Study On Wear Resistant Coatingsand Wear Mechanism Applied In Automobile Piston Ring

Piston ring and cylinder liner is the most important pairs in internal combustionengine. This pair, especially the piston ring, suffered the severest wear with thetechnology development in the automotive industry. In recent years, thermal sprayingtechnology showed a good prospect in the application of wear resistant coating ofpiston ring.The intention of the study was to optimize the composite coating prepared byblended powder using the method of mixture design. A ring-block tribotester and SRVhigh temperature tribotester was used to characterize the friction coefficient, wear lossof the coating and counterpart, which was made of boron-containing cast iron.Furthermore, the wear mechanism of the coating was discussed by analysing themorphology and composition of the worn surface.The composite powder of Mo-（NiCr-Cr3C2） was mechanically blended anddeposited using atmospheric plasma spraying. The mechanical property andtribological performance of the prepared coating were tested. The results showed thatthe mechanical property and tribological property were markedly affected by the Mocontent. The coating with the addition of20wt.%（mass fraction）Mo, which had thehighest hardness modulus ratio （H/E）, presented better performance in bothmechanical property and tribological property.The composite coating including of TiO₂-Cr₂O₃, Mo-NiCrBSiFe and Mo-Cr₂O₃were sdudied, preliminarily the results indicated that the TiO₂and73TiO₂-27Cr₂O₃coating showed lower friction coefficient. This phenomenon might be related with theMagnéli phase generated in the process of plasma spraying. In addition, theoptimization of the coating was carried out by mixture design using a software nameddesign expert. Twenty series of composite coating, mainly made up ofmulticomponent ceramic powder containing TiO₂, Cr₂O₃, NiCrBSiFe and C-Ni, wasinvestigated using SRV tribotester. The regression analysis was made. Thetribological properties of the coating demonstrated that there was a linear relationshipbetween the friction coefficient, mass loss of the counterpart and the coatingcomponent. The mass loss of coating had a special cubic function with the coating component. With the help of prediction by Design expert, the tribological propertiesof the composite coating seemed better with the following constraint exist,TiO₂=63.5wt%, Cr₂O₃=20wt%, NiCrBSiFe=5.7wt%, C-Ni=10.8wt%.The study on wear mechanism illustrated that, plasma sprayed Mo-（NiCr-Cr3C2）composite coating mainly endured abrasive wear and slightly adhesive wear. Thecoating containing large fraction of NiCr-Cr3C2was prone to be flaked during thewear and suffered severe abrasive wear. For multi-component composite coating, themain wear mechanism was abrasive wear.