纳米WC增强Ni基合金喷熔层组织结构与抗磨粒磨损特性

Microstructure and Abrasive Wear Resistance of Nano-WC Reinforced Ni-based Alloy Spray-melted Coatings

目的研究纳米WC对Ni基合金喷熔层抗磨粒磨损性能的影响。方法采用扫描电镜、X射线衍射分析了氧乙炔火焰喷熔Ni基合金层和两种不同结构WC增强Ni基合金喷熔层的微观组织和相结构,并通过磨粒磨损试验平台对三种涂层进行磨损性能测试。结果纳米WC粉末的加入,能有效提高喷熔层的宏观硬度。通过组织分析得出纳米WC增强Ni基喷熔层中除含有γ-(Ni,Cr)固溶体、Cr的碳化物、硼化物以及微米级WC颗粒之外,还含有一定量的纳米WC团聚体和少量高硬度的W_2C相。磨粒磨损实验结果显示,纳米WC增强Ni基喷熔层的磨损失重分别为Ni60和NiWC35涂层失重的56%和73%。对比磨损后涂层的表面微观形貌可知,纳米WC颗粒在涂层中能有效降低磨粒压入喷熔层的深度,从而控制磨粒对喷熔层的犁削量。结论纳米WC增强Ni基合金喷熔层中含有的γ-(Cr,Ni)固溶体、Cr_(23)C_6、Cr_7C_3、Cr_3Ni_2及未熔化的WC颗粒和WC脱碳形成的W_2C等硬质相,使镍基自熔合金涂层的硬度有较大提高,同时也大大提高了涂层的抗磨粒磨损性能。

The work aims to study effects of Nano-WC on abrasive wear resistance of Ni-based alloy spray-melted coating. Microstructure and phase structure of Ni-based alloy spray-melted in oxyacetylene flame as well as WC-reinforced Ni-based al- loy spray-melted coatings of two different structures were analyzed using scanning electron microscopy （SEM） and X-ray dif- fractometer （XRD）. Meanwhile, wear resistance of the three coatings was tested using abrasive wear testbed. Addition of na- no-WC powder could effectively improve macro hardness of spray-melted coating. Nano-WC reinforced Ni-based alloy spray-melted coatings contained not only 7-（Ni, Cr） solid solutions, Cr carbide, boride and micro-scale WC particles, but also acertain amount of nano-WC particles and a small amount of high-hardness W2C phase. The results of abrasive test showed that wear weight loss of nano WC-reinforced layer was 56% of that of NiWC35 coating and 73% of that of Ni60. Compared with surface microstructure of the worn coating, nano-WC particles in the coating could effectively reduce depth of abrasive particles impressed into the spray-melted layer, so as to control ploughing amount of the abrasive particles on the spraying layer. Gener- ally, the by y-（Ni,Cr） solid solutions, Cr23C6, Cr7C3, Cr3Ni2, unmelted WC particles and hardness phases such as W2C formed by WC decarburization in the nano WC-reinforced Ni-based alloy spray-melted coating can greatly improve hardness and abrasive wear resistance of the coating.