Effects of Temperature on Wear Behavior of a Plasma Sprayed Diesel Engine Cylinder 2012-01-1335
One of the main subjects in automotive industries is to enhance the efficiency of internal combustion engines. Wear between cylinder and ring is one of the major parameters reducing the engine performance. So many parameters are affecting the wear losses. Temperature plays a key role on the severity of wear condition in internal combustion engines. In conventional cast iron cylinders, it is not possible to increase the temperature from a defined level, as it causes excessive wear in contact area between cylinder liner and piston ring. One of the major benefits of using ceramic coating is their ability to withstand in higher temperatures, while having adequate hardness to improve wear rate and reduces coefficient of friction. High temperature wear characteristics between plasma-sprayed cylinder liner and piston ring were investigated to find the optimum operating temperature, using a designed wear test stand in lubricated condition. A 150 microns single layer Al₂O₃ - 12 wt% TiO₂ plasma sprayed on gray cast iron substrate. Test is conducted with a test stand designed for this purpose which can simulate the real conditions including type of movement, temperature and lubrication, while using the cylindrical geometry of the cylinder liner and piston ring. The mechanism is a reciprocating piston ring on cylinder liner specimen which can control the temperature up to 300°C. Test specimens are cut from a cylinder bore and tested against a standard piston ring. Three sets of specimens are tested, in 250, 150 and 25°C. At each temperature wear rate of a coated specimen and an uncoated one are compared. Wear rate is determined by using a profilemeter for cylinder liner and optical microscope for the ring. Friction coefficient is monitored during the test, which is also important in investigation of wear characteristic. SEM (Scanning Electron Microscope) images obtained from the worn surface show that mild wear and polishing are major wear mechanism in this system. In higher temperatures results demonstrate difference between coated and uncoated condition, while coefficient of friction (COF) and wear rate have lower amplitude in ceramic-coated specimens. Using plasma spray ceramic coating shows improvement in the wear characteristic of cylinder liner.