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Doctoral Dissertations Student Theses and Dissertations

1972

Effects of CR-plating and environment on the cracking of low alloy Effects of CR-plating and environment on the cracking of low alloy

steels at high temperatures steels at high temperatures

Robert C. Tooke

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Part of the Metallurgy Commons

Department: Materials Science and Engineering Department: Materials Science and Engineering

Recommended Citation Recommended Citation Tooke, Robert C., "Effects of CR-plating and environment on the cracking of low alloy steels at high temperatures" (1972). Doctoral Dissertations. 230. https://scholarsmine.mst.edu/doctoral_dissertations/230

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EFFECTS OF CR-PLATING ENVIRONMENT THE

OF LOW ALLOY STEELS AT HIGH TEMPERATURES

ROBERT C. TOOKE, 1941-

A DISSERTATION

Presented to the Facul of the Graduate

UNIVERSITY OF SSOURI-

In Partial lfillment of the for

DOCTOR OF PHI

in

T2812

METALLURGICAL . 1

1972

'lQ.c~ AdJfsor

IS

s s

46

OF

4

4

8

18 ..

19

20.

2

zone

zone

8

9

1

5

f

9

c 1 8 6 4 20 0

c R a. c B I I

E C I I I I

6 8 1

c 2

5

= 8 5

11

f s fo

c v 0

gases

analyzed

melt

f

copper

All gas

on the

at 1100°C

and al

surface be

to f

the test.. The

over the

copper

surfaces.

over the steel and Cr

Numerous were

the test was

bore ~~,, .. ~~ratures are unknown. However, there was

evidence that

the test

was at, or near, me

of

s. Furthermore,

lants are exces

desirable to make these tests at the

possible which allowed retent

gradient

gases,

sts on the

should be

intended to be

surrounding a

test

for a

after ass

the des

to f

was

s a

to

contact

that the test

test

of test

,

test

a

flame

,

zone

clos

1

llant

the

Tabul

other s

results

of arbon

The

fa

14

9

Cr

Cr

Cr

Cr

5

50% co , 5

5 , 6

co 0

,

0 %

00

0

5 6

I

0 I

2

Cu,

, 10 %

u ...........

u c

u

•

•

•

•

• Cr plated

un pia ted

rgon

T

5 F IL RE x100

a1

acks

h 1

e

which i

s very much in evidence at

the

base

s

t 5

1

5

2

be

re

s

acce

s had no s

f

cracks,

crack ch

Contras this Cr

erved

100

iner

it

s s

zone sugge

Uti z

a

contain

e1ded

tho e

cracks

area

9

0 and 21

c

s

s

s 2

f

r-

c

2

areas corre

r

the

v

ttled zone

Figure 23A 23

carburi

be

locat

4

the actur

s

4

25 as

cal ones have been

c ,Fe c6 and Cr,Fe

The

1 n

s

Te s

c

rbon

f

ter

ied

c 3

obs

can

that re

the zone,

might dlle

the

which Wot:l.ld

the

dis

is s

the zone was

Ase

Iy, DISCUSSION OF RESULTS

ef

gas

is

of the

to a oxygen

s, of course, s

these results. That

, characte of the 100% co tests

a

,

of a us

(i .. e ..

e1e:rnents

c s ..

no

, is re zed .. It is

s zone is s the result of

to a formed at

+ te or te)

for a zone

ch are known to be in

of the altered zone

enhancement was observed and

to be softer than the matrix.

an al to a 10 % co gas

e rt&in c f The gas consisted of co

ente r but the 1 f the

resu of (soot)

0 some s r content was

common t:eq_ces co sent s

of the sts. s the st co

s

4

I ..

the

carbon

was

etc ..

intrus

takes

more

when under

nature ch

of stress.

enhances

e

of

shed in the present

to the resu

is in basic th that envi

Heretofore we have

are that the

are 0 , Cr,

of

external

the of

the al

vanadium

free

is shown in F

11 sele

the

complex -X

their forma

Internal

steels

rnal

s ..

s

z

cal

to that

s

di

ss

s

the exact

has not

has

Fe-

II o Internal External xide ones

Fe-

llo Internal xide one

Fe xides

2

as

as

or Fe­

x ides

c

to

conclus

s

the

the

se that

s to

external

co ,

lure

s

Cr lated spe~_.....~-.lu":::J.lo

on persis s

surf

stress

factor

due to

to

The tensile

s because it

a more

5 Ll

5 L I

= 2 c 5

5

I

5 L I

2 L

V. SUMMARY

must be remembered that the

of these tests do not s

in the gun barrel. A

c factor

orders of

the rates

the conditions

fference is the

enced in gun barrels

It is assumed, how-

ever, that the trends observed in these

s can be lated to a better

unders vU . .L.I.\.A...I.. . .I..I. of possible chemical s in the gun

barrel ..

42

An obvious conclusion to the previous results is that

if the copper deposits are liquid at any time, the result­

ant attack will be catastrophic. Futher firing tests on

the 7.62 mm barrel excluding the copper cladding on the

projectiles would definitely determine the effect of the

copper.

The effect of the cracks in the Cr plating in

enhancing chemical attack is probably more pronounced in

these experiments than 1n the actual barrel. The same

mechanism of concentrated chemical attack at the root of

the existing crack would be operative in the Cr plated

barrels so the conclusion is identical, i.e. cracking

will be worse in Cr plated barrels. This does not imply

that a plated barrel is inferior to the unplated barrel

the uniform wear of the unplated barrels has not

been accounted for. From these results it is

that a cal to minimize barrel deteriotation

would be to deve crack-free p s. A less obvious,

but more e le, solution would be to

a chemical resistant intermedi

between the and substrate .. These

cate a major on of

initi the crack in the steel ..

cal effects in

Therefore, such a

r would retard

the steel ..

The oxygen

shown to affect the cr

of the crack in the Cr

ial of the gaseous was

low

oxygen al is desirable for z dete

of the barrel. factors such as pressure,

43

rature, and gas compos which exist the barrel

make exact corre s to 1 results s le.

It is felt that the most outcome of these

experiments is the qual how

cal react

st

0

BIBLIOGRAPHY

1.

2.

NDRC Technical

of the

on Gun Tube Eros

, Vol .. 1, 1946.

ce Technical Me

and Control, edited I .. Ahmad

and J. P. Picard, Wate Arsenal, 1970.

of Eros in 7.62 mm Gun Barrels,

, DAAF01-69C-0541, Rock Island Arsenal.

4. R .. W. , Trans. AIME, 188, 678, 1950 ..

5. G. C. Wood, Oxid of Metals, ~~ 11 1970 .

6.. R. A. , Corrosion, 21, 382 1965).

7 .. Kofstad,

1966 ..

8. J.

(1968)"

and E. F. Brush, Trans. AIME, 242, 35

9. N. Bredz and H. Schwartzbart Journal,

305-S (1959) ..

10 .. .. Hume, L. H. , and .. T.

il 1965, p. 169

11 .. A. E. and F

.. , 5 151 6 Trans 7981.

s ans.. 41,

, 19 7, 2

44

4

14 .. G. J .. Hill, Institute

of Metals, 1967, p. 312.

15 .. E. Krempl and c. D. Walker,

ture, ASTM STP 459, p. 75 (1968).

16. L. E. Coffin, General Electr (S , N y .. )

Report 71-C-108 (1971).

17. L. E. Coffin, Trans. ASM ~~ 339 (196 ) .

18. M. R. Achter, G. J. Danek, and

AIME , 2 2 7 , 12 9 6 ( 19 6 3 ) ..

19

20

C. J. McMahon and L. E. Coff

1, 3443 1970 ..

G. J. Danek H. H. Smith, and

ASTM 61, 7 5 1961).

, Trans ..

al i Trans

.. Achter,

21 .. an and M. R. Achter Trans. AIME 215,

(1959 ..

22. J. A. Webber ASM

23. D. Shechtman and S. Niedzwiedz

24 ..

25 ..

6

2

. 5 5 (1969) ..

w .. w .. Smeltz r, Acta Met ..

w .. Smelt r, Trans .. AIME

.. s .. and .. B ..

19 6 4) .

i

8 6

60

8 77

218, 6

r, Acta

6

ium 1937,

al S and

1960 "

4 1960) ..

Met 12, 35

r Acta

96

c

89 ..

30. I. s .. Koz i, Metal and at

l, 157 (1967).

31 .. A. and E. , Trans ..

(1947) ..

32. J .. L .. Meij , Acta Met .. , lr 15 5

33. s. s. Manson, Int1 .. Jnl .. Fracture .. , 2

(1966).

34. c. s .. , Trans .. AIME , 194

35 .. L .. H .. Van V1ack,

VITA

Robert c. Tooke was born 1 11, 1941

, Mis After education in the

schools, he attended

at Rolla and rece the

B . S . ( 19 6 2 ) and .. S .. ( 19 6 6 ) s in

Metal cal ional career

ludes: Metal st, Bethe 1

1962-65; Instructor, UMR, 1967-72; 1-

st, Command,

1967-1972; Control

.............................. , 1972- ..

APPENDIX A

EXPERIMENTAL PROCEDURE

A. Apparatus

A laboratory

which permitted the

was des and constructed

test of Cr-Mo-V

gun steel under alternating stress in selected environ-

ments. An overall of s has been shown

in 5 .. The ess 1 elements of the s

are shown in the block diagram of 31. The

s can be s functional es

cons is of: (1) test chamber; (2)

(3) stress app sm; 4) rature

control; (5) environment control. Each of these will now

be described in 1.

1 .. Test chamber:

enclosure which

(descr be

compress as a

of the chamber with a

The test chamber was a vacuum

the hot test specimen

alternate stressed (tens

lever beam. A led dr

in was

shown in

of the

gure 6. In add to the forced cool

48

1 was sealed with zon

st

2. A 450

a saturable core reactor

control 1 for

of The was a

Model T-5-3-KC-J-B a of 5 KW ..

The 1 used was made from n

o .. d .. copper and four turns

over a total of s .. The 1 is shown

32 a heated at 1000 c .. 3

les for the

3.. Stress app .I.U\;.,.•vJ.J.<;..;\,.LJ...J... srn: A

of the s the of e

sh the des stress Power was alter-

a DPDT re between two

the extens to

then the other The

srnal

:

II

1

8 900 1000 1100

TE PER TURE °C

0 = 3d • E . r

1

o = stress

d = distance traveled before hitt

E = modulus of e

r = radius of (gage

l = distance from gage section to s

In the values of d = 6" E = 15 X 10 100 C,

r = 0.1" and 1 3 .. 7" this

for o of 21 000 psi. This exceeds the eld

s al at l000°C so the stress s in c

range .. No was made to determine the actual

plastic strain involved these s.

4. control: measurement was

made th an Ircon Model 300T5C pyro­

meter and indi ine

focus lens was used which allowed

r on a

range 4-7

the above

re

as small

s from the

was fed

(L & N

between the f

( 0-Srna)

al

s 8 The interface

recorder-controller

s core 0-8

of the induction was a L & N Series

11900 silicon controlled recti£ power modified

for an load.

The development of a s s

and of the ation

considerable effort. 1 pyrometer

to measure direct on the surface of the

surface made failed because

sible to accurate determine the emittance value

for the surface. Therefore, it was desirable to create

a blackbody condi = 1) s the radi

pyrometer on a hole drilled in the sample.

The of the on lved

son

thermocouple ..

and a

other hole.

atures was

rature measured a Pt-Pt 10 Rh

Two holes were drilled in a 4" steel rod

was placed in one hole with Pt foil to

contact. The r was focused on the

of the measured

when an emittance sett of .. 92 was

used ch confirms the hole be a 1 when

the known loss of 8 the

chamber is cons Further conf

of measurement was

r

8

1

s walls of the test

in

to

sts

s

the

lt

54

5

the holes between the second and turns

of control te was

on a hole the s

the and turns of 1 so as not to

fere stress the gage of

the spe ( s the

dete ch was accom-

a two holes one between

the and second turns, and the other between the

second and turns

and

s test are

used

between the set

actual rature

accuracy is j

5 ..

to

or control

the gage

to be 10 C

u~~ .. ~·~r was estab

of argon

(99 .. 7

The results

1000 c ..

of

was 40 cc/min. The flowrate and of the ases was

governed by Matheson Model 665 Gas

blended the gases flowmeters .. All gas

mixtures were checked and recorded with a Fisher Gas

Partitioner 1 25V) and a Texas Instruments Servor

II recorder. Gas s s for were

an gas sampl valve .. is

of exit gases was also lable .. All mixtures

were burned after exit from the test~chamber.

B .. and Test

Two s of test spe ated and

were the

are represented in F 35 ..

from from the same heat of Cr-Mo-V

steel .. A

paper ..

ameter o

were

ana is gave the fol compos

C Mn 0.43 0.97

Si 0. 9

lus

of the

Cr l .

Mo

ori on was

After

1"

ctro hard

3" to .. " ho

the

se-

.. 22 "

8

and .045" diameter was drilled on the of each

for

ously.. The

acetone before us

purposes as described

were cleaned with

for a

test chamber after as

cal test clos

of the test spe~~m~~A

1 the desired gas, re

the

and al

the

1000°C)

the gas to flow for 15 minutes. At

was heated to the test rature

s t

(general

red less than 60 seconds and cycl

was Most tests were

was placed on the des

copper wire in situ at 1100°C

to failure ..

me

argon and al

se for the Cu to flow over the surface before

the test. The copper readi

over both the steel and Cr plated surfaces.

r

a fine

15

5