| 摘要 |
PURPOSE: To achieve a lightweight engine valve wherein tenancy and ductility are good, abrasion resistance and adhesion resistance of the front surface are improved, the coefficient of dynamic friction between a valve stem part and a valve guide is drastically improved, and the friction loss is little. CONSTITUTION: TiAl radical alloy is taken as a material, which contains Al of 40 to 49atom%, Cr of 0.1 to 2.0atom%, Si of 0.03 to 0.8atom%, Nb of 0.1 to 6.5atom%, B of 0.01 to 0.03atom%, Mn of 0.1 to 4.0atom% residue Ti and impurities, and has the lamellar tissue constituted of a crystal phase having two or more phases in whichγphase (L10 type TiAl) andα2 phase (D019 type Ti3 Al) are mainly taken. The front surface of the valve stem part has amorphous made of nitride of at least Ti, Cr or a compound layer of the crystal phase, and the surface roughness of the valve stem part is the center line mean roughness (Ra), and 0.02μm or more and 1.0μm or less.
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