Influence of substrate surface temperature on the microstructure and properties of plasma-sprayed Al_2O_3 coatings

摘要

Thermally sprayed ceramic coatings have a layered structure with a limited interface bonding. Substrate surface temperature prior to droplets impact during deposition significantly influences the microstructure and properties of the coatings. Through the controlling of substrate surface temperature, the lamellar interface bonding of the deposits could be possibly improved. Al_2O_3 coatings were deposited by atmospheric plasma spraying at the surface temperatures of 100, 275, 375, 480, 530 and 660°C. The fractured cross-section morphology was characterized by scanning electron microscopy. X-ray diffraction was used to analyse the phase contents. Micro-hardness, Young's modulus and thermal conductivity of the deposits were measured. It was observed that the interface area with columnar grain growth across splat-splat interfaces was increased with increasing deposition temperature. Consequently, micro-hardness, Young's modulus and thermal conductivity were increased with the increase of deposition temperature The improvement of properties suggest that the lamellar interface bonding in the deposits was improved as the substrate surface temperature is increased.