Surface properties of plasma-nitrided titanium alloys

Abstract

Titanium alloy WT3-1 with an σ + β structure was subjected to isothermal plasma nitriding at 730, 830 and 1030 °C, and cyclic plasma nitriding between 930 and 730 °C. The wear resistance of this alloy at a unit pressure of 400 MPa was determined using the “three rollers-taper” method whilst, for the assessment of the corrosion resistance in 15% H2SO4, the potentiodynamic technique was used. It has been found that the nitriding treatment enhances the wear resistance as well as the corrosion resistance of the alloy. Nitriding performed at 1030 °C results in a smaller increase in wear resistance than does nitriding carried out at below 930 °C. The nitriding temperature has no effect on the corrosion resistance of the layer. A comparison has been made between the properties of the differently nitrided layers produced on two opposite sides of the specimen. The layer formed on the upper side, exposed to ion bombardment, shows a higher wear resistance as well as higher corrosion resistance than that produced on the lower side. The wear resistance of the nitrided titanium alloy is higher than that of plasma-nitrided austenitic and martensitic steels. In addition to this, its corrosion resistance is higher in 0.05 M Na2So4 + 0.1 M NaCl.