Estudo da resistência ao desgaste de novas ligas de titânio visando aplicações ortopédicas

Abstract

Titanium and its alloys have shown important application in the biomedical sector because they present excellent and combined properties such as high specific strength/mass ratio, low modulus of elasticity, high corrosion resistance in body and saline environments and high biocompatibility. However, the Ti-6Al-V alloy, widely used in this sector, presents problems of resistance to wear and release of toxic ions. In this sense, alloys of the Ti-Si-B system have been shown as an alternative because they are composed of naturally occurring elements in the bone composition and, therefore, have superior biocompatibility. In particular, the ternary Ti6Si2B phase of this system has high corrosion resistance, potential resistance when subjected to wear conditions and remains stable when there is an increase of zirconium up to 7% atomic. The objective of this study was to verify the tribological behavior of new titanium alloys for orthopedic applications. Ingots of the Ti-6Zr-2Si-1B, Ti-6Zr-6Si-3B and Ti-6Zr-10Si-5B alloys were produced by arc fusion and then treated at 1100 ° C for 20 hours. To obtain microstructural information, samples of the alloys were characterized by scanning electron microscopy and energy dispersive spectrometry (SEM/EDS), X-ray diffraction (XRD) and atomic force microscopy (AFM). The mechanical characterization was performed by Vickers microhardness test and wear test in oscillatory movement mode in dry and lubricated environment. In all the alloys the presence of TiB, Ti3Si and Tiss phases was observed, and therefore, with the adopted processing route, it was not possible to observe the Ti6Si2B phase formation. The results also indicated that zirconium was preferentially dissolved in Ti3Si and Tiss phases. The sanding and polishing processes provided homogeneous surfaces for all samples so that the average roughness was less than 0.8μm, as recommended. The average values of microhardness were between 272.2 and 397.8 HV, values that showed to be increasing, as expected, with the increase of the Si and B metalloids. The Ti-6Zr-10Si-5B alloy presented the highest coefficient of friction at in the lubricated condition, although the Ti-6Zr-10Si-5B alloy continues to have the highest coefficient of friction, the same relation with the microhardness was not observed. The Ti-6Zr-2Si-B alloy showed the highest values of Ti-6Zr-10 Si-5B in the dry condition, while in the lubricated condition the highest loss was observed in Ti-6Zr-10Si-5B alloy. The wear mechanisms in all alloys in dry condition were abrasive, whereas in the lubricated condition, abrasive, adhesive and corrosive wear were detected, which is more evident in the Ti-6Zr-10Si-5B alloy.