Abstract: Experiment of 1Cr17Ni2 stainless steel repaired by laser additive Ni-based high temperature alloy powder was carried out. The effect of different laser heat input on microstructure and mechanical properties of the repaired 1Cr17Ni2 steel joints was studied. The results show that the laser additive repair joints of the 1Cr17Ni2 steel are divided into cladded zone, heat-affected zone and stainless steel matrix. The upper region of the cladded zone is uniformly distributed dendrite structure, and the primary arm is fully developed and its growth direction is consistent, which is roughly parallel to the height of cladding. The dendrite size decreases with the decrease of heat input and the gap between the dendrite grains increases. The middle and lower regions of the cladded zone are short columnar dendritic structure, and its growth direction is consistent, which size decreases slightly as the laser heat input decreases. The cladded zone is mainly composed of matrix phase γ, irregular phase δ and MC precipitated along grain boundary. The heat affected zone of the stainless steel side is mainly composed of massive δ ferrite, austenite, martensite and spherical pearlite, and there is a clear boundary with the cladded zone. With the decrease of laser heat input, the average hardness of the cladded zone increases at first and then decreases. When the laser heat input is 80 J/mm, the maximum hardness is 330.64 HV0.2, which is increased by 9.78% than that of stainless steel matrix.

Key words: 1Cr17Ni2 stainless steel, nickel-based superalloy powder, laser additive, laser heat input, microstructure, mechanical properties