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<p>The valve stem of a steam turbine is a core component that controls the operation of the turbine. It operates under harsh working conditions involving the coupling of high temperature, tensile–compressive stress, friction, and additional bending moment. During long-term service at temperatures above 600&#xa0;°C, its nitrided surface is prone to scratches and peeling of the nitrided layer, which can lead to jamming, and even valve failure or turbine overspeed accidents. Therefore, selecting appropriate materials and surface modification technologies to improve surface morphology and high-temperature wear resistance has become a research focus in this field. In this paper, different cladding layer microstructures were prepared on the surface of C422 steel substrate using high-speed laser cladding technology, aiming to study the improvements in microhardness and friction–wear properties of the cladding layers. The results show that different process parameters have a significant impact on the microstructure and properties of the coating. Under a power of 2000W, a scanning speed of 120&#xa0;mm/s is the optimal process parameter for the coating performance. Compared with conventional laser cladding coatings, the prepared coating exhibits better morphology, hardness, and wear resistance. Moreover, the enhancement of surface hardness and wear resistance of the coating mainly depends on the combined effects of solid solution strengthening, grain refinement strengthening, and dispersion hardening. Under high-temperature conditions, phase transformations in the coating are the main factor affecting high-temperature wear resistance.</p>

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Study on the Microstructure and High-Temperature Friction Properties of Ni-Co Alloy High-Speed Laser Cladding for Turbine Valve Stem

  • 期刊论文

  • 发表日期：

    2026年5月8日

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  • Xingdong Chen,
  • Jinwen Deng,
  • Yanhai Cheng,
  • Jiaye Geng,
  • Jiali Zhou

摘要

The valve stem of a steam turbine is a core component that controls the operation of the turbine. It operates under harsh working conditions involving the coupling of high temperature, tensile–compressive stress, friction, and additional bending moment. During long-term service at temperatures above 600 °C, its nitrided surface is prone to scratches and peeling of the nitrided layer, which can lead to jamming, and even valve failure or turbine overspeed accidents. Therefore, selecting appropriate materials and surface modification technologies to improve surface morphology and high-temperature wear resistance has become a research focus in this field. In this paper, different cladding layer microstructures were prepared on the surface of C422 steel substrate using high-speed laser cladding technology, aiming to study the improvements in microhardness and friction–wear properties of the cladding layers. The results show that different process parameters have a significant impact on the microstructure and properties of the coating. Under a power of 2000W, a scanning speed of 120 mm/s is the optimal process parameter for the coating performance. Compared with conventional laser cladding coatings, the prepared coating exhibits better morphology, hardness, and wear resistance. Moreover, the enhancement of surface hardness and wear resistance of the coating mainly depends on the combined effects of solid solution strengthening, grain refinement strengthening, and dispersion hardening. Under high-temperature conditions, phase transformations in the coating are the main factor affecting high-temperature wear resistance.