EFFECT OF PLASMA SPRAY COATING PARAMETERS ON THE MICROSTRUCTURE AND PERFORMANCE OF AN ALUMINA/COPPER COMPOSITE

摘要

A coating of alumina powder was plasma sprayed onto a Cu substrate to fabricate a composite with dielectric performance. The effect of the plasma spray coating parameters on the microstructure, thermal resistance, and dielectric properties of the alumina layer are discussed in this study. Experimental results indicate that higher power influences the fine powder process by forming a thicker layer with a deteriorated surface roughness for the alumina/copper composite. The thermal resistance of the alumina layer increases with surface roughness. The layer's microstructure, thickness, and absorbed moisture in the porosity affect the breakdown voltage of the alumina layer. The optimized parameters for plasma spray coating included an alumina powder with a particle size ranging from 22 to 45μm, a plasma power of 40 kW, a spraying velocity of 750 m/s, an argon flow rate of 45 L/min, a spraying distance of 140mm, and a spraying angle of 90°. With a coated layer thickness of 20μm, a relatively low thermal resistance (0.03 K/W), a low surface roughness (3.13 μm), and a highly reliable breakdown voltage (40 V/μm) was attained in this work.