激光熔覆原位自生复相陶瓷颗粒增强涂层

借助光学显微镜、X射线衍射仪、电子探针及显微硬度计等手段对熔覆层的组织、物相、元素分布和显微硬度分布特征进行了研究。熔覆层不同位置的凝固特征参数不同,形成的组织亦不同。陶瓷相的引入使得熔覆层晶粒细小,枝晶生长方向发生紊乱。原位反应生成的TiB2,Al2O3为亚微米颗粒,主要分布在晶粒内部,形成晶内复合,而未反应的TiO2,B2O3陶瓷颗粒分布在晶间。熔覆层物相主要为基体的γ相和基体上弥散分布的γ'相以及Al2O3,TiB2等陶瓷相等。研究了激光加工参数对显微硬度分布的影响。磨损试验表明,陶瓷增强颗粒的加入在很大程度上提高了覆层的抗磨损性能。

Laser cladding in situ formed polyphase ceramic particle reinforced coating

The microstructure,phase,element distribution and microhardness have been analyzed with the aid of microscope,X-ray diffraction,electron probe and microhardness-tester.It is shown that there are different solidification parameters for different zones in cladding layer,hence the different microstructure.Introduction of the ceramic made the microstructure very fine.Meanwhile,the growth direction of the dendrite is various because of the presence of the ceramic particle.It has been observed that the disperse Al₂O₃ and TiB₂ with the size of sub-micrometer formed in the grains and unreacted B₂O₃,TiO₂ are distributed along the grain boundary.There is a ceramic density-gradient distribution along the depth of the cladding layer.The highest value of microhardness was 434HV 0.2.Experimental results show that the γ-Ni,γ',Al₂O₃ and TiB₂ are the dominant phases in the cladding zone.The microstructure and hardness of the cladding layer are governed by the laser processing parameters and the coating's chemical composition.The hardness and the wear property of the layer are significantly enhanced due to the present of ceramic in the coating.