimited

FROMDistribution authorized to U.S. Gov't.agencies only; Test and Evaluation; DEC1972. Other requests shall be referred toAir Force Armament Laboratory, ATTN: DLDG,Eglin AFB, FL 32542.

AUTHORITY

AFATL ltr dtd 6 Feb 1976

THIS PAGE IS UNCLASSIFIED

AFATL-TR-72-226

DEVELOPMENT OF AN ELECTROCHEMICAL

MACHINING PROCESS FOR RIFLING LINED

GUN BARRELS

AERONUTRONIC DIVISIONPHILCO-FORD CORPORATION /D TO C

TECHNICAL REPORT AFATL-TR-72-226

DECEMBER 1972

Distribution limited to U. S. Government agencies only;this report documents test and evaluation; distributionlimitation applied December 1972. Other requests forthis document must be referred to the Air Force ArmamentLaboratory (DLDG), Eglin Air Force Base, Florida 32542.

AIR FORCE ARMAMENT LABORATORYAIR FORCE SYSTEMS COMMAND* UNITED STATES AIR FORCE

EGLIN AIR FORCE BASE, FLORIDA

Development Of An Electrochemical Machining Process

For Rifling Lined Gun Barrels

Richard A. Harlow

David L. Corn

Richard C. Kimball

Distribution limited to U. S. Government agencies only;this rerort documents test and evaluation; distributionlimitation applied December 1972. Other requests forthis document must be referred to the Air Force ArmamentLaboratory (DLDG), Eglin Air Force Base, Florida 32542.

77W-- -a-- ---

FOREVORD

This report was prepared by Philco-Ford Corporation, AeronutronicDivision, Newport Beach, California under Contract No. F08635-71-C-0209with the Air Force Armament Laboratory, Eglin Air Force Base, Florida.The report covers work performed from June 1971 to October 1972.Mr. David Uhrig (DLDG) was program monitor for the Armament Laboratory.

This technical report has been reviewed and is approved.

D M AVSDirector, Guns and Rockets Division

ii

ABSTRACT

A 16-month program was conducted to advance high performance gun

barrel technology by developing an electrochemical machining process for

rifling high performance barrel liner materials. A total of 15 electro-lytes and numerous electrochemical machining parameters were evaluated in

conducting electrochemical machinability studies on iron-nickel-base,nickel-base, and cobalt-base superalloys, and on refractory alloys of

columbium, molybdenum, tantalum, and tungsten.

Four materials (L-605, VM-103, CG-27, and alloy 718) were selected

for electrochemical rifling and fabrication into caliber .220 Swiftbarrel liners. The rifled liners were insulated externally and assembled

into outer barrel jackets using a drawing process, thus producinginsulated composite test barrels. A total of 12 test barrels compatible

with an MG-3 machine gun, representing the foui liner materials and three

jacket materials (H-11, A-286, and Pyromet X-15), were fabricated anddelivered to the Air Force. The results of this program indicated thatelectrochemical machining is a feasible process for obtaining high quality

and low cost rifling, and that extrapolation of this process to larger

calibers appears feasible.

Distribution limited to U. S. Government agencies only;

this report documents test and evaluation; distributionlimitation applied December 1972. Other requests forthis document must be referred to the Air Force Armament

Liboratory (DLDG), Eglin Air Force Base, Florida 32542.

iii

(The reverse of this page is blank.)

TABLE OF CONTENTS

Section Page

I INTRODUCTION . . . . . . .. . . . . . . . . .. .. . . I

II SUMMARY . . . . ...................... 3

2.1 Technical Approach . . . ............... 3

2.2 Conclusions and Recommendations . . . . . . ... 4

III PHASE I - FABRICQTION PROCESS DEVELOPMENT ........ 5

3.1 Liner Materials . . . .. . 53.2 Electrochemical Machinability Studies . ...... 53.3 Gun Drilling Tests . . . . . . . . . . . . . . .. 243.4 Electrochemical+Rifling Tests . ...... .......... 24

3.4.1 Stationary Electrode Development . . . . . . 323.4.2 Electrochemical Rifling, Short

Length Trials ............... 36

IV PHASE II - .220 SWIFT COMPOSITE BARREL FABRICATION . . . 42

4.1 Fabrication of Electrochemically RifledFull-Length Liners . . . . . . . . . . . . . . . . 42

4.1.1 Electrochemical Rifling ToolingDevelopment and Checkout . ...... . . 42

4.1.2 Fabrication of Deliverable Barrel Liners . . 42

4.2 Assembly, Drawing, and Final Machining ... ...... 55

v

*PRCEDI1Z PAGE BLANK-NOT FIZZ4ED.4

LIST OF FIGURES

Figure Title Page

I O.D. Rifling Test Fixture for Initial ElectrochemicalMachinability Studies (Disassembled) .............. . 6

2 O.D. Rifling Test Fixture for Initial ElectrochemicalMachinability Studies (Assembled) ...... ............ 7

3 Test Samples Used in O.D. Electrochemical Rifling Study . 16

4 Unetched Cross-Section of One Side of an ElectrochemicallyRifled Groove in L-605 (Magnification: 250X) . . . . . . 17

5 Unetched Cross-Section of One Side of an Electrochemically 17Rifled Groove in L-605 (Magnification: 250X) . . . ...

6 Unetched Cross-Section of One Side of an ElectrochemicallyRifled Groove in VM-103 (Magnification: 250X) . . . . . . 18

7 Unetched Cross-Section of One Side of an ElectrochemicallyRifled Groove in WC-3015 (Magnification: 250X) . . . . . 18

8 Photographs of Typical OD. ElectrochemicallyRifled Grooves in L-605 (Magnification: 7X) . . . . . . . 19

9 Photographs of Typical O.D. ElectrochemicallyRifled Grooves in TZM (Magnification: 7X) . . . . . . . . 20

10 Photographs of Typical O.D. ElectrochemicallyRifled Grooves in VM-103 (Magnificiation: 7X) . . . . .. 21

11 Photographs of Typical O.D. E±ectrochemicallyRifled Grooves in WC-3015 (Magnification: 7X) . . . . . . 22

12 Photographs of Typical O.D. ElectrochemicallyRifled Grooves in Cb-752 (Magnification: 7X) . . . . . . 23

13 Sketch of Electrochemical Gun-DrillingTest Apparatus ...... ...................... 25

14 Electrochemical Gun-Drilling Test Apparatus ....... 26

15 Sketch of Electrochemical Rifling Set-up

With Stationary Electrode . . .............. 33

vi

I BI lI I ~ g Iq I .. •••• -.--. ,. . , .. - -

LIST OF FIGURES (CONCLUDED)

Figure Title Page

16 Sketch of Short-Length Electrochemical Rifling ToolingUtilizing the Stationary Electrode Technique ... ....... 34

17 The Four Groove Shapes Evaluated ... ............. .... 35

18 Sketch of .220 Swift Rifling .... ............... .... 37

19 Sketch of Full-Length Electrochemical Rifling ToolingUtilizing the Stationary Electrode Technique ... ....... 44

20 Tooling and Liner for Full-Length ElectrochemicalRifling (Before Assembling) .... ............* . . . . 45

21 Assembled Tooling for Full-Length ElectrochemicalRifling of Liners ....... .................... .... 46

22 Process Flow Sheet for Electrochemically Rifled Composite

Barrel Fabrication ....... ..................... 56

23 Drawing Equipment Utilized for Composite Barrels . . . .. 57

24 Drawing Die Utilized for Composite Barrels .......... ... 58

25 .220 Swift/MG-3 Barrel ... ................ .. 60

vii

------4

LIST OF TABLES

Table Title Page

I O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with L-605 ........... . . 9

II O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with TZM ..... ........... 10

III O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with Pure Tungsten . . . . . . 11

IV O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with WC-3015 . . . . . . . . . 12

V O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with-Cb-752 .. ......... ... 13

VI O.D. Electrochemical Rifling Parameters forInitial Machinability Tests with VM-103 . . . . . . . . . 14

VII Compositions of the Electrolytes Evaluated . . . . . . . . 15

VIII Electrochemical Gun-Drilling Parametersfor L-605 Tests .... ................... . . 27

IX Electrochemical Gun-Drilling Parameters

for TZM Tests .. ... .... . ... .. . . . . . . . 29

X Electrochemical Gun-Drilling Parametersfor VM-103 Tests .......... ........ . . . . . 31

XI Initial I.D. Rifling Parameters used with StationaryElectrode in Short Length 4130 Specimens . . . . . . .. 38

XII Initial I.D. Rifling Parameters used with StationaryElectrode in Short Length L-605 Specimens . . . . .... 39

XIII Initial I.D. Rifling Parameters used with StationaryElectrode in Short Length Alloy 718 Specimens ...... 39

XIV Initial I.D. Rifling Parameters used with StationaryElectrode in Short Length VM-103 Specimens . . . . o . . . 40

XV Initial ID. Rifling Parameters used with StationaryElectrode in Short Length CG-27 Specimens . . . . . ... 41

viii

LIST OF TABLES (CONCLUDED)

Table Title Page

XVi Material Combinations for Delivered Barrels . . . . . . . . 43

XVII Electrochemical Rifling Parameters for the FullLength (24-inch) Linecs ................ 47

XVIII Final Bore and Groove Measurements Made After Test Firing 49

I,1

ix

(Tie reverse of this page is blank.)

-- .... ..-I

iW

SECTION I

INTRODUCTION I

During recent years, the necessity for improved gun barrel designshas become increasingly apparent with the inception of new high performancecased and caseless weapons. The requirements for high muzzle velocities,higher firing rates, and extended burst firing schedules have isolatedbarrels as perhaps the most performance-limiting gun components. The moresevere service requirements not only drastically increase barrel erosionrates but also cause a potential problem of barrel overheating and possiblepremature structural failure.

The Air Force has funded sev.eral research and development programswith the objective of developing new barrel concepts, materials, and fabri-cation processes applicable to high performance weapons. Particular emphasishas been placed on fully lined barrels or barrels with partial lengthinserts. More recently, the insulated composite barrel has also been inves-tigated under Contracts F08635-69-C-0156, "Equilibrium Temperature Gun Con-cepts"; r08635-70-C-0116, "Composite Barrel Materials Research and Develop-ment"; and a current program, Contract F08635-71-C-0181, "Development ofFull Length Insulated Composite Barrels for Aircraft Machine Guns." Theinsulated composite barrel consists of a high temperature erosion-resistant(refractory alloy or superalloy) liner surrounded by a thin layer of ceramicinsulation and encased within a high strength, lower temperature (steel orsuperalloy) outer jacket. The high temperature liner provides improvederosion resistance under extreme firing schedules; the insulator reduces theheat loads to the outer jacket, thereby providing a capability for moresevere firing schedules without structural failure or a significant increasein barrel weight. All this Air Force w3rk involving superalloy and refrac-tory metal l..ners as well as internplly funded barrel technology programsat the contractor facility has pointed out a very significant need forimproved fabrication processes, particularly in the areas of gun drillingand rifling. A general rule of thumb indicates that the more erosion-resistant materials arp also the most difficult to fabricate by conventionaltechniques. In fact, valid erosion tests of some promising materials (eventhough they can be gun drilled with difficulty) have not been possible dueto the lack of satisfactory rifling techniques.

A very promising approach to the rifling of materials that are diffi-cult or impossible to machine is electrochemical machining. This highlyproduction-oriented process has been widely used in aerospace industriesfor rapidly machining complex shapes for several years. In 1971, the AirForce awarded Contract F08635-71-C-0209, "Development of an ElectrochemicalMachining Technique for Rifling Refractory Lined Gun Barrels," with theprimary objective ot developing an elec-rochemical machining process for

high temperature refractory metal and superalloy liners. This consisted

of a 16-month two-phase effort that included electrochemical machiningprocess development and fabrication of caliber .220 Swift insulated com-posite test barrels with electrochemically rifled liners for delivery tothe Air Force. A summary of the program and resulting conclusions andrecommendations are presented in Section II. Sections III and IV presentdetailed procedures and results of the development effort conducted inPhases I and II, respectively.

2'II

fi 2

I , ISECTION II

SUMIARY 4

2.1 TECHNICAL APPROACH

The objective of the program was to develop an electrochemical machin-ing technique for rifling gun barrels or liners fabricated from advancedsuperalloys and refractory metal alloys. The intent was to develop a pro- 4

cess that could ultimately become a standard production technique for highperformance gun barrels.

Phase I of the program consisted of electrochemical machinabilitystudies wherein attempts to electrochemical machine simulated riflinggrooves on samples of L-605, VM-103, Cb-752, WC-3015, T-ll, TZM, and tung-sten were made utilizing various combinations of electrochemical machiningparameters and 15 different electrolyte compositions. The attemptson L-605, VM-103, WC-3015, and TZM were very successful. Marginal successwas achieved with Cb-752 and unalloyed tungsten, but poor surface finishesresulted. The T-lll could not be machined with any of the electrolytes orelectrochemical machining parameters investigated.

Concurrently, electrochemical gun-drilling was investigated whereinattempts to drill 0.21-inch-diameter by 3-inch-deep holes in samplesof L-605, TZM and VM-103 were made. This effort indicated that elec-trochemical gun drilling of this size was net attractive due to uncontrol-lable tool (electrode) chatter which precluded dimensional control.

However, larger caliber gun drilling appears feasible since a more rigidelectrode can be used.

A stationary electrode design and the required electrochemical machin-ing parameters were developed for caliber .220 Swift rifling of 6-inchlengths of conventionally gun-drilled and honed bars. The initial work was

performed on 4130 steel, then the parameters were refined for the deliver-able liner materials, L-605, Alloy 718, VM-103 and CG-27. The refractory

metals, TZM and WC-3015, were replaced as deliverables by Alloy 718 andCG-27. TZM had shown very poor erosion performance under Contract F08635-

71-C-0181, and acceptable WC-3015 could not be successfully fabricatedwithin the program schedule.

Phase II involved scaling up the short-length electrodes and electro-chemical machining parameters to full length (24-inch) caliber .220 Swift

liners. The initial work was accomplished on 4130 and then followed bydeveloping parameters for the deliverable L-605, VM-i03, Alloy 718, andCGt27. Rifling of three 14nper of each materias wa vcry successf.ul, au"dgood dimensional control and surface finishes were achieved.

3

The liners were then fabricated into full length insulated compositebarrels utilizing a drawing process developed under Contract P08635-71-C-0181. H-200 series zirconia insulators and jacket materials of H-11, Pyro-met X-15, and A-286 were utilized. The barrels were proof-test fired anddelivered to the Air Force for testing and evaluation which concluded thetechnical effort.

2.2 CONCLUSIONS AND RECOMMENDATIONS

Based on the effort briefly summarized above and detailed in Sec-tions TII and IV, the following conclusions and recommendations were made:

1. Electrochemical machining appears extremely attractive as a riflingprocess. Excellent surface finishes, good dimensional control, and verylow predicted production rifling costs are potential advantages of thisprocess.

2. It is recommended that further work be performed to extrapolatethe rifling technology developed on this program to larger calibers (20 to40mm). A significant cost saving over present conventional rifling tech-niques will result if successful.

3. The electrochemical machining process presently appears to beapplicable to all iron, nickel, cobalt or molybdenum-base alloys, and somecolumbium alloys. More development work is required to electrochemicalmachine the remaining columbium alloys, the tantalum-base alloys, andunalloyed tungsten. Higher voltages could improve the electrochemicalmachining characterif;tics of these materials and should be investigated asa first approach, since only minor equipment modifications would be required.

4. A basic study is recommended to isolate and correlate the signifi-cant parameters of the electrochemical machining process. Electrolyteselection in this program was based entirely on past experience and empir-ical additions to existing solutions. A more basic understanding of thevoltage-current-alectrolyte relationship to the metal removal mechanismwould be helpful in selection of electrolytes and current parameters.

5. Electrochemical gun-drilling should be investigated for applica-tion to larger calibers. The increased stiffness of the larger diameterelectrode should reduce vibration to an acceptable minimum and thusallow this process to be applied to materials which previously could notbe easily gun-drilled. Electrochemical gun-drilling could be verycost-competitive compared to conventional methods on difficult to machinematerials,

4

I

SECTION III

PHASE I - FABRICATION PROCESS DEVELOPMENT

The goal for Phase I was first to determine the electrochemicalmachinability of various refractory alloys and superalloys, and then,based on these results, develop :ifling techniques and parameters for fabri-cating liners in the deliverable .220 Swift barrels of Phase II The poten-tial fabrication methods were selected subh that the technology developedfor the ,220 Swift barrel liners would also be applicable to larger calibers.

3.1 LINER MATERIALS

Pure metale or alloys representing several classes of potential barrelliner materials were cunsidered during Phase I. These included: (1) CG-27,an iron-nickel base intermediate temperature superalloy; (2) Alloy 718,a nickel-base intermediate temperature superalloy; (3) L-605 and VM-103,high temperature cobalt-base superalloys; (4) WC-3015 and Cb-752, columbium-base alloys; (5) TZM, a molybdenum-base alloy; (6) T-ll1, a high strengthtantalum alloy; and finally (7) unalloyed tungsten. The intent was to

determine which classes of materials could be electrochemicallynmachined,and then to select those alloys with the highest predicted erosion resis-tance for delelopment of rifling parameters adequate for fabrication ofdeliverable test barrels. Although the superalloys can be rifled by con-ventional techniques, the process is comparatively slow and costly due totheir generally low machinability. Conventional rifling of Cb, Ta, andMo alloys is extremely difficult and results in poor surface finishes.Pure tungsten has also proven very difficult to machine, although it poten-tially offers excellent erosion resistance.

3,2 ELECTROCHEMICAL MACHINABILITY STUDIES

The initial machinability tests consisted of electrochemical machining0.075-inch-wide by 0.003-inch-deep by 2-inch-long grooves on the O.D. sur-face of the test specimens. These tests were designed to determine thebasic electrochemical machinability of the materials and, in addi-tion, permit evaluation of surface finishes obtained under electrochemicalmachining cunditions similar to those which exist during rifling, using thestationary electrode technique. The tooling for these tests, shown in Fig-ures 1 and 2, consisted of a slotted fiberglass epoxy block containing anadjustable copper shim. The shim could be moved up or down within the slotto obtain any desired electrode-work-piece distance. Figure 2 shows moreclearly the electrical cable attachment hole in the shim and the hose fittingthrough which the electrolyte is pumped. This particular set-up is not

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amenable to reversing the flow direction; however, for the initial machin-ability tests this feature was not necessary.

A total of fifteen electrolyte systems were evaluated in attemptingto electrochemically machine the seven materials being considered as candi-date barrel liner materials. The test conditions and electrolyte for each

of the materials evaluated are given in Tables I through VI. The composi-tions of the fifteen electrolyte systems are given in Table VII. Theseelectrolytes ranged from the standard sodium chloride solution to non-sludging acidic and basic electrolytes and included some special composi-tions that had not been previously evaluated. The special compositionswere formulated in an effort to machine the alloys which did not respond tothe more common systems.

Visual and metallographic examination of electrochemically machinedsurfaces of L-605, TZ4, and VM-103 indicated that these materials could besatisfactorily machined with sodium chloride electrolyte and IIC-3015 withthe sodium bromide/sodium nitrite/sodium nitrate/sodium fluoride electro-lyte. Pure tungsten could be machined with sodium hydroxide electrolyte,but a satisfactory surface finish could not be consistently obtained.Cb-752 could be machined with the sodium bromide/sodium nitrite electrolyte.Again a satisfactory surface finish could not be obtained consistently.T-ll could not be machined with any of,the fifteen electrolyte systemsevaluated. The 8even pieces of material evaluated during this portion ofthe program are shown in Figure 3.

Photomicrographs of acceptable groove cross-sections machined inL-605, TZM, VM-103, and WC-3015 are shown in Figures 4 through 7, respect-ively. No intergranular attack was observed for any of these alloys. Theradius of curvature at the surface intersection and the bottom of thegroove was about 0.006-to 0.010-inch whereas at the groove-bore intersec-tion the edge still appeared sharp at 250X. This geometry probably doesnot differ enough from conventionally machined radii to significantlychange the projectile spin-up and obturation characteristics of the gunbarrel. Photographs of the surface of typical grooves machined in L-605,TZM, VM-103, WC-3015, and Cb-752 during the O.D. rifling machinabilitytests are shown in Figures 8 through 12; respectively.

It should be mentioned that the maximum voltage used in conjunctionwith these electrolytes was 30 volts D.C. which is low compared to currentlyavailable D.C. power supplies. The lack of success with T-ll may be attri-buted to insufficiently high voltage. Electrochemical machining technologyhas not been sufficiently expanded to date to predict the importance ofthis variable; however, indications are that it might be significant basedon the behavior obtained in this investigation. Going to higher voltagespresents other problems (such as an increased chance of electrode arcing);however, these could probably be overcome.

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TABLE VII. COMPOSITIONS OF THE ELECTROLYTES EVALUATED

Type Composition

A Sodium Chloride I lb/gal

B Sodium Chloride I lb/galSodium Nitrate 3 oz/galSodium Citrate 6 oz/galRochelle Salt 4 oz/gal

C Sodium Chloride 0.55 lb/gal

D Sodium Nitrate 2 lb/gal

E Sodium Chlorate 2 lb/gal

F Sulfuric Acid 5 percent

G Sulfuric Acid 10 percent

H Sodium Bromide 1.5 lb/galSodium Nitrite 1.5 lb/galSodium Nitrate 0.1 lb/galSodium Fluoride 0.1 lb/gal

I Sodium Hydroxide 2 percent

J Sodium Hydroxide 6 percent

K Sodium Chloride 0.5 lb/gal

Sodium Hydroxide 0.5 lb/gal

Rochelle Salt 0.5 lb/gal

L Sodium Bromide 1.5 lb/galSodium Nitrite 1.5 lb/galSodium Nitrate 0.1 lb galSodium Fluoride 0.1 lb/galSodium Hydroxide 0.15 lb/gal

M Nitric/Hydrofluoric Acid (65/35) 12-1/2 percent

N Nitric/Hydrofluoric Acid (65/35) 25 percent

0 Nitric/Hydrofluori. Acid (65/35) 50 percent

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Figure 4. Unetched cross-Section of One Side of a Electrochemically

Rifled Groove in L-605 (Magnification: 250X)

i Figure 5. 11netehed Cross-Section of One Side of an Electrochemically

Rifld Goovein -60 (Manifcatin: 50I174

Figure 6. Unetched Cross-Section of One Side of an ElectrochemicallyRifled Groove in WC-3153 (Magnification: 250X)

18-

4i4

L-60 GroveNo. 2

L-605 -Groove 'No. 4

Figure 8. Photographs of Typical O.D. Electrochemically RifledGrooves in L-605 (Magnification: 7X)

19

-,- LL

TZM - Groove No. 3

Groove -

TZM' Groove No. 6

Figure 9. Photographs of Typical O.D. Electrochemically RifledGrooves in TZM (Magnificaton: 7X)

20

Groove 2

VM-103 -Groove Nos. I and 2

VM-103 -Groove No. 5

Figure, 10. Photographs of Typical O.D. Electrochemically RifledGrooves in VM4-103 (Magnification: 7X)

21

WC-3015 Groove No.1

WC-3015 -Groove No. 3

Figure ll.- Photographs of Typical O.D. Electrochemically RifledGrooves in WC-3015 (M4agnification:, 7X)

22

Cb-752 -Groove Nos. 1 and 2

* Cb-752 - Groove Nos. 8 and 9

Figure 12. Photographs of Typical O.D. Electrochemically RifledGrooves in Cb-752 (iMagnification: 7X)

23

3.3 GUN DRILLING TESTS

Since gun-drilling of superalloys and refractory metals has generallyproven difficult and time-consuming, a portion of the program was directedtoward establishing the feasibility of electrochemically gun drillingcaliber .220 Swift liners. This investigation consisted of the develop-ment of tooling and techniques to electrochemically gun drill 0.21-inchI.D. by 3-inch-deep holes in various te6it materials. This tooling con-sisted of a 4-inch-long piece of 0.188-inch O.D. by 0.049-inch wall stain-less steel tubing with a 0.200-inch O.D. by 0.090-inch I.D. by 0.030-inch-thick piece of copper-tungsten silver-soldered to one end to serve as thecutting tip. This tube was attached to a mounting plate on the electro-chemical machining hardware using standard tubing fittings and served asthe electrode for the drilling tests (see Figures 13 and 14). The O.D.of the tube was coated with epoxy insulation to prevent stray etching.

Electrochemical gun d ling tests were conducted with L-605, TZM,and VM-103 (Tables VIII, IX, and X, respectively) only using both a stan-dard sodium chloride electrolyte and a sodium chloride base electrolytecontaining special additives to improve machining characteristics. Prob-lems with tool vibration (resulting in shorting of the tool and work piece)were encountered during attempes to gun drill the 0.21-inch I.D. by 3-inch-deep holes. These problems were minimized by the use of a plexiglass guidefor the electrode and the addition of epoxy spacers on the outside of theelectrode shank. However, vibration ofthe tool still persisted to anunacceptable degree. Although the resulting holes were not of acceptablequality for this caliber, they were close enough to merit serious consider-ation of developing electrochemical gun drilling for larger calibers wheretool stiffness would be much higher. Additional evidence to support thisis found in Reference 1 where five-inch gun barrels were successfully gun-drilled using the electrochemical machining process.

3.4 ELECTROCHEMICAL MACHINING RIFLING TESTS

Two different methods were considered for electrochemical rifling;i.e., rifling with either a moving or a stationary electrode. The movingelectrode would be similar to an electrical discharge machinin', (EDM)electrode, which is translated and rotated simultaneously to achieve thedesired rifling twist. This method was considered undesirable due toanticipated tool chatter which would have the same detrimental effect ondimensional control as was demonstrated with the moving gun-drilling elec-trode. The tooling design and fabrication complexity of this method madeit appear less attractive than the stationary electrode, described below.

24

ELECTROLYTE INTOOL

.200

41

Figure 13. Sketch of Electroczhemical Gun-Drilling Test Apparatus

25

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The stationary electrode approach for electrochemically rifling gunbarrels uses a metal electrode insulated on the outside diameter whichextends through the length of the barrel to be rifled. This electrode hasgrooves machined through the insulation which correspond to the dimensionsand configuration of the desired rifling in the gun barrel. This electrodeis placed inside the barrel to be rifled, electrolyte is pumped through thegrooves in the electrode and, when current is applied, corresponding riflinggrooves are electrochemically machined into the barrel (see Figures 15 and16). This approach has the advantage of much greater economy, since theentire barrel is rifled at one time. The moving electrode travel would belimited by the electrochemical machining removal rate, and rifling would bemuch more time-consuming and costly.

3.4.1 STATIONARY ELECTRODE DEVELOPMENT

The initial objective of this portion of the program was to developa satisfactory stationary electrcle. Rifling tests were conducted usingrelatively short (approximately 6-inch) length 4130 steel tubes to deter-mine optimum groove shape, evaluate various types of insulation materialsand application techniques, and to establish electrochemical machiningparameters. Machining tests conducted with aluminum electrodes revealedthat the aluminum was eroded during machining operations, leaving roughedges at the corners of the electrode groove. Changing the electrode mate-rial to a tellurium-copper alloy eliminated this effect.

These initial tests were -conducted with electrodes having a thin(0.002-inch) coating of epoxy insulation, which produced a smooth groovewith a rough radius adjacent to the land area. As a result, electrodeswere fabricated having a thick (0.025-inch) coating of insulation whichproduced grooves with a smooth radius. Therefore, all subsequent electro-chemical, machining rizling was accomplished with electrodes having thethick insulation coating.

In parallel to the above epoxy insulation thickness evaluation, testswere conducted using electrodes insulated with the thin (0.002-inch) coat-ing of epoxy which had four different groove shapes (Figure 17), theobjective being to determine the effect of groove shape on machining char-acteristlz.. No difference in machining characteristics among grooveshapes was observed. Because groove shape B" was most like conventionalrifling, it was selected for all subsequent rifling.

A second parallel effort consisted of evaluating various electrodeinsulation materials to determine which was most suitable. Epoxy,, acrylic,phenolic, polycarbonate, and acetal plastics were investigated. Of these,the ........... a .po ,c ate matarial.s peiformed best. The final glegtrodedesign used a 0.169-inch-diameter tellurium-copper rod whichb- was coatedwith epoxy using a fluidized-bed application technique, The electrode wascoated oversize and then centerless-ground to the final 0.219-inch diameter.

32

77

rII -ELECTROLYTE CHANNEL BEFORE

MAC.INING0I /-GROOVE TO BE MACHINED

"w' "LINER

NS..INSULATION

/ STATIONARY ELECTRODE

Figure 15. Sketch of Electrochemical Rifling Set-up WithStationary, Electrode

°33

_-STATIQOrAR:YELECTROLYTE ELECTRODE

OUT 1 .

-*-WORKPIECE TUBE

_ _ f WORK HOLDER

INI

Figure ~ ~ ~ 16 Sktho hr-eghEetrceia iln cln

t'**.iing Ith Statonar Elctod ec.iu

* -~.:- ~ 34

AB

c D

Figure 1.7. The Four Groove "hapes Evaluated

1 35

Rifling grooves 0.070-inch wide by 0.025-inchl deep were then machined inthe electrode.

3.4.2 ELECTROCHEMICAL MACHINING RIFLING SHORT LENGTH TRIALS

Having obtained a satisfactory stationary electrode, the next objec-tive was to use the O.D. electrochemical rifling results described in sub-section 3.1 to develop electrochemical machining parameters for internalrifling of the candidate liner materials. The required dimensions for.220 Swift rifling are shown in Figure 18.

Initially, four materials--L-605, VM-103, TZM and WC-3015--were ten-tatively selected as the deliverable barrel liner materials. In the courseof the program, CG-27 and Inconel 718 were substituted for TZM and WC-3105by mutual agreement with the contract monitor. TZM was dropped because ofthe poor erosion resistance it demonstrated during testing under Air ForceContract F08635-71-C-0181. WC-3015 was dropped because procurement ofacceptable WC-3015 tubing could not be accomplished within the schedule ofthis program. However, WC-3015 is still an attractive future candidatesince it was shown to be electrochemically machinable. CG-27 and Inconel718 were selected as substitutes because of their known good electrochemicalmachinability, good erosion resistance (CG-27 was used successfully as abarrel material for the XM-140), and the fact that both were candidates forthe GAU-8/A and other high performance weapons.

I.D. rifling tests, using short length barrels were run on five mate-rials: 4130, L-605, VM-103, CG-27 and Inconel 718. These results, allsuccessful, are given in Tables XI through XV, respectively. The electro-chemical machining parameters developed in these tests were then used asa guide to fabricate the full length liners for the deliverable barrelsunder Phase II of the program.

36

I

tI

0074 +.002-. 000

.2240 +01-0000

32/

2190--.0000

Not To Scale

Rifling

6 Grooves

I Turn in 10 inches - Right Hand

Figure 18. Sketch of .220 Swift Rifling

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SECTION IV

PHASE II - .220 SWIFT COMPOSITE BARREL FABRICATION

The goal for Phase II was to fabricate and deliver to the Air Force

12 barrels whose liners had been electrochemically rifled. The combinationsof materials selected for these barrels are given in Table XVI.

A

4.1 FABRICATION OF PLECTROCHEMICALLY RIFLED FULL-LENGTH LINERS

4. I. 1 ELECTROCHEMICAL MACHINING TOOLING DEVELOPMENT AND CHECKOUT

The design of the full-length (24-inch) tooling for electrochemical

rifling, based on the results obtained in Phase ; is sketched in Figure 19.

Photographs of the full-length tooling are given in Figures 20 and 21.

Initial tests were conducted using a three-groove electiode which was indexed

once to produce the six required rifle grooves. However, difficulty was

encountered with insulation breakage, and a new electrode was fabricated

having only two grooves. This electrode was indexed twice to produce the

six grooves and was tound zo perform satisfactorily.

Using the successful two-groove electrode, two checkout 4130 full-

length barrels (B-21 and B-23) were satisfactorily electrochemically rifled

prior to fsbrication of the remaining liners. After the first L-605 liner

was rifled, a change in rifling twist from one turn in 14-inch to one turn

in 10-inch was requested by the Air Force. A new electrode was fabricated,

and two additional checkout 4130 full-length barrels (B-25 and B-26) were

electrochemically rifled to the new twist. These two were equally

satisfactory.

4.1.2 FABRICATION OF DELIVERABLE BARREL LINERS

Using conventional techniques, the gun barrel liners were gun-drilled,

honed, and final machined on the O.D. They were then electrochemically

rifled uring the conditions given in Table XVII. A total of four barrels

of L-605 and three barrels each of VM-103, CG-27, and Inconel 718 were elec-

trochemically rifled. All full-lengt'i liners were air-gauged immediately

after electrochemical rifling and agzin after assembly and final test firing.

The two sets of data were identical within the error of the air gauge.

Therefora, only the final set is reported (Table XVIII).

The bore data were very consistent, as expected, because the bore was

honed to a constant I.D. before electrochemical rifling. All bore diameters

.ere ... .. . -. . ..... .f thi. iJ.i sun tolarariczu, 0.219-Lu 0.220-inch, thevast majority being between 0.2187-inch and 0.2193-inch. The groove diam-

eters were either in tolerance or within 0.0010-inch undersize. These

42

.. . .. ,m,, ,.,ra .,, - -,-- ,m m, *., ' ' " .- II I

- --."

-- --- . .--- .--- - -- ;-

TABLE XVI. MATERIAL COMBINATIONS FOR DELIVERED BARRELS

Barrel Liner Jacket a

Number Material Material Liner Code

93-1 S.H.T.b VM-103 A-286 B-2

93-2 20% C.W. VM-103 Pyromet X-15 B-C

93-3 20% C.W. VM-103 H-i1 B-i

93-4 20% C.W. L-605 A-286 B-12

93-5 20% C.W. L-605 Pyromet X-15 B-i1

93-6 20% C.W. L-605 H-i1 B-9

93-7 CG-27 A-286 B-i

93-8 CG-27 Pyromet X-15 B-2

93-9 CG-27 H-Il B-3

93-10 Inconel 718 A-286 B-4

93-11 Inconel 718 Pyromet X-15 B-3

93-12 Inconel 718 H-i B-5

aee Table XVII for correlation with electrochemical

rifling conditions.bS.H.T. - Solution heat treated only.

c 20% C.W. - 20 percent reduction in diameter at room temperature by

swaging.NOTE: Insulation was H-203 in all cases.

43

TOOL HOLMING

FIXTURE777r,

E'LECTROLYTE

IN

WORKPIECE--

STATIONARY-ELECTRODE 21

INSULATE DLANDS (6) ilk

ELECTROLYTEOUT

'-WORK HOLDINGFIXTURE

I Figure 19. Sketch of Full-Length Electrochemical R~ifling ToolingUtilizing the Stationary Electrode Technique

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48

TABLE XVIII. FINAL BORE AND GROOVE MEASUREENTS MADE AFTER TEST FIRING

93-1

(A-286 Jacket: S.H.T. VM-103 Insert)

Distance From Rear of Breech in Inches

3 5 7 9 16 20

Groove A 0.2232 0.2239 0.2245 0.2249 0.2249 0.2242

Groove B 0.2234 0.2246 0.1246 0.2249 0.2250 0.2242

Groove C 0.2233 0.2244 0.2245 0.2251 0.2251 0.2247

Land A a a a a a a

Land B a a a a a a

Land C a a a a a a

(Pyromet X-15 Jacket; 20% C.W. VM-103 Insert)

___93-2

Groove A 0.2232 0.2242 0.2250 0.2254 0.2248 0.2236

Groove B 0.2235 0.2244 0.2253 0.2259 0.2251 0.2240

Groove C 0.2234 0.2241 0.2250 0.2256 0.2256 0.2239

Land A 0.2185 0.2185 0.2191 0.2193 a a

Land B a a a a a a

Land C a a a a a a

Average Groove 0.0025 0.0029 0.0030 0.0032 b b

aAir gage would not fit into bore at this station.bNot calculated.

49

TABLE XVIII. FINAL BORE AND GROOVE MEASUREMENTS MADE AFTERTEST FIRING (Continued)

93-3

(H-11 Jacket; 20% C.W. VM-103 Insert)

Distance From Rear of Breech in Inches

3 5 7 9 16 20

Groove A 0.2240 0.2245 0.2246 0.2245 0.2251 0.2247

Groove B 0.2239 0.2241 0.2243 0.2246 0.2245 0.2241

Groove C 0.2238 0.2241 0.2244 0.2247 0.2250 0.2246

Land A 0.2188 0.2187 0.2187 0.2188 0.2186 0.2188

Land B 0.2187 0.2187 0.2187 0.2188 0.2186 0.2187

Land C 0.2187 0.2187 0.2187 0.2189 0.2186 0.2188

Average Groove 0.0026 0.0028 0.0029 0.0030 0.0032 0.0029Depth

(A-286 Jacket; 20% C.W. L-605 Insert)

93-4

Groove A 0.223J 0.2233 0.2235 0.2238 0.2241 0.2236

Groove B 0.2234 0.2234 0.2236 0.2240 0.2242 0.2236

Groove C 0.2232 0.2233 0.2235 0.2239 0.2242 0.2236

Land A 0.2186 0.2185 0.2187 0.2185 0.2186 0.2189

Land B 0.2187 0.2186 0.2185 0.2187 0.2185 0.2187

Land C 0.2186 0.2186 0.2186 0.2185 0.2186 0.2187

Average Groove 0.0024 0.0024 0.0025 0.0027 0.0028 0.0024Depth

50

TABLE XVIII. FINAL BORE AND GROOVE MEASUREMENTS MADE AFTER

TEST FIRING (Continued)

93-5

(Pyromet X-15 Jacket; 20% C.W. L-605 Insert)

Distance From Rear of Breech in Inches

3 5 7 9 lb 20

Groove A 0.2241 0.2245 0.2245 0.2246 0.2247 0.2246

Groove B 0.2241 0.2245 0.2249 0.2243 0.2248 0.2248

Groove C 0.2240 0.2241 0.2243 0.2244 0.2250 0.2249

Land A 0.2187 0.2187 0.2187 0.2187 0.2187 0.2191

Land B 0.2185 0.2188 0.2187 0.2187 0.2189 0.2191

Land C 0.2187 0.2188 0.2188 0.2188 0.2190 0.2191

Average Groove 0.0028 0.0028 0.0030 0.0029 0.0030 0.0029Depth

93-6

(H-il Jacket; 20% C.W. L-605 Insert)

Groove A 0.2238 0.2240 0. 2240 10.2239 0.2245 0.2239

Groove B 0.2238 0.2241 0.2241 0.2240 0.2245 0.2242

Groove C 0.2238 0.2239 0.2241 0.2242 0.2245 0.2241

Land A 0.2196 0.2191 0.2187 0.2187 0.2188 0.2190

Land B 0.2189 0.2188 0.2188 0.2187 0.2189 0,2188

Land C 0.2188 0.2190 0.2187 0.2187 0.2187 0.2188

Average Groove 0.0024 0.0025 0.0027 0.0027 0.0029 0.0026

51

TABLE XVIII. FINAL BORE AND GROOVE MEASUREMENTS MADE AFTERTEST FIRING (Continued)

93-7

(A-286 Jacket; CG-27 Insert)

Distance From Rear of Breech in InchesI

3 5 7 9 16 20

Groove A 0.2230 0.2232 0.2236 0.2236 0.2242 0.2242

Groove B 0.2230 0.2235 0.2237 0.2243 0.2241 0.2244

Groove C 0.2230 0.2236 0.2241 0.2244 0.2240 0.2245

Land A 0.2189 0.2190 0.2190 0.2191 0.2191 0.2195

Land B 0.2191 0.2191 0.2190 0.2191 0.2191 0.2192

Land C 0.2190 0.2191 0.2191 0.2191 0.2192 0.2195

Average Groove 0.0020 0.0022 0.0024 0.0025 0.0025 0.0025Depth

93-8

(Pyromet X-15 Jacket: CG-27 Insert)

Groove A 0.223T7 0.2237 0.2245 0.2242 0.2244 0.2237

Groove B 0.2237 0.2239 0.2242 0.2247 0.2236 0.2238

Groove C 0.2238 0.2244 0.2244 0.2248 0.2239 0.2240

Land A 0.2193 0.2193 0.2192 0.2194 0.2195 0.2195

Land b 0.2193 0.2195 0.2197 0.2194 0.2193 0.2191

Land C 0.2194 0.2192 0.2195 0.2195 0.2193 0.2191

Average Groove I0.0022 I0.0024 10.0025 10.0026 C.002 ' 0.0023Depth __ _ __ _ I__ _ __ _ __ _ I__ _I

52

TABLE XVIII. FINAL BORE AND GROOVE MEASUREMENZTS bADE AFTERTEST FIRING (Continued)

93-9

(H-11 Jacket; CG-27 Insert)

Distance From Rear of Breech in Inches

3 5 7 9 16 20

Groove A 0.2236 0.2241 0.2244 0.2247 0.2242 0.2240

Groove B 0.2236 0.2241 0.2243 0.2246 0.2242 0.2239

Groove C 0.2237 0.2242 0.2244 0.2247 0.2242 0.2241

Lend A 0.2190 0.2190 0.2190 0.2191 0.2187 0,2187

Land B 0.2190 0-2190 0.2190 0.2189 0.2188 0.2188

Land C 0.2191 0.2190 0.2190 0.2190 0.2187 0.2188

Average Groove 0.0023 0.0026 0.0027 0.0029 0.0028 0.0026Depth

93-10

(A-286 Jacket; 718 Insert)

Groove A 0.2238 0.2243 0.2245 0.2246 0.2246 0.2245

Groove B 0.2239 0.2243 0.2247 0.2248 0.2248 0.2245

Groove C 0.2241 0 2244 0.2247 0,2248 0,2248 0,2247

Land A 0.2187 0.2185 0.2185 0.2185 0.2187 0.2188

Land B 0.2187 0.2185 0.2185 0.2185 0.2187 0.2187

Land C 0.2188 0.2185 0.2185 0.2185 0.2188 0.2188

Average Groove 0.0026 0.0028 0.0031 0.0031 0.0030 0,0029Depth ,

53

TABLE XVIII. FINAL BORE AND GROOVE MEASUREMENTS MADE AFTER

TEST FIRING (Concluded)

93-11

(Pyromet X-15 Jacket; 718 Insert)

Distance From Rear of Breech in Inches

3 5 7 9 16 20

Groove A 0.2233 0.2245 0.2245 0.2244 0.2239 0.2237

Groove B 0.2233 0.2242 0.2240 0.2239 0.2234 0.2234

Groove C 0.2234 0.2243 0.2242 0.2240 0.2237 0.2236

Land A 0.2192 0.2195 0.2193 0.2192 0.2187 0.2187

Land B 0.2190 0.2196 0.2193 0.2193 0.2187 0.2189

Land C 0.2191 0.2196 0.2194 0.2190 0.2187 0.2187

Average Groove 0.0021 0.0024 0.0025 0.0025 0.0025 0.0024Depth

93-12

(1.-11 Jacket; 718 Insert)

Groove A 0.2247 0.2247 0.2250 0.2255 0.2257 0.2255

Groove B 0.2249 0.2252 0.2253 0.2255 0.2255 0.2254

Groove C 0.2250 0.2253 0.2253 0.2256 0.2256 0.2255

Land A 0.2194 0.2191 0.2191 0.2191 0.2189 0.2192

Land B 0.2193 0.2192 0.2190 0.2189 0.2188 0.2193

Land C 0.2194 0.2101 0.2190 0.2189 0.2189 0.2193

^ . . Groove 0.0098 0.0030 0.0031 0.0033 0.0034 0.0031

54

two measurements, the bore and groove diameters, were averaged, subtracted,and divided by two to obtain the av3rage groove deptt (Table XVIII). Atendency of the electrochemical rifling process to produce shallowergrooves at each end of the barrel was readily observed. An attempt tocounteract this effect was made by trimming one inch of length from eachend; however, the data show this did not eliminate the effect completely.In all barrel liners, station 3 has the shallowest groove depth. Groovedepths at station 20 were less tn-c those at station 16 in eight of tcnbarrel liners (they were equal for the remaining two liners). All barrelsmet the groove depth tolerance of 0.002 to 0.003 inch except 93-10 and 93-12,which were too deep by 0.0001 inch and 0.0004 inch, respectively, at somestations. Since the barrels were electrochemically rifled separately, itis thought that better control would be achieved if they were run in batches,although the dimensional control achieved here is still good.

All WI-103 liners were gun-drilled using the electrical dischargemachining process because conventional machining has been proven to be tooslow to be economically feasible. The bores were drilled with a half-lengthelectrode - one-half was drilled starting from one end and the other halfwas drilled from the other end. This resulted in a mismatch at the middleof the barrel length where the two holes met. Final honing did not elimi-nate this mismatch entirely which existed in all of the VM-103 barrelsdelivered. It is suggested that during final testing of the barrelb thisarea be given special scrutiny.

4.2 ASSEMBLY, DRAWING, AND FINAL MACHINING

The electrochemically rifled liners were processed according to theflow chart (Figure 22). This process for fabricating full length insulatedcomposite barrels, which was developed under Contract F08635-71-C-0181,includes a drawing operation wherein the insulated liners are slip fittedinto the barrel jackets, and the assembly is drawn through a sizing die tocollapse the jacket down onto the linar, thereby providing a good mechanicalbond. Photographs of the draw bench and sizing dies are shown in Figures 2,and 24, respectively. The H-11 jackets were heated to -800'F prior toassembly, and then immediately drawn. Subsequent cooling of the jacketfurther improved the degree of mechanical bonding. The other two jacketmaterials, Pyromet X-15 and A-286, were drawn at 450°F and ambient tempera-ture respectively, then subsequently subjected to the aging treatments indi-

cated in Figure 22. The aging treatments caused the jackets to contractfurther (- 0.0005 in./in. for the Pyromet X-15 and -0.001 in./in. for theA-286), thereby increasing the mechanical bond strength. Since the linershad already been partially aged as discussed below, it was assumed thatfurther liner shrinkage was negligible. Further details of the drawing

55

Procure Liner MaterialProcure Jacket Material I 9

Ii CG.27 With H.11:1450OF 16 hr 1200*F 16 hrHeat Treat (H-11 only) CG-27 With A-286 and Pyromet X-15: 1450OF

Gun Drill, Counterbore, Hone AGE 16 hr only.Inconel 718 With H-1:132?F 8 hr, F.C. to

0. D. Machine For Drawing 1150*F 8 hrs.

Inconel 718 With A-286:1325 F 4 hr only.Inconel 718 With Pyromet X.15:1325°F 6 hr only.

Cold Swage (VM-103, L-605 only)

Conventional Gun Drill and Hone (EDM VM-103)

Electrochemical RifleIStraighten (If Required)

Air Gage

O.D. Machine For Insulation

InsulateIO.D. Grind and Thread For Assembly

Assemble

Draw

I fA"286 Jacket: 13250 F 6 hrAGE Pyromet X-15: II00°F4 hr + 1250°F 4 hr

I tH-11: none

O.D. Machine

Attach Breech Retainers

Chamber

Proof - Test Fire

(H-ll: MIL-C-13924, Class 3.3.1Black Oxide Conversion Coat Pyromet X-15: MIL-C-13924, Class 3,3.3

Gag A-286: MIL-C-13924, Class 3.3.3Air Gage

Ship to Eglin Air Force Base

Figure 22. Process Flow Sheet for Electrochemically Rifled

Composite Barrel Fabrication

56

4J4

I-4

0'4

57

-a -~-. ~r e 4c

, I

I

-41

2 A

C - ,o5 8

• O0

A 58

00g

process and how it was developed are included in the final report of Con-tract F08635-71-C-0181. A sketch of the fully assembled barrel is givenin Figure 25.

It should be noted that each liner material was delivered in severalslightly varying heat-treated conditions, depending upon its respectivejacket material. This was necessary to make sure the fabrication sequencedid not overage the liner material. For instance, the CG-27 liner withthe H-lI jacket was aged per AMS '6'3 (1450OF for 16 hours, air cool,1200OF 16 hours). With the A-286 jacket, it was aged at 1450OF for 16 hours,assembled, and then given the A-286 age (1325'F 16 hours). With the Pyro-met X-15 jacket, it was again single-aged at 1450OF for 16 hours, assembled,and then given the Pyromet X-15 age (11000F for 4 hours, air cool, 1250°Ffor 4 hours). These alternate aging treatments were selected withoutavailability of time-temperature aging data but were estimated to resultin properties similar to those achieved by standard processes. Furtherefforts to optimize combination aging treatments for jacket and liner mate-rials may be worthy of future consideration.

The barrels were conventionally O.D. machined, chambered, and inspected.

They were then subjected to a ten-round proof test firing burst on a MG-3machine gun at dpproximately 1150 spm. Borescope examination and blackoxide treatments followed. A sealing arrangement was constructed to pre-vent the black oxide solution from reaching the bore or the insulationbetween the liner and jacket. Finally, the barrels were air gauged

(Table XVIII), coated with a preservative oil, packaged, and shipped tothe Air Force.

59

I 7L

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zd

C14

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60

REFERENCES

1. McMahon, D., "An Electrochemical Machining Machine Design for Deep-Hole Boring". Society of Manufacturing Engineers, MR77-541, 1972.

Ja

61(The reverse of this page is blank)

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63

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__ _UCLASSIFIED

DOCUMENT CONTROL DATA.- R &DktIt6In ti c & s iton, aI title. body ot nbsra r I and index Ing anno to ton nmst hco ntored when the a vernif report 1% rin& sift actI

A Is.'N & It NG AC I IVI TY (Cofporetle author) 120, RrFPORT SECURITY CLASSIFICATIONJAeronutronic Division UnclassifiedPhilco-Ford Corporation Mb GROUP

Newport Beach, California 926633 REPORT TITLE

DEVELOPMENT OF AN ELECTROCHEMICAL MACHINING PROCESSFOR RIFLING LINED GUN BARRELS

4 £)ESCRIPTIVI NOTES (Ty'pe of report and inClusive dales)

* Final Report - June 1971 to October 1972--- A. TOR(S) (First name, mifddle initial. lost flame)

Richard A. HarlowDavid L. CornRichard C. Kimball

6 REPORT CATt 70. T-orAl No. OF PAG"b 7b. NO. OF REFS

Dacember 1972 7On. CONTRACT OR GRANT NO go. ORIGINATOR'S REPORT NJMaER(S)

F08635- 71-C-0209b, P110JECT NO 670A

cTask No. 02 9b. OTHER REPORT NO(S) (Any other numbers that may be assignedthsreport)

d.Work Unit No. 032 AFATL-TR-72-22610 OISTRIS11UTION STATEMENTDistribution limited to U. S. Government Agencies only; this report documents testand evaluation; distribution limitation app lied December 1972. Other requests forthis document must be referred to the Air Force Armament Laboratory (DLDG),EglinAirForceBase,_Florida_32542. ____________________

Is SUPPLEFIENTARY, NOTE~S rt2. SPONSOR iG MILITARY ACTIVITY

Air Force Armament LaboratoryAvailable in DDC Air Force Systems Command

___________________ ____________ Eglin Air Force Base, Florida 3254213 ABSTRACT

A 16-month program was conducted to advance high performance gun barreltechnology by developing an electrochemical machin~ing process for rifling highperformance barrel liner materials. A total of 15 electrolytes and numerous electro-chemical machining parameters were evaluated in conducting electrochemical machin-ability studies on iron-nickel-base, nickel-base, and cobalt-base superalloys, andon refractory alloys of columbium, molybdenum, tantalum, and Lungsten.

Four materials (L-605, VM-103, CG-27, and alloy 718) were selected forelectrochemical rifling and fabrication into caliber .220-Swift barrel liners.The rifled liners were insulated externally and assembled into outer barrel jacketsusing a drawing process, thus producing insulated composite test barrels. A totalof 12 test barrels compatible with an MG-3 machine gun, representing the four linermaterials and three jacket materials (H-11, A-286, and Pyromet X-15), were fabricatedand delivered to the Air Force. The results of this program indicated thatelectrochemical machining is a feasible procczs for obtaining high quality and low

feasible.

DD FORM 1 7DD Nov ei,5I473 UNCLASSIFIED

Security ClassifiCation

, Bty ! i.,,fieation

14 LINK A LINK B LINK -KEY WOROS .

ROLE WT ROLE WT ROLE WT

Aircraft guns

Automatic weapons

Gun barrel cooling

Gun barrel heating

High Temperature materials

Gun barrels

Equilibrium temperature gun

Ordnance concepts

Gun concepts

Electrochemical Machining

Security Classification