Design of surfacein situmetal–ceramic composite formation via laser treatment

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 problems associated with the production of a metal matrix composite layer freefrom porosity, cavities, and cracks, with a satisfactory distribution of ceramic were considered. Optimum laser processing conditionsfor Al–SiCp gave a well distributed ceramic withfew defects, but limited to 35 μm thickness. This was increased to 250 μm using a preplaced mixture of Al powder and SiCp. A prep laced SiCp layer on commercially 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 produced via laser surface melting associated with preplaced SiCp which showed a similar wear resistance to bulk metal matrix composite Al alloy–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.MST/3003