Formation of a wear resistant surface on Al by laser aided in-situ synthesis of MoSi2

Reduction in the weight of engines forms a key element in improving the fue l efficiency of automobile engines. The use of Al as the engine material of fers a viable option, but is limited by the poor wear resistance of the met al, especially in the cylinder bores. Laser induced surface modification of the cylinder bores, by the addition of second phase particles offers one s uch viable option. An attempt was made to produce in-situ nano/micron-sized particles of molybdenum disilicide (MoSi2) in the laser melted zone of the Al (A-356 alloy) substrate. The in-situ formation of MoSi2 was conducted b y adding a mixture of Mo and Si precursor powder layer followed by melting the layer and substrate under a laser beam. A partial mixing of the interme tallic layer with the substrate Al was obtained. The partial mixing with Al resulted in a ternary non-stoichiometric phase that improved the hardness and the ductility as compared to that of the pure intermetallic phase. The addition of 5 wt.% titanium to the precursor powders resulted in an increas e in the fluidity of the intermetallic layer, thereby promoting better inte rmixing with the substrate Al. (C) 1999 Elsevier Science S.A. All rights re served.