Task of a valve which is used in internal combustion engines is basically to help charge fresh air into combustion chamber and discharge mixture of fired fuel and air out of engine. Valve is one of the most critical parts in engine because they stand extreme temperatures, pressures and hitting impact. Because temperature which intake and exhaust valves stand is different from each other; different materials, structure and manufacturing methods are implemented on each valve. Manufacturing of the valves includes various methods such as forging, machining, welding, nitriding, coating etc.
This paper explains alternative engine valve manufacturing methods, critical parameters for each manufacturing stage, potential failure modes and some corrective actions which can be taken. During study, various methods which are alternative of each other to produce engine valves were tried. Advantages & disadvantages, difficulties, failure modes and best way to correct them are recorded. To understand impact of critical process parameters on valve quality such as temperature, time, layer thickness for nitriding, work rest blade slope angle and material for centerless grinding, seat angle for seat wear etc. many tested valves were inspected to find valve's surface defects under magnifier glasses and to understand valve's micro structure under microscope.
See papers presented at SAE World Congress & Exhibition, April 2009, Detroit, MI, USA, Session: Reliability and Robust Design in Automotive Engineering: Reliability-Based Design Optimization and Robustness
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