| LI Bao-cheng,CUI Hong-zhi,SONG Xiao-jie,YIN Ze-liang,ZHU Yu-ming.Wear Resistance of Ultra-high Speed Laser Cladding Ni625/WC Composite Coatings[J],52(11):237-247 |
| Wear Resistance of Ultra-high Speed Laser Cladding Ni625/WC Composite Coatings |
| Received:October 30, 2022 Revised:March 08, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.11.018 |
| KeyWord:brake discs of high-speed trains ultra-high-speed laser cladding frictional wear Ni-based coating |
| Author | Institution |
| LI Bao-cheng |
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 |
| SONG Xiao-jie |
School of Materials Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| YIN Ze-liang |
School of Materials Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
| ZHU Yu-ming |
School of Materials Science and Engineering, Shandong University of Science and Technology, Shandong Qingdao , China |
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| Abstract: |
| High-speed train brake disc is one of the important components to ensure the safe and reliable operation of high-speed trains. Its main failure form is thermal damage and wear that occurs on or near the friction surface. The use of ultra-high-speed laser melting and other surface strengthening technologies to improve the wear resistance and high-temperature performance of brake discs and other key components is an effective way to ensure the safe operation of high-speed trains. At present, there are many studies on the wear performance of Ni-based WC coatings, but there are relatively few studies on the application of key parts such as brake discs in high-speed trains. In this paper, Ni625/WC composite coatings was prepared on the surface of 24CrNiMo cast steel for high-speed train brake discs using ultra-high-speed laser melting technology. Since the high specific gravity of WC affected the quality and wear resistance of the coatings, a three-layer gradient coating design was used to improve the distribution of WC particles in the coatings.The phase composition, microstructure and element distribution of the coatings were analyzed by an X-ray diffractometer (XRD), a transmission electron microscope (TEM) and a scanning electron microscope (SEM). The hardness, coefficient of friction and wear resistance of the coatings at room temperature and 600 ℃ were tested with a microhardness tester, a friction and wear tester and a 3D morphology tester, respectively, and the friction and wear mechanisms of the coatings were analyzed. The high-temperature oxidation resistance and tissue stability of the coatings were investigated with a TGA-DSC simultaneous thermal analyzer. The results showed that the coatings are well bonded to the substrate, metallurgically, and the total thickness of the coatings was about 300 μm. The coatings were mainly composed of γ-Ni solid solution, WC, W2C and M23C6 phases. The partial melting and decomposition of WC particles generated different types and multi-scale secondary carbide phases distributed in the intergranular region of the γ-Ni solid solution. In addition, there were lamellar fine eutectic tissues composed of γ-Ni and secondary carbides generated. The hardness distribution of the coatings were relatively uniform, and the average microhardness reached 440HV0.2~610HV0.2, which was 1.25~1.7 times of the matrix hardness (360HV0.2), and the thickness of the heat-affected zone was about 200 μm with a hardness of 410HV0.2. With the increase of WC content, the main wear mechanism at room temperature was abrasive wear, and the volume of wear decreased to 20.8%, 6.8%, 4.4% and 4.2% of the matrix, and the corresponding coefficients of friction were slightly lower than that of the matrix. At 600 ℃, it was mainly abrasive wear and slight oxidation wear, and the coefficients of friction were higher than that of the matrix. The high toughness γ-Ni was firmly combined with WC, diffusely distributed secondary carbides and other reinforcing phases, which played the role of wrapping and supporting WC particles, and the multi-scale carbides, mainly WC particles, could effectively resist the indentation of grinding balls, thus reducing plastic deformation and wear. The coatings have good oxidation resistance and tissue stability, which are beneficial to the stability of frictional wear at high temperature. The spherical WC particles play an important role in improving the wear resistance of the coatings. |
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