Effects of TIG surface treating on microstructural characteristics and mechanical properties of Al₂O₃–TiB₂ coating by APS

Abstract

The pulsed DC tungsten inert gas (TIG) method was employed to post-spray treat an electroconductive Al₂O₃–TiB₂ coating by atmosphere plasma spraying (APS) Al₂O₃–30 wt-%TiB₂ powder. The microstructure and mechanical properties of the coatings before and after treatment were comparatively investigated by scanning electron microscopy, laser scanning confocal microscopy, X-ray diffraction, microhardness tester and block on ring wear tester. It was detected that the treated coating presented a two layer structure consisting of the remelted zone and the sintered zone, which was comprised of TiB₂ and single α-Al₂O₃; surface roughness of the treated coating exhibited a remarkable decrease while microhardness and wear resistance showed a significant increase. These experimental results could be ascribed to the effect of high heat input and discharge plasma during the pulsed DC TIG treating.

Keywords:

• Al₂O₃–TiB₂
• Atmosphere plasma spray
• TIG
• Surface treating
• Microstructure
• Mechanical property

Acknowledgements

The authors gratefully acknowledge financial support provided Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality. Special thanks to Mr Li Guodong, an international welding engineer (International Institute of Welding), College of Material Science and Engineering, Beijing University of Technology (Beijing China), for his help during the experiments.