Ni包B_4C陶瓷颗粒增强Ni基合金激光熔覆层的性能

Preparation and property of B_4C ceramic particles reinforced Ni-based coating by laser cladding with Ni and Ni coated B_4C powders

利用3 kW高功率半导体激光器,在304钢基体上制备不同含量Ni基Ni包B_4C复合陶瓷涂层,分别用扫描电镜(SEM)、X射线衍射(XRD)、显微硬度计及摩擦磨损试验机对熔覆层的显微组织、物相、硬度及耐磨性进行研究。结果表明:熔覆层主要由γ-Ni固溶体、B_4C、Fe_3B、Ni_4B_3、Cr_5B_3、CrB、Cr_3C_2、Cr_2Ni_3等物相组成;熔覆层底部晶粒以近似垂直于基体界面的细小树枝晶的形态生长的,中部以一定方向柱状晶和树枝晶存在,上部是杂乱无章的等轴枝晶;Ni包B_4C含量为40%时,熔覆层组织均匀致密、晶粒细小,与基体冶金结合,显微硬度最高1261 HV,是基体的5.7倍,耐磨性也相对较好,是基体的12倍。

Nickel-based composite coatings were prepared on 304 stainless steel by laser cladding using Ni and Ni coated B_4C powders with different contents of B_4C. Microstructure,phase composition,hardness and wear resistance of the laser clad coatings were studied by means of scanning electron microscopy（ SEM）,energy dispersive spectrometer（ EDS） analysis,X-ray diffraction（ XRD） and friction and wear test. The results show that the laser clad coatings are composed γ-Ni,B_4C,Fe_3B,Ni_4B_3,Cr_5B_3,CrB,Cr_3C_2 and Cr2Ni3. The microstructure of the coatings exhibits a cell structure perpendicular to the interface of the coating and the substrate at the bottom,columnar crystal and dendritic structure growing with a single direction for the central layer,and dendrites with random direction for the upper layer. When the content of Ni coated B_4C is 40%,the microstructure of the clad coating is uniform and compact with metallurgical bonding with the substract,the hardness of the coatings reaches 1261 HV,which is 5. 7 times of that of the substrate and its wear increases by 12 times compared with that of the substrate.