Titanium alloys are extensively used, especially in the aerospace industry, where high strength to weight ratio is of prime consideration. However, they suffer from poor surface wear which limits further application in tribological systems.

A number of surface modification techniques have been used to improve surface wear properties and these include conventional nitriding and chemical/physical vapor phase coatings. However, nitriding is a high temperature technique requiring a long processing time, and the success of vapor deposition to produce titanium nitride coatings is limited by the adhesive strength of the coat to the titanium alloy.

This study developed a laser surface modification process to increase the wear resistance of titanium alloys. A multidisciplinary approach including microstructure, wear, finite element, heat transfer, residual stresses, image processing and neural network analysis is used.

Resolidified region treated under a pure nitrogen (100% vol.) gas shield

An ANSYS finite element analysis of temperature distribution

An ANSYS finite element analysis of the distribution of residual stresses

The distribution of residual stresses within a single laser melt track (left) and within overlapping, adjacent laser melt tracks, and a comparison between the results obtained by x-ray diffraction with those obtained by the finite element method

Images obtained by online sensing of the molten pool. The shape of the molten pool is used to control the depth of nitriding during the surface modification process.