Thermal stability and hydrogenation behavior of Zr-1Nb alloy with TiN_x and Ti/TiN_x coatings

Titanium nitride coatings were deposited by reactive dc magnetron sputtering (dcMS) to protect Zr-1Nb alloys from hydrogen embrittlement. Dense titanium (Ti) interlayer was prepared between TiN_x protection film and a Zr substrate to improve thermal stability and adhesion between the TiN_x and the substrate at high temperatures. Hydrogen absorption of Zr- 1Nb with TiN_x and Ti/TiN_x at 623 K was reduced in comparison with uncoated Zr-1Nb. No peeling or cracks of Ti/TiN_x coatings is observed after thermal cycling up to 1073 K. The high temperature (1073 K) hydrogenation behaviour differs from the hydrogenation at lower temperature by increasing the amount of dissolved hydrogen in the β-phase of zirconium. The higher rate of hydrogen absorption by Zr-1Nb with TiN_x was observed due to the coating delamination as a result of differences in thermal expansion coefficients, while Ti/TiNx demonstrates the lower hydrogen absorption at 1073 K and good adhesion strength. (paper)