WC-Co High Energy Thermal Sprayed Coatings-Structures and Mechanical Properties-
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Coatings of WC-Co system alloys have been applied by thermal spraying to add wear resistance to metal substrates. However, compared with sintered WC-Co alloys, conventional plasma sprayed coatings carried out in air do not possess satisfactory mechanical properties, possibly due to the fact that tungsten carbides decompose in a high temperature plasma jet. Three types of spraying methods (conventional plasma spraying in air, high energy gas flame spraying and low pressure plasma spraying) are examined, and the relation between the structure and mechanical property of the coatings produced by each spraying method is discussed. In the high energy spraying process, the decomposition of WC in WC-Co powders involves a thermal activation reaction which results in dissociation of the carbon. This reaction is accelerated in an oxygenating atmosphere. The Vickers hardness of WC-Co sprayed coating can be described by the product of two factors-the dispersion hardening strengthened by WC particles and layer binding strength affected by melted W produced by the WC decomposition reaction.
- Trans. JWRI
Trans. JWRI 14(2), 67-73, 1985