Use of Plasma Arc Welding Process to Combat Hydrogen Metallic Disbonding of Austenitic Stainless Steel Claddings
Cracking resistance increased when the plasma arc process with a hot wire filler metal was used to clad Cr-Mo base metal
BY O. A. ALEXANDROV, O. I. STEKLOV AND A. V. ALEXEEV
ABSTRACT. A separation type crack, small width and hardness of the transi hydrogen is cooled down. Figure 1 metallic disbonding, occurred between tion zone, which included the marten shows the distribution of hydrogen in austenitic stainless steel weld metal sitic layer as-welded and the carbide the wall of a vessel during operation cladding and 2V
506-s I NOVEMBER 1993 ^2i6 Materials and Experimental Procedures
Clad Sample Production
The PAW process using a hot wire filler metal was performed with experi mental equipment, which was designed in the research laboratory at the State Academy of Oil and Gas in Moscow. This equipment is shown in Fig. 2. A schematic is shown in Fig. 3. The base metal was identical for all test specimens. It is 2'/.iCr-1Mo steel, Fig. 1 — The distribu which is usually chosen for high-tem tion of hydrogen in a perature, high-pressure hydrogen envi pressure vessel wall ronments to avoid hydrogen attack prob during processing and lems (Refs. 1-3). Stainless weld metal after cooling (15 MPa, cladding either of Cr25-Ni1 3 or Cr1 9- 400°C, 20"C/h). 1) Dur Ni9 was used for the first layer and ei ing processing, 2) after ther Cr20-Ni9-Nb-V or Cr1 9-Nil O-Nb 7.5 of cooling, 3) after was used for a second layer. The chem 15 of cooling. ical composition of the second layer does not influence the disbonding (Refs. 1, 2). Welding processes were of two Table 1 — Welding Conditions of Cladding by SAW and PAW Processes types: SAW with a strip electrode and PAW with a hot wire electrode. The Frequency Protective welding conditions of these processes of and are given in Table 1. Chemical compo Size Travelling Plasmatron Oscillation Plasma- Heat (a) sitions of the base metal and consum Welding Electrode, Current, Voltage, Speed, Oscillation, Amplitude, formation lnput, ables are given in Table 2. Chemical Process V m/h Hz m Cas kj/mm analyses of the first layer of deposited SAW 1st 65 X 0.7 800-850 32-34 8-10 10.2-11.8 claddings are given in Table 3. layer 9.7-11.2 2nd 65 X 0.7 800-850 32-34 8-10 Metallic Disbonding Test layer PAW 1st
WELDING RESEARCH SUPPLEMENT I 507-s Power source of Additional Power sourse of main plasmatron power sourrse additional plasmatron
Feed mechanism )T of wire electrode Main plasma arc Additional plasma arc
Fig. 2 — Equipment for plasma arc welding process. Fig.3- Schematic of plasma arc welding process with hot wire elec- trode.
examination. The crack percentage test conditions. The PAW specimens was calculated on the disbonded area with Cr25-Ni13 are more resistant Autoclave Gas Charging in reference to the total PAW or SAW to metallic disbonding. At some test clad surface area. conditions, cracks were not found. Figure 8 shows the results of au All specimens were investigated for The PAW clad metal of the type toclave gas charging. The correla metallic disbonding after PWHT at Cr19-Ni9 had the best resistance to tion between autoclave gas charg 650°C for 1 2 h (furnace cooling). disbonding. Less than 5% cracks ing and cathodic charging is good. were found at all charging condi It can be seen that SAW clad weld Results tions. metal generally cracks more exten Figure 7 shows the effect of sively than PAW clad metal. The Electrolytic Hydrogen Charging charging time on the disbonding at SAW specimens had 18 to 20% the current density of 0.2 mA/m2. It cracks, whereas the PAW specimens Table 4 shows the effects of ca is seen that increasing charging time type Cr25-Ni1 3 had only 8% cracks thodic charging on the disbonding promotes the disbonding. However, and type Cr19Ni9 had 2 to 4% for different values of current den the total crack length is longest with cracks. The clad metal type Cr25- sity and charging times. It is seen the SAW specimens at all charging Ni 1 3 resisted disbonding 3 to 4 that PAW clad weld metal is more time variations. The disbonding for times better with the PAW process resistant to the disbonding than PAW specimens with type Cr19-Ni9 compared to the SAW process. The SAW clad metal at all charging con after 30 h was less than 5%, the PAW clad metal type Cr19-Ni9, ditions (current density 0.05-0.2 PAW specimens of type Cr25-Ni1 3 which has a Cr and Ni content ap mA/m2, charging time 1 2-30 h). The had 1 5 to 20% cracks and the SAW proximately matching the SAW clad SAW specimens had cracks with all specimens had 60 to 70% cracks. metal Cr25-Ni13, is more resistant
overlaid metal Side view 7 mm
weld bond base metal 1 mm
10 mm 2 mm
Bottom view 10 mm
Electrolite
Fig. 4 — Shape of the specimen for cathodic charging test. Fig. 5 — Setting of the specimen in the electrolyte.
508-s ! NOVEMBER 1993 manual cladded weld metal
second cladded layer " 7 mm,: Table 4 — Effect of Charging Conditions on first cladded layer Metallic Disbonding
Current Testing Time (h) mA/m2 12 18 24 30 0.2 on * •a* •a* •3 * 0.1 o • •n * •a • ca* 0.05 • • •D* •a* ca •
OD* — no disbonding Fig. 6 — Shape of the specimen for autoclave gas charging test. QLT* — slight disbo.iding (<5% cracks) • ••-serious disbonding (>5% cracks) * - SAW process (Cr25-Ni 13) to metallic disbonding. charging). As can be seen, the transgranular O- PAW process (Cr25-Ni 13) • -PAW process (Cr19-Ni'l) fracture surface is generally dominant on both Characteristics of Metallic Disbonding these specimens. There are in some places an intergranular brittle fracture surface. The PAW Table 5 — Dimension of Austenite Grains, Typical metallic disbonding charac specimen has more of these places than the Carbide Layer and Transition Zone teristics are shown in Fig. 9 for cathodic SAW specimen. The content of Cr and Ni on and autoclave gas charging. It is note the fracture surface is -12% Cr and -5% Ni Width lam) worthy that cracks have a tendency to with the PAW process and ~11 % Cr and -6% Type of Grain(a) Carbide Transition (b) occur at the center of a specimen and Ni with the SAW process. The distribution of Electrode (cm) Layer Zone are located in the transition zone be these alloying elements (Fig. 11) and data of Cr25Ni13- 100-500 20-40 80-100 tween the stainless steel weld metal Table 5 show that these cracks occurred in strip (SAW) 200-250 cladding and the base metal. According the transition zone. In the case of the PAW Cr25Ni13- 10-20 20-30 to many investigations (Refs. 5, 8, 9), the process, the crack is located inside the car 70-750 wire (PAW) metallic disbonding is a result of two bide layer (-15 pm from the fusion line) and 150-200 15— 25 25—35 types of cracks: 1) cracks occurring in in the case of the SAW process, it is located Cr19Ni9- 50-400 wire (PAW) the carbide layer at the interface; and 2) outside the carbide layer (-55-60 pm from 120-160 cracks occurring along coarse austenite the fusion line). The transgranular type of (a) Numerator - min and max dimention of grains near the grain boundaries near the weld inter cracking is, presumably, connected with the weld bond in the overlaid melal. face. In the present study (Fig.9), the peculiarities of cathodic charging. Denominator - mean value. (b) Mean value. cracks microscopically were located in The results of cracking tests show that ca bonding than by using autoclave gas charg the carbide layer at the interface, as well thodic charging pretty well reproduces char ing. as along the austenite grain boundaries acteristics of metallic disbonding obtained within the clad metal adjacent to the from autoclave gas phase charging, with more base metal. There was a combination of Discussion pronounced cracking along austenite grain these two types of cracks, and a trans boundaries inside the clad metal close to base granular type of crack was also found in Grain Morphology metal in one case and the development of the investigation. transgranular type of cracking in another case. Grains in the y phase close to the in Figure 10 shows examples of the fracture It can be seen that by using cathodic charg terface, where the disbonding occurs, surface for PAW and SAW samples (cathodic ing it is possible to get even more severe dis- were found to be planar and coarse in
Disbonding, % 20
i 1,
Cr25Ni13 SAW 16
^r A \ 12,
A1 /j ^^^^-^CrtSNMS PAW < 8 1
I I —•• . I| flCM9Ni9 PAW
4 Testing time, hours Fig. 7 — Effect of charging time on the metallic disbonding (current density i = 0.2 mA/m2). 0
Cr25Ni13 Cr25Ni13 CM9Ni9 SAW PAW PAW Fig.8. — Resistance to the disbonding after
autoclave gas charging test. Type of cladded weld metal
WELDING RESEARCH SUPPLEMENT I 509-s tv OVER LAID. / METAL I
•" . ?' N x:-i kf ' i • Cw ' ,<> vv **~-
rfi^W %•.••;: BASE METAL
OVERLAID METAL
Fig. 9 — Typical ex amples of the metal lic disbonding. 500X. A — SAW specimen, cathodic charging; B — PAW specimen, cathodic charging; C — SAW specimen, autoclave gas charging.
Fig. 10 — The fracture surface of clad weld metal type Cr25-Nil3. A — PAW; B — SAW. 300X.
510-s I NOVEMBER 1993 Cr,%
-20 0 20 40 DISTANCE y Fig. 71 — The distribution of Cr and Ni in the transition zone. 780X. A — PAW specimen, type Cr25-NH3. • OVERLAID! MEIAL \'M METAL HAZ icrij .. ifeAWW 1 1 |7T| 0 20 40 60 Hy^Vw****^ DISTANCE (Mm) •• .. ...... - . •Hi B — PAW specimen, type Cr19-Ni9. BASE • OVERLAID METAL j METAL . y: .. .-..•••• BjQHSj >j f^SSKk\•:. • :• } 5 ':*" ';•••• |CrjH| A 40 60 ^^^^^^^f^^^ DISTANCE (um) ^ , •'•• '• "i-fjj t \ C— SAW specimen, type Cr25-Nil3. WELDING RESEARCH SUPPLEMENT I 511-s OVERLAID OVERLAID METAL ^/^iK^v* •/•;-: • '4:;":.; #.K vt ryy:iy>-;ymiym.^:f• 1 BASE HH Fig. 12 — The microstructure of the transition zone. 200X. A — PAW specimen, type Cr25-NH3; B — PAW specimen, type Cr19-Ni9; C — SAW specimen, type Cr25-Ni 13. the case of SAW compared to PAW — Table 5. The worst disbonding occurred a OVERLAID •;• > in SAW specimens with y coarse grain boundaries parallel to the fusion line — METAL Fig. 1 2C. Specimens with a finer grain structure and smaller length of grain boundaries parallel to the weld fusion line (Fig. 1 2A) were more resistant to metallic disbonding. The best crack re sistance was with the clad metal type Cr19-Ni9, which had the smallest austenitic grains and no specific grain boundary near the interface — Fig. 1 2B. One preventive measure against metallic disbonding is to promote a finer structure without a y coarse grain bound ary parallel to the fusion line. The metal lic disbonding usually locates micro scopically along these grain boundaries (Refs. 2, 5,15). This is fundamental re garding resistance to hydrogen embrit tlement (Refs. 6, 1 3). Finer grains will mean that hydrogen, carbon and harm •t~ mm A ful impurities, such as sulfur and phos phorus, will be less concentrated at the boundaries. Impurity segregation has a negative influence on the granular ad hesion and decreases the surface energy value of a crack. Investigations (Refs. 7, 12, 16) show that sulfur, phosphorus, yyf- silicon and carbon influence cracking along the grain boundary. Also, the grain orientation toward stresses at the inter BASE face when cooling down will not be the MFTAL S>V-.» • j .: *&$&&. .? ^ 512-s I NOVEMBER 1993 same. The formation mechanism of ycoarse TZT diagram in PAW cladded metal type Cr26Ni1 3 grain boundaries can be stated as fol lows (Ref. 5): the austenite grains at the -Transition zone in overlaid metal fusion boundary in the heat-affected zone (HAZ) formed in the 8 —> y trans L formation during cooling are going to grow into the clad metal. Before that, however, other y grains have already nu S_ 1400 I'lOO cleated and have been growing in the transition zone near the composite re gion from the reaction of liquid —> liq Q-1300 uid + 8 —> liquid + 8+ y during solidifi cation. Therefore, when the y grains from the HAZ grow only a little into the clad metal, the y grains from the HAZ and the 20 clad metal collide with each other in the Distance (yu m] transition zone at about 1350°C, and this collision makes the y grain bound B ary parallel to the fusion boundary. This y grain boundary shifts a little accompa TZT diagram in PAW cladded metal type Cr1 9Ni9 nying the disappearance of 8 during cooling from 1 350° to 1 300°C, and the -Transition zone in overlaid metal - zone between the grain boundary and L ISOO the carbide layer formed after PWHT is regarded as the y coarse grain. Zhang, ef al. (Ref.5), show also that if the y coarse grain boundary is located inside the carbide layer (the intersection of 8 + y—>y boundary line with 1300°C, it is a stopping point for the y grain boundary), and it is effective in prevent ing cracking. IZOO The authors have used the transition 20 30 Distance [um] zone transformation (TZT) diagram (Ref. 5) and Fe-Cr-Ni phase diagram (Ref. 1 7) TZT diagram in SAW cl dd id metal type Cr25Ni13 for the design of a new TZT diagram for the investigated specimens on the basis -*—-Transition zone n overla , I of an imaginary Cr and Ni distribution ======- in the transition zone. Figure 11 shows O 1S00 - L - a gradient in alloy level from the ferritic substrate into the weld metal extending cT over a distance of 20 to 35 pm in the - Ihoo Fig. 13—An example PAW samples and 80 to 1 00 pm in the cT+ of TZT diagram. A — SAW samples. The distribution of liq SAW specimen, type uidus, solidus 8 —> 8 + yand S + y —>y CX Cr25-Nil3; B — PAW transformation temperatures in the tran £ 1300 specimen, type Cr 19- sition zone is roughly shown in Fig. 1 3. X Ni9;C —SAW speci -•- Carbide layer-*-! men, type Cr25-Nil3. The abscissa is the distance from the fu IZOO sion boundary to the inside of the clad 20 JI0 B0 no "00 metal, and the origin is set to the fusion Distance [u m] boundary. The right border, namely the composite region (terminology of dification. It is noteworthy that the tem the contrary, this specific boundary is Zhang, ef ai), is the solidification as it perature of the 8 + y —> y boundary line hardly formed inside the transition zone. proceeds from liquid (L)L + 8—>L+S + drops below 1 300°C in the vicinity of Similar grain morphology was observed y —> 8 + y in type Cr25-Ni13 clad metal the fusion boundary. in the real specimens. The clad metal of — Fig. 1 3A and C. The transition zone As can be seen, the intersection of type Cr1 9-Ni9 showed no ycoarse grain in this case, except the part near the the 8 + y —> y boundary line at 1 300°C boundary paralleling the fusion bound composite region, solidifies as a single in the deposit type Cr19-Ni9 locates in ary, but in deposites of the Cr25-Ni1 3 8 phase. The liquidus, the solidus and side the carbide layer formed after type, this specific grain boundary was the 8 + y —> y boundary lines fall nearly PWHT. But this line is always above found. monotonously together with the dis 1 300°C in type Cr25-Ni1 3 deposits (for The difference of the austenite grain tance, but the 8 —> 8 + y boundary line both PAW and SAW). This means that morphology in the transition zone be falls a little then rises to a maximum, and no ycoarse grain boundary paralleling tween the SAW and PAW clad metal can again falls near the composite region. the fusion line is formed in the transi be explained by the effect of welding Figure 13B shows that the clad metal tion zone of the former clad metal. Usu process parameters. The PAW process type Cr1 9-Ni9, including the transition ally the ygrain boundary paralleling the has a low heat energy that leads to a high zone, solidifies as primary 8 phase, and fusion boundary forms outside the car cooling rate and a short contaction time y is formed after the completion of soli- bide layer. In both of the other cases, on for the solid and liquid phase during so- WELDING RESEARCH SUPPLEMENT I 513-s % Ferrite -. > 0 presumably, on the quantity of 8 ferrite, 20 since the heat input in both cases was \ Austenite Cr25M13 strip / / / / the same. 16 £r25Ni13wire Due to the low dilution characteris A + M ^ tic of the PAW process, this austenite- 12 ' C£l9NBwire ferrite microstructure was obtained in the cladding. The dilution in the PAW Martensite \. A + F specimens was 7 to 10% , but it was 20 Fig. 14 — Schaeffler 8 ^^ ^ to 25% in the SAW samples. That might diagram. 1) PAW, l/ / sA + M + F explain the higher content of Cr and Ni Cr25-Ni13, first layer 4 in the PAW cladding (22.2% Cr and deposit; 2) PAW, Cr19- \ \ 2,2SC*iMoplat^^^e Ni9, first layer deposit; F \ M + F 13.7% Ni) compared with the SAW 3) SAW, Cr25-NH3, • \ Ferrite specimen (18.5% Cr and 11.3% Ni). The first layer deposit. 0 M \ consumables are also similar in this re gard: type Cr25-Ni13 strip (SAW) hav Chromium Equivalent = % Cr + % Mo + 1,5 x % Si + 0.5 x % Cb ing a content of 22.5% Cr and 1 3% Ni; and the wire (PAW) having 24.2% Cr lidification. As can seen from Table 5, contraction of melted clad metal with and 13.8% Ni. Carbon content in the the heat input during PAW (2 to 2.4 the base metal irrespective of the cool first layer was 0.072% with PAW and kj/mm) was four times less than when ing rate. It is thought that the width of 0.094% with SAW at the same carbon using SAW (9.7 to 11.2 kj/mm). As a re the transition zone formed in the melt percentage in the consumables. sult, the HAZ should be above the A3 ing state, i.e., the distribution of alloy transformation temperature for a shorter ing elements is one of the major factors Nature of the Transition Zone time with PAW. The welding pool is for the ycoarse grain. This can be clearly more overcooled, and more new solidi seen in the case of PAW clad metal of As is known, the metallic disbonding fication centers in front of the growing the type Cr19-Ni9, which has an alloy occurs only in PWHT material (Ref. 7), grains are formed from the HAZ. All content approximately matching SAW so the disbonding depends on the struc these factors confirm a smaller size for clad metal type Cr25-Ni1 3. ture and properties of the hardened car austenitic grains. As can be seen from bide layer. The influence of PWHT on Table 5, austenitic grain size close to Nature of the Cladding the metallic disbonding is a result of car the interface is on the average 120 to bon migration from the low-alloy base 200 pm in the PAW specimens and 200 According to Schaeffler's diagram metal to the deposited high-alloy clad to 250 pm in the SAW samples. A (Fig. 14), the chemical composition of metal with carbide precipitation at the smaller width for the transition zone in the first layer of deposits is such that the interface. Figure 1 5 shows the influence the PAW samples is a result of smaller microstructure consists of austenite and of PWHT on the disbonding (Ref. 12). It depth of penetration into the base metal ferrite in PAW samples and austenite in is necessary to point out that the real when using the plasma arc process and the SAW clad metal. The PAW speci PWHT for the pressure vessels usally is lower weld pool mixing (Refs. 14, 18). mens of type Cr25-Ni1 3 have -5% fer 690°C during 24 to 30 h, but the PWHT The width of the transition zone af rite and type Cr19-Ni9 has 5 to 10% fer in the present study (650°C for 12 h) was fects the ratio of the y coarse grain be rite. Metallographic analyses (Fig. 12) enough to promote the metallic dis cause the coarse grain is formed inside also show the austenite structure with a bonding. the transition zone. It was shown (Ref. small quantity of ferrite in the case of The conclusions of many investiga 5) that the ratio of the y coarse grain has the PAW specimens. The ferrite in the tions (Refs. 4, 7, 20, 21) are that the de an increasing linear correlation with the austenitic stainless clad metal also af crease of carbon migration during the fects the grain size PWHT and the prevention of carbide by changing the precipitation in the transition zone de solidification pro crease the metallic disbonding. Metal 'C cess (Refs. 18, 19). lographic examination showed that in The 8 ferrite estab the as-welded condition the fusion zone 7100 o lishes new solidifi of all specimens consists of HAZ, tran cation centers in sition area with austenite-martensite front of growing _ C structure adjacent to the fusion line, and columnar grains. austenite or austenite-ferrite clad metal. Due to this effect, This observation follows those of nu 900 o o the austenite grains merous other investigations (Refs. 2, 7, are going to be 18, 19, 22). The martensite layer mor smaller. In com phology had an open texture that devel X paring the size of oped in the direction of solidification. disbondinCL. austenite grains of The martensite region at the interface is PAW clad metal supposed to be an area with less than no < •- o o V x X XX X for types Cr25- 7% Ni (Refs. 1 9, 22). As can seen from Ni13 and Cr19- Fig. 11, this corresponds to the width of Ni9 (Table 5), it the martensite layer (15 to 20 pm) in the o O ' ' can be seen that PAW samples, which is 3 to 4 times less austenite grains than in the SAW specimen (-60 pm), 1 Q 1 close to the inter 500 1 1 mainly due to the low penetration of the t 15 7 5 10 so f]t JK/?S face in the second base metal in the case of the plasma arc case are smaller, process (Ref. 1 8). Fig. L - Influence of PWHT on the metallic disbonding. which depends, Microhardness tests (Fig. 16) indi- 514-s I NOVEMBER 1993 As - welded After PWHT 450 450 H, Overlaid metal : Base meta! Overlaid metal Base metal 410 L 410 370 I 370 I l 330 iW 330 I on 290 / , ! 290 i J--D--C j^-0"-!] ) 250 "K^-ri P^J 250 r^'~\J^*i yf>-0 ' r*^ 210 d 2I0 Y.> yp—o~ H rO& 8-o 170 sMl^ 170 Fusion Ii 5" 130 130 0,3 0,1 0 0,1 0,3 0,5 0,3 0,1 0 0,1 0,3 0,5 DISTANCE, mm DISTANCE, mm A B Fig. 76 — Microhardness distribution (100 g) near weld interface. • PAW specimen, type Cr25-Nil3; 3 PAW specimen, type Cr19-Ni9; O SAW specimen, type Cr25-Nil3. cated that the HAZ of the 2%Cr-1Mo turally changed as a consequence of dis can be wider than the carbide layer with steel is about 240 to 280 HV. As the fu persion hardening and resolidification. the SAW process. So not only the struc sion boundary was approached, a low After PWHT, the hardness in the HAZ ture and properties of the hardened car hardness value was recorded (200-220 is reduced, and that region, which in the bide layer influence metallic disbond HV) as a result of decarburization dur as-welded condition had a value of ing, but also the properties of the whole ing welding. As can be seen, this effect about 240 to 280 HV, was found to be region where the martensite structure is less for the PAW specimens, possibly 180 to 200 HV after heat treatment. The can be formed during welding. It was as a result of a higher cooling rate and hardness was lowest near the boundary pointed out (Ref. 6) that the metallic dis less development of the diffusion pro (1 55-180 HV), which is also lower than bonding increases with dilution because cess. Once the fusion line was crossed, in the as-welded condition. The weld with a high dilution value more carbon microhardness rose rapidly, reaching a metal contains a hardness peak just in will be present at the interface along peak before falling rapidly for the bulk side the stainless steel layer. This is the with a wider and more irregular marten of the first layer (240-275 HV). The hard region clearly showing carbide precipi sitic layer. ness of the martensite zone was highest tation. The width of the carbide layer The results obtained indicate that the for the SAW cladding (450 HV). The along the fusion line after PWHT was ir smallest width and lowest hardness for PAW cladding had values of 410 HV regular, but it was less in the PAW spec the fusion boundary martensite in the (Cr19-Nj9) and 345 HV (Cr25-Ni1 3). imens (1 5-25 pm) compared to the SAW as-welded condition and the interface After PWHT, carbide precipitation specimens (20-40 pm) —Table 5. In the hard zone after PWHT on the stainless along the fusion line was found (the dark plasma arc deposits, the hardness peak steel side, including the carbide layer, layer at the interface on the stainless is considerably smaller (360-370 HV) are displayed in the PAW samples. steel side — Fig. 12), and a decar- than in the submerged arc deposit (-420 The better resistance to metallic dis bonization zone developed in the base HV). A little farther from the boundary bonding (cracks in the carbide layer and metal. Precipitation was also seen on the hardness falls again, but in the SAW the transgranular cracks in the decom the austenite grain boundaries close to sample, the hardened zone is wider and posite martensitic layer), after PAW pro the interface. The carbide precipitation harder. At 100 pm from the fusion line, cess, can be explained in this case by had clearly occurred in the region that SAW values were around 375 HV as improved properties in the transition was martensitic in the as-welded condi compared to 305 HV (Cr19-Ni9) and zone. tion. The martensite layer during PWHT 235 HV (Cr25-Ni1 3) in the PAW sam ples. had a structural transformation, yet it Conclusions kept the morphological peculiarities of The results of the present study show virgin martensite (acicular structure). that the metallic disbonding occurred in The main conclusions obtained are The decomposition of the original inter the stainless clad metal close to the base as follows: facial martensite structure during the metal where the martensitic structure 1) The plasma arc process for de tempering can seen in the case of de was found. Also, the transgranular type positing stainless steel cladding is more posited metal for types Cr19-Ni9 and of cracking was observed in this zone. resistant to metallic disbonding than the Cr25-Ni13 (SAW). The hardness peak is This region with the martensitic struc submerged arc welding process. Type higher in the as-welded condition com ture can include the carbide layer after Cr25-Ni13 clad weld metal generally pared to after the heat treatment. The PWHT if using welding processes with cracks more than type Cr19-Ni9 clad cladding during PWHT is also struc a low dilution rate, such as PAW, or it weld metal. WELDING RESEARCH SUPPLEMENT I 515-s 2) The increasing resistance to metal 4. Matsuda, F., Nakagawa, H., Tsuruta, excellent resistivity against disbonding. J. Jron lic disbonding in the case of the plasma S., and Yoshida, Y. 1984 Disbonding between and Steel Institute of Japan, 70(5): 669. arc welding process can be explained 27.Cr-1Mo steel and overlaid austenitic stain 13. Vainerman, A. E., Shorshorov, M. Ch., less steel by means of electrolytic hydrogen Veselcov, V. D. and Novoselov,V. S. 1969. by the favorable characteristics of this charging technique. Trans, of JWRI, 1 3(2): Plasma arc welding process for cladding of surfacing process, which include a lower 263-272. metals. Mashinostroenie, Leningrad. heat energy and penetration, higher 5. Zhang, Y., Nakagawa, H., and Mat 14. Steklov, O. I., etal. 1989. A high-pro cooling rates, shorter time for the solid suda, F. 1987. Proposal of TZT diagram for ductivity process of plasma arc hot wire sur and liquid phase during solidification, microstructural analysis of transition zone in facing. Welding International, 12: and lower mixing and dilution. All these dissimilar metal welding. Trans, of JWRI, 1058-1059. factors contribute to the fine grains of 16(16): 103-113. 15. Libra, O., and Soukup, K. 1985. K austenite structure adjacent to the weld 6. Pressoure, C, Chaillet, J., and Valette, problematice tvoreni vodikem indukovanych interface, the least length of y coarse G. 1 982. Parameters affecting the hydrogen trhlin u vysokotlakych nadob s navary. disbonding of austenitic stainless cladded Svaranie, 34(10): 297-303. grain boundary parallel to the fusion steels. Current Solution to Hydrogen Prob 16. Sakai, T., Asami, K. , and Katsumata, line, and the smallest width and hard lems in Steel. ASM, New York, pp. 349-355. M. 1 982. Hydrogen induced disbonding of ness of the transition zone, including the 7. Imanaka, T., Shimomura, I., and weld overlay in pressure vessels and its pre martensitic layer (as-welded) and the Nakano, S. 1985. Hydrogen attack in Cr-Mo vention. Current Solutions to Hydrogen Prob carbide layer (after PWHT). steels and disbonding of austenitic stainless lems in Steels. ASM, New York, pp. 340-348. 3) The results of the cathodic charg weld overlay. Kawasaki Steel Technical Re 17. Rivlin, V. C, and Raynor, C. V. 1980. ing test pretty well reproduced the re port, 13(9): 109-119. Critical evaluation of constitution of sults of the autoclave gas phase charg 8. Okada, H., Naito, K., and Watanabe, chromium-iron-nickel system. International ing test. The cracks along the grain J. 1982. Hydrogen-induced disbonding of Metals Review 1: 21-38. stainless steel weld overlay in hydrodesulfur 18. Livshits, L. S. 1979. Science of metals boundaries were more pronounced in izing reactor. Current Solution to Hydrogen for welders. Mashinostroenie, Moscow. the austenite stainless clad metal close Problems in Steel. ASM, New York, p. 331- 19. Gotalskij, Y.N. 1980. Welding of het to the base metal in one case, and trans 339. erogeneous steels. Mashinostroenie, granular failure developed in the transi 9. Naito, K., Okada, H., and Watanabe, Leningrad. tion zone with the decomposite marten J. 1980. Study on hydrogen embrittlement of 20. 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This conference was sponsored by the American Welding Society, the American Welding Institute, and the National Institute of Standards and Technology. Topics include data formats and searchable standards, welding engineering applications, quality and non destructive examination, weld sensing for real-time control, weld controllers and control systems, and databases and welding procedures. (Hardbound) Code CP-1192 List: $125.00 AWS Members: $93.75 International Conference on Underwater Welding This 169 page conference proceedings includes thirteen papers by recognized authorities in the underwater welding field presented at the conference held in New Orleans, LA, March 20-21, 1991. Topics cover state- of-the-art developments in the underwater industry including welding equipment and processes, mechanical and internal weld properties, maintenance and inspection procedures, and welding applications in shallow and deep water. 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