The Wear Behavior of HVOF Sprayed Near-Nanostructured WC-17%Ni(80/20)Cr Coatings in Dry and Slurry Wear Conditions
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JMEPEG DOI: 10.1007/s11665-017-2739-y
The Wear Behavior of HVOF Sprayed Near-Nanostructured WC-17%Ni(80/20)Cr Coatings in Dry and Slurry Wear Conditions Tarek A. Ben Mahmud, Anas M. Atieh, and Tahir I. Khan (Submitted September 8, 2016; in revised form April 10, 2017) The ability to deposit nanostructured feedstock by using high-velocity oxygen-fuel (HVOF) spray offers potential improvements in coating hardness, wear resistance and toughness for applications in the oil sands industry. In this study, the wear behavior of a near-nanostructured coating was compared under dry and slurry abrasive wear test using an uncoated AISI-1018 low-carbon steel substrate as a reference. The coating microstructures were analyzed in the as-sprayed, dry and slurry test conditions using scanning electron microscopy, x-ray diffraction and microhardness measurements. Wear behavior of the steel and coating surfaces were assessed using a pin-on-plate wear test under various loads. The results showed that a coating could be successfully deposited using the HVOF spraying technique and with retention of the nearnanosized WC dispersion within the coating structure. The wear rate under dry test conditions was greater for the steel and coating compared to tests performed under slurry conditions. Examination of the wear tracks revealed that the wear mechanism was different for the two test conditions. Wear in the dry test condition resulted from 2-body abrasion, while 3-body abrasion dominated wear in slurry conditions. The latter showed lower wear rates due to a lubricating effect of the oil. Keywords
cermet coatings, HVOF thermal spraying, near-nanostructured WC-17NiCr powder, pin-on-plate sliding wear
1. Introduction Abrasive and erosive wear is the most common process causing failure of engineering components used in the oil sands industry (Ref 1-3). In order to prevent this form of surface degradation, various heat treatments and surface coatings techniques are being explored (Ref 4-7). Surface protection by depositing a hard coating onto surfaces by thermal spraying techniques such as high-velocity oxygen-fuel (HVOF) thermal spraying has been successfully developed for various industrial applications (Ref 8-13). HVOF spraying can be used to deposit cermet-based coatings (Ref 1, 10, 11, 14). The HVOF technique is capable of producing better properties (compared to other coating techniques), those properties include dense coatings with high hardness and superior wear resistance, and hence, HVOF spraying has considerable potential for applications in abrasive/erosive environments (Ref 9, 15). Further-
more, the HVOF spraying process has been used to produce nanostructured coatings by different researchers (Ref 16-20), however, retention of the nanosized WC particles in the sprayed coatings was not achieved and decarburization often resulted in a brittle W2C phase forming in the coating. This resulted in the nanostructured coating having lower hardness and poor wear resistance compared to microstructured coatings of the same composition. Fu
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