Influence of process parameters and rare earth content on the properties of niobium carbide coatings synthesized by pack cementation

This research studied the influence of specific processing parameters (deposition temperature, holding time, and rare earth element) on the thickness, microstructure, and tribological properties of niobium carbide coatings. The researcher used the pack cementation method to prepare niobium carbide coatings on the surface of AISI 1045 steel. Equipment used to observe the metallographic cross-section of the samples and the coatings' surface topography, and to measure the microhardness and friction behavior of the niobium carbide coatings, included an optical microscope, a scanning electron microscope, an x-ray diffractometer, a Vickers hardness tester, a multifunctional tester, and a three-dimensional (3D) profiler. The results show that optimal process parameters for rare earth co-cementation were obtained: 950 °C, 5 h, and 1.5 wt% lanthanum oxide (La₂O₃). The coating prepared with these processing parameters had the best wear resistance, with the volume wear rate reduced by a factor of 2. In addition, the coating's thickness was found to reach 10 μm, and its microhardness exceeded 1,100 HV_0.2. (paper)