A Descriptive Study of the Hardness and Microstructure Profiles of SKD61 Steel Plunger Tip (Local Material) after Plasma Nitriding

The Hardness and Microstructure Profiles of SKD61 Steel Plunger Tip (local material) after Plasma Nitriding have studied. To improve SKD61 quality for high temperature use, a plunger tip can be hardened through surface treatment using a plasma/ion nitriding technique. To test the success of the surface treatment, the nitriding temperature was varied from 350ºC to 550ºC with step for 50ºC for the nitriding process completed for 10 hours. The results, it can be seen that the optimum surface hardness was achieved when the nitriding temperature was 500ºC with Vickers hardness (HV) was 955.29 HV with a depth of up to 100 m from the surface of the specimen. At such a nitriding temperature, the hardness increased 1.79 times in comparison with that after hardening only, and it increased 2.076 times in comparison with that of the initial hardness. From the results of the study, it can be concluded that plasma nitriding temperature affects the amount of nitrogen concentration diffused into the substrate material. Metallographic observation of SEM-EDS shows that the nitriding temperature affects the concentration and depth of diffusion of nitrogen in the SKD61 material. Nitride layer formed was possibly of Fe N, Cr2N, VN, Fe, and Fe.