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Fakhreddin Ashrafizadeh - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolutions in dissimilar welds between AISI 310 austenitic stainless steel and Inconel 657
    Journal of Materials Science, 2010
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    This investigation has been performed to characterize dissimilar metal welds between type 310 austenitic stainless steel (SS) and Inconel 657 superalloy. The welds were produced using four types of filler materials: Inconel 82, Inconel A, Inconel 617, and type 310 SS. The weldments were characterized in detail using optical metallography and scanning electron microscopy. It can be concluded that Inconel A weld metal does not promote severe Hot Cracking. Continuous NbC precipitates in the Inconel 82 weld metal can sensitize the weld metal to solidification Cracking. The presence of high amounts of Mo in Inconel 617 weld metal led to the formation of brittle phases. In addition, continuous precipitates were observed in the 310 SS weld metal, which can lead to poor resistance of the weld metal to Hot Cracking. In the aged condition, Inconel 82 and Inconel A exhibited good thermal stability, whereas Inconel 617 and type 310 SS exhibited poor thermal stability. Also, after subjecting the heat-affected zone and interface between Inconel weld metal and base metals to aging treatment, unmixed zone of Inconel 657 base metal side has disappeared. Elimination of this region can be attributed to high-temperature interdiffusion of alloying elements. Finally, it is found that Inconel A and Inconel 82 weld metals are the best choices for the dissimilar welds performed here, respectively.

  • dissimilar welding of aisi 310 austenitic stainless steel to nickel based alloy inconel 657
    Journal of Materials Processing Technology, 2009
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    Abstract The current work was carried out to characterize welding of AISI 310 austenitic stainless steel to Inconel 657 nickel–chromium superalloy. The welds were produced using four types of filler materials; the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and 310 austenitic stainless steels. This paper describes the selection of welding consumables for the joint. The comparative evaluation was based on Hot-Cracking tests (Varestraint test) and estimation of mechanical properties. According to Varestraint tests, Inconel A showed the least susceptibility to Hot Cracking. In tension tests, all weldments failed in the weaker parent metals (i.e., Inconel 657). Moreover, Inconel A weldment had the highest strength and total elongation. On the other hand, the weld metals failed by ductile fracture except Inconel 617, which exhibited mixed fracture mode. At last, it was concluded that Inconel A filler material offered the best compromise for the joint between Inconel 657 and 310 stainless steel.

H Naffakh - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolutions in dissimilar welds between AISI 310 austenitic stainless steel and Inconel 657
    Journal of Materials Science, 2010
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    This investigation has been performed to characterize dissimilar metal welds between type 310 austenitic stainless steel (SS) and Inconel 657 superalloy. The welds were produced using four types of filler materials: Inconel 82, Inconel A, Inconel 617, and type 310 SS. The weldments were characterized in detail using optical metallography and scanning electron microscopy. It can be concluded that Inconel A weld metal does not promote severe Hot Cracking. Continuous NbC precipitates in the Inconel 82 weld metal can sensitize the weld metal to solidification Cracking. The presence of high amounts of Mo in Inconel 617 weld metal led to the formation of brittle phases. In addition, continuous precipitates were observed in the 310 SS weld metal, which can lead to poor resistance of the weld metal to Hot Cracking. In the aged condition, Inconel 82 and Inconel A exhibited good thermal stability, whereas Inconel 617 and type 310 SS exhibited poor thermal stability. Also, after subjecting the heat-affected zone and interface between Inconel weld metal and base metals to aging treatment, unmixed zone of Inconel 657 base metal side has disappeared. Elimination of this region can be attributed to high-temperature interdiffusion of alloying elements. Finally, it is found that Inconel A and Inconel 82 weld metals are the best choices for the dissimilar welds performed here, respectively.

  • dissimilar welding of aisi 310 austenitic stainless steel to nickel based alloy inconel 657
    Journal of Materials Processing Technology, 2009
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    Abstract The current work was carried out to characterize welding of AISI 310 austenitic stainless steel to Inconel 657 nickel–chromium superalloy. The welds were produced using four types of filler materials; the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and 310 austenitic stainless steels. This paper describes the selection of welding consumables for the joint. The comparative evaluation was based on Hot-Cracking tests (Varestraint test) and estimation of mechanical properties. According to Varestraint tests, Inconel A showed the least susceptibility to Hot Cracking. In tension tests, all weldments failed in the weaker parent metals (i.e., Inconel 657). Moreover, Inconel A weldment had the highest strength and total elongation. On the other hand, the weld metals failed by ductile fracture except Inconel 617, which exhibited mixed fracture mode. At last, it was concluded that Inconel A filler material offered the best compromise for the joint between Inconel 657 and 310 stainless steel.

Morteza Shamanian - One of the best experts on this subject based on the ideXlab platform.

  • Microstructural evolutions in dissimilar welds between AISI 310 austenitic stainless steel and Inconel 657
    Journal of Materials Science, 2010
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    This investigation has been performed to characterize dissimilar metal welds between type 310 austenitic stainless steel (SS) and Inconel 657 superalloy. The welds were produced using four types of filler materials: Inconel 82, Inconel A, Inconel 617, and type 310 SS. The weldments were characterized in detail using optical metallography and scanning electron microscopy. It can be concluded that Inconel A weld metal does not promote severe Hot Cracking. Continuous NbC precipitates in the Inconel 82 weld metal can sensitize the weld metal to solidification Cracking. The presence of high amounts of Mo in Inconel 617 weld metal led to the formation of brittle phases. In addition, continuous precipitates were observed in the 310 SS weld metal, which can lead to poor resistance of the weld metal to Hot Cracking. In the aged condition, Inconel 82 and Inconel A exhibited good thermal stability, whereas Inconel 617 and type 310 SS exhibited poor thermal stability. Also, after subjecting the heat-affected zone and interface between Inconel weld metal and base metals to aging treatment, unmixed zone of Inconel 657 base metal side has disappeared. Elimination of this region can be attributed to high-temperature interdiffusion of alloying elements. Finally, it is found that Inconel A and Inconel 82 weld metals are the best choices for the dissimilar welds performed here, respectively.

  • dissimilar welding of aisi 310 austenitic stainless steel to nickel based alloy inconel 657
    Journal of Materials Processing Technology, 2009
    Co-Authors: H Naffakh, Morteza Shamanian, Fakhreddin Ashrafizadeh
    Abstract:

    Abstract The current work was carried out to characterize welding of AISI 310 austenitic stainless steel to Inconel 657 nickel–chromium superalloy. The welds were produced using four types of filler materials; the nickel-based corresponding to Inconel 82, Inconel A, Inconel 617 and 310 austenitic stainless steels. This paper describes the selection of welding consumables for the joint. The comparative evaluation was based on Hot-Cracking tests (Varestraint test) and estimation of mechanical properties. According to Varestraint tests, Inconel A showed the least susceptibility to Hot Cracking. In tension tests, all weldments failed in the weaker parent metals (i.e., Inconel 657). Moreover, Inconel A weldment had the highest strength and total elongation. On the other hand, the weld metals failed by ductile fracture except Inconel 617, which exhibited mixed fracture mode. At last, it was concluded that Inconel A filler material offered the best compromise for the joint between Inconel 657 and 310 stainless steel.

K. Nishimoto - One of the best experts on this subject based on the ideXlab platform.

  • influence of minor and impurity elements on Hot Cracking susceptibility of extra high purity type 310 stainless steels
    2011
    Co-Authors: K. Nishimoto, Kazuyoshi Saida, K Kiuchi, Junpei Nakayama
    Abstract:

    The Hot Cracking behaviour of extra high-purity stainless steels was investigated with respect to type 310 stainless steel with various amounts of minor and impurity elements such as C, P, S and Mn. The purity of the type 310 stainless steels used was enhanced in the order of Type 310Hot Cracking susceptibility was evaluated by the transverse-Varestraint test. This test revealed that two types of Hot cracks occurred in these steels; solidification and ductility-dip cracks. The solidification Cracking susceptibility was significantly reduced as the amount of C, P and S decreased, and that Type 310EHP steel reached a level so low that solidification Cracking did not occur in practical welding. On the other hand, the ductility-dip Cracking susceptibility adversely increased as the purity of the steels was enhanced. However, the ductility-dip Cracking susceptibility of Type 310EHP steel was sufficiently as low as not to yield ductility-dip Cracking in practical welding. Numerical analysis suggested that the reduced solidification Cracking susceptibility upon refining C, P and S could be attributed to the reduced solidification brittle temperature range due to the suppression of solidification segregation of minor and impurity elements. The quantitative contribution of minor and impurity elements to the Hot Cracking susceptibility of extra high-purity type 310 stainless steels was evaluated by using lab-melted steels with different amounts of C, P, S and Mn. The essential influence on solidification Cracking was the ratio of P:S:C=1:1.3:0.5, while Mn negligibly ameliorated solidification Cracking in the extra low S (and P) steels. On the other hand, a molecular orbital analysis to estimate the binding strength of the grain boundary suggested that the increased ductility-dip Cracking susceptibility in extra high-purity steels was caused by grain boundary embrittlement due to the refining of beneficial elements for grain boundary strengthening such as C.

  • Hot Cracking behaviour and susceptibility of extra high purity type 310 stainless steels
    Science and Technology of Welding and Joining, 2010
    Co-Authors: Kazuyoshi Saida, K. Nishimoto, K Kiuchi, Y Okabe, K Hata, Junpei Nakayama
    Abstract:

    AbstractRecent progress in the refining technology has enabled the production of highly pure commercial stainless steels. The Hot Cracking behaviour of these stainless steels was investigated with respect to type 310 stainless steel. For comparison, four types of 310 stainless steels with various amounts of minor and impurity elements such as C, P and S were used. The purity of type 310 stainless steels used was enhanced in the order of type 310Hot Cracking susceptibility was evaluated by the transverse Varestraint test. Two types of Hot cracks occurred in these steels by Varestraint test; solidification and ductility-dip cracks. The solidification Cracking susceptibility was significantly reduced as the amount of C, P and S decreased, and that in type 310EHP steel reached a level so low that solidification Cracking did not occur in practical welding. On the other hand, the ductility-dip Cracking susceptibility adversely increased as the purity of the steels ...

  • Hot Cracking susceptibility in laser weld metal of high nitrogen stainless steels
    Science and Technology of Advanced Materials, 2004
    Co-Authors: K. Nishimoto, H. Mori
    Abstract:

    High nitrogen stainless steels are used as structural materials required to possess high strength and fracture toughness at low temperatures. The solidification mode in weld metals of stainless steels is generally designed to be the primary ferrite solidification mode to prevent Hot Cracking. The weld metals in some high nitrogen stainless steels, however, exhibit the primary austenite solidification mode because of an austenitizing effect of nitrogen, which enhances Hot Cracking susceptibility. In addition, laser welding provides the primary austenite solidification mode in weld metals of stainless steels due to the high solidification rate. Therefore, the laser weld metal of high nitrogen stainless steels likely occurs Hot Cracking.This study was conducted to make clear an effect of nitrogen and the solidification rate on Hot Cracking susceptibility in the laser weld metals of type 304 stainless steels varied with nitrogen content. The Hot Cracking susceptibility was examined by the preloading tensile strain (PLTS) Cracking test. The PLTS test results showed that Hot Cracking susceptibility was remarkably increased with increase in the solidification rate and the nitrogen content. On the other hand, the solidification mode in the weld metal was changed from the primary ferrite to the primary austenite, as the solidification rate was raised. The primary austenite solidification mode was also observed in the weld metals with higher nitrogen content at lower solidification rate conditions. The experimental results indicated that the increase in Hot Cracking susceptibility is in agreement with the transition of solidification mode from the primary ferrite to the primary austenite in the weld metal. The transition of solidification mode in the weld metals of high nitrogen stainless steels could be predicted by the calculation using the modified Kurz–Giovanola–Trivedi model considering the effect of nitrogen.

Haiyang Fan - One of the best experts on this subject based on the ideXlab platform.

  • Laser powder bed fusion of Hastelloy X: Effects of Hot isostatic pressing and the Hot Cracking mechanism
    Materials Science and Engineering A, 2018
    Co-Authors: Quanquan Han, Sam L. Evans, Brecht Van Hooreweder, Maria Luz Montero Sistiaga, Kim Vanmeensel, Rossitza Setchi, Raya Mertens, Haiyang Fan
    Abstract:

    Hastelloy X is the trademark for a nickel-based, high-temperature superalloy that is increasingly applied in gas turbine engines because of its exceptional combination of oxidation resistance and high-temperature strength. The superalloy suffers from Hot Cracking susceptibility, however, particularly when processed using additive manufacturing and laser powder bed fusion (LPBF). This paper systematically studies for the first time the effect of post-treatment Hot isostatic processing (HIP) on the microstructure and mechanical properties of LPBF-fabricated Hastelloy X, with an emphasis on fatigue performance. The experimental results demonstrate that despite the very small number of remaining gas-filled micropores due to pressure counteraction, the high temperature and high pressure during the HIP process promote recrystallisation and closing of the internal microcracks and gas-free pores. The HIP-processed specimens are shown to be roughly 130 MPa and 60 MPa weaker than the non-processed specimens in yield strength and ultimate tensile strength, respectively. The HIP-processed Hastelloy X exhibits significant improvements in fatigue life, however: the effect of the HIP processing is apparent once the applied stress decreases. This improvement in fatigue performance is attributable to the reduction in stress concentration and residual stress release caused by the HIP process. The paper also studies the Hot Cracking mechanism and finds that intergranular microcracks generally occur along high angle grain boundaries; the interdendritic liquid pressure drop between dendrite tip and root is found to be a significant factor in the Hot crack mechanism. The significance of this research is in developing a comprehensive understanding of HIP processing on the fatigue behaviour of the LPBF-fabricated Hastelloy X. The insights on the Cracking mechanism, which presents a significant step towards using additive manufacturing to produce complex crack-free parts from this superalloy.