| Abstract: |
The 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 the HVOF sprayed coatings for sliding applications, such as pistons of combustion engines, pumps and other hydraulic devices. In practice the producers and users of thermally sprayed coatings face the problem of the interaction of the coatings and their counterparts with presence of other media such as fuels, or in the case of sliding wear more often, the lubricants. In the paper, the friction properties of seven different HVOF sprayed coatings are evaluated by pin-on-disc test according to ASTM G-99 under dry and lubricated conditions and lubricated block-of-ring test according to ASTM G77. Several types of lubricants designed for combustion engines were used to compare their influence on coatings sliding wear behavior. Based on the results, the suitability of coatings for application on the engines parts is discussed and the effect of counterpart material and different types of lubricants on the coefficient of friction and coatings wear rate is analyzed. It was confirmed, that the CrC-based coating are more suitable for application in condition corresponding to combustion engines, e.g. elevated temperature and steel counterpart, than the WC-based coatings. From group of CrC-based coatings, the superior behavior was observed for CrC-CoNiCrAlY coating, which matrix material offers the further enhancement of sliding wear behavior.
|
|
