激光熔覆FeCrSi_(x)NiCoC涂层高温耐磨性能

Wear Resistance of Laser Cladding FeCrSixNiCoC Coating at High Temperature

Si含量对Fe基合金高温耐磨性能影响机理研究已有很多,但尚缺乏Si含量对Fe基涂层高温耐磨性能的研究.采用激光熔覆技术制备不同Si含量(5wt.%、10wt.%、15wt.%)的FeCrSi_(x)NiCoC涂层,在温度为500℃和载荷200 N的条件下,测试FeCrSi_(x)NiCoC涂层高温耐磨性能.结合X射线衍射仪(XRD)、金相显微镜(OM)、扫描电子显微镜(SEM)、能谱分析仪(EDS)分析涂层显微组织、相组成和磨损机理.结果表明:随着Si含量增加,涂层中γ-Fe相(Si以固溶方式存在于γ-Fe相中)向金属硅化物Fe3Si相转变,显微组织也由树枝晶向等轴晶转变,涂层硬度由312±21.7 HV0.5增加至588±31.3HV0.5.在温度500℃和载荷200 N下的摩擦磨损试验中,Si含量为10%的涂层磨损率最低,高温耐磨性能最好,其磨损机理主要为黏着磨损和氧化磨损.通过优化Fe基合金中Si含量得到耐磨性能良好的涂层,可对该类涂层的开发、制备和应用提供一定的技术支持.

Fe-based alloys are among the most important materials for engineering applications owing to their low cost and high hardness/strength,and wear and corrosion resistance.However,with the development of industry,the working conditions of mechanical parts have deteriorated.Therefore,it is essential to develop Fe-based alloy materials with enhanced wear and corrosion resistance,especially at high temperatures.The addition of alloying elements,such as Si,can significantly improve the high-temperature performance of Fe-based alloys.A typical example is high-silicon cast iron.Many studies have been conducted on the influence of the Si content on the high-temperature properties of Fe-based alloys.However,studies on the high-temperature properties of Fe-based repair coatings with Si content remain few.In this work,FeCrSi,NiCoC coatings with different Si content(5 wt.%,10 wt.%,and 15 wt.%Si,called Sis,Sio,and Siis,respectively)were prepared using laser cladding technology after a systematic study of laser parameters.The metallurgical bond,microstructure,phase,and hardness of the coatings were studied using X-ray diffraction,metallographic microscopy,scanning electron microscopy,and energy dispersive analysis.The high-temperature wear resistance of FeCrSi,NiCoC coatings was tested at 500°C and a load of 200 N.The results show that the FeCrSi,NiCoC coatings had no cracks and formed good metallurgical bonds with the substrate.With the increase in the Si content,the-Fe phase in the coating(Si exists in the-Fe phase as a solid solution)transformed into the metal silicide FesSi phase,and the microstructure gradually changed from columnar dendrites to equiaxed grains.The hardness increased from 312±21.7 HVo.s to 588±31.3HVo.5,which indicates that the increase in Si content has a significant impact on the phase,microstructure,and hardness of the coatings.In the friction and wear tests,the FeCrSi,NiCoC coatings showed excellent high-temperature wear resistance,much better than that of the substrate.In addition,owing to the solid solution strengthening mechanism of Si addition,the Sio coating exhibited the best high-temperature wear resistance among the three samples,with a wear rate of 28μg/m.The grinding debris consisted mainly of fine powder and irregularly shaped particles,indicating that the main wear mechanisms are adhesive and oxidation wear.The Sis coating contained a large amount of brittle phase FesSi,and produced a significant amount of large debris during wear,resulting in a high wear rate.However,no black oxides were observed on the surface of the Sis coating,indicating its resistance to high-temperature oxidation.Therefore,it can be inferred that the appropriate amount of Si can significantly improve the high-temperature wear resistance of the coating.When the Si content is too high,the brittleness significantly increased despite the improvement in hardness and high-temperature oxidation resistance,which eventually decreased the high-temperature wear resistance.Therefore,solving the brittleness problem caused by the addition of Si needs to be further explored.In this study,FeCrSi,NiCoC coatings with good wear resistance were obtained by optimizing the Si content,which can provide technical support for the development,preparation,and application of such coatings.