Comparison of chemical composition and wear of iron and nickel aluminide coatings applied by plasma spraying

Abstract

Given such properties as wear resistance, corrosion resistance, heat resistance, contact and cyclic strength, iron and nickel aluminides can be used as coatings in friction pairs for various purposes. The object of research is the process of obtaining plasma-sprayed coatings from powders based on iron and nickel aluminides. The task of research is the determination and comparison of the structure, chemical composition, and wear resistance of coatings from powders of iron aluminide and nickel aluminide, obtained by the method of atmospheric plasma spraying. To reduce the oxidation of powders during spraying, the conditions for generating a laminar plasma jet were created. Such conditions were provided by the specially developed structure of the electric arc plasma gun and the operating parameters of coating spraying. As a result of the correct choice of spraying modes, completely melted splats were formed during the collision of powder particles with the surface. The resulting coatings had a layered microstructure with microcracks and peeling. The porosity and characteristics of the delamination of the coatings depend on both the modes and the spraying technology. Tribological tests of the coatings were carried out under conditions of dry metal-on-metal sliding friction in a pair with high-speed steel. It is shown that the wear of nickel aluminide coatings under these conditions is 2–2.5 times lower than that of iron aluminide coatings. The coefficient of friction of iron aluminide coatings is slightly lower than that of nickel aluminide coatings. The wear of samples made of 30CrMnSi steel is 3–4 times higher than samples with coatings. The difference in the wear of the coatings is explained by the more intense oxidation of iron aluminide in the friction process. Conclusions were drawn regarding the possibility of using the investigated coatings in various friction pairs of structural elements, in particular in the automotive industry