激光熔覆WC-Ni基超硬梯度复合涂层的组织与性能

利用激光宽带熔覆技术在45钢表面制备了WC-Ni基超硬梯度复合涂层.对激光熔覆层用SEM、EDS、XRD进行观察和分析.对比研究了单一熔覆层、梯度熔覆层的熔覆层形貌、缺陷状态、硬度及其分布.结果表明,单一熔覆层易出现宏观裂纹、界面处熔合差等缺陷;梯度激光熔覆层逐级过渡的结合形式缓解了应力集中,使应力合理分布.在优化的工艺参数下,通过连续控制微观结构要素,可以实现成分、组织的梯度变化,获得无气孔、无裂纹的梯度熔覆涂层.其中,梯度熔覆层组织主要是由γ-Ni、WC等相组成,涂层的硬度值从熔覆层至基体呈梯度降低趋势,外层平均硬度可达2000 HV0.1以上.

Microstructure and properties of laser clad WC-Ni base superhard gradient composite coating

The WC-Ni base superhard composite tungsten carbide coatings were fabricated by wide-band laser cladding technique on 45 steel.The morphology of laser clad layer was observed by scanning electronic microscope（SEM),the composition analysis was applied by EDS,and the phase transformation was characterized by XRD.The microstructure,hardness,and distribution of two types of laser clad coatings were contrastively investigated,including single cladding coating and gradient cladding coating.The results show that single cladding coating usually has cracks existing in the interface area,and the inferior in interface bind.In the gradient cladding coating,stress concentration is released through step-by-step transition and distributed properly.Under optimized processing parameters,the gradient structure can be realized by sequential controlling microstructural elements.The gradient cladding coating is free of pores and cracks.Thereinto,the main structure of gradient cladding coating is composed of the phase of γ-Ni,WC etc.The trend of hardness distribution is gradually decreased from the coat to the substrate.The average hardness of the outer layer is above 2000 HV0.1.