原位生成NbC颗粒增强镍基激光熔覆层

激光熔覆技术是金属材料表面强化和改性的有效方法之一。利用该技术,在A3钢表面激光熔覆预置涂层,成功制备出了原位生成NbC颗粒增强的镍基复合涂层,并进行了硬度、摩擦性能测试,X射线衍射(XRD)和显微组织分析。扫描电镜(SEM)、能谱分析(EDS)和X射线衍射分析结果表明,原位生成NbC颗粒增强的镍基复合涂层与基材呈现良好的冶金结合,熔覆层的组织为先共晶析出的树枝晶(Cr,Fe碳化物相)和原位生成的NbC颗粒相均匀分布在γ(Ni Fe)基体中。硬度测试和摩擦磨损实验表明,激光熔覆原位生成NbC颗粒增强镍基复合涂层平均硬度高达HV0.31200,耐磨性是纯Ni60激光熔覆层的2.5倍。分析认为,其硬度和耐磨性提高的原因在于涂层中形成了大量的、原位生长的NbC颗粒增强相,且均匀分布于基体中。

In Situ Synthesized NbC Particulate Reinforced Ni-Based Composite Coatings by Laser Cladding

Laser cladding is the one of the efficient methods for the surface hardening and modifying of metal material. Using this technology, NbC particulate reinforced Ni-based composite coating has been successfully in situ synthesized on steel A3 substrate by prior to pasting. The microstructure observation and hardness test on the cross-section of the laser clad layer were performed. And that X-ray diffraction (XRD) analysis and tribotesting on the surface of the coatings were also accomplished. The microstructural and metallographic analyses by a scanning electron microscope (SEM), energy-dispersive spectrometer (EDS) and X-ray diffractometer reveal that the coating epitaxial growing from the substrate with excellent bonding between the coating and substrate is ensured by the strong metallurgical interface and suggest the presence of the in situ synthesized NbC particles in the clad layer. These NbC particles together with the carbide dendrites present as reinforcements of the composite coatings and are homogenously dispread in the γ(Ni Fe) matrix. The experimental results show that the composite coating gives high average hardness of HV0.31200 and excellent wear resistance, which is 2.5 times as high as that of pure Ni60 coatings. The improvement of wear resistance is due to the presence of the substantive in situ synthesized NbC particles and their homogenous distribution in the coatings.