SiC-AlSi composite coatings on piston alloys for diesel engine motors

Plasma spray technique was used to deposit SiC-AlSi composite coatings, having approximate thickness of 400 μm, of commercially available AlSi alloy powders fabricated thereby mixing with SiC particles. The coating microstructure was investigated by a combination of optical microscopy, SEM, EDX and XRD. The coatings had layered morphologies because of deposition and solidification of successive melted or semimelted particles. SiC particles were randomly distributed in AlSi layers. The coatings were subjected to dry sliding wear against hardened steel counterbodies using pin-on-disc type apparatus and microhardness measurement was carried out through a standard microhardness tester. It has been found that these coatings possess porosities, and the hardness values and wear behaviour of the coatings strongly depend on porosity, oxidized, unmelted and semimelted particles.