| 摘要 |
<p>This invention provides an inlet or exhaust valve for internal combustion engines, which satisfies the requirements of light weight, heat resistance, and durability. The engine valve comprises a columnar shaft 2 and conical face 3 which is continuously formed from the said shaft part. The shaft 2 and face 3 are made of titanium aluminide, and the shaft 2 is coated with TiN 8, the face 3 is coated with Ni alloy 7, and the shaft end is covered with the steel cap 8. The titanium aluminide structuring of the shaft 2 and face 3 is preferably a TiAl intermetallic compound formed by a reaction sintering process comprising, a. mixing Ti powder of 150 mu m or less particle size with AlMn powder of 150 mu m or less particle size to form a composition of (in mass %) : Al 32 - 35 %, Mn and/or Cr 2 - 3 % remainder Ti and unavoidable impurities, b. forming said mixture into a compressed powder body by a CIP ( cold isostatic pressing) process, c. sealing said compressed powder body into an Al-can and degassing it, d. processing the body in a hot press to prepare a billet of 100 % filling factor (measured by weight to volume), e. extruding said billet and cutting it to a designated form, f. forging it into a preform of a shape of an inlet or exhaust valve g. processing said preform by a HIP (hot isostatic pressing) process to conduct reactive sintering, h. machining said preform to obtain a base body having the valve shape, i. forming a concave into the conical face of said base body, j. flame coating of Ni-alloy on the concave k. machining the excess build up into a smooth surface to form a Ni-alloy coating layer, l. fixing a steel cap onto the shaft end, m. coating TiN on the surface of said shaft by ion plating. <IMAGE></p> |
