Erosive Wear Study of Rare Earth-Modified HVOF-Sprayed Coatings Using Design of Experiment
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atpal Sharma (Submitted April 22, 2011; in revised form July 16, 2011) In the present study, the effect of CeO2 addition in 1006 powder coatings on microstructure, microhardness, and high-temperature erosion resistance were studied. The CeO2 addition refines microstructure, forms new phases, and increases microhardness of HVOF-sprayed coatings. The erosive wear behavior of coatings were investigated by Response Surface Methodology (RSM). To investigate and develop an erosive wear model of unmodified 1006 (without CeO2) and modified 1006 (CeO2 addition) coatings four factors: velocity, impact angle, temperature, and feed rate, each factor at three levels were used. ANOVA was carried out to determine the significant factors and interactions. Thus, an erosive wear model was developed in terms of main factors and their significant interactions. A comparison of modeled and experimental results showed 4-7% error. The modified 1006 coating showed high erosive wear resistance as compared with unmodified 1006 coating. This is due to increase in hardness and refined microstructure of the modified 1006 coating.
Keywords
ceria, design of experiment, erosion resistant coating, HVOF, microhardness
1. Introduction Surface coatings are one of the cost-effective approaches against surface degradation of various engineering components. Weld surfacing, laser cladding, plasma spraying, flame spraying, and high-velocity oxyfuel (HVOF) spraying are the various techniques used for coating deposition but HVOF spraying has often been used to form dense, adherent and homogeneous coatings to protect critical components from wear, corrosion and oxidation in many industrial applications (Ref 1-3). But because of the inhomogeneous and particulate nature of the deposition material, erosion or erosion/corrosion may occur, and it is therefore important to understand the erosion resistance of HVOF coatings if they are to be used in high-temperature environments (Ref 2). This is because the tribological characteristics of such coatings differ significantly from that of the bulk materials (Ref 4). Erosion is a serious problem in many engineering systems, including steam and jet turbines, pipelines, and valves used in slurry transportation of matter, and fluidized bed combustion systems (Ref 5). Cobalt-based alloys are exceptionally good for application requiring resistance
Satpal Sharma, Gautam Buddha University, Greater Noida 201310, UP, India. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
to hot corrosion, erosion, cavitations, and wear (Ref 6-8). Various researchers (Ref 9-12) studied the room- and high-temperature erosion behaviors of WC-Co, and Co-Ni matrix containing WC deposited by various processes without any modification with rare-earth elements. Wang and coworkers (Ref 13-18) were the first to introduce the application of rare-earth elements to improve wear and corrosion resistance of various types of coatings. Various studies (Ref 13-19) have shown that the addition of rare-earth elements (CeO2, La2O3,
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