DESIGN OF SURFACE IN-SITU METAL-CERAMIC COMPOSITE FORMATION VIA LASERTREATMENT

The creation of wear resistant surface metal matrix composites in both aluminium alloys and titanium via the incorporation of preplaced SiCp has been successfully undertaken by using a 5 kW CO2 laser. The probl ems associated with the production of a metal matrix composite layer f ree from porosity, cavities, and cracks, with a satisfactory distribut ion of ceramic were considered. Optimum laser processing conditions fo r Al-SiCp gave a well distributed ceramic with few defects, but limite d to 35 mu m thickness. This was increased to 250 mu m using a preplac ed mixture of Al powder and SiCp. A prepared SiCp layer on commerciall y pure Ti resulted in a dissolution of SiCp and precipitation of TiC, or the partial dissolution of SiCp and agglomeration into a hard layer (1400 HV). Pin on disc wear tests indicated that surfaces could be pr oduced via laser surface melting associated with preplaced SiCp which showed a similar wear resistance to bulk metal matrix composite Al all oy-SiCp, and an improvement of an order of magnitude for commercially pure Ti-SiCp surface metal matrix composites, over a commercially pure Ti laser treated surface. (C) 1994 The Institute of Materials.