17.6.2002 Surface coating

High Temperature Behaviour of Plasma Transferred Arc and Laser Co-based Alloy Coatings

Surface engineering is a topic of great relevance on today’s engineering. Surface features can be improved from the point of view of the material being deposited or from the point of view of the depositing process. The present work characterises coatings of a cobalt-based alloy, deposited by PTA welding on an AISI 304 stainless steel substrate. Samples were subjected to temperature cycling at 1050 8C. As-deposited features and their stability to high temperature were study, results are presented and compared with similar samples obtained by laser cladding. The performance of hardfaced material was evaluated by microstructure, chemical analysis and microhardness measurements. For the processing conditions tested, results showed that, for operating conditions that do not require elevated temperature, laser hardfacing shows the bests results, due to the refine solidification structure produced. However, for the high temperature tested, PTA deposits exhibited superior microstructural stability whereas laser deposits undergo significant changes.