Effect of heat treatment on microstructure and mechanical properties of laser melting deposited 1Cr12Ni2WMoVNb steel

Effect of heat treatment on microstructure and mechanical properties of the laser melting deposited (LMD) martensitic stainless steel 1Cr12Ni2WMoVNb was investigated. Samples of the steel were solution treated at different austenitizing temperatures and then oil quenched. Subsequently, the 1150 °C solution treated sample was further tempered at 580 °C. Results of solution treatments reveal the columnar-to-equiaxed grain transition as a result of austenitization. Furthermore, after solution treatment at 1150 °C, the interlayer heat-affected zone (ILHAZ) is almost eliminated and the interdendritic phases are almost dissolved, while solution treatment at 1050 °C results in the insufficient homogenization. Ultimate tensile strength of the quenched-and-tempered steel is superior to the as-deposited steel and the wrought counterpart. Elongation and reduction in area of the steel are noticeably higher than that of the as-deposited steel, but are slightly lower than that of the wrought counterpart. Impact toughness of the quenched-and-tempered steel is slightly lower than that of the wrought counterpart, and the impact toughness values of the steel are dispersive. The lower and dispersive impact toughness values could be due to the existence of lack-of-fusion porosity in the laser deposited steel.