1996 年 1996 巻 41 号 p. 1-5
We have investigated the influence of aging conditions on fatigue strength of titanium alloy and studied the wear resistant coatings for titanium alloy. Utilizing the results, we have developed the valve spring made of titanium alloy in order to increase engine speed and lighten engine weight.
The main results obtained are summarized as follows:
1) Tensile strength dependence of fatigue strength in Ti-13V-11Cr-3Al alloy is opposite to tensile strength dependence in steel.
2) Settling performance of Ti-13V-11Cr-3Al alloy is improved as increasing tensile strength, and settling performance is equivalent to steel with higher strength.
3) Ni-P electroless plating and Ni-P+Au-Ni electroless plating are excellent methods as wear resistant coating for titanium alloy.
4) Ti-13V-11Cr-3Al alloy springs with optimum tensile strength and coating by Ni-P electroless plating or Ni-P+Au-Ni electroless plating pass the motoring test.
5) Titanium alloy springs with optimum tensile strength and coating by Ni-P electroless plating or Ni-P+Au-Ni electroless plating in comparison with steel springs lead to a 13 percent decrease in free height and a 57 percent decrease in weight.