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1.
A nickel base weld filler metal alloy with nominal composition of 67 pct Ni, 20 pct Cr, 3 pct Mn, 3 pct Fe, and 2.5 pct Nb
(Cb) is used to make austenitic-ferritic dissimilar metal joints. Tensile properties were determined for this alloy over the
range 25 to 732°C at strain-rates of 3×10−6 and 3×10−4/s. Above about 450°C, both the yield strength and the ultimate tensile strength in the low strain-rate tests showed significant
increases over the strengths at the higher strain-rate. The enhanced values for the yield strength persisted to the highest
test temperature (732°C), whereas the ultimate tensile strength for the low strain-rate fell below the curve for the higher
strain-rate at about 600°C. Above 600°C, the ultimate tensile strength dropped off rapidly and at 677°C approached the yield
strength (i.e., the uniform elongation dropped to less than 1 pct). The strain-rate effects have been attributed to “K-state” formation,
an effect that investigators have attributed to short range order in other Ni−Cr base alloys. 相似文献
2.
Type 308 weld metal overlaid on a low-alloy steel by a submerged arc welding (SAW) process using wide strip electrodes can
become sensitized by not only postweld heat treatments (PWHTs) at around 600 °C but also low-temperature aging (LTA) at 500
°C for 24 hours after PWHT. A slow strain-rate test (SSRT) in oxygenated, high-temperature pure water revealed that type 308
SAW weld metals after PWHT were susceptible to intergranular stress corrosion cracking (IGSCC) when sensitized such that the
intergranular corrosion (IGC) rate in the modified ASTM A262E test exceeds 1 μm/h. The effect of microstructure (ferrite phase distribution) on the sensitization behavior was evaluated using a microstructural
parameter N
L
β−γ
. Though mostly useful, the average N
L
β−γ
was not always accurate in distinguishing IGC-susceptible, SAW overlay weld metals. However, local N
L
β−γ
, newly introduced to deal with a rather large fluctuation in ferrite distribution within SAW overlay weld metals, was partly
able to explain the IGC susceptibility of a theoretically resistant heat with a high average N
L
β−γ
. The beneficial effect of surface remelting by plasma arc on the IGC resistance was described. 相似文献
3.
The effect of oxygen content on the susceptibility of high-strength weld metal to hydrogen cracking is examined. Increasing
oxygen content had a detrimental effect on the cracking susceptibility of weld metal containing a dψusible hydrogen content
of 4.7 ppm. In weld metal containing a much lower dψusible hydrogen content (0.87 ppm), increasing weld metal oxygen content
had no detrimental effect on hydrogen cracking susceptibility. These results are explained by a model which proposes that
hydrogen cracking occurs when a critical oxide inclusion density promotes intergranular fracture at prior austenite grain
boundaries and when a critical level of hydrogen is present in the weld metal. For the same level of hydrogen (moisture) contamination,
high-strength weld metals containing oxygen contents greater than 200 ppm will be much more susceptible to hydrogen cracking
than deposits made using inert gas-shielded or vacuum-operated welding processes.
Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto 相似文献
4.
The effect of oxygen content on the susceptibility of high-strength weld metal to hydrogen cracking is examined. Increasing
oxygen content had a detrimental effect on the cracking susceptibility of weld metal containing a dψusible hydrogen content
of 4.7 ppm. In weld metal containing a much lower dψusible hydrogen content (0.87 ppm), increasing weld metal oxygen content
had no detrimental effect on hydrogen cracking susceptibility. These results are explained by a model which proposes that
hydrogen cracking occurs when a critical oxide inclusion density promotes intergranular fracture at prior austenite grain
boundaries and when a critical level of hydrogen is present in the weld metal. For the same level of hydrogen (moisture) contamination,
high-strength weld metals containing oxygen contents greater than 200 ppm will be much more susceptible to hydrogen cracking
than deposits made using inert gas-shielded or vacuum-operated welding processes.
Formerly Visiting Scientist, Department of Metallurgy and Materials Science, University of Toronto 相似文献
5.
J. Daniel Whittenberger 《Metallurgical and Materials Transactions A》1979,10(9):1285-1295
The tensile behavior of the oxide dispersion strengthened iron-base alloy MA 956 was investigated as a function of strain-rate
ranging from 3.3×10−2 to 8.3×10−8 s−1 at 1366 K. All tests were conducted in the longitudinal direction on specimens machined from bar stock. Because of the microstructure
of this alloy, all specimens were either single crystals or bicrystals with the boundary parallel to the gage length. Testing
revealed that the strength was rather insensitive to strain-rate, the tensile ductility decreased with decreasing strain-rate,
and for strain-rates ≤8.3×10−5 s−1, the alloy fractured in brittle manner. Evidence of transgranular cracking perpendicular to the applied stress was observed
at all strain-rates; failure at strain-rates ≤8.3×10−5 s−1 was due to cracks which grow by the joining together of cavities ahead of the running crack. This alloy appears to possess
a critical stress intensity factor for rapid crack growth. 相似文献
6.
C. T. Fujii 《Metallurgical and Materials Transactions A》1981,12(6):1099-1105
The stress-corrosion cracking (SCC) behavior of high-strength steel weld metals, as indexed by KIscc, was examined with emphasis on the relative influences of yield strength, electrochemical potential, welding process, and
weld metal composition. The weld metals were from weldments fabricated by the gas metal arc (GMA) or gas tungsten arc (GTA)
process. Filler metals with four different compositions—designated 120S, 140S, AX140 and HY-130—were used. The multi-pass
welding procedures and their associated thermal cycles produced very complex martensitic-bainitic type microstructures. The
GTA weld metals were considerably more fine-grained and more highly tempered than the GMA weld metals. This enhanced the fracture
toughness of all four of the higher strength GTA weld metals but improved the SCC properties of only two GTA weld metals—HY-130
and 140S. The effectiveness of microstructural influences on SCC behavior is correlated with the sulfur content of the weld
metals assuming that hydrogen is the cause of SCC in these materials. The role of sulfur is presumed to be that of catalytic
poison for the hydrogen recombination reaction which increases opportunities for nascent hydrogen absorption. The results
show that the weld metals with improved SCC properties contain the lower concentrations of sulfur. 相似文献
7.
Jeffrey W. Sowards Dong Liang Boian T. Alexandrov Gerald S. Frankel John C. Lippold 《Metallurgical and Materials Transactions A》2012,43(4):1209-1222
The solidification behavior of a Cr-free welding consumable based on the Ni-Cu system was evaluated in conjunction with Type
304L stainless steel. The weld metal microstructure evolution was evaluated with optical and secondary electron microscopy,
energy dispersive spectroscopy, X-ray diffraction, button melting, and thermodynamic (CALPHAD-based) modeling. Solidification
partitioning patterns showed that higher dilutions of the filler metal by Type 304L increased segregation of Ti, Cu, and Si
to interdendritic regions. Button melting experiments showed a widening of the solidification temperature range with increasing
dilution because of the expansion of the austenite solidification range and formation of Ti(C,N) via a eutectic reaction.
The model predictions showed good correlation with button melting experiments and were used to evaluate the nature of the
Ti(C,N) precipitation reaction. Solidification cracking susceptibility of the weld metal was shown to increase with dilution
of 304L stainless steel based on testing conducted with the cast pin tear test. The increase in cracking susceptibility is
associated with expansion of the solidification temperature range and the presence of eutectic liquid at the end of solidification
that wets solidification grain boundaries. 相似文献
8.
Improvement in Laser Weldability of INCONEL 738 Superalloy through Microstructural Modification 总被引:1,自引:0,他引:1
A.T. Egbewande H.R. Zhang R.K. Sidhu O.A. Ojo 《Metallurgical and Materials Transactions A》2009,40(11):2694-2704
Microstructural study of laser-beam-welded IN 738 superalloy was carefully performed to better understand the causes of heat-affected
zone (HAZ) cracking and to determine an improved approach of alleviating the weldability problem. The HAZ cracks in the alloy
were intergranular liquation cracks that resulted from the liquation reaction of both secondary solidification products (MC
carbides and γ-γ′ eutectic) and solid-state reaction products (γ′ particles) present in the preweld material. In contrast to the expectation based on Chadwick’s equation, a reduction of
grain boundary liquid film thickness did not produce a decrease in HAZ cracking owing to increased base alloy hardness that
accompanied a preweld heat treatment designed to reduce the intergranular liquation. Moreover, a major factor limiting the
effectiveness of an existing preweld heat treatment with low base alloy hardness in reducing HAZ cracking was found to be
the formation of intergranular M5B3 boride particles during the heat treatment. These borides can widen the HAZ brittle temperature range (BTR) during weld cooling
and increase the propensity for cracking. Based on the results, a new preweld heat treatment that induces a moderate hardness
and precludes grain boundary boride formation was found and was shown to produce a significant reduction in HAZ cracking in
the welded alloy compared to the most effective pre-existing preweld heat treatment. 相似文献
9.
The influence of entrapped helium on microstructural damage and residual mechanical properties subsequent to applying low-penetration
gas metal arc (GMA) weld overlays was examined for an AISI Type 304 stainless steel. Two helium levels were examined: 22.5
and 85.0 atomic parts per million (appm) He. Detailed scanning electron microscopy (SEM) revealed the presence of intergranular
cracks in the weld heat-affected zone (HAZ). The crack surfaces exhibited a dimple structure that was characteristic of a
gas bubble embrittled material. Transmission electron microscopy (TEM) revealed that the size and spacing of the grain boundary
helium gas bubbles remained virtually unchanged (relative to that established by the charging and aging procedure) at distances
greater than 1 mm from the fusion line. Within this first millimeter, the diameter of the bubbles increased rapidly, and the
bubble spacing increased to the characteristic spacing of the dimples that decorated weld-induced cracks. Mechanical testing
revealed a loss in strain-to-fracture and ultimate tensile strength (UTS) at the higher helium level. While the majority of
the fracture occurred in a transgranular, ductile manner, some deformation-induced intergranular cracking was observed. This
cracking occurred over a very narrow region localized to the HAZ of the weldment. At the lower helium level, ductility and
strength were unaffected compared to helium-free specimens. 相似文献
10.
Sunil Goyal K. Laha K. S. Chandravathi K. Bhanu Sankara Rao 《Transactions of the Indian Institute of Metals》2010,63(2-3):461-466
Creep tests were carried out on 2.25Cr-1Mo ferritic steel base metal and its fusion welded joint at 823 K over a stress range of 100–240 MPa. The weld joint possessed lower creep rupture strength than the base metal and the reduction was more at lower applied stresses. The failure occurred in the intercritical region of heat-affected zone (HAZ) of the joint, commonly known as Type IV cracking. Type IV cracking in the joint was manifested as pronounced localization of creep deformation in the soft intercritical region of HAZ coupled with preferential creep cavitation. The creep cavitation in intercritical HAZ was found to initiate at the central region of the creep specimen and propagate outwards to the surface. To explain the above observations, the stress and strain distributions across the weld joint during creep exposure were estimated by using finite element analysis. For this purpose creep tests were also carried out on the deposited weld metal and simulated HAZ structures (viz. coarse-grain structure, fine-grain structure, and intercritically annealed structure) of the joint. Creep rupture strength of different constituents of joint were in the increasing order of intercritical HAZ, fine-grain HAZ, base metal, weld metal and coarse-grain HAZ. Localized preferential creep straining in the intercritical HAZ of weld joint as observed experimentally was supported by the finite element analysis. Estimated higher principal stress at the interior regions of intercritical HAZ explained the pronounced creep cavitation at these regions leading to Type IV failure of the joint. 相似文献
11.
M. Valsan D. Sundararaman K. Bhanu Sankara Rao S. L. Mannan 《Metallurgical and Materials Transactions A》1995,26(5):1207-1219
A comparative evaluation of the low-cycle fatigue (LCF) behavior of type 316LN base metal, 316 weld metal, and 316LN/316 weld
joints was carried out at 773 and 873 K. Total strain-controlled LCF tests were conducted at a constant strain rate of 3 ×
10−3 s−1 with strain amplitudes in the range ±0.20 to ±1.0 pct. Weld pads with single V and double V configuration were prepared by
the shielded metal-arc welding (SMAW) process using 316 electrodes for weld-metal and weld-joint specimens. Optical microscopy,
scanning electron microscopy (SEM), and transmission electron microscopy (TEM) of the untested and tested samples were carried
out to elucidate the deformation and the fracture behavior. The cyclic stress response of the base metal shows a very rapid
hardening to a maximum stress followed by a saturated stress response. Weld metal undergoes a relatively short initial hardening
followed by a gradual softening regime. Weld joints exhibit an initial hardening and a subsequent softening regime at all
strain amplitudes, except at low strain amplitudes where a saturation regime is noticed. The initial hardening observed in
base metal has been attributed to interaction between dislocations and solute atoms/complexes and cyclic saturation to saturation
in the number density of slip bands. From TEM, the cyclic softening in weld metal was ascribed to the annihilation of dislocations
during LCF. Type 316LN base metal exhibits better fatigue resistance than weld metal at 773 K, whereas the reverse holds true
at 873 K. The weld joint shows the lowest life at both temperatures. The better fatigue resistance of weld metal is related
to the brittle transformed delta ferrite structure and the high density of dislocations at the interface, which inhibits the
growth rate of cracks by deflecting the crack path. The lower fatigue endurance of the weld joint was ascribed to the shortening
of the crack initiation phase caused by surface intergranular crack initiation and to the poor crack propagation resistance
of the coarse-grained region in the heat-affected zone. 相似文献
12.
Raghuvir Singh Mukesh Kumar Mainak Ghosh Gautam Das P. K. Singh I. Chattoraj 《Metallurgical and Materials Transactions A》2013,44(1):173-187
Low temperature sensitization of 304LN stainless steel from the two pipes, differing slightly in chemical composition, has been investigated; specimens were aged at 623 K (350 °C) for 20,000 hours and evaluated for intergranular corrosion and degree of sensitization. The base and heat-affected zone (HAZ) of the 304LN-1 appear resistant to sensitization, while 304LN-2 revealed a “dual” type microstructure at the transverse section and HAZ. The microstructure at 5.0-mm distance from the fusion line indicates qualitatively less sensitization as compared to that at 2.0 mm. The 304LN-2 base alloy shows overall lower degree of sensitization values as compared to the 304LN-1. A similar trend of degree of sensitization was observed in the HAZ where it was higher in the 304LN-1 as compared to the 304LN-2. The weld zone of both the stainless steels suffered from cracking during ASTM A262 practice E, while the parent metals and HAZs did not show such fissures. A mottled image within the ferrite lamella showed spinodal decomposition. The practice E test and transmission electron microscopy results indicate that the interdendritic regions may suffer from failure due to carbide precipitation and due to the evolution of brittle phase from spinodal decomposition. 相似文献
13.
K. Banerjee N. L. Richards M. C. Chaturvedi 《Metallurgical and Materials Transactions A》2005,36(7):1881-1890
The effect of filler alloys C-263, RENé-41, IN-718, and FM-92 on heat-affected zone (HAZ) cracking susceptibility of cast
IN-738 LC, which is a high-temperature Ni-based superalloy used at temperatures up to 980 °C and is precipitation hardened
by the γ′ (Ni3Al,Ti) phase, by gas-tungsten-arc (GTA) welding was studied. In addition, autogenous welds were also made on the IN-738 parent
material. The preweld treatments consisted of the standard solution treatment at 1120 °C for 2 hours followed by air cooling,
and a new heat treatment, which was developed to improve the HAZ cracking resistance of IN-738 LC. This heat treatment consisted
of solution treating at 1120 °C followed by air cooling then aging at 1025 °C for 16 hours followed by water quenching. Welds
were observed to suffer intergranular HAZ cracking, regardless of the filler alloy; however, the autogenous welds were most
susceptible to HAZ cracking. In general, the cracking tendency for both heat treatments was maximum for C-263 and RENE-41
fillers and decreased with the use of FM-92 and IN-718 filler alloys. The HAZ cracking was associated mainly with constitutional
liquation of γ′ and MC carbides. On some cracks, liquated low melting point containing Zr-carbosulfide and Cr-Mo borides were also observed
to be present. The cooling portion of the weld thermal cycle induced precipitation hardening via γ′ phase in the γ matrix of the weld metal. The HAZ cracking increased as the weld metal lattice mismatch between γ′ precipitates and γ matrix of the weld and its hardness (Ti + Al) increased. However, the weld-metal solidus and solidification temperature range,
determined by high-temperature differential scanning calorimetry, did not correlate with the HAZ cracking susceptibility.
It is suggested that the use of filler alloys with small γ′-γ lattice mismatch and slow age-hardening response would reduce the HAZ cracking in IN-738 LC superalloy welds. 相似文献
14.
The hot cracking susceptibility of fillers 52 and 82 in a alloy 690 weldment is analyzed by the Varestraint test. Weld characteristics,
microstructure, hardness distribution, and thermal analysis of the two filler metals are also examined. The weld metal of
both fillers develops an extremely dense oxide layer. A stainless steel brush cannot remove the oxide layer, and a grinder
may be needed between weld passes to assure a sound weld. Differential temperature analysis (DTA) shows that filler 82 has
a lower melting point and a wider melting/solidification temperature differential (Δ T). These characteristics correlate with greater hot cracking susceptibility of filler 82 than 52 in Varestraint tests. The
hot cracks are intergranular and are caused by elements segregating in grain boundies. 相似文献
15.
K. LAHA K.S. CHANDRAVATHI P. PARAMESWARAN K. BHANU SANKARA RAO S.L. MANNAN 《Metallurgical and Materials Transactions A》2007,38(1):58-68
In the postweld heat-treated (PWHT) fusion welded modified 9Cr-1Mo steel joint, a soft zone was identified at the outer edge
of the heat-affected zone (HAZ) of the base metal adjacent to the deposited weld metal. Hardness and tensile tests were performed
on the base metal subjected to soaking for 5 minutes at temperatures below Ac1 to above Ac3 and tempering at the PWHT condition. These tests indicated that the soft zone in the weld joint corresponds to the intercritical
region of HAZ. Creep tests were conducted on the base metal and cross weld joint. At relatively lower stresses and higher
test temperatures, the weld joint possessed lower creep rupture life than the base metal, and the difference in creep rupture
life increased with the decrease in stress and increase in temperature. Preferential accumulation of creep deformation coupled
with extensive creep cavitation in the intercritical region of HAZ led to the premature failure of the weld joint in the intercritical
region of the HAZ, commonly known as type IV cracking. The microstructures across the HAZ of the weld joint have been characterized
to understand the role of microstructure in promoting type IV cracking. Strength reduction in the intercritical HAZ of the
joint resulted from the combined effects of coarsening of dislocation substructures and precipitates. Constrained deformation
of the soft intercritical HAZ sandwich between relatively stronger constitutes of the joint induced creep cavitation in the
soft zone resulting in premature failure. 相似文献
16.
Elmar K. Tschegg Christian Tauschitz Stefanie E. Stanzl 《Metallurgical and Materials Transactions A》1982,13(8):1483-1489
Fatigue crack growth curves(Δa/ΔN =f(K
max
)) were measured with 2.5 mm thick sheets of electron beam welded iron base superalloy A286. Fatigue testing frequency was
21 kHz,R = −1 (mean stress zero) and the environment was noncorrosive silicone oil at 20 °C. Two series of samples with different
welding conditions were tested. One series was welded perfectly, whereas the second contained microcracks within the weld
and the heat affected zone. It was shown that the crack growth rate in the base metal is slower than in the weld. The threshold
stress intensity factorK
th
of the base metal is 14 MNm-3/2 and that of the weld, 10 MNm
-3/2
. However, at higherK
max
values, the crack grows more rapidly in the weld than in the base metal; for example, the crack growth rate is 16 times higher
at Kmax = 20 MNm
-3/2
. Microcracks introduced by an imperfect welding process do not influence the fatigue cracking behavior in the threshold regime;
atK
max
= 15 MNm-3/2, however, the crack growth rates differ by an order of magnitude. Fractographic examination shows considerable differences
in the fracture appearance of weld, heat affected zone, and base material. Weld and base metal display ductile fracture surfaces
and the heat affected zone is characterized by crystallographic fracture facets. 相似文献
17.
The sensitization behavior of types 308 and 316 stainless steel weld metals as internal overlays for reactor pressure vessels
(RPVs) was studied with respect to the effects of postweld heat treatment (PWHT) at about 600 °C during RPV fabrication and
low-temperature aging during operation. For the study, a criterion for the rate of intergranular corrosion (IGC) for detecting
the susceptibility to intergranular stress corrosion cracking (IGSCC) in high-temperature oxygenated pure water was established
by quantitatively evaluating the results from a modified ASTM A262E test. A criterion for expecting satisfactory resistance
to IGSCC was found to be an IGC rate of about 1 μm/h. Type 308 weld metal can be sensitized as indicated by an IGC rate >1 μm/h, and can be healed, as indicated by an IGC rate <1 μm/h, depending on the length of PWHT. However, this healed weld metal can be resensitized by exposing it to 500 °C×24 h; in
this condition, it shows a relatively high susceptibility to IGSCC. On the contrary, type 316 weld metal was almost immune
to sensitization under the same heat treatments. By transmission electron microscopy (TEM), its excellent resistance was attributable
to carbon fixation by molybdenum carbide precipitation within ferrite phases during PWHT. Reheat embrittlement of type 316
weld metal was also examined. 相似文献
18.
R. E. Ricker E. U. Lee R. Taylor C. Lei B. Pregger E. Lipnickas 《Metallurgical and Materials Transactions A》2013,44(3):1353-1364
The influence of chloride ion activity on the susceptibility of aluminum alloys 5083-H131 and 7075-T6 to stress corrosion cracking (SCC) was investigated by conducting slow strain-rate tensile tests at a strain-rate of 10?7 s?1 in naturally aerated aqueous solutions with varying NaCl mass fraction (0.001 to 20 pct) and in a 3.5 pct mass fraction NaCl solution with varying strain-rates (10?8 to 10?4 s?1). This study found that both alloys exhibited reduced strengths and failure strains (times) in the solutions compared with laboratory air. The extent of these reductions was greater in alloy 5083 for the conditions examined. The strength and ductility of both alloys decreased with chloride ion activity in a manner that indicates a chemical reaction is responsible. The strength and ductility of both alloys decreased with strain-rate in a sigmoidal manner, but the transition in alloy 7075 occurred at slower strain-rates of approximately two orders of magnitude. It was deduced that the chloride ion interacts chemically with the passivated surface in the potential gradient at the crack tip to cause SCC. While no mechanism of cracking can be eliminated on the basis of these results alone, the results are consistent with the hypothesis that the absorbed hydrogen causes cracking in alloy 7075 while cracking in 5083 is the result of a dissolution mechanism. 相似文献
19.
H. Shaikh H. S. Khatak S. K. Seshadri J. B. Gnanamoorthy P. Rodriguez 《Metallurgical and Materials Transactions A》1995,26(7):1859-1868
This article deals with the effect of the microstructural changes, due to transformation of delta ferrite, on the associated
variations that take place in the tensile and stress corrosion properties of type 316 L stainless steel weld deposits when
subjected to postweld heat treatment at 873 K for prolonged periods (up to 2000 hours). On aging for short durations (up to
20 hours), carbide/ carbonitride was the dominant transformation product, whereas sigma phase was dominant at longer aging
times. The changes in the tensile and stress corrosion behavior of the aged weld metal have been attributed to the two competitive
processes of matrix softening and hardening. Yield strength (YS) was found to depend predominantly on matrix softening only,
while sig-nificant changes in the ultimate tensile strength (UTS) and the work-hardening exponent, n, occurred due to matrix
hardening. Ductility and stress corrosion properties were considerably affected by both factors. Fractographic observations
on the weld metal tested for stress-corrosion cracking (SCC) indicated a combination of transgranular cracking of the austenite
and interface cracking. 相似文献
20.
M. J. Cieslak J. J. Stephens M. J. Carr 《Metallurgical and Materials Transactions A》1988,19(3):657-667
The weldability and weld metal microstructure of Cabot Alloy 214 have been investigated with a variety of experimental and
analytical techniques. These include Varestraint hot crack testing, hot ductility testing, pulsed Nd:YAG laser welding, scanning
and analytical electron microscopy, electron microprobe analysis, and X-ray diffraction. A heat of Alloy 214 containing intentionally
alloyed B (0.003 wt pct) and Zr (0.07 wt pct) was much more sensitive to both fusion zone hot cracking as quantified by the
Varestraint test and to simulated heat-affected-zone (HAZ) cracking as quantified by hot ductility testing than a heat of
Alloy 214 containing no intentionally added B (0.0002 wt pct) or Zr (0.02 wt pct). Scanning electron microscopy of the high
B and Zr alloy showed the presence of dendritically-shaped, Zr-rich constituents in interdendritic regions in the gas-tungsten-arc
(GTA) welds. Electron microprobe analysis of these welds revealed a segregation pattern of Cr, Al, Mn, and Zr enrichment in
interdendritic regions and Ni and Fe enrichment in dendrite core regions. Analytical electron microscopy revealed the presence
of ZrX (X = B, C, N, O), M23C6, andγ′ in the fusion zone of GTA weld specimens,γ′ was also found in the as-received base metal and in the GTA weld HAZ. X-ray diffraction analysis of extractions from the
high B and Zr GTA weld metal also indicated the presence of a ZrX-type constituent. The results of this study are in qualitative
agreement with earlier work performed on alloys such as NIMONIC 90 and INCONEL 718∗ relative to the detrimental effect of B and Zr additions on fusion zone and HAZ hot cracking susceptibility.
Formerly with Sandia National Laboratories, Albuquerque, NM 相似文献