Creep behavior study at 500°C of laser nitrided Ti-6Al-4V alloy

Titanium and its alloys are excellent for applications in structural components submitted to high temperatures owing to their high strength to weight ratio, good corrosion resistance and metallurgical stability. However, the affinity by oxygen is one of main factors that limit its application as structural material at high temperatures. The objective of this study was to estimate the influence of laser treatment on the creep of the Ti-6Al-4 V alloy. Constant load creep tests were conducted with Ti-6Al-4 V alloy at 500 °C. The creep tests were conducted on a standard creep machine at stress of 319 MPa to 520 MPa. Samples with a gage length of 18.5 mm and a diameter of 3 mm were used for all tests. When the Ti-6Al-4 V was tested the effect of the oxidation was smaller and the behavior of the creep curves showed that the life time was better. There was a decreasing of ductility of material (final strain) and life time was increased. Occurred a decreasing of steady state creep in function of the reduction of oxidation process, showing that for the Ti-6Al-4 V alloy their life time was strongly affected by the superficial treatment that was submitted because the oxidation suffered by the material.