Influence Of Ultrasonic Shot Peening On The Microstructure Changes And Fatigue Properties In 2205 Duplex Stainless Steel

Because of the excellent excellent toughness and strength, the 2205 duplex stainless steel (DSS) has been widely used in chemical, petrochemical and petroteum industries and has been recognized as one kind of the most popular duplex stainless steels in the 21st century; meanwhile, with the development of mechanical industry, people put forward higher requirements on material performance. As a main form of surface strengthening treatment methods, shot peening can do promote the comprehensive performance of materials effectively. In this work, a 2205 duplex stainless steel has been treated by ultrasonic shot peening. The microstructural evolution was characterized by means of different techniques. The research contents and conclusions can be summarized as follows:(1) The 2205 duplex stainless steel was prepared using four different shot peening parameters(480N、360N、240N、120N) and the microstructure of the DSS were greatly influenced by applied forces. The results indicate that with the increase of forces, the micro-hardness and tensile strength increases gradually, elongation decreases.(2) Ultrasonic shot peening induced a’-martensite phase transformation, X-ray diffraction results show the maximum amount of a’-martensite was 40.1% obtained with the maximum force applied (480N) near the surface of specimens. α’-martensite is brittle phase can significantly improve the strength of 2205duplex stainless steel.(3) At high strain amplitude (△ε/t/2≥0.6%), the fatigue life of shot peening sample was lower than the life of as-received samples, at low stain amplitude (△εt/2≤0.4%), the fatigue life of shot peening sample was obviously superior than that of as-received samples. It’s also indicate that the nano-structured layer on the surface has high resistance to the fatigue-crack initiation and the interior coarse grain can retard the growth of the fatigue cracks, both of them improved the fatigue lives. At high strain amplitude, the crack initiation rapidly and the strength of nano-structure layer is not obvious.