Structural Characterization and Mechanical Properties of a Titanium Nitride-Based Nanolayer Prepared by Nitrogen Ion Implantation on a Titanium Alloy

Abstract EN

A functionalized surface nanolayer less than 200 nm in thickness was prepared by nitrogen ion implantation at fluences of 2 · 10 17 , 4 · 10 17 , and 6 · 10 17 c m - 2 and at an accelerating voltage of 90 kV on the Ti6Al4V alloy.

The evolution of the surface mechanical properties and the structural mechanism of the hardening were investigated.

X-ray diffraction showed a great number of αTi+N interstitial nitrogen atoms and finely dispersed TiN precipitates in the modified surface nanolayer.

The functionalized surface nanolayer on the sample with applied fluence of 2 · 10 17 c m - 2 had a predominant amount of αTi+N of about 45 wt% with minority TiN compound up to 20 wt%.

The TiN content increased dramatically with increasing fluence of the implanted nitrogen.

Nanoindentation investigations found that the indentation hardness improved up to 408% and that the reduced elastic modulus was increased up to 140%.

The main hardening mechanism varied with the nitrogen concentration.

Nitrogen ion implantation at low fluence of 2 · 10 17 c m - 2 led to a functionalized surface nanolayer in which the hardening was mainly caused by the microstrain due to the large amount of interstitially located nitrogen.

Applied fluences of 4 · 10 17 and 6 · 10 17 c m - 2 increased the content of TiN compounds, which became the predominant hardening mechanism.