Scanning velocity influence on microstructure evolution and mechanical properties of laser melting deposited 12CrNi2 low alloy steel

Abstract 12CrNi2 low alloy steels were prepared by laser melting deposition (LMD), aiming at investigating the effect of laser scanning velocity on phase composition, microstructure, microhardness, residual stress and tensile properties of the specimens. Experimental results showed that the α-Fe diffraction peaks in the specimens shifted to lower angle due to the solid solution of ferrite-forming elements. The microstructure of LMD-processed 12CrNi2 alloy steel was mainly composed of ferrite (F) and granular bainite (GB). High microhardness (348 ± 8 HV0.2) and low residual tensile stress (57 ± 5 Mpa) can be achieved by optimizing the laser parameters. As the laser scanning velocity increased, the average granular size was refined and the majority of grains had smaller sizes close to 2–3 μm, which was significantly finer compared with those prepared by conventional process. LMD-processed 12CrNi2 alloy steel exhibited satisfactory mechanical properties with ultimate tensile strength (1000 ± 17 MPa), yield strength (960 ± 12 MPa) and higher elongation (10.02%), which could reach the requirements of low alloy steel components due to the satisfactory strength and toughness.