Wear properties of niobium carbide coatings performed by pack method on AISI 1040 steel

A series of experiments was performed to evaluate tribological properties of niobium carbide coated AISI 1040 steel. In coating process, thermo-reactive diffusion treatment by pack method was performed at the temperatures of 800, 900 and 1000 °C for 1-4 h, respectively. Depending on coating process time and temperature, the thickness of niobium carbide layer formed on substrate ranged from 3.4±0.5 to 12±2 μm. The hardness of niobium carbide layers on the steel sample is 1792 HV. The presence of carbides (e.g. NbC, Nb2C) formed on the surface of coated AISI 1040 steel was confirmed by X-ray diffraction analysis. Dry wear tests for uncoated and coated AISI 1040 steel against AISI D2 steel were carried out on pin-on-disk configuration and at sliding speed range of 0.5, 1, 2 and 5 m/s, and under 15 N and 30 N loads. The results showed that the average coefficient of friction for coated and uncoated AISI 1040 steel were 0.3 and 0.5, respectively. The specific wear rates for uncoated and coated steel are 4.47×10-5 mm3/N.m to 4.29×10-4 and 4.37×10-7 to 3.55×10-5 mm3/N.m.