Effect of diffusion annealing on boride layer produced on AISI 1040 steel

Although AISI 1040 steel is a widely used steel in industry, it has some limitations due to its low surface hardness. Various surface treatments are made for use in larger areas. In this study, boriding process was carried out for 4 hours by using Ekabor-2 powder at 900 °C and 950 °C, using the box boriding method. Following the boronizing process, Diffusion Annealing was carried out in a mixture of 95% SiC and 5% Bentonite powder at 950 °C and 1000 °C for 4 hours. The morphology of the boride layer obtained as a result of Boronizing and Diffusion Annealing Process (DAP) on the surface of AISI 1040 steel was determined using optical and SEM microscopy. The hardness of the obtained boride layer was determined by using the microhardness device, and the phases formed in the boride layer were determined by the XRD method. It was seen in XRD analyzes that a boride layer consisting of single-phase Fe2B phase was obtained by DAP treatment at 1000 °C for 4 hours. While the surface hardness of AISI 1040 steel was 233 HV0.05, it increased to 1950 HV0.05 with boronizing and DAP treatment. Wear tests were carried out using the ball-disc wear method at a sliding speed of 0.3 m/s and a sliding distance of 500 meters in a dry environment under 10 N load. Wear resistance increased with boronizing process and diffusion annealing temperature. It provided the best wear resistance at high Diffusion annealing temperature. Electrochemical corrosion tests were carried out in 3.5% NaCl environment of boronized and DAP applied AISI 1040 steel. It has been determined that the highest corrosion resistance is in single-phase boride layers consisting of Fe2B phase at 1000 °C. Keywords: AISI 1040 Steel, Pack Boriding, Duffusion Anneling Process, Wear.