PURPOSE: To obtain an iron-base sintered gear with enhanced fatigue resistance in the range where cracks occur and raised service limit surface pressure by hardening and tempering a selected material to form austenite phase in the surface and martensite phase in the interior.
CONSTITUTION: A material forming austenite phase in the surface by hardening such as Fe-8Ni-0.45Mo-0.15Mn alloy is selected, and a sintered body of the material is manufactured. The sintered body is oil hardened from about 860°C and tempered at about 180°C. By the treatment austenite phase having 0.02W 0.3mm depth is formed in the surface to improve the fittability, and the internal structure is converted into martensite phase, resulting in enhanced fatigue resistance in the range where cracks causing pitting occur. Thus, an iron-base sintered gear with raised service limit surface pressure is obtd.
HAYASAKA TADAO
TOKITANI MITSUOKI
WATANABE HISAKAME
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