A. Scrivani, G. Rizzi, Turbocoating SpA, Rubbiano Solignano - PR -, Italy
From the point of view of the tribological properties the use of hard materials as thermal sprayed coatings allows to improve drastically the in-service behaviour of components used in several application.
HVOF (High Velocity Oxygen Fuel) process allows to get good coatings for these purpose: the coating are very hard and dense with excellent cohesion and adhesion. The low porosity give to these coatings a good behaviour in aggressive environments. Namely tungsten carbide cobalt-chromium and chromium carbide nickel chromium based are widely used in application where resistance to wear and low friction coefficient are requested. Interesting application for these coating is the wire drawing industry, where Cu and steel wires are produced. Carbides show good performances but show some problems due to decomposition when in contact with other substances at certain temperatures.
This paper addresses the study of novel ceramic and metallic coatings sprayed by innovative plasma spray methods which could be an alternative or a complement for the above mentioned carbides.
In particular Yttria Partially Stabilised Zirconia (YPSZ) and NiCr alloys has been used for the deposition of the novel coatings and their characteristics have been compared with the ones of the tungsten and chromium carbides. The coatings have been characterized form the metallographic point of view: thickness, porosity, microstructure, phases presence and Vickers hardness have been determined.
Specific test for wear determination in pin-on-disk condition has been developed, based on standard ASTM G 99-03
Namely YPSZ coatings show good behaviour as antiwear coating and looks very promising for these kind of application.
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