Processing Of Composite Al/Sic Powders For Plasma Spraying

The use of aluminum in automobile engine blocks and other critical parts such as cam rods and valves requires superior surface properties. This has led 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 suitable than current metallic or ceramic coatings. To eliminate inhomogeneities arising from blended powders, composite powders were prepared by mechanical 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 from 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 alloying. The 44 to 140 mu m powders were sprayed using an axial feed plasma torch. Adhesion strength, hardness, abrasive and erosive wear resistance of the coatings were assessed.