is 7739-4 (1975): code of practice for preparation of

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IS 7739-4 (1975): Code of Practice for Preparation ofMetallographic Specimens, Part 4: Copper and its alloys andtheir examination [MTD 22: Metallography and HeatTreatment]

Ls:7739(PartIV)-1975

Indian Standard CODE OF PRACTICE FOR

PREPARATION OF METALLOGRAPHIC SPECIMENS

PART IV COPPER AND ITS ALLOYS AND THEIR EXAMINATION

( First Reprint FEBRUARY 1988 )

UDC 620.182.2:669.3

BUREAU OF INDIAN STANDARDS hlANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

NEW DELHI 110002

Gf 2 December 1975




Metallagraphy and Heat-Treatment Sectional Committee, SMDC 27

R@resmtitJg International Nickel ( India ) Pvt Ltd, Bombay

Mining & Allied ‘Machinery Corporation Liniited, Durgapur

SHBI N. V. RA~R~AN ( Alternate ) SEEI N. C. BA~CEI National ,Tcst House, Calcutta SEEI S. N. BAXB~~JEE Indian Institute of Metals, Calcutta SEXI S. S. BEATNAGAR National Metallurgical

Jamshedpur Laboratory ( CSIR ),

Dn S. K. CEATTERJEE Guest, Keen, Williams Ltd, Howrah SHBI S. K. BAEU ( Alternate )

SERI DA~ARATHA The Mysore Iron & Steel Ltd, Bhadravati SHRI B. HARIDASACEAR ( Alternate )

SHBI D. M. DA~AR Premier Automobiles Ltd, Bombay J~PUTY DIRECTOR ( MET )-3, Ministry of Railways

RDSO, LTJCKNOW CHEMIST & MPITALLURQIST ( AItcrnntc )

SHRI A. K. GUXIA Directorate General of Supplies & D%posals

SHRI P. C. ~STAFI ( Alternate ) ( Inspection Wing ). New Delhi

SFIRI H. A. JATSINGIHANI Mahindra & Mahindra Ltd, Bombay SHRI A. R. RAXADI~E ( Alternate )

Saar M. L. KATYAL DR D. M. LAKHIANI

Bajaj Auto Ltd, Poona Indian Iron & Steel Co Ltd, Burnpur

SHRI D. R. DAS~UPTA ( Ahrnate ) SEEI N. MAJUMDAR Indian Aluminium Co Ltd, Calcutta

SERI S. N. BOSE ( Alternate ) DR G. MUKRERJEE Hindustan Steel Ltd, Ranchi

SERI D. K. BA~OHI ( Altcrnatc ) SERI A. PADXANABAN SERI B. M. PA1

Ashok Leyland Ltd, Madras The Alloy Steel Producers’ Association of India,

Bombay SERI S. A. MALWADE ( Alternate )

( Continued on )a## 2 )

@ G$pight 1975

BUREAU OF INDIAN STANDARDS

Tbii publicaiion is protected under the Indian Copyright Act ( XIV of 1957 1 and reproduction in whole or in part by any means except with written pcrmisslon of the publisher shall be deemed to be an infringement of copyright under the said Act.

16:773!3(PartIv)-1975

( Gmlinuedfrompage 1 )

Members Rs~resenting Da P. S. PATTIHU Tata Engineering & Locomotive Co Ltd, Jamshedpur

SERI J. C. KAPOOR ( Alternate ) SEEI N. M. RAJU Hindustan Motors Ltd, Uttarpara SH~I B. RAMA KRISHNA Indian Telephone Industries Ltd, Bangalore

SHRI J. NAQESH BEAT ( Alternate ) SEE1 V. RAB%ASWAMY Ministry of Defence ( DGI ), Department of Defence

Production Srrn~ R. H. G. RAW Mukand Iron & Steel Works Ltd, Bombay SERS G. G. SAHA Ministry of Defence ( R C D ) SEXI H. N. Swaa Textile Machinery Corporation Ltd, Belgharia DB L. R. VAIDYANATH Indian Copper Information Centre, Calcutta

SERI V. 8. BIUNDARY ( Alternate ) SERI V. V. VIRABIUDRAYYA Directorate General of Technical Development,

Srrnx K. L. CEATTERJEE S-EIU SUBHASH WA~IUVAN SEIU C. R. RUA RAO,

Director ( Strut & Met )

New Delhi ( Alternate )

Murarka Engineerin Works, New Delhi Director General, BI 5 .( E.v-L@~.o- Mmbn )

SHRI B. MUKEEIWI

Deouty Director ( Met ), BIS

2

IS : 7739 ( Part IV ) - 1975




0. FOREWORD

0.1 This Indian Standard ( Part IV ) was adopted by the Indian Standards Institution on 31 July 1975, after the draft finalized by the Metallography and Heat Treatment Sectional Committee had been approved by the Structural and Metals Division Council.

0.2 The primary object of metallographic examination is to reveal the constituents and the structure of metals and their alloys by means of the microscope. In view of the diversity in available equipment, the wide variety of problems encountered and the personal element, this standard gives for the guidance of the metallographer only those practices which experience has shown are generally satisfactory.

0.3 This standard is ‘being issued in parts covering general. features, polishing, etching and examination of different metals. This art is fourth in the series and covers copper and its alloys. R Other parts in t is series are:

Part I General features

Part II Electrolytic polishing

Part III Aluminium and its alloys and their examination

Part V Iron and steel and their examination Part VI Lead and its alloys and their examination

Part VII Magnesium and its alloys and their examination Part VIII Nickel and its alloys and their examination

Part IX Precious metals and their examination

Part X Tin and its alloys and their examination

Part XI Zinc and its alloys and their examination

0.4 In the preparation of this standard assistance has been derived from ASTM E3-62 ‘ Standard methods of preparation of metallographic specimens ‘a issued by the American Society for Testing and Materials.

3

IS : 7739 ( Pai% IV ) - 1975

0.5 For the purpose of deciding whether a particular requirement of this standard is complied with, the final value, observed or calculated, express- ing the result of a test or analysis, shall be rounded off in accordance with IS : 2-1960*. The number of significant places retained in the rounded off value should be the same as that of the specified value in this standard.

1. SCOPE

1.1 This standard ( Part IV ) covers the polishing, etching and examination of copper and its alloys.

2. POLISHING

2.0 For microscopic examination, secure a plane surface by filing, by rubbing over sheets of .abrasive on a hard flat surface, or by use of an emery wheel copiously supplied with water.

2.1 Polishing is usually carried out in three stages, using wheel speeds varying over a wide range, depending on the alloy, abrasives, polishing cloth, and polisher’s preference ( speeds from 250 to 1800 rev/min have been used ) . The first polishing wheel may be covered with sheets of abrasive paper of finenesses down to about No. 400. Usually, however, it is covered with canvas cloth to which is applied grit NO. 500 silicon carbide, or No. 400 or finer grades of aluminium oxide. Cover the second wheel iith wool broadcloth and use crushed sand stone as the abrasive. Cover the final wheel with either fine grade wool or a ‘ kitten’s ear ’ broadcloth and employ a water suspension of aluminium oxide or finely powdered magnesium oxide as the abrasive.

2.2 Keep all polishing wheels wet during use by a water drip and keep the specimens, between steps, wet and thoroughly rinsed free of abrasives. After removal from the final wheel, the specimen may be immediately etched or rinsed in alcohol and quickly dried prior to etching. In much of the routine preparation of specimens, the final etching is depended upon to remove many shallow scratches.

2.3 Pure copper is more difficult to polish than its alloys, since a nearly perfect surface is required in order to detect the presence of cuprous oxide in the unetched specimen.

2.4 For macroscopic examination, the specimen may be prepared by grinding and rough polisbing or by finishing with a fine tool on a shaper.

*Rules for rounding off numerical values ( rcvirad).

4

ISr7739(PartN)-1975

3. ETCHING

3.1 The etching.reagents commonly recommended for copper and its alloys are given in Table 1.

3.2 The constituents of etching reagents specified in the above table should conform to the following Indian Standards:

Constituent Indian Standard

Ammonium hydroxide 799- 19551 Distilled water I’s” :: 1070-19602 Hydrogen peroxide IS : 2080-19623 Chromium trioxide IS : 330-19684 Hydrochloric acid IS : 265-19625 Nitric acid IS : 264-19686 Ferric chloride IS : 711-1970’ Ethyl alcohol IS : 321-1964a Potassium permanganate Sulphuric acid ;g ; ;;;:;;;p

Sodium chloride IS : 4408-!967’l Ferrous sulphate IS : 262-1967ls Sodium hydroxide IS : 376-1969l* Acetic acid ( glacial ) IS : 695-1967”

4. EXAMINATIOM AND IDENTIFICATION OF COiiSTITUENTS

4.1 Combination of etches are frequently employed in the examination of copper alloys in order to secure cdntrast between several constituents. For instance, when alpha and beta structures are both present a ferric chloride etch following the ammonium hydroxide-hydrogen peroxide etch will darken the .beta constituent. Similarly, a beautiful colouration of copper and phosphor-bronze may be obtained by following an ammonium hydroxide-hydrogen peroxide etch with a few seconds of electrolytic etching. In etching the copper-beryllium alloys, the specimen is frequently given a slight initial etch in potassium dichromate, followed by 10 to 15 seconds in the electrolytic solution.

‘Specification for ammonia, liquor, technical. *Specification for water distilled quality ( reutied ). sSpecification for stabilized hydrogen peroxide. ‘Specification for chromium trioxide (J&t r&ion ). sSpecification for hydrochloric acid ( revised ). ‘Specification for nitric acid (fist revision ).

‘Specification for ferric chloride, technical ( jrst reoisivn ).

sSpecification for absolute alcohol ( revised ). %pecification for potassium permagnate (first revision ). ‘%pecification for sulphuric acid ( revised ). 9pecification for sodium chloride, analytical reagent. “Specification for ferrous sulphate, heptahydrote (JFrst revision ). “Specification for sodium hydroxide, analytical reagent (Jrst r&n ). “Spe-cification for acetic acid (Jirst revision ).

5

TABLE 1 ETCHING REAGENTS FOR COPPER AND ITS ALLOYS

(clazf.M3.1)

SL ETCEI-IWJ REAQENT

No.

(1) (2)

1. Ammonium hydroxide -hydrogen peroxide

2. Ammonium hydroxide 0,

3. Ammonium hydroxide- ammonium perSUl- phate

4. Ammonium persulphate

5. Chromic acid

6. Chromic acid

7. chromic acid-hydro- 00s ( 10 to 15 percent ) 56ml chloric acid HCl 1 to2drops

cbxPOsITION

(3) NH,OH 5 parts Us0 5 parts HsOs ( 3 percent ) 2 to 5 parts

Diluted solutions

NH,OH 1 part HsO 1 part

I NH, )I SsOs 2.5 percent )

2 parts

tHJg4 ) SSSOS 10 g S 90 ml

Saturated aqueous solution ( CrOs )

1 percent aqueous solution ( CrOs )

REMABKS

(4)

Peroxide content varies directly with copper content of alloy to be etched. Immersion or swabbing for about 1 minute. Fresh HsOs is desuable for good results

Immersion

Immersion

Use either cold or boiling. Immersion

Immersion or swabbing

Use electrolytically at 6 V, with alumi- nhun cathode, for 3 to 6 s

Add HCl at time of use immersion

USE

(5)

Generally used for cop per and many of its alloys. Film on etched aluminium bronze removed by weak Grard’s solution

Polish-attack etching of brass and bronze

Polish-attack of copper and some alloys

Copper, brass, bronze, nickel silver, aluminium bronze

Copper, brass, bronae, rriry silver (plam

Aluminium bronze and beryllium copper

Same as reagent No. 5. Colour by electrolytic etching or FeCls reagents

cd

!i 2

,

*. %rc acid-nitric

9. Copper ammonium 10 percent aqueous solution of cop chloride.ammonium hy- ammonium chloride plur NH, B” H droxide to neutrality or alkalinity

10. Ferric chloride FeC& 5 19 5 25 1 8 10 3 HCl 50 6 10 25 20 25 1 10 H,O 100 100 100 100 100 100 180 100

v I I. Ferric chloride

12. Nitric acid

HNO( 5Oml cro, 20 g Ha0 30 ml or HNO, 5 ml CrO* 20 g I&C 75 ml

FeClS 5g Ethyl alcohol y y HCl m

Various concentrations

13. Potasrium dichromatc IWhO, I-MO, t;1 NaCl ( saturated solution )1$ n$ I-LO

Immersion Aluminium bronze; film from poliahin removed by 10 percent %IF

Immersion. Wash spe- Best for darkening large cimen thoroughly areas of beta in alpha-

beta brass, copper, brass, nickel silver

Immersion or swab- Copper, brass, bronze, bing. Etch lightly aluminium bronze; dark- or by etr;cssive ens beta in brass; gives light. to contrast following di- requrred results chromate and other

etchen

Immersion or swabb- Copper, aluminium, mag- ing for 1 second to nesium nickel and zinc several minutes alloys, etc

Immersion or awabb- Deep etching ing, AgNOs (0.15 to 0.3 percent) added to 1 : 1 nitric acid rolution gives a brilliant deep etch

NaCl can be replaced Copper; copper alloys of by 1 drop of HCI to 25 ml solution

beryllium manganese, and silicon; nickel silver,

added just before bronze; and chromium using immersion . Followed by

f,Fh!f:r other contrast

( Gmlirrurd)

TARLRI RTCHtNG RRAGRNTS FOR OOPPER AND IT8 ALLOYS - Cbnrd 6 3

St ETOEING REAQENT thlPOSITION RrvrBra UeP. No.

(1) (2) M (4) (5) I 14. Electrolytic etch

15. Electrolytic etch

FeSO, 30 g 2:; 4 g

H:O ’ lOOm1

19OOml

HN?I 10 nd zla;d acetic 5 d

HIO ‘85 ml

UueO:lAat8tolOY. Generally not over 15s. Donotswab surface after etcb- bg

Darkens beta in brass fp; contrast afte; 2

I I etch. Nickel y silver bronze and other alloys z

3 Is Very satisfactory for

etching high-nickel alloys such as 20 to 30

cupro-nickel a~~~~onel. It tends to minimize the stria- tiOllS Which

after etching XT coring effect

--

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