Abstract
Cr–Mo steel and Ni–Cr–Mo steel have higher strength and hardness than carbon steel, and they are occasionally used in harsh environments where high temperatures and high pressures are simultaneously applied in an oxidizing gas atmosphere. In general, in order to improve the fatigue strength of a material, it is important to impart compressive residual stress to the material surface to improve crack resistance and corrosion resistance. Conventionally, the most famous technique for imparting compressive residual stress by surface modification of a material is shot peening processing. However, in shot peening processing, there is concern that particles adhere to the surface of the material or the surface of the material becomes rough. Therefore, in this study high temperature and high-pressure cavitation was applied and the material surface was processed at the time of collapse. A theoretical and experimental study on a new processing method giving compressive residual stress was carried out. In the present study, we will report stress relaxation behavior due to the heat of cavitation in processed Cr–Mo steel and Ni–Cr–Mo steel.
Highlights
Cr–Mo steel and Ni–Cr–Mo steel refer to steel having a total of alloying elements of about 5% or less, including chromium molybdenum steel, molybdenum steel, high tensile strength steel, weathering steel, fireproof steel, and low-temperature steel
Experimental study on stress relaxation behavior due to heat of low alloy steels subjected to high-temperature and high-pressure cavitation (MFC) processing revealed the following: (1) Both Cr–Mo steel (SCM435) and SNCM 630 (Ni–Cr–Mo steel) showed higher values of initial compressive residual stress in MFC-worked material compared to WJC-processed material
(2) In the stress relaxation test, under heat treatment at 500 ◦ C for 5 h, the stress was not sufficiently relaxed and the state in which the compressive residual stress was imparted was maintained, but at 1000 ◦ C it relaxed in about 5 min
Summary
Cr–Mo steel and Ni–Cr–Mo steel refer to steel having a total of alloying elements of about 5% or less, including chromium molybdenum steel, molybdenum steel, high tensile strength steel, weathering steel, fireproof steel, and low-temperature steel. Applications of Cr–Mo steel include automobile clutches and flywheel parts, and applications of Ni–Cr–Mo steel include aircraft parts and engine parts Since these parts are sometimes used in an environment exposed to high temperature, the measurement results of temperature dependence become important. It is considered important for improving the crack resistance and corrosion resistance to impart compressive residual stress to the surface of the material as a method for improving the fatigue strength of the metallic material [1,2]. Ultrasonic waves were irradiated to cavitations (bubbles) generated by injecting
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