Interface Microstructure and Tribological Properties of Flame Spraying NiCr/La 2 O 3 Coatings
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Zhenyu Zhang, Bunv Liang, and Hongjian Guo (Submitted April 14, 2014; in revised form August 18, 2014) NiCr alloy coatings with 0.5, 1.0, 1.5 and 2.0 wt.% of La2O3 were deposited on 1045 carbon steel by a flame spraying and melting processing. Interface microstructure investigations of the coating/substrate systems were conducted by field emission gun scanning electron microscopy, with attached energy dispersive spectroscopy. The effect of La2O3 addition on the tribological properties of the coatings was investigated under dry sliding wear conditions. The result showed that the microstructure of the NiCr alloy coatings are refined with proper amounts of La2O3, and the microhardness and wear resistance of the coatings show best enhancement with 1.0% La2O3.
Keywords
interface, lanthanum oxide, NiCr alloy, tribological properties, wear resistance
1. Introduction The addition of rare earth elements (RE) in metal materials has multi-functions, such as purification, modification and alloying, and thus can improve a series of properties of metal materials to different extents, for example, in metallurgy, casting, heat processing, and mechanical properties (toughness and low-temperature brittleness) (Ref 1-4). Rare earth elements and their compounds have been broadly used to modify the solidification process and microstructure of various coatings, decrease the melting point of alloys and form rich compound in eutectic structure, showing refining and purifying effects (Ref 5-8). So far, some commonly used RE elements and compounds have been doped into various surface protective materials through a variety of surface processing
Zhenyu Zhang and Bunv Liang, Department of Material Engineering, Lanzhou Institute of Technology, Lanzhou 730050, Gansu, China; and Hongjian Guo, State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730050, China. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
techniques. Much attention has been paid to the improvement of the surface properties of various working components by RE, which is of significance in engineering to combat wear, corrosion, and oxidation of surface engineering components in harsh environments, e.g., at elevated temperatures (Ref 9-12). An area of current interest is the modification of RE to surface engineering, such as Ni-based alloy coatings (Ref 4, 10). China has plenty of RE resources, and applying RE to the materials surface engineering is a very important aspect of expanding the application field of RE. However, there is still little published work on the modification effects of RE oxide La2O3 in thermal spraying and remelting of coatings. In this paper, the effects of RE oxide La2O3 on the microstructure and tribological behaviors of flame spraying and melting NiCr alloy composite coatings on carbon steel is studied so as to offer an experimental basis to expand a new promising field of RE.
2. Experimental The 1045 carbon steel was used as the substrate material. The substrate
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