Author(s)

Š. Houdková, M. Kašparová & F. Zahálka

Abstract

The friction between a piston, piston rings and a cylinder is responsible for almost 55% of total power loss in engines. The decrease of friction in the piston area leads to a significant fuel saving and also to emission reduction. Application of a surface treatment, such as PEO, PVD, HVOF, plasma sprayed coatings, surface texturing, etc. on engine components is a way to reduce corrosion, friction, wear and weight of engines. In the paper, the potential of the application of HVOF sprayed coatings on the engine components is discussed with respect to their sliding friction properties. The technology of thermal spraying enables one to create the surface coating approximately 50 μm thick, which provides functional surface protection of the coated parts. HVOF technology offers the possibility of creating the coatings of materials based on the principle of hardmetals with high wear resistance and favourable sliding properties. Such a combination predestinates HVOF sprayed coatings for sliding applications, such as pistons of combustion engines, pumps and other hydraulic devices. In this application area they are used on a regular basis. In practice, the producers and users of thermally sprayed coatings face the problem of the interaction of the coatings and their counterparts with the presence of other media, fuels, or, in the case of sliding wear more often, lubricants. The paper describes the methodology of measurement suitable for lubricated HVOF coatings using the pin-on-disc test according to ASTM G-99 and on the evaluation of the influence of lubricants on the friction properties, wear rate and mechanism of HVOF sprayed coatings. The pin-on-disc test according to ASTM G-99 was performed on the thermally sprayed Cr3C2-25%NiCr coating to determine and describe their sliding wear behaviour under different test conditions. The influence of various test parameters (load, wear track diameter, temperature, lubrication, counterpart

Keywords

HVOF, coating, sliding friction, ASTM G-99, pin-on-disc