| 摘要 |
PROBLEM TO BE SOLVED: To improve the strength and abrasion resistance of the valve made of titanium alloy, which consists of shaft and ambrella shaped part, by foring an oxidized layer on the surface of some areas contacting with other valve driving elements, and also by forming a carbonized layer on the surface of valve where the abrasion resistance and fatigue strength are required. SOLUTION: Some areas of the valve 3 which is made of Ti-Al group alloy, consists of shaft 1 and ambrella shaped part 2 thereunder, are required to have high abrasion resistance and fatigue strength, therefore, oxidized layers 4 containing TiO2 with the thickness of approximately 10-15μm are formed on the surface of those areas such as valve face 5 contacting with valve seat, middle part 6 of shaft 1 sliding on the valve guide, annular groove 7 contacting with cotter and end surface of shaft 8 contacting with rocker arm or tappet. The environmental layers between oxidized layers and valve element material are formed by needle crystal. Carbonized layer including TiC with the thickness of approximately 3-5μm are formed on the whole surface of valve element by carbonizing treatment.
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