WEAR AND WEAR MECHANISM SIMULATION OF HEAVY-DUTY ENGINE INTAKE VALVE AND SEAT INSERTS

A silicon-chromium alloy frequently used for heavy-duty diesel engine intake valves was tested against eight different insert materials with a valve seat wear simulator, Wear resistance of these combinations wa s ranked, For each test, the valve seat temperature was controlled at approximately 510 degrees C, the number of cycles was 864,000 (or 24 h ), and the test load was 17,640 N, The combination of the silicon-chro mium valve against a cast iron insert produced the least valve seat we ar, whereas a cobalt-base alloy insert produced the highest valve seat wear, In the overall valve seat recession ranking, however, the combi nation of the silicon-chromium valve and an iron-base chromium-nickel alloy insert had the least total seat recession, whereas the silicon-c hromium valve against cobalt-base alloy, cast iron, and nickel-base al loy inserts had significant seat recession, Hardness and microstructur e compatibility of valve and insert materials are believed to be signi ficant factors in reducing valve and insert wear. The test results ind icate that the mechanisms of valve seat and insert wear are a complex combination of adhesion and plastic deformation, Adhesion was confirme d by material transfer, while plastic deformation was verified by shea r strain (or radial flow) and abrasion, The oxide films formed during testing also played a significant role, They prevented direct metal-to -metal contact and reduced the coefficient of friction on seat surface s, thereby reducing adhesive and deformation-controlled wear.