Laser cladding of stellite and silica on aluminum substrate

Recently the interest in cladding one material on another is greatly increasing because of the fact that engineers and designers are becoming more and more aware of the advantages afforded by the many advanced surfacing techniques. Among many cladding processes, laser cladding is one of the latest developments. Because of the high optical reflectivity and thermal conductivity, laser surface treatment of aluminum alloys still seems to be difficult, especially for cladding some wear resistant material with a high melting point onto them. So far, few successful cases have been reported in the literature. The aim of this study is to investigate the feasibility of laser cladding of Stellite and Silica on aluminum substrate in order to develop the potential application of aluminum alloys in the tribological field. The blown powder laser cladding technique was used in this study. The aluminum substrate used was AlCu4SiMg (H15). The powders used were Stellite 6 and pure silica. To clad Stellite on aluminum substrate, there exists a lot of difficulties. The main problems are: (1) the cladding track is very likely to peel off; and (2) the cladding track is prone to cracking, especially when overlap treatment is used. Because there exists no direct metallurgical bonding between aluminum and cobalt, the only way to bond Stellite and aluminum together is to sandwich it in with intermetallic compounds. So, an alloying zone is essentially needed, and some dilution is unavoidable. The elementary experiments for cladding silica on aluminum substrate seem to be successful. A uniform cladding bead of silica on aluminum has been obtained. This is a prospective future for applications of aluminum in the area where thermal conductivity and electrical isolation are both required.