ABSTRACT
The new continuous cooling bainitic steels (CCBS) are an excellent alternative when high hardness, toughness and fatigue resistance are required. However, it is estimated that the wear rate of the CCBS is insufficient for application in highly mechanical loaded components, being necessary to improve the surface properties. The objective of this study is to analyze the effects of plasma nitriding on the microstructure and wear properties of DIN18MnCrSiMo6-4 continuous cooling bainitic steel. Therefore, treatments lasting 6 hours were conducted with a pressure of 3 mbar, a gas mixture composed of 76% N2 + 24% H2, and a temperature of 400, 450, 500 and 550 °C, respectively. The samples were analyzed by scanning electron microscopy, X-ray diffraction, microhardness and reciprocal sliding wear tests. Under the conditions investigated, it was possible to obtain a compound layer and to achieve an increase of up to 393% in surface hardness, however, the use of higher processing temperatures favored the extension of the depth layer. In all the nitrided samples, the major presence of ε-Fe2-3N nitrides phase was observed, and the γ'-Fe4N phase content was smaller. In the reciprocal sliding tests, there was a decrease in the wear of nitrided samples at temperature of 550 °C.
Keywords
Continuous Cooling Bainitic Steel; Plasma Nitriding; Microstructure and Wear Properties
