Abstract

Improvement of the high velocity oxy-fuel deposition (HVOF) process in the last decade has enhanced the microstructure of coatings in order to better perform against wear and corrosion. Indeed cermet and metal HVOF coatings are reliable and have excellent performance under slurry erosion and provide therefore an alternative to the use of high-priced material. This paper presents the results of a study undertaken within the core research program of the National Research Council of Canada technology group in surface engineering, "SURFTEC", in which the performance of ten HVOF erosion-resistant coatings was evaluated. Ten different types of HVOF coatings were studied including: six grades of WC with either Co or a Ni based matrix, one grade of Cr3C2 in a Ni-Cr matrix, and three grade of metallic alloy: Ni alloy, Co alloy and a SS 316- L. The performance of coatings was evaluated with respect to: the volume ratio and composition of metallic binder in carbide coatings, type of carbide, coating microstructure, impinging angle and the size of the erodent particles. All coatings were produced using the HVOF JP-5000 system controlled by the Hawcs-ll controller. Slurry erosion tests were conducted with a jet impingement rig with a 10 %w/w alumina particle/water slurry. The volume loss of material under various slurry erosion conditions was related to the coating properties and microstructure. Results indicate that the behavior of HVOF sprayed materials is dependent on the erodent particle size, to the erosion impinging angle to some extent and to the corrosion resistance of the cermet matrix.

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