高強度マルテンサイト系ステンレス鋼のガソリン燃料浸漬下における疲労強度特性

抄録

In recent years, materials used in automobile engines are required to be used in harsh environments, and there is concern that the material strength will be lowered due to corrosion caused by deteriorated fuel and increase in pressure. Therefore, this study conducts the fatigue test in the same environment as actual condition. The test uses type 440C martensitic stainless steel under corrosive atmospheric environment which is used as a part of automobile engine. However, this type of testing machine had not been available in past. Therefore, a small sized tension and compression fatigue testing machine for fatigue tests under corrosive and air environments were developed. In addition, this study established tension and compression fatigue testing method. This machine can also carry out the tests using a small sized specimen in flammable liquid, and allows testing at high frequencies. Then, the fatigue strengths in air, regular petrol, and deteriorated petrol conditions were compared to examine the effect of corrosion. The fatigue life in the regular petrol was almost equivalent to that in the air environment regardless of the stress amplitude. However, in the deteriorated petrol environment, the fatigue life was largely reduced compared to former two conditions which will be discussed from the fracture surface morphology.