Abrasive wear of plasma coatings with different structures on titanium alloys
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ABRASIVE WEAR OF PLASMA COATINGS WITH DIFFERENT STRUCTURES ON TITANIUM ALLOYS V. I. Pokhmurs’kyi, O. S. Kalakhan, I. Yu. Zavalii, H. H. Okhota, and R. V. Denys
UDC 620.172.186
We study the influence of plasma coatings having different structural and phase compositions on the serviceability of TS-5 titanium alloy under different kinds of abrasive wear. By means of Xray phase analysis, we have detected significant changes in the composition of plasma coatings in comparison with the initial composition of the powders, interphase interaction between the components of these coatings, and the formation of complex coatings with nonidentified phases. We have corroborated that the intensity of abrasive wear under conditions of nonrigidly fastened abrasive particles is lower. The greatest changes in the test chart take place in the case of abrasive wear of the plasma coating POAN-30. The highest abrasive resistance is characteristic of a plasma coating with complex titanium and chromium carbide.
To protect and repair titanium articles, it is customary to apply plasma coatings [1 – 3], the efficiency of which was investigated under conditions of fretting fatigue [4 – 7]. In the present work, we evaluate the serviceability of plasma coatings having different structural and phase compositions on titanium alloys under different kinds of abrasive wear. Materials and Testing Procedure We studied plasma coatings sprayed with powders of dispersivity 40 – 100 µm, which had been dried preliminarily at a temperature of 403 – 423 K for 2 h. In order to impart the necessary roughness to the surface and to take away the oxide film, we subjected the surface to abrasive blasting with electrocorundum with a grain size of 500 – 1000 µm. X-ray phase analysis was carried out on a DRON-3.0 diffractometer in CuKα-radiation, and the lattice parameters were computed by the Crystal Structure Determination (CSD) programs [8]. The microhardness of the surface of plasma sprayed coatings was measured on a PMT-3 instrument. We evaluated abrasive wear under conditions of a nonrigidly (sand feed into the zone of contact between the specimen and a rubber disk, GOST 23.208-79 [9]) or rigidly (an abrasive wheel) fastened abrasive [10]. Results and Analysis The heterogeneous structure of the coatings under study consists of discrete particles with more or less clearly pronounced interfaces (Fig. 1). The high heterogeneity of the coatings is attributable to different kinds of boundaries (intergranular, interphase, between deformed particles or layers, and between the coating and the base) as well as to additional phases formed in the course of spraying and solid solutions supersaturated with certain elements [11]. In addition, we observe a clearly pronounced interface. Comparative metallographic investigations of the structure of Karpenko Physicomechanical Institute, Ukrainian Academy of Sciences, Lviv. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 63 – 69, July – August, 2004. Original article submitted January 28, 2004. 504
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