Advantages of hard coatings and deposition technologies such as HVOF have opened new opportunities for the production of wear parts operating in an abrasive environment. Thermally sprayed hardmetal coatings are widespread in industrial applications for wear, but not usable under impact wear conditions. To widen the scope of thick hard coating applications, powder coatings, produced by plasma spraying and powder spray-fused coatings using laser remelting, were studied. Nickel-and iron-based self-fluxing alloy powders and WC-Co hardmetal powders were used as spray materials. The microstructure of coatings and the influence of heat treatment on the structure and composition of coatings as well as on the composition of the substrate were studied. The duplex-treated surfaces were tested under the conditions of abrasion and abrasive erosion and impact wear and the mechanisms of coating degradation were analysed. Prospects of coatings, containing thermal spray-fused iron-based metal-matrix WC-Co hardmetal for erosive wear conditions, are demonstrated. Based on the comparative studies of abrasive, erosive and impact wear resistance, recommendations for materials and coatings are formulated.
High-velocity oxy-fuel sprayed, iron alloy-based powder coatings, reinforced with tungsten carbide-cobalt (WC-Co) and titanium carbide-nickel molybdenum (TiC-NiMo) cermet particles, are compared under high-temperature abrasive-erosive wear conditions. Both WC-Co and TiC-NiMo particles underwent fracture, as well as dissolution, during the spraying process, but in the case of WC-Co particles this process was remarkably less intensive. Under the low impact angle conditions, the WC-Co particle-reinforced coating exhibited 1.1 times lower wear than the TiC-NiMo particle-reinforced coating because of the larger amount of the reinforcement remaining. Under the normal impact angle conditions, the WC-Co particle-reinforced coating showed 1.2 times lower wear than the TiC-NiMo particle-reinforced coating because of the resulting larger size of the WC-Co reinforcement and a more ductile matrix.
The resistance of high velocity oxy-fuel (HVOF) sprayed TiC-NiMo and Cr3C2-Ni cermet particles reinforced NiCrSiB self-fluxing alloy coatings to high temperature erosion wear was studied. Microstructure of the coatings was examined by SEM, phase composition was determined by XRD. A four-channel centrifugal particle accelerator was applied to study the high temperature erosion wear of the coatings. The angles of impingement were 30º and 90º, initial particle velocity was 50 m/s, the average temperature of the test-650 ºC. Volume wear of the coatings was calculated and compared to the respective values of the reference materials. Wear mechanisms were studied by SEM. HVOF sprayed coatings exhibited lower wear, than WC-15Co hardmetal and steel HARDOX 400, but higher wear than steel AISI 304. TiC-NiMo particles reinforced self-fluxing alloy coating demonstrated virtually the same wear resistance, as the Cr3C2-Ni particles reinforced self-fluxing alloy coating, at 30º and the better wear resistance at 90º.
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