Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137
Costs are increasing due to the addition of alloying elements such as V, W, and Mo to prevent damage to Cr-Mo steel for fastening bolts, but field tests have shown that it is not an appropriate solution for improving physical properties through heat treatment. In this study, the characteristics of f...
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2024-12-01
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| author | Seung-Hoon Nahm Sang-Koo Jeon Dong-Kyun Kim Min-Soo Suh Chang-Min Suh |
| author_facet | Seung-Hoon Nahm Sang-Koo Jeon Dong-Kyun Kim Min-Soo Suh Chang-Min Suh |
| author_sort | Seung-Hoon Nahm |
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| description | Costs are increasing due to the addition of alloying elements such as V, W, and Mo to prevent damage to Cr-Mo steel for fastening bolts, but field tests have shown that it is not an appropriate solution for improving physical properties through heat treatment. In this study, the characteristics of fatigue cracks using Cr-Mo steel for fastening bolts before and after UNSM (ultrasonic nanocrystal surface modification) treatment were studied using fracture mechanics and fracture analysis methods. Specifically, using untreated and UNSM-treated materials: (1) the characteristics of small surface fatigue cracks existing on the surface, and (2) the surface fatigue cracks in the depth direction were observed and analyzed. The microstructure of Cr-Mo steel was refined by severe plastic deformation (SPD) from the surface to a depth of about 100 μm according to the static load of UNSM, and the fatigue limit increased by 30% as a large compressive residual stress was formed. Additionally, like the untreated materials, fisheye cracks did not occur in UNSM-treated materials, even when inclusions were present, and all specimens fractured while forming surface cracks. Accordingly, one or more of the multiple small surface fatigue cracks (MSFC) grew and developed into a major crack that determines the fatigue life, and a major ridge was formed among the many micro-ridges in the internal direction. In other words, this major crack grew and developed a major ridge in the internal direction, determining the lifespan of the test specimen. |
| format | Article |
| id | doaj-art-54cc4dee01a94b3982d30a893b1e6008 |
| institution | Kabale University |
| issn | 2073-4352 |
| language | English |
| publishDate | 2024-12-01 |
| publisher | MDPI AG |
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| spelling | doaj-art-54cc4dee01a94b3982d30a893b1e60082025-01-24T13:28:07ZengMDPI AGCrystals2073-43522024-12-011514510.3390/cryst15010045Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137Seung-Hoon Nahm0Sang-Koo Jeon1Dong-Kyun Kim2Min-Soo Suh3Chang-Min Suh4Korea Research Institute of Standards and Science, Daejeon 34113, Republic of KoreaKorea Research Institute of Standards and Science, Daejeon 34113, Republic of KoreaDT Task, LG Innotek, Seoul 07796, Republic of KoreaKyoto University, Kyoto 606-8501, JapanKyungpook National University, Daegu 41566, Republic of KoreaCosts are increasing due to the addition of alloying elements such as V, W, and Mo to prevent damage to Cr-Mo steel for fastening bolts, but field tests have shown that it is not an appropriate solution for improving physical properties through heat treatment. In this study, the characteristics of fatigue cracks using Cr-Mo steel for fastening bolts before and after UNSM (ultrasonic nanocrystal surface modification) treatment were studied using fracture mechanics and fracture analysis methods. Specifically, using untreated and UNSM-treated materials: (1) the characteristics of small surface fatigue cracks existing on the surface, and (2) the surface fatigue cracks in the depth direction were observed and analyzed. The microstructure of Cr-Mo steel was refined by severe plastic deformation (SPD) from the surface to a depth of about 100 μm according to the static load of UNSM, and the fatigue limit increased by 30% as a large compressive residual stress was formed. Additionally, like the untreated materials, fisheye cracks did not occur in UNSM-treated materials, even when inclusions were present, and all specimens fractured while forming surface cracks. Accordingly, one or more of the multiple small surface fatigue cracks (MSFC) grew and developed into a major crack that determines the fatigue life, and a major ridge was formed among the many micro-ridges in the internal direction. In other words, this major crack grew and developed a major ridge in the internal direction, determining the lifespan of the test specimen.https://www.mdpi.com/2073-4352/15/1/45ultrasonic nanocrystal surface modification (UNSM)compressive residual stressmultiple small surface fatigue cracksridgeCr-Mo steel |
| spellingShingle | Seung-Hoon Nahm Sang-Koo Jeon Dong-Kyun Kim Min-Soo Suh Chang-Min Suh Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 Crystals ultrasonic nanocrystal surface modification (UNSM) compressive residual stress multiple small surface fatigue cracks ridge Cr-Mo steel |
| title | Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 |
| title_full | Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 |
| title_fullStr | Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 |
| title_full_unstemmed | Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 |
| title_short | Small Surface Fatigue Crack Behaviors of Cr-Mo Steel AISI4137 |
| title_sort | small surface fatigue crack behaviors of cr mo steel aisi4137 |
| topic | ultrasonic nanocrystal surface modification (UNSM) compressive residual stress multiple small surface fatigue cracks ridge Cr-Mo steel |
| url | https://www.mdpi.com/2073-4352/15/1/45 |
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