Abstract
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Abstract
Engine valve and seat insert wear is one of the most important factors affecting engine performance. The engine valve and seat insert must be able to withstand the severe environment that is created by: high temperature exhaust gases generated while the engine is running, rapid movement of the valve spring, high pressure generated in the explosive process, and cylinder head distortion due to the non-uniform cooling system. In order to overcome such problems, a simulator has been developed to generate and control high temperatures and various speeds during motion. The wear simulator is considered to be a valid simulation of the engine valve and seat insert wear process with various speeds during engine activity. This work focuses on the various degrees of wear of four different test valve materials (STR 35, STL #6, STL #32, FNV (face nitrided valve)). Throughout all tests performed in this study, the outer surface temperature of the seat insert was controlled at 350℃, the test load was 1960N, and the seat insert material was HVS1-2. The mean (± Standard Deviation) wear depth of the valve and seat insert at STR 35 was 31.8 (±1.3)㎛ and 44.3 (±3.3)㎛, respectively. The mean (± Standard Deviation) wear depth of FNV (face nitrided valve) and seat insert was 14.0 (±2.2)㎛ and 56.0 (±2.1)㎛, respectively. The mean (± Standard Deviation) wear depth of the valve and seat insert at STL #6 was 25.8 (±4.7)㎛ and 46.7 (±3.0)㎛, respectively. The mean (± Standard Deviation) wear depth of the valve and seat insert at STL #32 was 8.5 (±2.0)㎛ and 54.7 (±1.9)㎛, respectively. It was discovered that under ideal test conditions (temperature, valve displacement, cycle number, test load, seat insert material), the valve with a FNV or STL deposited face had a greater degree of wear resistance than the general type valve (STR 35 type). It was also found that among the STL deposited valve faces, the STL #32 having a higher hardness, and higher wear resistance than STL #6. However, the higher the valve surface hardness, the greater the seat insert wear. For this reason, the valve material must be developed in accompanied with the seat insert as counter material. Adhesive wear, shear strain and abrasive wear could all be observed in the wear mechanisms of valves.