Effect of bulk and surface mechanical treatments on the tribological properties of Ti-13Nb-13Zr alloy for biomedical applications

Abstract

Ti-13Nb-13Zr (TNZ) alloy has great potential in the biomedical field due to its fully biocompatible composition and lower Young modulus value compared to the standard titanium biomaterials. As for the commercially pure Ti, the hardness and mechanical strength of TNZ can be enhanced by bulk (cold-rolling) and surface (shot-peening) mechanical treatments. However, it is still unknown how these processes, especially their combination, affect TNZ tribological properties in the simulated body fluids. This work responds to this aspect by investigating the tribological performance of TNZ in the microcrystalline, cold-rolled, shot-peened, and cold-rolled + shot-peened states. The wear behavior of the samples was tested by the pin-on-plate method (with a pin made of Al₂O₃) in the Hanks’ solution at 37°C. Tribological tests were supplemented with surface characterization using microscopy and profilometry techniques, microhardness tests and electrochemical corrosion analysis. The combination of the strengthening processes: cold rolling + shot peening resulted in the highest hardness (approx. 330 HV0.2 – almost 100 units more than for the initial state) and the lowest abrasive wear with an average volume loss of 2.881 mm³, while for the unstrengthened alloy, it amounted to 3.521 mm³. Corrosion tests revealed a correlation between surface treatment (shot peening, which significantly developed topography) and corrosion resistance, as for the grinded samples, passive current density was approx. 2.5–4 times lower than for the shot-peened alloy – for both: initial and cold-rolled states. Nevertheless, for all samples good corrosion properties in Hanks’ solution were received. The presented investigation revealed that the combination of cold rolling and shot-peening is the most promising in terms of TNZ tribo-corrosion performance. Moreover, this study shed light on TNZ degradation mechanisms, which are relevant during the wear process in Hank’s solution.