Properties of surface layers on titanium alloy produced by thermo-chemical treatments under glow discharge conditions

Abstract

The recent rapid progress in surface treatment techniques dictates that the titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The present paper describes a modification of the plasma discharge nitriding treatment of titanium alloys, i.e. the glow discharge-assisted oxycarbonitriding, which by introducing oxygen, nitrogen and carbon into the surface zone of the layer [a Ti(NCO) type layer improves its useful properties, primarily the resistance to frictional wear and the resistance to corrosion [1,2]. This is because titanium shows a good affinity to oxygen, carbon and nitrogen, whereas the chemical composition of the layer depends on the chemical composition of the low-temperature plasma that forms under the conditions of glow discharge. The present paper also discusses the results of the corrosion behaviour of the OT4-0 titanium alloy in simulated human body fluids before and after the sterilization process. The isothermal and cyclic plasma nitriding and carboxynitriding processes on titanium alloys can be carried out in a specially modified glow discharge chamber designed for the plasma nitriding process.