Cobalt Base Surfacing of Inconel 718-WJ_1973_12_s550

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Cobalt Base Surfacing of Inconel 718

Of several suggested causes of microfissuring, this

study finds coarse grained ma terial a necessary but not

sufficient condition

B Y R . A . D O U T Y A N D H. S C H W A R T Z B A R T

ABS TRAC T. The p rope r t i es o f I ncone l

718

suggest i ts use as a mater ia l o f

con s t ruc t i o n in the l i qu id sod ium

coo led fas t b reeder reac to r . I n some

of i ts uses i t would be des i rab le that i t

be su r faced fo r ha rdness w i th a

cobal t base a l loy . Because of pr ior

obse rva t i ons o f m ic ro f i ss u r ing i n the

w e l d i n g o f I n c o n e l

7 1 8 ,

a s tudy w as

c o m p l e t e d t o d e t e r m i n e w h e t h e r t h i s

p h e n o m e n o n w o u l d b e e n c o u n t e r e d

i n t r a n s f e r r e d a r c p l a s m a s u r f a c i n g ,

a n d ,

if so, the in f lu en ce of va r iou s

m e t a l l u r g i c a l a n d p r o c e s s p a r a m e t e r s

on i t s occu r rence .

S i x - i n c h r o u n d s o f I n c o n e l 7 1 8

f rom d i f f e ren t hea ts and sou rce s

w e r e s u r f a c e d w i t h C o C r A b y t h e

t rans fe r red a rc p lasma p rocess . The

v a r i a b l e s s t u d i e d w e r e 7 1 8 p r o c e s s

ing h i s to ry , compos i t i on , g ra in s i ze ,

and hea t i npu t du r ing su r fac ing .

A p r i o r researcher had p roposed

the use o f f i l l e r l ess gas tungs ten -a rc

w e l d i n g ( G T A W ) t o i n d i c a t e t h e s u s

cep t i b i l i t y o f I ncone l 718 t o m i c r o f i s

s u r i n g .

T h e r e f o r e , t h i s p o s s i b il i ty w a s

R. A. DOUTY is associated with, and H.

SCHWAR TZBART is Director Materials

Engineering of, Rockw ell International

Corporation, Pittsburgh, Pa.

Paper was selected as alternate for the

54th AWS Annual Meeting held in

Chicago during April 2-6, 1973.

s tud ied i n the p resen t p rog ram .

Of the va r iab les s tud ied , on l y th e

g ra in s i ze o f t he Incone l 718 ap

peared to have any s ign i f i ca n t and

s y s t e m a t i c e ff e c t o n m i c r o f i s s u r i n g

behav io r . Coarse g ra ined mate r ia l

was more p rone to c rack ing than f i ne

g ra ine d ma te r ia l . A l l o f t he c rack ing

occur red under the depos i t , con f i ned

en t i re l y to the g ra in boundar ies i n the

hea t -a f fec ted zone o f t he base meta l .

None o f t he f i l l e r l ess gas tungs ten -

a rc we lds exh ib i ted any c ra ck ing .

The re fo re , i n th i s s tudy , GTA W d id

no t se rve as an i nd i ca to r o f c rack ing

suscep t ib i l i t y .

In t roduc t ion

I ncone l 718 has been cons ide red

as a ma te r ia l o f con s t ruc t i on i n th e

l i qu id sod ium coo led fas t b reeder

reactor , and re la t ive to i ts use in

va l ves , i t s su r fac eab i l i t y w i th coba l t

base a l loys is o f in teres t . In i t ia l

a t t e m p t s to s u r f a c e I n c o n e l 7 1 8 w i t h

CoCrA us ing the t rans fe r red a rc

p lasma p rocess gave r i se to de fec ts

o n d y e p e n e t r a n t i n s p e c t i o n , u l t i m a t e

l y t raced to i n te rg ranu la r m ic ro f i s

su res i n the hea t -a f fec te d zone . I t ,

t h e r e f o r e , b e c a m e d e s i r a b l e t o

c o n

duc t a p rog ram re la t i ng p rocess

p a r a m e t e r s a n d m a t e r i a l v a r i a b l e s t o

t e n d e n c y f o r m i c r o f i s s u r i n g .

Severa l s tud ies (Re fs . 1 -9 ) have a l

r e a d y b e e n c o n d u c t e d o n m i c r o f i s

s u r i n g i n t h e w e l d i n g o f I n c o n e l

7 1 8 .

T h e s e h a v e a d d r e s s e d t h e m s e l v e s t o

the var iab les of gra in s ize (Refs . 2 , 4 ,

5 , 7 - 9 ) , c h e m i c a l c o m p o s i t i o n ( e s p e

c i a l l y m a n g a n e s e a n d s i l i c o n

con ten ts ) (Re fs . 1 -4 , 9 ) , so lu t i on an

nea l i ng tempera tu re (Re fs . 2 -4 , 6 , 7 ,

9) ,

and hea t i npu t (Re fs . 4 -6 ) . The

resu l t s o f t he p rese n t i nve s t i ga t i on o n

s u r f a c i n g f o r h a r d n e s s w i l l b e c o m

p a r e d t o t h e f i n d i n g s o n t h e w e l d i n g

s tud ies .

Thompson (Re f . 8 ) has p roposed

the use o f f i l l e r l es s GT AW fo r i n

d i ca t i ng the suscep t ib i l i t y o f I ncone l

71 8 to m ic ro f i s su r in g . Th i s poss ib i l i t y

w a s e x a m i n e d i n t h e p r e s e n t p r o

g r a m .

E x p e r i m e n t a l M a t e r i a l s

a n d P r o c e d u r e s

Thre e d i f f e r en t hea ts o f I ncone l

7 1 8 , f r o m d i f f e r e n t s o u r c e s a n d w i t h

d i ff e re n t t h e r m o m e c h a n i c a l h i s

t o r i e s , w e r e s t u d i e d . T h e i r c o m p o s i

t i ons a re p resen te d i n Tab le 1.

The mate r ia l was rece i ved i n the

fo rm o f 6 i n . d iam bars , some fo rg ed

and some ro l l ed . S i x tes t s pec ime ns

were p rocessed , s tudy ing a range o f

m a t e r i a l a n d s u r f a c i n g p r o c e s s

5 5 0 - s I D E C E M B E R 1 9 7 3



Table 1

C

M n

P

S

Cu

Fe

Ni

Co

T i

Si

Al

Cb

Cr

B

M o

— Exper im enta l Base Mate r ia ls

Heat no.

Re p o r t e d

( a )

0 .05

.10

.002

. 0 0 4

.01

—

5 3 . 2 4

.12

1.03

.12

.50

5 .12

1 8 . 3 9

. 0 0 4

3 .09

8 5 4 6 7

Check

0 . 0 4 1

.045

.007

. 0 0 6

. 0 1 8

1 8 . 1 0

54.15

.10

.86

.08

.36

5.11

18.04

. 0 1 " "

3 .05

Heat no.

Re p o r t e d

0 . 0 4

.10

.01

. 0 0 3

.10

—

53 .5

—

1.05

.10

.47

5 .32

18 .3

—

3 . 0 0

9 0 3 5 4

Check

0 . 0 4

.05

0 0 5

. 0 0 7

.02

1 9 . 1 2

5 3 . 3 0

.092

.86

.07

.26

5 .08

1 8 . 0 5

.01(b)

3 .02

Re p o r t e d

0 .05

.33

.009

. 0 0 7

.06

17.49

5 3 . 5 9

.04

1.05

.18

.36

5 .21

1 8 . 6 3

. 0 0 4

2 .98

Check

0 . 0 4 4

.19

. 0 0 8

. 0 0 6

. 0 2 6

18.10

5 4 . 0 5

. 0 3 4

.87

.16

.33

5 .05

18.11

01<b)

3 .01

(a) Analyses as reported by vendor.

(b) Not detected. The

number

indicates the minimum limit of detection.

MIN CLEAN UP

Fig. 1 — Test specimen. (A) before hard-

surfacing, (b) after hardsurfacing

Table 2

Tes t

no.

3

4

5

6

7

8

— P r o g r a m V a r i a b l e s '

3

Hea t

no.

8 5 4 6 7

9 9 C3 E Y

99C3EY

9 0 3 5 4

9 9 C3 E Y

9 0 3 5 4

F o r m

Forged

Ho t ro l l ed

Ho t ro l l ed

Fo rged

Ho t ro l l ed

Fo rged

Co n d i t i o n

A g e h a r d e n e d '

0

'

S o l n . a n n e a l e d

A g e h a r d e n e d




T e c h

n i q u e

, b )

A

B

B

B

C

C

Cu r r e n t ,

A

190-200

190-200

190-200

1 9 0 - 2 0 0

1 3 5 - 1 4 5

1 3 5 - 1 4 5

Prehea t ,

F

8 0 0

8 0 0

8 0 0

8 0 0

No n e

No n e

P o wd e r

f l o w

g / m i n

3 8 . 0

3 8 . 0

3 8 . 0

3 8 . 0

3 3 . 4

3 3 . 4

Trave l

speed ,

i pm

5

5

5

5

8

6

P o s t we l d t r e a t m e n t

1 h . 80 0 F, s l ow coo l

1 h . 800 F s l ow coo l

1 h . 800 F s lo w c oo l

1 h . 800 F s lo w c oo l

Ai r coo l

Ai r coo l

(a) The following surfacing parameters were held constant for all experiments: (1) Powder type and size: modified CoCrA (Alloy 156)-100 +270 mesh;

(2) Torch type: Linde heavy duty; (3) Torch lead +5 deg; (4) Electrode type and size: 2% thor iated, 5 /3 2 in. diam; (5) Electrode setback: 5/32 in.;

(6) Center gas 8 cfh argon;

(7) shielding

gas: 50 cfh argon; (8) Powder gas: 20 cfh helium;

(9)

Arc initiation: High frequency; (10) Voltage: 28 - 30;

(11)

Torch-to-work d istance:

3

A

in.

b)

3/I6

t

z.

I

3/16

X

1-1A

/

t

i

1-1/4

'

s s \

t I

1 1/4

(c)

1325-1400 F for 8 h.

Cooled at 100

F

per

h

to

11

50-1 200 F and held for 8 h

then air

cooled.

- j > -

v

'- -V

Fig. 2 — Setup of surfacing eguipment.

The small positioner for the test cylinders

is

at the right and the plasma-arc spray

head is below the boom at the center of

the photograph

p a r a m e t e r s . T h e s e a r e d e s c r i b e d i n

Tab le 2 .

T h e c o m p o s i t i o n o f t h e s u r f a c i n g

coba l t a l l oy po wd er i s sh ow n in Tab le

3 . I t app rox im a tes the rang e cove red

b y A W S C o C r A , a l t h o u g h t h e c a r b o n

s l i gh t l y exceeds tha t i n the A W S

spe c i f i ca t i o n , and the fo r m o f t he

a l l oy i s pow der ra th e r tha n the w i re

c o v e r e d by t h e A W S s p e c i f i c a t i o n .

S p e c i m e n s u t i li z e d i n t h e p r o g r a m

are sh ow n in F ig . 1 . The pa r t i cu la r

c o n f i g u r a t i o n s h o w n w a s s e l e c t e d b e

c a u s e it w a s r e p r e s e n t a t i v e o f a c o m

ponen t i n a

1

f a b r i c a t e d l i q u i d s o d i u m

va lve . A f te r i n i t i a l m ach in in g of t he

c y l i n d r i c a l t e s t s p e c i m e n s , t h e y w e r e

t h o r o u g h l y c l e a n e d i n a c e t o n e t o

remov e a l l t r ace s o f o i l and o the r fo r

e i g n m a t e r i a l , a n d t h e n t h e y w e r e

f i t t ed w i th a s ta in less s tee l band to

f a c i l i ta t e h a n d l i n g a t e le v a t e d t e m p e r

a t u r e s . T h e s p e c i m e n s w e r e t h e n

charg ed in to a sm a l l e lec t r i c f u rna ce

a n d p r e h e a t e d a t

800

F fo r t h re e

h o u r s . D u r i n g p r e h e a t i n g , t h e t e m p e r

a tu re of t he spe c ime ns wa s a l so

p e r i

od i ca l l y checked w i th a con tac t py

romete r to i nsu re tha t t hey were a t

t h e p r o p e r te m p e r a t u r e . A f t e r t h e

s o a k i n g p e r io d a t t h e p r e h e a t i n g t e m

p e r a t u r e , t h e c y l in d e r s w e r e t r a n s

f e r r e d t o t h e s u r f a c i n g e q u i p m e n t a n d

s u r f a c e d w i t h C o C r A p o w d e r s w i t h

the p lasma t rans fe r red a rc p rocess .

T h e e x p e r i m e n t a l s e t u p f o r t h e s u r

fac ing i s sh ow n in F ig . 2 . A t t h e end

o f the su r fac ing cyc le , t he spe c im ens

w e r e r e t u r n e d t o t h e h o t p r e h e a t i n g

oven and s tab i l i zed fo r one hour a t

800 F be fo re they we re pu t i n to an

i n s u l a t i n g c o m p o u n d f o r s l o w c o o l i n g

W E L D I N G R E S E A R C H

S U P P L E M E N T

551



' -^t$ir'

'I^W

&; ?

.. .

T

. •

J - J t ^ U ^ f

/ « • / , - >

i .

;

' / i J * ' . » . - ' - '

:

'

•

> ' ' - * .

' • • ' - r.

Sr | f

Jfe****

y s ^ ' V

v

<

' rV »%•• *

* ' V

v

? > '

•*

±

..

v

F/V7. 3

— Typical base metal microstructure

of test no. 3, one inch from the OD Fig. 7—Variation in ASTM grain size in test no. 3 (specimen no. B-44). 5% chromic acid

Chromic acid etched

(X100,

reduced 46%) etched

(X100,

reduced 54%)

Fig. 4 — Typical base metal microstructure

of test no. 4, one inch from the OD Oxalic Fig. 8 — Variation in grain size in test no. 4 (specimen no. B-45). Oxalic acid etched

(X100,

acid etched

(X100,

reduced 46%) reduced 54%)

•-•rT

VI

1

»

- * w

;

« *»

N?

&**•

•' * K

i

•'-

* * • "

5

Fig.

5

—

Typical

base

metal

microstructure

'

v

"*

*'

' * " " '"" ' -

of test no. 5, one inch from the OD Oxalic Fig. 9 — Variation in grain s ize in test no. 5 (specimen no. B-46). Oxalic acid etched

(X100,

acid etched(XI00, reduced 46%) reduced 54%)

Fig. 6 — Typical base metal microstructure . «. .* . .

-

'•' \ .' J .

•». • V is fe* '

.

of test no. 6, one inch from the OD Oxalic

Fig.

10 — Variation in grain size in test no. 6 (specimen no. B-47). Oxalic acid etched

acid etched (X100, reduced 46%) (X' 00. reduced 54%)

5 5 2 - s I D E C E M B E R

1 9 7 3



t o ro o m t e m p e r a t u r e . T h e t i m e i n t h e

i n s u l a t i n g c o m p o u n d w a s a p p r o x

ima te l y 20 h .

A f t e r t h e s p e c i m e n s h a d b e e n s u r

f a c e d a n d c o o l e d t o r o o m t e m p e r

a tu re , t he y we re tu rne d ove r and a

f i l le r l e s s g a s t u n g s t e n - a r c w e l d w a s

depos i ted on the face oppos i te the

s u r f a c e d f a c e . T h i s w e l d w a s m a d e

appro x ima te l y one i nch i n f ro m the

e d g e a n d w a s 360 deg in l eng th p lus

a 10 deg ove r lap .

U p o n c o m p l e t i o n o f t h e s u r f a c i n g

a n d w e l d i n g o p e r a t i o n s , t h e te s t s p e c

i m e n s w e r e d y e p e n e t r a n t i n s p e c t

e d a n d t h e n f i n i s h m a c h i n e d a c c o r d

ing to F ig . 1 . A f t e r be ing f i n i sh ma

ch ine d , the CoCrA su r fac ing (ha rdsu r

f a c i n g ) w a s a g a i n d y e p e n e t r a n t i n

spec ted fo r c racks and po ro s i t y .

T h e m e t a l l u rg i c a l e x a m i n a t i o n ,

w h i c h i n c l u d e d m e t a l l o g r a p h i c s c a n s

o f t h e m i c r o s t r u c t u r e , m i c r o a n d

m a c r o h a r d n e s s t r a n s v e r s e s , a n d

c h e m i c a l a n a l y s e s w a s p e r f o r m e d o n

CoCrA su r face d (ha rdsu r fa ced) r i ngs

a n d g a s t u n g s t e n - a r c w e l d e d d i s k s

t h a t h a d b e e n r e m o v e d f r o m t h e t e s t

cy l i nde rs .

R e s u l t s a n d D i s c u s s i o n

Visual Examinat ion

V i s u a l e x a m i n a t i o n o f t h e a s -

w e l d e d h a r d s u r f a c i n g a n d G T A W d e

pos i t s d id no t revea l any c racks o r

po ros i t y excep t i n the te r m ina t i o n

area of the GTA

w e l d .

T h i s c o n d i t i o n

w a s c a u s e d b y t h e a b r u p t s h u t - d o w n

c h a r a c t e r i s t i c s o f t h e G T A W e q u i p

ment and the lack of f i l le r meta l to f i l l

i n t he c ra te r . I n subseq uen t e xam

ina t i ons , t he a rea i n w h i ch th e GTA

w e l d s w e r e t e r m i n a t e d w a s d i s c a r d

ed because th i s p rob lem had no bear

ing on the subject o f th is s tudy.

Penetrant Examinat ion

D y e p e n e t r a n t e x a m i n a t i o n o f t h e

G T A w e l d s s h o w e d n o i n d i c a t i o n o f

c rack ing o r po ros i t y excep t i n the te r

m ina l c ra te r .

E x a m i n a t i o n o f t h e a s - d e p o s i t e d

h a r d s u r f a c e s w i t h d y e p e n e t r a n t r e

vea led som e po ros i t y i n the te r m i na l

a reas . A t t he 8 00 F p reh ea t used fo r

t h e s e t e s t s , t h e e l e c t r ic a l s h u t - d o w n

c h a r a c t e r i s t i c s o f t h e e q u i p m e n t b e

c a m e e x t r e m e l y c r i t i c a l a n d t h e t e r

m ina l a rea po ros i t y cou ld no t be e l im

ina ted i n the l im i ted num ber o f t es ts

c o n d u c t e d i n t h i s i n v e s t i g a t i o n .

A g a i n ,

t h i s p rob le m i s no t pe r t i n en t t o

the main subject o f th is s tudy.

D y e p e n e t r a n t e x a m i n a t i o n o f t h e

f i n i s h m a c h i n e d o v e r l a y s d i d n o t

revea l any c rack ing and the on l y

p o r o s i t y d e t e c t e d w a s i n t h e t e r m i n a l

area on test no. 6.

m ic ros t ruc tu res a re o f t he tes t cy l i n

de rs taken one i nch f rom the OD and

are in the approx ima te l oca t i on o f t h e

G T A w e l d a n d ID o f t he f i n i shed

over lay . The m ic ros t ruc tu re i n F ig . 3 ,

tes t no . 3 , shows a p ronounced

v a r i

at ion in gra in s ize, Ni

3

Cb need les , T i

ca rbon i t r i des (CN) pa r t i c l es , and sev

e r a l o t h e r p h a s e s w h i c h w e r e n o t

i den t i f i ed . F igu re 4 dep ic t s the m ic ro -

s t ruc tu re o f t es t no . 4 . Th i s m ic ro -

s t ruc ture is re la t ive ly c lea n and in

cont rast to test no. 3 , the gra in s ize is

re la t i ve l y un i fo rm . The s t r i nge rs a re

Ti (CN) and p roba bly o th er typ es of

c a r b i d e s w h i c h w e r e n o t i d e n t i f i e d .

The m ic ros t ruc tu re o f t es t no . 5 , F ig .

5 , is s im i lar to that o f test no. 4 . Th e

d i f f e renc e i n appeara nce is due to the

d i f f e ren t response o f t he a l l oy to the

e tcha n t a f te r ag ing . The m ic ros t ru c

ture of test no . 6 is sh ow n in F ig . 6 .

T h i s m a t e r i a l a l s o h a s a p r o n o u n c e d

var ia t i o n i n g ra in s i ze i n th i s a rea s i m

i la r to that found in test no. 3 , but

w i t h o u t t h e n u m e r o u s o t h e r p h a s e s

p r e s e n t . T h e s t r i n g e r s c o n t a i n e d

som e T i (CN) , i den t i f i ed by the i r

o range co lo r and square sha pe , a nd

a n o t h e r u n i d e n t i f i e d p h a s e w h i c h i s

p robab ly a ca rb ide .

To de te rm ine the va r ia t i on i n g ra in

s i ze th rou gho u t the sec t i on , t he 1 /2

i n . t h i c k d i s k s c o n t a i n i n g t h e G T A W

depos i t were cu t i n ha l f t o g i ve two

sem ic i r cu la r sec t i ons . These sec t i on s

\ ..

•

• • •

- • • • ;

• , • • • • .

' . ' • ' • ' .

••

•

J ' ; J ) K * ? . • ' • • ' • • .

:

Fig. 11 — Fillerless GTA weld metal-base

metal interface in test no. 3. Chromic acid

etched (X100, reduced 46%)

T

w e r e m e t a l l o g r a p h i c a l l y e x a m i n e d a t

seven pos i t i ons on a d iam ete r . F igu re

7 i s a c o m p o s i t e p h o t o m i c r o g r a p h

m a d e u p o f p h o t o m i c r o g r a p h s t a k e n

a t equa l l y spaced in te rva l s on a d iam

eter o f test no. 3 . Th is f igure shows a

la rge g ra in s i ze (ASTM No . 2 - 1 / 2 ) on

the OD and a cons ide rab ly f i ne r g ra in

s ize (AS TM No. 6) in the cente r . A t

i n te rmed ia te l oca t i ons the re i s a

dup lex s t ruc tu re o f l a rge and sma l l

g ra ins . The cause o f t he va r ia t i on i n

g ra in s i ze i s unknown because the

de ta i l s of t he fo rg ing p rocedu re we re

no t ava i l ab le ; however , e i t he r f i n i sh

ing a t t oo l ow a tempera tu re o r a t t oo

sma l l a f i na l redu c t i on can cause a b

n o r m a l g r a i n g r o w t h i n n i c k e l - b a s e

supe ra l loys (Ref. 10) . Th is s t ruc ture

does appear to have resu l ted f rom ab

no rm a l g ra in g ro wt h . The g ra in s i ze

scan of test no. 4 is sh ow n in F ig . 8 .

Th is ma te r ia l has a un i fo rm g ra in s i ze

o f AS TM N o . 2 -1 /2 , bu t because i t

was ho t ro l l ed and no t f o rged , i t

wou ld no t be expec ted to show the

mixed g ra in s i zes foun d in the fo rg ed

samp les . Tes t no .

5,

shown in F ig . 9 ,

is the sam e ma ter ia l as test no. 4

excep t tha t t es t no . 5 was age-ha rd

e n e d . T h i s t r e a t m e n t o b v i o u s l y h a d

l i t t le e f fect on the gra in s ize which is

essen t ia l l y t he same as be fo re ag ing .

F igu re 10 sh ow s the g r a in s i ze va r

ia t ion in test no. 6 . Th is m ate r ia l w as

fo rged and exh ib i t s a l a rge g ra in s i ze

Fig. 13 — Filler/ess GTA weld metal-base

metal interface in test no. 5. Oxalic acid

etched (X100,

reduced

46%)

m

M e t a l l o g r a p h i c E x a mi n a t i o n

Typ ica l base meta l m ic ro s t ruc tu res

a re sh ow n in F igs . 3 th rou gh 6 . Thes e

Fig. 12

—

Fillerless GTA weld metal-base Fig. 14

—

Fillerless GTA weld metal-base

metal interface in test no. 4. Oxalic acid metal interface in test no. 6. Oxalic acid

etched(XIOO, reduced46%) etched(X100, reduced46%)

W E L D I N G R E S E A R C H

S U P P L E M E N T

5 5 3 - s



(ASTM N o . 2 - 1 / 2 ) on the OD and a

f ine gra in s ize (ASTM No. 6) a t the

center s imi lar to that found in test no.

3 . A t i n te rm ed ia te l oca t i ons a dup lex

g ra in s t ruc tu re i s p resen t . The s im i l a r

i ty o f the s t ructures in tests 3 and 6 is

unders tandab le because bo th o f

these mate r ia l s were fo rged by the

same shop and were p robab ly ex

posed to s im i l a r f o rg ing p rocedures .

The m ic ros t ruc tu res a t t he

w e l d -

base meta l i n te r face o f t he f i l l e r l ess

GTAW depos i t s a re shown in F igs . 1 1

t h r o u g h 1 4 . I t wa s hoped tha t t he b e -

• T * 5 « < * *

J

B

Fig. 15 — Heat-affected zone of plasma

hardsurface on test no. 3 (X300, reduced

46%);

(A) unetched, (B) oxalic acid etched

A

«

f

*?*( -*. •

« " •

•^sl y

" $j?

.;,, iwS*f .

N ^

*o

*

1 W

A

J

ejT\

B


hardsurface on test no. 4

(X150,

reduced

46%); (A) unetched, (B) oxalic acid etched

hav io r o f t he hea t -a f fec ted zones o f

the GTA we lds cou ld be co r re la te d

w i th the behav io r o f t he hea t -a f fec ted

zones o f ha rd fac ing depos i t s ; how

ever , th is d id not prove to be poss ib le

because as can be seen in the f igures,

none o f t he GTAW hea t -a f fec ted

zones con ta ine d c racks wh ere as , as

w i l l be sh ow n shor t l y , mos t o f t he

hard fac ing hea t -a f fec ted zones d id

con ta in c racks .

M e t a l l o g r a p h i c e x a m i n a t i o n s o f t h e

hardsu r fac es we re pe r fo rm ed by

quar te r i ng the 1 /2 i n . t h i ck r i ng s

w h i c h h a d b e e n r e m o v e d f r o m t h e 3

i n .

l ong cy l i nde rs and moun t ing fou r

t ransve rs e sec t i ons , one f rom each

quar te r . Each o f t hese sec t i ons wa s

then tho rough ly examined in bo th the

e tched and une tched co nd i t i on fo r

cracks, lack of bond and poros i ty .

F i g

ures 15 th ro ugh 18 sho w typ i ca l

areas in test nos. 3, 4, 5 and 6,

respec t i ve l y , i n bo th the e tched and

Table 3 — Comp osi t ion of C obal t Base

Sur fac ing powder

Element

C

Si

Cr

Ni

W

Fe

Co

Percentage

1.71

1.39

28.52

2.50

3.49

0.23

Rem.

^_

A

<,

-

•

y+ *

•

*

-

*

•

- :

•


hardsurface on test no. 5 (X75, reduced

46%}; (A) unetched, (B) oxalic acid etched

u n e t c h e d c o n d i t i o n . T h e a r e a s s h o w n

represen t the wors t de fec ts found

excep t fo r t es t no . 6 wh ich d id no t

exh ib i t any c racks . As the e tched pho

tomic rog ra phs show , a l l t hese c racks

w e r e a s s o c i a t e d w i t h g r a i n b o u n

da r ies i n the Incone l 718 base me ta l .

N o n e o f t h e s a m p l e s e x a m i n e d

c o n

t a ined c racks wh ich pene t ra ted i n to

the ove r lay , no r were the re any

c racks con f i ned to the ove r lay .

The d i f f e rence i n c rack ing be hav io r

o f t he two fo rged samp les , t es t nos . 3

and 6 , bo th o f w h i ch have du p lex

s t ruc tu res appeared to be re la ted to

the obv ious d i f f e renc es i n the am oun t

and types o f seconda ry phases p res

ent . I t may a lso be re la ted to the ra t io

of smal l to large gra in present in the

a rea i n ques t i on ; howe ver , t h i s w as

imposs ib le to de te rm in e because the

g ra ins were d i f f i cu l t t o c lea r l y reso l ve

in sam ple no . 3 . The re d iss o lv in g o f

the var io us prec ip i ta tes in test no. 3

could a lso have had an ef fect on i ts

c rack ing behav io r , bu t t h i s wou ld

p robab ly be depe nden t to som e

degree on the gra in s ize.

Mult ipass Tests

Because o f t he unexpec ted poor be

hav ior o f the hot ro l led Incon el 7 18

( test nos. 4 and 5) , In ternat ional

N icke l Company was con tac ted fo r

de ta i l s o f t es ts i n wh ich they c la imed

to have had no base meta l c rack ing

p rob lems du r ing manua l cove red

e lec t rode su r fac ing o f I ncone l 71 8

w i th ECoCrA f i l l e r me ta l s . As a re

s u lt of t h e c o m m u n i c a t i o n s , t w o a d

d i t i ona l t es ts , nos . 7 and 8 , were un

der ta ken to eva luate the ef fect o f hea t

i npu t on the c rack ing behav io r o f

the Incone l 718 base meta l .

The mate r ia l used fo r t hese tes ts

was l e f tove r s tock f rom tes t nos . 5

a n d 6 w h i c h w a s a p p r o x i m a t e l y 1 -1 / 2

in .

t h i ck by 6 i n . d ia m. Bo th p ieces

w e r e i n t h e a g e h a r d e n e d c o n d i t i o n .

T h e p l a s m a p a r a m e t e r s , w h i c h w e r e

se lec ted to g i ve the sam e hea t i npu t

as tha t used by In te rna t i ona l N icke l

fo r t he i r cove red e lec t rode w ork , a re

g iven in Table 2. To fur the r red uce the

to ta l hea t i npu t , t he p rehea t was a l so

e l i m i n a t e d e v e n t h o u g h I n t e r n a t i o n a l

N icke l had used bo th 80 0 F and

1200 F p rehe a ts . B ecause o f t he

reduc t i on i n hea t i npu t f rom approx

i m a t el y 7 0 , 0 0 0 J / i n . to 3 0 , 0 0 0 J / i n . ,

t he ove r la y ing techn iq ue a l so had to

be chan ged f rom a s ing le we av e pass

per layer to thr ee s t r in ge r bead s per

laye r to i nsu re p roper fus ion .

V isua l examina t i on o f t he ove r lays

d isc losed no c rack ing , and the te s ts

w e r e s u b s e q u e n t l y f u r t h e r p r o c e s s e d

f o r m e t a l l o g r a p h i c e x a m i n a t i o n .

F ig

ures 1 9 and 20 sho w tha t t he reduc

t i on i n hea t i npu t d id no t chan ge the

c rack ing behav io r o f t hese two hea ts

o f m a t e r i a l ; t h e c o a r s e g r a i n e d m a t e

r i a l in tes t no . 7 c racke d in the sam e

ma nne r as tes t no . 5 and the f i n e r

5 5 4 - s | D E C E M B E R 1 9 7 3



gra in ed mate r ia l i n tes t no . 8 d id no t

c r a c k, w h i c h is in a g r e e m e n t w i t h t h e

resul ts o f test no. 6 (see F ig .

18).

Hardness Examination

H a r d n e s s s u r v e y s w e r e t a k e n f r o m

the cen te r to the edge of t he 6 i n .

rounds to see i f th is d isc losed any

r e l a t i o n s h i p w i t h m i c r o f i s s u r i n g t e n

dency . These su rveys showed tha t f o r

t h e f o r g e d m a t e r i a l , t h e m a x i m u m

h a r d n e s s s p r e a d w a s 3 - 1 / 2 p o i n t s

R o c k w e l l " B " (a n n e a l e d c o n d i t i o n ) .

A l l t h e a g e h a r d e n e d mater ia^fel l in

t h e h a r d n e s s ra n g e R o c k w e l l " C "

39 .5 and 43 .0 (ave rage o f t h ree r e a d

i ngs ) and the ha rd ness ra nge fo r t h e

annea led ma te r ia l ( t es t no . 4 ) was

R o c k w e l l " B " 8 5 . 5 t o 8 9 . 0 . T h e s e v a r

i a t i o n s i n h a r d n e s s w e r e c o n s i d e r e d

to be w i th in reasonab le p rodu c t i on

l im i t s , w i th in spec i f i ca t i on , and no t

respons ib le fo r t he va r ia t i on i n c rack

ing behavior .

M i c r o h a r d n e s s s u r v e y s a c r o s s t h e

hea t -a f fec ted zones o f t he th ree age

hardened mate r ia l s , t es t nos . 3 , 5 ,

and 6, are g iven in F igs. 21 thr ou gh

2 3 . These resu l ts show a redu c t i on i n

ha rdness be low the ove r lay to a l ow

o f 2 0 0 - 2 4 0 K H N ( 9 0 - 9 5 R

B

) an d a

zone o f reduced ha rd nesse s ex

tend ing f rom 0 .425 to 0 .430 i n .

be low the ove r lay .

Chemica l Composi t ion

T a b l e 1 g i v e s t h e c h e m i c a l c o m

posi t ions of the three heats o f Inconel

718 used i n th i s i nv es t i ga t i on . A l l t h e

ana lyses , bo th the repor ted and

c h e c k s , a r e w i t h i n A M S 5 6 6 3 - B f o r

Incone l 71 8 and do no t revea l any

obv ious reasons fo r t he d i f f e renc es i n

c rack ing behav io r f oun d in th i s w ork .

C h e m i c a l c o m p o s i t i o n v a r i a t i o n s ,

espec ia l l y t he manganese and s i l i con

con ten ts , have rece ived cons ide rab le

a t ten t i on as a poss ib le cause o f t he

m i c r o f i s s u r i n g p r o b l e m s . O n e g r o u p

of invest igators (Refs . 1 ,4) cons ider

manganese con ten ts i n excess o f

Fig.

18

— Heat-affected zone of plasma Fig.

19

— Heat-affected zone of multipass

hardsurface on test no. 6 (X100, reduced plasma overlay on test no. 7 (X100, re-

46%,);

(A) unetched, (B) oxalic acid etched duced

46%>);

(A) unetched, (B) oxalic acid

etched

B

Fig. 20 — Heat-affected zone of multipass

overlay on test no. 8 (X100, reduced

46%>);

(A) unetched, (B) oxalic acid etched

4 2 0

4 0 0

380

360

3 4 0

320

3 0 0

280

2 6 0

2 2 0

Overlay

\

\

\

\

\

\

.

Base

M e ta l

1

1

1

'

_ |

t

Y

-

K

**^~*

1

•

X

•

J

/

/

/

/

420

400

3S0

360

3,0

320

J» 1

280

260

240

220

200

Overla

1

\

\

\

\

\

y

\

»

1

•

\ •

•

Bas« Metal

• i

*•

•

J

/

/

/

/

/

/

4

/•

•

— * 7

•

2 3 4

Inches fro m Surface x 10

Fig. 21 — Hardness variation of the base-metal under the

hardsur

face on test no. 3

Inches from Surface x

10


hardsurface on test no. 5

W E L D I N G R E S E A R C H S U P P L E M E N T 5 5 5 -s



Overlay

O 340

-«

-H

> * -

1

-J-

^

t L

\

J

jn 2_

V

%/'

11 • /

L /

\ *

./̂

j v-^

Inches from Surface x 10


hardsur

face on test no. 6

•.

B

Fig. 24 — Relationship between position

in bar from test no. 3 (grain size) and

fissuring on deposit laid down along a

bar diameter. Oxalic acid etched (X200,

reduced

50%,);

(A)

center,

(B) outside

0 .20% and s i l i con con te n ts i n excess

o f 0 .25% necessary to avo id m ic ro f i s

sur ing; o ther invest igators (Ref . 2)

cons ide r man gane se and s i l i con

c o n

t e n t s b e l o w 0.15 necessary to avo id

c rack ing ; t he th i rd schoo l o f t hough t

(Refs.

3 ,9) cons iders the ef fects o f

c o m p o s i t i o n a l v a r ia t i o n s , w i t h i n s p e c

i f icat ion, to be un impor tant , or a t

l eas t ove rs had owe d by mo re imp or

tan t f ac to rs . The p resen t da ta suppor t

the th i rd pos i t i on because o f t he l ack

o f c o r r e l a t i o n b e t w e e n m a n g a n e s e

and s i l i con con ten ts and p ropen s i t y

fo r m ic ro f i ss u r ing . Tes t nos . 4 , 5, and

7 had re la t i ve l y h igh ma nga nes e a nd

si l icon, and test no. 3 had re la t ive ly

low manganese and s i l i con , bu t bo th

hea ts exh ib i ted s im i l a r c rack ing .

Grain Size

The resu l t s d i scussed up to now

po in t on l y to grain s ize as be ing s ign i f

i can t re la t i ve to m ic ro f i ssu r ing

t e n

dency . Coarse g ra ined mate r ia l was

more p rone to f i ssu r ing than f i ne

g ra ined mate r ia l . Bear i n m ind tha t i n

a l l t he exper im en ts d esc r ibed up to

th i s po in t , t he ove r lays were depos

i ted around the outs ide of the bars , so

tha t i n no s ing le ove r lay was the re a

var ia t ion in gra in s ize.

T h e a p p a r e n t r e l a t i o n s h i p b e t w e e n

gra in s i ze and f i ssu r ing tendency

s u g

ges ted the obv ious c r i t i ca l e xper i

men t o f l ay ing dow n a depos i t a long

the d iamete r o f t he fo rged ba rs ( tes t

nos. 3 and

6) ;

w h i c h s h o w e d c o a r s e

gra in s ize near the sur face and f ine

gra in s ize in the ce nter . I f gra in s ize

w e r e a s i g n i f i c a n t d e t e r m i n a n t o f

f i s

s u r i n g o c c u r r e n c e , t h e n o n e w o u l d

expect to see f issures near the

sur face but not a t the center .

F igu re 24 shows the expec ted

resul t on the bar f rom test no. 3 . F is

su r ing has i ndeed occu r red i n the

la rge g ra in ed m ate r ia l c l ose to the

outer edge, but not in the f iner

g ra ined mate r ia l nea r the cen te r .

M e t a l l o g r a p h i c e x a m i n a t i o n o f t h e

bar f rom tes t no . 6 d id not d isc lose

any f i ssu r ing anywhere . Th i s i s i den t i

c a l t o th e p e r f o r m a n c e w i t n e s s e d

be fo re i n the c i r cu la r depos i t . Th e

on ly d i f f e renc e no ted be tw een the

ma ter ia l o f test no. 3 (heat no . 85 46 7)

and tes t no . 6 (hea t no . 903 54) wa s

the need le - l i ke p rec ip i t a te i n the

fo rmer .

In any even t , i t wa s obse rved in t he

p resen t s tudy tha t c rack ing may o r

may not occur in coarsegrained m a t e

r ia l ,

but w h e n i t does occur i t has

a lways been in coa rse g ra ined ma te

r ia l .

Obv ious l y the amoun t o f re

s t ra in t , deg ree o f second phase me l t

i ng , a n d p r i o r t h e r m o m e c h a n i c a l h i s

tory are a l l coming in to p lay, but how

they a re re la ted and to wha t deg ree

has no t been reso lved by th i s o r any

p r io r pub l i shed work .

C o n c l u s i o n s

Under ce r ta in cond i t i ons , I ncone l

718 i s sens i t i ve to m ic ro f i ssu r ing

dur ing ha rd fac ing w i th CoCrA su r

fac ing ma te r ia l s .

The fac to r wh ich appeared to have

the g rea tes t e f fec t on c rack ing be

hav io r under the p rocedures es tab

l ished for th is s tudy was gra in s ize.

C o a r s e g r a i n e d m a t e r i a l w a s m o r e

prone to c rack ing than f i ne g ra ined

mate r ia l .

N o r e l a t io n s h i p b e t w e e n c o m p o s i

t i on o f t he base meta l and f i ssu r ing

tendency wa s apparen t , no r be twe en

hea t i npu t du r ing ha rdsu r fac ing and

f i ssu r ing tendency .

References

1. Morr iso n, T. M., et al , "The Inf luence

of Minor Elements on Al loy 718 Weld

M i c r o f i s s u r i n g , " W e l d i n g R e s e a rc h

Council Symposium, "Effect of Minor

Elements on the Weldabi l i ty of High-

Nickel Alloys ," p. 47 to 67, Oct.,

1

967.

2. Lucas, M. J. Jr., et al, "The Weld

Heat Affected Zone in Nickel Base Alloy

7 1 8 , " Welding Journal, Res. Suppl., p. 46s

to

54s,

Feb.,

1970.

3. Valdex, P. J., et al, "Effect of Com

posit ion and Thermal Treatments on the

Weldabi l i ty of Nickel Base 718 Al loy,"

Welding Research Counci l Symposium,

"Effects of Minor Elements on the Weld

ability of High Nickel Alloys," p. 93 to

120,

Oct., 1967.

4.

Prager, M., et al, Welding of Precip

itation Hardening Nickel Base Alloys

Welding Research Council Bulletin No.

128, Feb., 1968.

5. Hoppin, G. S., et al, "Fusion Welding

of Age Hardenable Superalloys" SAE

Paper 6901 02, Jan., 196 9.

6. Gordine, J., "S ome Problems in

Welding Inconel 718," Welding Journal,

Res. Suppl., p. 480s to 484s , Nov.,

1971.

7. Gordine, J., "W elding of Inconel

7 1 8 , " Welding Journal, Res. Sup pl., p.

531s to 537 s, Nov.,

1970.

8. Thomp son, E. G., "H ot Cracking

Studies of Alloy 718 Weld Heat Affected

Zones," Welding Journal, Res. Sup pl., p.

70-S to

79-S,

Feb., 1969.

9. Bologna, D. J . , "M et a l l ur g ic a l

Factors Influencing the Microfissuring of

Alloy 718 W e ldmen ts ," Metals Engineer

ing Quarterly, p. 37 to 43, Nov., 1 969.

10. Sabroff, A. M., et

al .

Forging Mate

rials and Practices, Reinhold Book Co.,

New York,

1968.

5 5 6 - s I D E C E M B E R 1 9 7 3



V

WRC

Bullet in

No. 107

A u g . 1965

(Repr in ted Apr i l 1972)

Local Stresses in Spherical and Cylindrical Shells

Due to External Loadings

by K. R. W ich m an , A . G . Hoppe r and J . L . M e r sho n

Several years ago, the Pressure Vessel Research Commit tee sponsored an analyt ical and experimen

ta l research program aimed at providing methods of determining the s t resses in pressure vessel nozzle

connect ions subjected to various forms of external loading. The analyt ical port ion of this work was ac

complished by Prof. P. P. Bijlaard of Cornell University. Development of the theoretical solutions

involved a number of s impl i fying assumptions , including the use of shal low shel l theory for spherical

vessels and f lexible loading surfaces for cyl indrical vessels . These c i rcumstances l imi ted the potent ia l

usefulness of the results to d /D ratios of perhaps 0.33 in the case of spherical shells and 0.25 in the

case of cyl indrical shel ls . S ince no data w ere avai lable for the larger diameter ra t ios , Prof. Bijlaard later

supplied data, at the urging of the design engineers, for the values of B = 0.375 an d 0.50 dj/D, rat ios

approaching 0.60) for cylindrical shells. In so doing,

Prof.

Bi j laard included a specif ic warning

concerning th e poss ible l imi ta t ions of these d ata .

Fol lowing complet ion of the theoret ical work, experimental work was undertaken in an effort to

verify the theory. Whereas this work seemingly provided reasonable verification of the theory, i t was

limited to relatively small

d /D

l

ratios—0.10

in the case of spherical shells and 0.126 in the case of

cyl indrical shel ls . S ince vi r tual ly no data , e i ther analyt ical or experimental , were avai lable covering the

larger diameter ra t ios , the Bureau of Ships sponsored a l imi ted inves t igat ion of this problem in spheres ,

a imed at a part icular des ign problem, and the Pressure Vessel Research Commit tee undertook a

somewhat s imilar inves t igat ion in cyl inders . Resul ts of this work emphas ized the l imi ta t ions in

Bi j laard 's da ta on cyl indrical shel ls , part icular ly as i t appl ies to thin shel ls over the extended ran ge.

Incident to the use of Bi j laard 's data for des ign purposes , i t had become apparent that des ign engi

neers somet imes h ave di ff icul ty in interpret in g or properly app lying this work. As a resul t of such experi

ence, PVRC felt i t desirable tha t all of Bijla ard 's work be sum ma rized in con ven ient, cookb ook form to

facili tate i ts use by design engineers. However, before this document could be issued, the above men

t ioned l imi ta t ions became apparent present ing an unfortunate di lemma, viz . , the data indicate that the

da ta a re pa r t i a l ly inadequa te , bu t

the

exact nature and magni tude of the error i s not known, nor is any

bet ter analyt ical t reatm ent of the problem a vai lable (for cyl inders) .

Under these c i rcumstances , i t was decided that the bes t course was to proceed wi th issuing the

cookbook, extend ing Bi j laard 's curves as bes t as poss ible on the bas is of avai la ble tes t da ta . This deci

s ion was based on the premise that a l l of the proposed changes would be toward the conservat ive (or

safe ) s ide and that des ign engineers would cont inue to use Bi j laard 's extended range data unless some

alternative were offered. This paper was therefore presented in the hope that i t would facili tate the use

of Bijlaard's work by design engineers.

Since the paper was original ly issued, a number of minor errors have been discovered and incor

porated in revised print ings as suppl ies were exhaus ted. The thi rd revised print ing was issued in Apri l

1972.

T he

price

ot Bulletin No. 107 is $3.00. Copies m ay be ordered from the W elding Research Council

Ea st 47th St., New Y ork, N. Y. 10017.

345

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