固体法制备碳化铌渗层的灰口铸铁的耐磨性能

Wear Properties of a Gray Cast Iron Coated with Niobium Carbide Produced by Pack Process

灰口铸铁由于其成本低廉、减振和切削加工性能良好获得应用。这些突出优点源自游离态石墨的存在和液态金属的良好流动性,后者有利于制作形状复杂的薄壁铸件。适合的渗层能改善灰口铸铁的耐磨性,从而扩大其应用范围。高硬度的碳化铌可以达到这一目的。本文研究用的灰口铸铁试样成分为3.47%C-2.39%Si-0.55%Mn-0.15%Ni-0.65%Cu-Fe(余量),采用Fe-Ni合金、NH_4Cl和Al_2O_3的粉末混合物进行热反应扩散渗铌,温度900℃,时间2 h。碳化铌渗层的硬度可达2 000 HV,微黏着磨损和微磨粒磨损试验证明,固体渗铌处理可显著提高灰口铸铁的耐磨性。

Gray cast iron is used mainly due to its low cost, high damping capacity and high machinability. These outstanding properties are due to the presence of free graphite and the high fluidity of the mohen metal what allows the casting of complex parts with thin walls easily. Suitable coatings can increase their wear resistance while expanding its usability range. Niobium carbide, with its high hardness may be a good candidate for this purpose. In this work, samples of this material with the composition 3.47% C-2.39% Si-0. 55% Mn-0. 15% Ni-0. 65% Cubalance Fe were subjected to niobizing powder thermo-reaetive diffusion treatment using a coating mixture composed of Ferro-niobium, NH4Cl, Al2O3 at 900℃ for 2 hours. Layers hardnesses of 2 000 HV, typical for niobium carbides, were obtained. Micro-adhesive and micro-abrasive wear tests demonstrated a substantial increase in wear resistance obtained with this treatment.