NAK80模具钢表面2种激光器熔覆Ni基碳化钨合金层组织结构及耐磨性比较

为了研究激光器对Ni基碳化钨合金熔覆层组织结构和性能的影响,分别采用Nd:YAG与CO2激光熔覆技术在NAK80模具钢表面制备了Ni基碳化钨合金层,利用X射线衍射仪(XRD)、扫描电镜(SEM)、能谱仪、显微硬度计以及摩擦磨损试验机测试分析了2种熔覆层的组织结构、显微硬度及耐磨性能。结果表明:2种熔覆层与基体之间均呈现良好的化学冶金结合;熔覆层组织主要为粗大的未熔碳化钨颗粒和均匀分布的树枝晶,Nd:YAG激光熔覆层的组织比CO2激光熔覆层的细小;2种熔覆层相结构主要包括WC,W2C,Cr23C6,NiCr,CrB2以及γ-Ni等;2种激光器熔覆处理后,NAK80模具钢表面硬度和耐磨性都得到显著改善,CO2激光熔覆层的硬度和耐磨性高于Nd:YAG激光熔覆层,2种激光熔覆试样的磨损机制均为磨粒磨损。

Comparison of Microstructure and Wear Resistance of Laser Cladding Nickel- Based Tungsten Carbide Alloy Coatings Prepared on NAK80 Mould Steel Substrate Using Two Kinds of Lasers

Laser cladding Ni-based tungsten carbide alloy coatings were fabricated on NAK80 mould steel substrate using a Nd: YAG laser and a CO2 laser.The phase structure,morphology and elemental composition of the two kinds of laser cladding coatings were analyzed by means of X-ray diffraction,scanning electron microscopy and energy dispersive spectrometry.Moreover,the microhardness and wear resistance of the laser cladding coatings were evaluated using a hardness meter and a friction and wear tester.It was found that both the two kinds of laser cladding coatings were combined with the substrate via chemical metallurgical bonding.Both the two kinds of laser cladding coatings mainly contained coarse unmelted tungsten carbide particles and evenly distributed dendrites,while the coating prepared with Nd: YAG laser had finer structure than the one prepared with CO2 laser.Besides,they were mainly composed of WC,W2C,Cr23C6,NiCr,CrB2 and γ-Ni.In the meantime,laser cladding with the two types of lasers helped to significantly increase the hardness and wear resistance of the mould steel,and the laser cladding coating obtained with a CO2 laser had higher hardness and wear resistance.Moreover,the wear mechanisms of the two kinds of laser cladding coatings were both dominated by abrasive wear.