Improved wear resistance of AISI-4340 steel by Ti–Nb–C–N and MoS2 composite coating by cathodic cage plasma deposition

Abstract

A cathodic cage plasma deposition (CCPD) system was used to deposit titanium-niobium-carbon-nitrogen (Ti–Nb–C–N) and molybdenum-disulfide (MoS2) composite coating with a modification in the lid of the cathodic cage by inserting composite material rings in the holes. For this purpose, the combination of mixed material rings made up of (80 % TiO2+10 % graphite and 10 % Nb2O5) and 100 % MoS2 were uniformly inserted into the cage lid holes. The nano-hardness of untreated steel (2.7 GPa) was upgraded to 9.3, 11, and 12.4 GPa by composite coating at 300, 350, and 400 °C, respectively. The coating comprised TiN, Ti2N, NbN, NbC, and MoS2 phases, irrespective of the processing temperature. The thickness of the composite coating was 10.5, 13.8, and 18.6 μm. The wear volume (245 × 10−6 mm3) was reduced significantly in each condition, specifically at 400 °C temperature (∼0.1 × 10−6 mm3). The friction coefficient was smoother and lower by coating deposition, whereas the machining temperature during the wear test was reduced. The novelty of this work is that besides improving hardness, wear resistance is also improved due to the self-lubrication performance of the composite coating. In addition, the coating deposition by this system is a single-step process; less treatment time is required, and treatment is relatively low-cost.