Measurement of Internal Residual Stress of Three-Directional Components and Estimation of Inherent Strain in Carburized Steel for Large Rolling Bearings by Combining the Contour Method and XRD Method

• Published in: MATERIALS TRANSACTIONS Vol. 65; no. 9; pp. 1099 - 1107
• Main Authors: Ma, Ninshu, Watanuki, Daisuke, Yamagami, Shota, Tsutsumi, Masako, Miyamoto, Yuji, Narasaki, Kunio
• Format: Journal Article
• Language: English
• Published: Sendai The Japan Institute of Metals and Materials 01.09.2024; Japan Science and Technology Agency
• Subjects: Carbon content; carburized steel; Carburizing; Compressive properties; contour method; Contour rolling; Cooling rate; Elastic analysis; heat treatment; inherent strain; internal residual stress; Martensitic transformations; Nickel chromium molybdenum steels; Residual stress; Roller bearings; rolling bearing; Strain analysis; Strain distribution; Tensile stress; X-ray diffraction
• ISSN: 1345-9678; 1347-5320
• DOI: 10.2320/matertrans.MT-Z2024009

To predict the failure of mechanical parts, it is necessary to understand the residual stress and its source, i.e., inherent strain. In this study, the distribution of three-directional residual stress components in a carburized 18NiCrMo14-6 cylindrical roller test piece with a diameter of 80 mm and length of 240 mm, was measured using the extended contour method (XCM), which combines the contour method and X-ray diffraction. Thereafter, an inverse analysis was applied to the measured residual stress to reproduce the associated inherent strain distribution. First, it was shown through numerical experiments of a carburized cylindrical specimen that the distribution of the three-directional residual stress components can be accurately reproduced using XCM. Next, it was demonstrated that the distribution of the three-directional residual stress components could be obtained using general-purpose equipment by physically measuring the same type of specimen. The inherent strain distributions were evaluated. Compressive residual stress and corresponding tensile inherent strain were detected in the carburized layer. By contrast, tensile stress and inherent contraction strain were determined in the non-carburized layer just before the carburized crust. Finally, the mechanism of inherent strain generation was investigated using a thermal–elastic–plastic analysis. Possible explanations include (i) increase in transformation strain due to a change in carbon content, (ii) delay in martensitic transformation, and (iii) decrease in the martensitic transformation rate due to a decrease in the cooling rate at the core. This Paper was Originally Published in Japanese in J. Soc. Mater. Sci., Japan 72 (2023) 550–557. The abstract, the captions of Figs. 2, 4–9, 11–14, and the section 4.3 are slightly modified.