Mechanical behavior of a chromium coating on a zirconium alloy substrate at room temperature

The mechanical behavior of a 15 mu m-thick chromium coating deposited on a zirconium alloy substrate using a particular physical vapor deposition process is studied at room temperature using several exper-imental techniques at different scales: biaxial tests (internal pressure + axial tension) with several stress biaxiality ratios on outer-coated tubes; in situ tensile tests in a scanning electron microscope (SEM) on coated sheet samples. The cracking and plasticity of the coating are studied using acoustic emission, dig-ital image correlation and SEM observations. The results show that the first channeling cracks in the coating initiate at 0.3-0.4% macroscopic strain, when the substrate starts to yield. Under further loading, the crack density increases first rapidly then more slowly, before reaching saturation. Plastic strain of the non-cracked coating regions is observed, in addition to the increase of crack opening. No interface de-cohesion of the coating is observed. The cracks, both transgranular and intergranular, do not penetrate significantly into the substrate. (c) 2021 Elsevier B.V. All rights reserved.