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BN增强Ni60–Cr3C2超高速激光熔覆涂层微观组织及性能

Microstructure and properties of BN-reinforced Ni60–Cr3C2 coatings fabricated by ultra-high-speed laser cladding

  • 摘要: 以Cr3C2粉末、h-BN粉末、Ni60粉末为原料,采用超高速激光熔覆技术在调质态40Cr圆柱形棒材表面熔覆BN增强Ni60–Cr3C2涂层。采用X射线衍射仪、光学显微镜、扫描电子显微镜、维氏显微硬度测试、摩擦磨损实验及电化学测试系统分析了BN对Ni60–Cr3C2涂层微观组织与性能的影响。结果表明,Ni60–Cr3C2涂层主要由Cr3Ni2、Cr1.12Ni2.88、Cr7C3、Fe3C组成。在添加BN后,涂层中原位生成了Fe2B、Cr2N、Cr2B3,BN能促进涂层中残留Cr7C3分解以及富Cr枝晶网络形成。BN增强Ni60–Cr3C2涂层组织均匀性与耐磨性能显著提升,其体积磨损量较Ni60–Cr3C2涂层降低53.3%。此外BN增强Ni60–Cr3C2涂层腐蚀电流密度为1.28×10−6 A·cm−2,较Ni60–Cr3C2降低81.0%,其电荷转移电阻达5562 Ω·cm2,为Ni60–Cr3C2涂层的2.2倍,表现出更优的耐腐蚀性能。

     

    Abstract: Taking Cr3C2 powder, h-BN powder and Ni60 powder as raw materials, BN-reinforced Ni60–Cr3C2 composite coatings were fabricated on the surface of quenched and tempered 40Cr cylindrical bars via ultra-high-speed laser cladding technology. The effects of BN on the microstructure and properties of Ni60–Cr3C2 coatings were systematically investigated by X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test, friction and wear test, and electrochemical measurement. The results show that the Ni60–Cr3C2 coating is mainly composed of Cr3Ni2, Cr1.12Ni2.88, Cr7C3 and Fe3C phases. After the addition of BN, in-situ synthesized Fe2B, Cr2N and Cr2B3 phases are formed in the coating. BN can promote the decomposition of residual Cr7C3 and the formation of Cr-rich dendritic networks within the coating. The microstructure uniformity and wear resistance of the BN-reinforced Ni60–Cr3C2 coating are significantly improved. Compared with the pure Ni60–Cr3C2 coating, its volume wear loss is reduced by 53.3%. In addition, the BN-reinforced coating exhibits an enhanced corrosion resistance, with a corrosion current density of 1.28×10−6 A·cm−2, which is 81.0% lower than that of the Ni60–Cr3C2 coating. Its charge transfer resistance reaches 5562 Ω·cm2, 2.2 times that of the original Ni60–Cr3C2 coating.

     

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