Effect of laser scanning and powder addition on microstructure and mechanical properties for hot-wire-feed laser additive manufacturing

Powder is generally used as a filler material for laser additive manufacturing of metal components, but it is unsatisfactory for aspects such as deposition efficiency, material utilization ratio, environment adaptability, and powder milling cost. Wire-feed additive manufacturing of metal components has attracted more and more attention. However, the poor melting stability of filler wires hampers its industrial application, let alone other unbeneficial factors like weak material flexibility, low dimension accuracy, and low energy efficiency. The benefits of hot wires have been reported by preheating filler wires. However, it is still difficult to get equivalent properties after additive manufacturing without bulk heat treatment. This work aims to establish a hot-wire-feed laser additive manufacturing technology to repair metal components with high efficiency and quality. A martensite stainless steel wire was used as a filler material. The microstructure and mechanical properties of the deposited layers were investigated. The heterogeneous distribution of the microstructure was observed. The overall mechanical properties of the as-cladded layer deteriorated. Laser scanning during idling time between layers was used to temper the deposited metal and to obtain a homogeneous microstructure without bulk heat treatment. The effect of laser scanning parameters on the thermal history and microstructure evolution was discussed. With the addition of feeding TiC nanopowder, the chemical composition of deposited metals was adjusted further. The tensile strength of the clad layer got close to that of the substrate. The ductility and impact toughness of the clad layer are even better than those of the substrate.