Characterisation of heat-treated gradient alloy steel fabricated by laser melting deposition

A gradient alloy steel prepared by laser melting deposition (LMD) was subjected to two heat treatments (quenching-intercritical quenching denoted as Q-IQ and quenching-intercritical quenching-tempering denoted as Q-IQ-T). Results showed that martensite microstructure was changed to a duplex microstructure of martensite and ferrite after heat treatment, with a small number of Cr23C6 phases appearing. The samples before and after heat treatment exhibited random crystallographic orientation, while the grain was refined and the fraction of Cr23C6 increased after heat treatment. The samples after heat treatment possessed more slip systems and exhibited a decrease in hardness and wear resistance in comparison with LMDed sample. The corrosion resistance decreased in the order of Q-IQ > Q-IQ-T > LMDed samples in 3.5 wt-% NaCl solution.