Processing of composite Al/SiC powders for plasma spraying

The use of aluminum in automobile engine blocks and other critical parts su ch as cam rods and valves requires superior surface properties. This has le d to the development of thermally sprayed surface coatings for this type of component. To impart maximum bond strength, and superior wear resistance, a plasma sprayed aluminum based composite (Al-SiC) was found to be more sui table than current metallic or ceramic coatings. To eliminate inhomogeneiti es arising from blended powders, composite powders were prepared by mechani cal alloying of 6061 Al alloy with SiC particles. The concentration of SiC was varied between 20 and 75v/o. The size of the reinforcement was varied f rom 8 to 37 mu m in the Al-50v/o SiC composites. An organic process control agent was used to modify tbe morphology of the powders during mechanical a lloying. The 44 to 140 mu m powders were sprayed using an axial feed plasma torch. Adhesion strength, hardness, abrasive and erosive wear resistance o f the coatings were assessed.