粉末包埋法制备NbC涂层在不同钢基体上的生长动力学和摩擦性能

Growth Kinetics and Tribological Properties of NbC Coating on Different Steel Substrates Prepared by Pack Cementation Method

摘要:

采用粉末包埋法，以铁铌粉、氯化铵和氧化铝为主要原料，在不同温度（1123~1273 K）、不同处理时长（1~4 h）下分别研究了NbC涂层在40Cr和45钢上的生长动力学过程及摩擦磨损性能。结果表明：涂层结构致密且与基体界面结合良好，主要由NbC相组成。在40Cr和45钢基体上，涂层厚度分别为1.703±0.285~8.457±0.240和1.987±0.355~9.247±0.275 μm。生长动力学研究表明，涂层生长受扩散过程控制，厚度与时间呈抛物线变化关系；在40Cr和45钢基体上，NbC相生长过程的活化能分别为113.80和102.76 kJ/mol。在1273 K下保温4 h，NbC涂层的硬度可达21 560 MPa以上，为钢基体硬度的5.49~8.06倍。以GCr15钢球作为对磨材料，测得40Cr/NbC和45钢/NbC材料的平均摩擦系数分别为0.393和0.342，而基体的平均摩擦系数为NbC涂层的1.3~1.6倍。NbC涂层的体积磨损率约为钢基体的34.9%~37.5%，表明NbC涂层具有优异的耐磨减磨性能，其摩擦磨损机理主要是磨粒磨损、粘着磨损和氧化磨损。

Abstract:

The growth kinetics process and tribological properties of niobium carbide (NbC) coatings prepared by the pack cementation method on the 40Cr and 45 steel substrates were investigated with the main raw materials of iron niobium powder, ammonium chloride, and alumina under the conditions of different temperatures (1123~1273 K) and different treatment durations (1~4 h). Results show that the coating is compact and well bonded with the substrate interface, and it is mainly composed of NbC phase. The thickness of the coatings on 40Cr and 45 steel substrates is 1.703±0.285~8.457±0.240 and 1.987±0.355~9.247±0.275 μm, respectively. The growth kinetics study shows that the coating growth is controlled by the diffusion process, and the thickness has a parabolic relationship with the treatment duration. The activation energies of the NbC growth process on the 40Cr and 45 steel substrates are 113.80 and 102.76 kJ/mol, respectively. After treatment at 1273 K for 4 h, the hardness of NbC coating reaches more than 21 560 MPa, which is 5.49~8.06 times higher than that of the steel substrate. With GCr15 steel ball as the grinding material, the average coefficient of friction of NbC coating on the 40Cr and 45 steel substrates is 0.393 and 0.342, respectively; the average coefficient of friction of substrate is 1.3~1.6 times higher than that of the NbC coating. The volume wear rate of NbC coating is about 34.9%~37.5% of that of the steel matrix, indicating that the NbC coating has excellent wear resistance and wear reduction performance. The friction and wear mechanism of NbC coating is abrasive wear, adhesion wear, and oxidation wear.