Two step coating of a hypereutectic PM Al–Si alloy

The aim of the present work was to combine the high strength of Al–Si alloys produced via Rapid Solidification (RS) and Spray Forming (SF) with a wear resistant surface coating, designed for high temperature use. The surface coating, composed mainly of nickel and chromium, was applied in a two step process: plasma spray followed by laser surface alloying using a diode laser. The microstructure and hardness of the surface coating were analysed. In the Al–Si alloys produced via Rapid Solidification, gas bubble formation was observed during the laser alloying process. In the Spray Formed alloys, globules of the coating material and a needle-like microstructure formed, in detriment to the mechanical properties of the alloyed layer.