Influence of Beam Power on Young’s Modulus and Friction Coefficient of Ti–Ta Alloys Formed by Electron-Beam Surface Alloying

Stefan Valkov,Peter Petrov,Ruslan Bezdushnyi,Nikolay Ivanov,Dimitar Dechev,Maria Ormanova

doi:10.3390/met11081246

Stefan Valkov, Peter Petrov + Show 4 more

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https://doi.org/10.3390/met11081246

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Abstract

In this study, we present the results of Young’s modulus and coefficient of friction (COF) of Ti–Ta surface alloys formed by electron-beam surface alloying by a scanning electron beam. Ta films were deposited on the top of Ti substrates, and the specimens were then electron-beam surface alloyed, where the beam power was varied from 750 to 1750 W. The structure of the samples was characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD). Young’s modulus was studied by a nanoindentation test. The coefficient of friction was studied by a micromechanical wear experiment. It was found that at 750 W, the Ta film remained undissolved on the top of the Ti, and no alloyed zone was observed. By an increase in the beam power to 1250 and 1750 W, a distinguished alloyed zone is formed, where it is much thicker in the case of 1750 W. The structure of the obtained surface alloys is in the form of double-phase α’and β. In both surface alloys formed by a beam power of 1250 and 1750 W, respectively, Young’s modulus decreases about two times due to different reasons: in the case of alloying by 1250 W, the observed drop is attributed to the larger amount of the β phase, while at 1750 W is it due to the weaker binding forces between the atoms. The results obtained for the COF show that the formation of the Ti–Ta surface alloy on the top of Ti substrate leads to a decrease in the coefficient of friction, where the effect is more pronounced in the case of the formation of Ti–Ta surface alloys by a beam power of 1250 W.

Highlights

Titanium and its alloys are commonly used in the field of modern biomedicine and for the manufacturing of implants due to their biocompatibility, superior corrosion resistance, and static and fatigue strength [1,2,3]
In work [18], the Ti–Ta alloys were manufactured by selective laser melting, and the results showed that the Ta amount is of major importance for the phase composition, microstructure, mechanical, and corrosion properties
The average values of the friction coefficient were investigated, and the results reveal that the coefficient of friction (COF) of the Ti substrate was about 0.52; the COF of the Ti–Ta alloy formed by a beam power of 1250 W was about 0.18; the COF of the Ti–Ta alloy formed by a beam power of 1750 W was about 0.36

Summary

Introduction

Titanium and its alloys are commonly used in the field of modern biomedicine and for the manufacturing of implants due to their biocompatibility, superior corrosion resistance, and static and fatigue strength [1,2,3]. Some health problems related to the release of metallic ions exist, which could lead to adverse reactions and implant failure [4]. Young’s modulus of these materials significantly differs from that of the human bones, which can cause the resorption of adjacent bone tissues [7]. The ideal implant should exhibit low Young’s modulus (very close to that of the human bones), excellent wear resistance, and biocompatibility [8]. The discussed requirements for the implant material depend mostly on the surface properties of the alloys, and can be achieved by an appropriate technique for surface modification

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