Modificação e caracterização do aço astm F138 por meio da nitretação iônica em gaiola catódica de titânio

Abstract

The stainless steel ASTM F138 is used in implants due to the combination of its mechanical and biocompatibility properties, in order to improve these properties, superficial modifications are necessary, one of the forms of feasible modification is the plasma nitriding using a cathodic titanium cage. This technique allows the formation of an outer layer due to the deposition of titanium nitride (TiN) films, which influence characteristics such as; wettability and roughness, essences to improve the performance of the biomaterial. The deposited film varies in thickness, depending on the conditions of time and temperature of the treatment, which affects the hardness, a characteristic associated with the mechanical resistance of materials, thus prolonging its useful life. For this purpose, samples of ASTM F138 stainless steel were subjected to a plasma nitriding process using a cathodic titanium cage. For this study, a plasma reactor with stainless steel chamber with a continuous voltage source and a gas atmosphere of a mixture of hydrogen gas and nitrogen in the proportion of 80% H2 and 20% N2 were used. The treatments were performed at different combinations of times (3h, 4h and 5h) and temperatures (350ºC, 400ºC and 450ºC). After treatment, all samples were characterized by optical microscopy, scanning electron microscopy (SEM), using the technique (EDS), X-ray diffraction (XRD), Raman spectroscopy, Vickers hardness, roughness, contact angle and surface tension. Finally, it was verified the deposition of titanium nitride films on the samples with thicknesses varying according to the treatment parameters, this fact contributed to increase the surface hardness and the average roughness (Ra), which gave a character hydrophilic in all samples and also maintained the polar characteristic.