Microstructure and Property of Ni76Cr19AlTi Side in Inertia Friction Weld Joint of the Superalloy Ni76Cr19AlTi and the Martensite Stainless Steel 4Cr10Si2Mo

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The inertia friction welding process was used to weld the nickel base superalloy Ni76Cr19AlTi to martensite steel 4Cr10Si2Mo. Ni76Cr19AlTi is a f.c.c superalloy strenthened by precipitates of γ′. 4Cr10Si2Mo is a martensite stainless steel strenthened by martensite transformation and precipitates of carbides. The microstructure evolution on the nickel base superalloy Ni76Cr19AlTi side of the weld was studied. It was found that the welds formed can be divided into three zones: thermomechanically affected zone, heat affected zone and base metal. The thermomechanically affected zone consisted of two subzones: one is the mixed chemical composition zone of about 100 μm in width formed by mechanical stirring and interdiffusion of alloying elements and the other was pure shear zone located adjacent to the mixedchemical composition zone. In the chemical composition mixture zone, a large number of carbides with sizes of less than 100 nm formed in the austenite matrix. However, no γ′ phase can be observed in this region. The dislocation density decreased gradually as the distance to the weld interface increased. The dislocation density in the pure shear zone was very high. Grain size coarsened markedly in the heat affected zone, in which the γ′ phase was precipitated. The primary mechanism of the grain growth was the bulging of grain boundary between two adjacent grains with high-angle boundary.