期刊
JOURNAL OF MATERIALS PROCESSING TECHNOLOGY
卷 277, 期 -, 页码 -出版社
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jmatprotec.2019.116420
关键词
Ultrasonic nanocrystal surface modification; AISI M4; Direct energy deposition; Residual stress; Roughness; Wear resistance
资金
- National Research Foundation of Korea (NRF) from the Ministry of Science and ICT [2017R1C1B5076047]
- Ministry of Trade, Industry and Energy (MOTIE)
- Korea Institute for Advancement of Technology (KIAT) through the European International RD Collaboration [G02P03040000701]
- Korea Evaluation Institute of Industrial Technology (KEIT) [P0005450] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
- National Research Foundation of Korea [2017R1C1B5076047] Funding Source: Korea Institute of Science & Technology Information (KISTI), National Science & Technology Information Service (NTIS)
Tensile residual stress in the laser-deposited M4 fabricated by direct energy deposition (DED) may reduce the fatigue performance and tool life. Ultrasonic nanocrystal surface modification (UNSM) can induce compressive residual stress by generating severe plastic deformation of the material surface, and improve the wear resistance through surface texture refinement. In the present study, we investigated the changes in the metallurgical and mechanical properties of DEDed M4 specimens as induced by UNSM treatment. An X-ray diffraction analysis showed that the DEDed M4 austenite was transformed into martensite after UNSM processing. The change in the full width at half maximum revealed a grain size decrease of 25.8%. Conversion of the tensile residual stress within the DEDed M4 to compressive residual stress through UNSM treatment was confirmed. These changes in the metallurgical characteristics yield a 24.1% increase in the DEDed M4 hardness. A wear test was conducted to evaluate the wear resistances of heat-treated D2, DEDed M4 on D2, and UNSM-DEDed specimens. Ball -on-disk wear tests revealed that the DEDed M4 specimen wear rate was 68.3% lower than that of the H-D2. In addition, the DEDed M4 wear rate was reduced by 85.7% through UNSM treatment. The surface roughness was reduced by up to 88.3%, while micro-dimple shapes were formed on the DED-treated M4 surface. This study has demonstrated that UNSM can be applied to a DED-treated M4 surface to enhance its metallic and mechanical properties.
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