Intermetallic coatings produced by TIG surface melting

The titanium aluminide intermetallic alloys possess high specific strength, high hardness and high temperature capabilities up to 800 degreesC such as corrosion and oxidation resistance. These alloys can be suitable replaceme nts for the conventional ceramic coatings applied in many components of che mical plants and aircraft engines to protect against high temperature oxida tion and corrosion. The initial feasibility study of the forming of interme tallic alloy coatings on titanium surfaces was undertaken using powder prep lacement and TIG surface melting processes. The present paper describes the process parameters that are associated with this route of formation of int ermetallic alloy coatings and other issues that include the ability to achi eve a defect-free uniform intermetallic layer with superior mechanical prop erties, and constitutional and microstructural uniformity across the sectio n. The alloy coatings were characterised in terms of microstructures, defec ts. wear, and hardness using microscope, microhardness tester, tribometer a nd XRD. Melting conditions were optimised to produce Ti3Al and TiAl coating s without any pores, cavities and cracking. The coating layers yielded a ha rdness of over 500 HV. (C) 2001 Elsevier Science B.V. All rights reserved.