Analysis of the Mechanical Properties of an Arc Sprayed WC-FeCSiMn Coating: Compression, Bending, and Tension Behavior
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W. Tillmann and J. Nebel (Submitted April 29, 2010; in revised form September 12, 2010) This paper is concerned with the elastic and plastic forming behavior of arc sprayed WC-FeCSiMn coatings. The mechanical properties were investigated by indentation, bending, and tensile tests. These were performed on coated mild steel substrates as well as spark eroded and ground freestanding coatings with different geometries. The results of the indentation, bending, and tensile tests were evaluated concerning the coating microstructure, element, and pore distribution, as well as the local microhardness. The critical role of pores and inhomogeneities within the sprayed coating was examined in detail. Microand macrocracking were investigated by scanning electron microscopy after the indentation and tensile tests. It was figured out that the WC-FeCSiMn coating featured a distinctive brittle behavior. During the bending and tension tests, brittle forced fracture of the layer appeared almost without plastic deformations. A significant difference was determined between the compression and tensile performance of the coating. For instance, the YoungÕs modulus for compression strains was measured to be approximately 60% higher than the tension case.
Keywords
arc spraying, bending test, hardness, nanoindentation, porosity, tensile test
1. Introduction Because of their high hardness and toughness, WC-based cermet coatings have been used for wearresistance applications for many decades. Milling heads, crushers, and conveyor systems in the construction, stone, agriculture, and waste disposal industries are typical examples that have been improved by this kind of coating (Ref 1-4). Correlating with the industrial acceptance of WC cermet coatings the application areas are currently continuously expanding. New devices such as landing gears, hydraulic seals, or cylinder surfaces in high-pressure applications characteristically show a higher tribological complexity and require advanced accuracy and reliability (Ref 3, 5). In particular, features such as stiffness, strength, This article is an invited paper selected from presentations at the 2010 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray: Global Solutions for Future Applications, Proceedings of the 2010 International Thermal Spray Conference, Singapore, May 3-5, 2010, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2011. W. Tillmann and J. Nebel, Institute of Materials Engineering, TU Dortmund, Dortmund, Germany. Contact e-mails: jan. [email protected] and [email protected].
Journal of Thermal Spray Technology
and crack resistance of the coating are of particular interest (Ref 6). However, the identification of these mechanical coating properties such as hardness, bending strength, fracture toughness, and YoungÕs modulus are challenging because of the inhomogeneity and anisot
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