| Summary: | In this study, we propose a rapid plasma-assisted nitriding process using H<sub>2</sub>/N<sub>2</sub> mixture gas in an atmospheric pressure plasma jet (APPJ) system to treat the surface of SKD11 cold-working steel in order to increase its surface hardness. The generated NH radicals in the plasma region are used to implement an ion-bombardment for nitriding the tempered martensite structure of SKD11 within 18 min to form the functional nitride layer with an increased microhardness around 1095 HV<sub>0.3</sub>. Higher ratios of H/E and H<sup>3</sup>/E<sup>2</sup> were obtained for the values of 4.514 × 10<sup>−2</sup> and 2.244 × 10<sup>−2</sup>, referring to a higher deformation resistance as compared with the pristine sample. After multi-cycling impact tests, smaller and shallower impact craters with less surface oxidation on plasma-treated SKD11 were distinctly proven to have the higher impact wear resistance. Therefore, the atmospheric pressure plasma nitriding process can enable a rapid thermochemical nitriding process to form a protective layer with unique advantages that increase the deformation-resistance and impact-resistance, improving the lifetime of SKD11 tool steel as die materials.
|
|---|
