Improvement of the tribological characteristics of VT6 titanium alloy surface layers by diffusion saturation with interstitial elements

Keywords

Titanium alloy VT6, modification of surface layers, chemical-thermal treatment, oxidation, nitridation, phase composition, tribological characteristics, friction mechanism.

Cite as

Student М. М., Pohrelyuk І. М., Luk’yanenko A. G., Student О. Z., Zadorozhna Kh. R., and Hvozdetskyi V. М. Improvement of the tribological characteristics of VT6 titanium alloy surface layers by diffusion saturation with interstitial elements. Physicochemical Mechanics of Materials. 2025. 61(6), 57-64.

https://doi.org/10.15407/pcmm2025.06.057

Abstract

This study investigates the influence of surface modification of VT6 titanium alloy with interstitial elements (nitrogen and oxygen) on its tribological behavior under dry sliding conditions against a Cr18Ni10T steel counterbody. Tests were conducted at a specific load of 1 MPa for 600 s. Diffusion-hardened surface layers were produced by thermochemical treatment. Phase composition analysis revealed that nitriding (or oxidation) of the VT6 alloy results in the formation of titanium nitride (or titanium oxide) in the surface region, accompanied by a pronounced hardness gradient across the modified layer. During sliding tests, the friction coefficient of the nitrided VT6 alloy in contact with Cr18Ni10T steel increased progressively, reaching a value of approximately 0.6. This behavior is attributed to sharp asperities on the nitrided surface acting as micro-cutting edges that remove material from the stainless steel counterbody. In contrast, for the oxidized VT6 alloy, gradual surface smoothing at the friction interface led to a decrease in the friction coefficient to 0.15–0.2. Moreover, the wear resistance of both nitrided and oxidized layers during reciprocating sliding by steel and ceramic balls was found to improve significantly – by nearly a factor of five – at specific loads of 10 MPa.

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