X-ray diffraction, optical microscopy, and microhardness studies of gas nitrided titanium alloys and titanium aluminide

Thermochemical surface gas nitriding of β21s, Timetal 205 and a Ti–Al alloy was conducted using differential scanning calorimeter equipment, in nominally pure nitrogen at 850 °C and 950 °C (β21s), 730 °C and 830 °C (Timetal 205), and 950 °C and 1050 °C (Ti–Al) for 1 h, 3 h and 5 h. X-ray diffraction analyses showed new phases formed in the nitrided layer, depending on the alloy and the time and the temperature of nitriding. Microstructures were analyzed using optical microscopy. Cross-sectional microhardness profiles of cross-sectional samples after nitriding were obtained using a Knoop indenter.