Investigation of the Tribological and the Corrosion Behavior of Liquid Nitrided EN31 Steel

EN31 steel is a high-carbon alloy steel used for several industrial applications like drilling & power tools. The novelty of this study lies in the optimization of liquid nitriding duration for the EN31 steel, which enhances the surface properties and a prolonged service life in tribological applications. In order to overcome the limitations, this study has aimed to investigate the impact of liquid nitriding at 570°C for 30, 60, and 90 minutes to study the hardness, corrosion and wear properties of EN31 steel. As a thermochemical surface treatment for EN31 steel, the study explores the application of liquid nitriding. Compared to traditional methods like gas nitriding, carburizing, hard chrome plating and hardening, the liquid nitriding provides uniform compound layer formation, enhanced surface hardness, and faster processing with less distortion. Performance of the modified EN31 steel post nitriding process was evaluated through various tests, like the pin-on-disk method to assess wear resistance and neutral salt spray testing as per ASTM B117 to measure corrosion resistance. Noticeable improvements in the steels tribological and anti-corrosive properties after nitriding were demonstrated through the test results. Upon analysing the microstructure, a uniform, defect-free nitride layer was revealed. The study evaluated that the 90-minute nitriding cycle resulted in the best performance related to corrosion resistance, wear resistance and surface hardness. A maximum hardness of 31.7 HRC would be achieved during the 90 minute cycle. Interestingly, this cycle also produced the deepest effective case depth thereby enhancing durability of steel under intense load bearing conditions. In addition, the outstanding corrosion resistance of steel was confirmed during 24-hour salt spray testing as no red rust was detected on the nitride samples. The test findings are validated the liquid nitriding as an economical surface treatment process for improving performance as well as durability and also reducing maintenance needs of EN31 steel for applications like drilling tools and for enhancing its reliability in abrasive and corrosive environments.