Publications Details
Welding metallurgy of Alloy HR-160
The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in Alloy HR-160 was investigated by Varestraint testing, differential thermal analysis and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 °C and initiated solidification by a primary L→γ reaction in which Ni, Si and Ti segregated to the interdendritic liquid and cosegregated to the γ dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at ≈1162 °C by a eutectic-type L→[γ+ (Ni,Co)16(Ti,Cr)6Si7] reaction. The (Ni,Co)16(Ti,Cr)6Si7] phase is found to be analogous to the G phase that forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [γ+(Ni,Co)16(Ti,Cr)6Si7] eutectic-type constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 °C and the presence of 2-5 vol-% solute-rich interdendritic liquid that preferentially wets the grain boundaries and interdendritic regions.