Modification of the Microstructure and Properties of Ti-1Al-1Mn Titanium Alloy due to Nitriding and Oxynitriding under Glow Discharge Conditions

摘要

Titanium - a material with specific chemical and physical properties - has been increasingly applied as an attractive constructional material. Titanium has a low specific gravity, a high corrosion resistance and a high relative strength. Moreover it shows a good biocompatibility in the environment of human cells and tissues, which is important in such areas as the manufacture of artificial human bone fragments, prosthetic implants and endoprostheses of human joints, and in joining human bones. A drawback is its low hardness and rather poor frictional wear resistance, but these properties can be improved by subjecting titanium to various surface treatments, such as thermal spraying, PVD, anodic oxidation, ion implantation, laser treatment and various glow discharge assisted treatments. The most promising methods seem to be those involving the glow discharge assisted synthesis of various surface layers, which permits a full control of the process of the layer formation, i.e. the desired modification of the layer structure and chemical composition, and thus of its properties. Among these methods are glow discharge assisted nitriding and carbonitriding in a glow discharge activated gaseous enviroment. The use of titanium alloys in, for example, aircraft engines and load carrying constructional elements imposes the requirement of a high resistance to fatigue failure. It has been found that the fatigue strength of titanium alloys strongly depends on the heat treatment they are subjected to. The thermochemical treatments employed in modern technologies, such as boron and nitrogen implantation, laser-assisted nitriding and gas nitriding also improve the fatigue properties of titanium and its alloys. The present paper discusses the effect of the glow discharge assisted nitriding and oxynitriding processes on the properties of the Ti-1Al-1Mn titanium alloy.