Fatigue properties of inertia dissimilar friction-welded stainless steels

Due to economical and technical advantages in friction welding application, heat-resisting and anti-corrosive materials are widely used in the industrial production fields of the mechanical components such as gas turbines, engines, nuclear power plants, automobile industry, and so on. The objective of this paper is to study fatigue characteristics on dissimilar friction welding zone according to defect positions. In order to achieve the objective, dissimilar steels commonly used as valve materials for vehicle were friction welded. And a small circular defect was precisely worked on weld interface, 0.5 and 1.0 mm distance away from the interface, respectively, to closely analyze the welding zone. Fatigue limits of STR3 and STR35 base metal were 429.0 and 409.4 MPa, respectively. In comparison with fatigue lives on the basis of the same defect positions, fatigue life of the STR35 was about 190% for base metal specimen, about 82% for 1.0 mm HAZ specimen. It was higher than that of the STR3. But in case of 0.5 mm defect position, the STR35 showed about 35% lower fatigue life than that of STR3. And the fatigue life of STR3 was about 99% for 1.0 mm HAZ and 640% for 0.5 mm HAZ. It was higher than that of base metal. And fatigue life of STR35 was about 25% for 1.0 mm HAZ and 82% for 0.5 mm HAZ. It indicates that the nearer weld interface, the higher fatigue life. But the weld interface notched specimen had much lower fatigue life than the other specimens because of appearance of the interface separation.