Investigation of effect of boron doped coating on piston ring-cylinder liner pair surface to engine friction losses

Performance losses of internal combustion engine are mostly due to mechanical losses. The most important part of these losses is friction losses which are composed by friction component inside the engine. Friction losses composed inside the engine effect the engine performance and fuel economy negatively.Nowadays, material coating methods are improving continuously. In piston ring applications, traditional electrochemical chrome coating method which is used widely replaces different coating methods. These coating methods are CVD, PVD, atmospheric plasma and HVOF. The most important features of the coating applications are their applicability to materials having high resistant of wear and solid lubricant.In this study the die cast piston rings were coated with NiCrBSi and WC- NiCrBSi powders by HVOF method. These coatings were compared with electrochemical chrome coating in terms of wear and friction performance. All coatings were reproduced. First, friction coefficient of all coatings were determined in wear test bench and then wear rate were compared each other. All experiments were applied under different temperatures, loads and speeds conditions. After friction and wear tests the engine tests were done. The coated piston rings were assembled to a SI engine and the friction losses of the test engine were measured under different temperature and speeds. At last, optimum tests conditions and efficient factors were determined for all tests by applying Taguchi design method.