Heat treatment of bimetals produced by selective laser melting of MS1 maraging steel on conventionally produced 42SiCr martensitic steel

Abstract

One approach to producing hybrid bimetallic parts is to additively manufacture a new material onto a conventionally manufactured base material. This technique can expand the potential applications of additive manufacturing and offer new solutions for the engineering design of hybrid parts. In this work, laser powder bed fusion was used to deposit MS1 maraging steel on a conventionally produced (cast and hot-rolled) 42SiCr martensitic steel base material. Despite the profoundly different chemical compositions and hardening behaviours of these materials, their yield and ultimate tensile strengths in solution-annealed and hardened conditions are quite similar. Various heat treatments were performed to optimise the mechanical properties of the resulting hybrid part. The highest yield strength of 1400 MPa and tensile strength of 1483 MPa was achieved with a post-processing heat treatment which consisted of annealing at 900 °C for 25 min followed by water quenching and subsequent very short tempering at 490 °C. In the tensile tests, all the hybrid parts, regardless of heat treatment parameters, fractured within the base material and neither in the joint nor in the adjacent heat-affected zone. The interface areas and the microstructures of both materials were documented in detail in the as-built state and also after the heat treatment.