Microstructure and property of micro-plasma-sprayed Cu coating

Cu coating is deposited by a micro-plasma spraying system under a low power of 2.8–4.2 kW. The effects of the main processing parameters including plasma arc power, operating gas flow and spray distance on the particle velocity during spraying, and the microstructure and microhardness and the oxygen content in the coating are investigated. The microstructure of the coating are examined using optical and scanning electron microscopy (SEM). The property of the coating is characterized by cross-sectional microhardness. The particle velocity during in-flight is measured using a particle velocity/temperature measurement system based on thermal radiation. The dependency of the microstructure and property of the coating on spray particle conditions is examined through comparing the particle velocity, microstructure, and microhardness of the coating deposited by the micro-plasma spray with that by the conventional plasma spray at a power one order higher. It has been found that a dense copper coating comparable to the conventional plasma-sprayed one can be produced by the micro-plasma spray under a power one order lower. The present results confirm that the coating of comparable microstructure and property can be produced regardless of the plasma power level provided that the comparable particle velocity and molten state are achieved.