摘要
A needle valve is a key component of a diesel injector.The needle valve body of the diesel engine, made of R18CrNi8 steel, cracked and failed during the working process.The cracking failure reasons for the carburized injector valve body through chemical composition analysis, metallographic examination, scanning electron microscope(SEM) analysis, and energy spectrum analysis, were investigated.The results reveal that the original material of the needle valve is in conformity with the manufacturing requirement.Due to the high carburizing quenching temperature, the best carburized layer structure was not obtained, and the machining defect from which the crack emanated was not identified.The cracks expanded and eventually led to fracture under the action of altered stress and the high-temperature combustion environment during the operation of the engine.
