Influence of indentation depth on the determination of the apparent Youngʹs modulus of bi-layer material: Experiments and numerical simulation

Depth sensing indentation experiments have been conducted on stainless steel thin films deposited by reactive magnetron sputtering on AU4G aluminium-alloy substrates to highlight that elastic response of bi-layer materials can be specific of the coating alone only for very low indentation depths. It is shown experimentally that Bückleʹs rule is at least one order of magnitude too high when applied by default to determine coating-specific elastic response. These results have been confirmed by boundary element numerical simulation underlining that elastic response of a thin film deposited on substrate deviates from the coating’s response above relative indentation depth around 1–2%.