Microstructure of heat-affected zone of laser forming repaired 2Cr13 stainless steel

2Cr13 martensitic stainless steel is widely used in the manufacturing of heavy load components, which are easy to be damaged due to their severe service environment. If these damaged components can be repaired rapidly, considerable savings in materials, processing and time costs can be achieved. Four kinds of laser forming repairing for 2Cr13 stainless steel sample, single-track single-layer, multi-track single-layer, single-track multi-layer and multi-track multi-layer, was conducted to investigate their microstructure characteristic and evolution of heat-affected zone (HAZ). The formation mechanism of microstructure was analyzed based on the temperature field simulation. It is found that microstructure varies continuously from substrate zone (SZ) to the bottom of laser repaired zone (RZ), in which the main phases varied as α→ ferrite→α ferrite+ martensite → martensite+α ferrite → martensite, and the appearance of the martensite led to a rapid increase in hardness. Meanwhile, the primary M₂₃C₆ dissolved gradually and disappeared eventually. It is interesting to note that the dissolving of intragranular carbides occurred prior to the intergranular carbides. With the carbides dissolving, δ ferrite particles appeared, coarsened and connected into skeleton patterns eventually when closing to the bottom of RZ. As the deposited layers increased, the hardness peak decreased, and the grains were refined in the partial region of the middle of HAZ. The carbides precipitated again in the grain boundary at the top of HAZ, meanwhile, δ skeleton is gradually interrupted by the grain boundary.