TRIBOLOGICAL PROPERTIES OF Al2O3 + TiO2 COATINGS MANUFACTURED BY PLASMA SPRAYING

Abstract

In the paper the results of tribological, microscopic, and mechanical research of Al2O3 + TiO2 coatings manufactured by plasma spraying are presented. The feeding material was a powder Al2O3 + 13 wt.% TiO2 (Metco 6221, OerlikonMetco) with grain size – 45 ± 15 μm. The cylinder substrates made from stainless steel (X5CrNi18-10) had a diameter equal to 25 mm and 2 mm of thickness. The variable spray parameters were plasma torch velocity in terms of substrate and spray distance. The morphology of obtained coatings was tested by scanning electron microscope (SEM), and the microstructure was investigated by light optical microscopy (LOM) and SEM. The results of mechanical properties examinations revealed the dependence of the microhardness and fracture toughness on the spray parameters. Tribological examinations were made in the ball-on-disc mode in technical dry friction conditions. Two loads were used, 5 N and 10 N. Based on the carried out tests, it could be concluded that a shorter spray distance and a reduction of the torch velocity allows one to achieve a more compact structure, which is characterized by good adhesion at the coating-substrate interface (in range from 11 to 14 MPa) and good wear resistance.