| GAO Yu-long,MA Guo-liang,GAO Xiao-hua,CUI Hong-zhi.Microstructure and Wear Resistance of CoCrNiMnTix High-entropy Alloy Coating by Laser Cladding[J],51(9):351-358, 370 |
| Microstructure and Wear Resistance of CoCrNiMnTix High-entropy Alloy Coating by Laser Cladding |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.09.037 |
| KeyWord:laser cladding high-entropy alloy microstructure wear resistance surface strengthening |
| Author | Institution |
| GAO Yu-long |
CRRC Qingdao Sifang Co., Ltd., Shandong Qingdao , China |
| MA Guo-liang |
School of Materials Science and Engineering,Shandong University of Science and Technology, Shandong Qingdao , China |
| GAO Xiao-hua |
School of Materials Science and Engineering,Shandong University of Science and Technology, Shandong Qingdao , China |
| CUI Hong-zhi |
School of Materials Science and Engineering,Shandong University of Science and Technology, Shandong Qingdao , China;School of Materials Science and Engineering, Ocean University of China, Shandong Qingdao , China |
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| Abstract: |
| For the key parts of high-speed and strong wear such as high-speed rail brake discs, CoCrNiMnTix high-entropy alloy coating by laser cladding was designed to improve the hardness and wear resistance of the surface. The CoCrNiMnTix (x=0, 0.25, 0.5, 0.75, 1) high-entropy alloy coating was prepared on the surface of Q235 steel by laser cladding technology, and the microstructure of the coating was characterized by XRD and SEM. The hardness of the coating was tested by a microhardness tester and a nanoindenter. The friction-abrasion testing machine and the three-dimensional profiler were used to study the friction-abrasion performance of the coating. The CoCrNiMnTix coating prepared by laser cladding technology had good coating quality and no defects such as pores or cracks. It is found that in the CoCrNiMnTix coating by laser cladding, with the increase of Ti content, the coating phase changes from a single FCC phase to FCC+Laves phase, and the diffraction peak of FCC solid solution gradually shifted to the left. The microstructure of the CoCrNiMn coating is columnar crystals. When the Ti content is 0.25, it transforms into equiaxed crystals; when the Ti content is higher than 0.5, Laves phase and eutectic structure appear in the intergranular region. Under the dilution effect of the laser cladding, the Fe on the surface of the Q235 substrate diffuses into the coating, and the Fe elements enrich. The inside of the crystal grain is the FCC matrix phase, and the intergranular area is the (Co,Fe)2Ti Laves phase. Due to the solid solution strengthening and the increase of the Laves phase content, the microhardness of the coating continues to increase. The hardness of CoCrMnNiTi reaches 523HV0.1, and the highest nanohardness reaches 6.91 GPa. CoCrNiMnTix-based coatings have similar elastic modulus. With the increase of Ti content, the wear resistance of the coating shows a rising trend. As the Ti content increases, the average friction coefficient of the coating decreases, and it is the lowest at Ti0.75. According to the analysis of wear volume and wear scar morphology, when the Ti content is 0.75, it has the lowest wear volume, and the width and depth of the wear scar are the lowest, showing the best wear resistance. However, when the Ti content further increases, due to the brittle and hard Laves phase gradually increases. the wear form gradually changes from adhesive wear with low Ti content to abrasive wear with high Ti content, which reduces the wear resistance of the coating. CoCrMnNiTix coating by laser cladding can significantly improve the wear resistance of the substrate. When the Ti content is added to 0.75, a small amount of Laves phase is formed in the FCC substrate, which not only improves the hardness, but also achieves a strong and tough fit. The coating shows the best wear resistance performance. Therefore, when the addition amount of Ti element is 0.75, the CoCrNiMnTi0.75 high-entropy alloy coating has the best performance, which can be used for surface strengthening and repair of high-speed rail brake discs, and improve the service life and reuse of high-speed rail brake discs. |
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