The directed energy deposited (DED) alloys show higher hardness values than the welded alloys due to the finer microstructure following the high cooling rate. However, defects such as microcracks, pores, and the residual stress are remained within the DED alloy. These defects deteriorate the wear behavior so post-processing such as heat treatment and hot isostatic pressing (HIP) are applied to DED alloys to reduce the defects. HIP was chosen in this study because the high pressure and temperature uniformly reduced the defects. The HIP is processed at 1150°C under 100 MPa for 4 hours. After HIP, microcracks are disappeared and porosity is reduced by 86.9%. Carbides are spherodized due to the interdiffusion of Cr and C between the dendrite and interdendrite region. After HIP, the nanohardness (GPa) of carbides increased from 11.1 to 12, and the Co matrix decreased from 8.8 to 7.9. Vickers hardness (HV) decreased by 18.9 % after HIP. The dislocation density (10-2/m2) decreased from 7.34 to 0.34 and the residual stress (MPa) changed from tensile 79 to a compressive -246 by HIP. This study indicates that HIP is effective in reducing defects, and the HIP DED Stellite 6 exhibits a higher HV than welded Stellite 6.

It is essential to select materials with excellent mechanical properties to prevent chemical and mechanical damage to the surfaces of materials used in machines and structures and to extend their lifespan. Co-based stellite alloy, which has wear resistance, heat resistance, and corrosion resistance, is essential for products used in harsh environments. However, due to the problem of enormous costs, research on hard facing, which uses a stellite coating layer only on the contact surface, is urgently required. Currently, high-facing research on Stellite coating layers is focused on powder, and GMAW research using wire is relatively lacking. In this study, welding experiments were performed to form stable weld beads using stellite 6 welding wire, and the correlation between parameters and weld beads was analyzed. A CMT welder was used to minimize the heat effect on the base material.