Avaliação do estado de superfície obtido no fresamento de ligas de titânio com ferramentas comerciais

Abstract

The fulfilment of physiological performance criteria that lead to the proper structural and functional connection between bone and implant, called osteointegration, is closely related to the surface characteristics of the biomaterial, which depend on the processes involved in its manufacture. Therefore, the present work aims to expand the understanding about the influence of machining conditions on the surface integrity of commercially pure grade 4 titanium and Ti-6Al-4V ELI components submitted to the milling operation. For this purpose, based on a 2^3 complete factorial design, was selected as influencing factors the type of tool: high-performance cutter and conventional cutter, machined titanium alloy and cutting speed. Three different roughness parameters were used as response variables on the surface state, namely: mean roughness (Ra), asymmetry (Rsk) and flatness (Rku) of the profile. An additional analysis verified the wettability of the machined surfaces through four different ways of measuring the contact angle. The analysis of variance (ANOVA) indicated that the cutting tool corresponds to the main influencing factor of this study, being significant on all response variables. The machined titanium alloy was also influential on the average roughness results, while the cutting speed showed a significant influence on both the average roughness and the asymmetry parameter. Precisely regarding to skewness, it is noteworthy that the different cutters employed produced consistently opposite results, that is: while one tool model resulted in a surface composed predominantly of peaks, the other model resulted in surfaces composed of valleys. Finally, the surface wettability analysis indicated that the milling of Ti-6Al-4V ELI with high performance cutter and high cutting speed results in the surface with higher contact angles among those analysed, characterizing the condition of maximum cell viability within the mean surface roughness limit obtained.