On the failure mechanisms of Cr-coated 316 stainless steel in bending fatigue tests.

• Fully reversed bending fatigue tests on uncoated and Cr-coated stainless-steel specimens. • Opposing trends of Cr-coating influence on fatigue life at high and low stress amplitudes. • A coating/substrate interfacial crack formation mechanism due to substrate shear steps identified experimentally. • Accompanying finite element stress analysis corroborates experimental findings. • The importance of interface engineering in coating applications to fatigue resistance highlighted. Fully-reversed cyclic bending tests were conducted on uncoated and Cr-coated 316 stainless steel specimens. At high stresses, the uncoated specimens outperformed the Cr-coated ones, while the trend reversed at low stresses. For Cr-coated specimens subjected to high stress amplitude loading, experimental observations showed crack initiation at the Cr/substrate interface due to shear steps formed from dislocation activities in the substrate—a conclusion supported by accompanying finite element analysis. Interfacial crack initiation was not observed under low stress amplitudes. This difference in fatigue crack initiation mechanisms induced an opposite trend in fatigue life between high and low stress amplitudes. [ABSTRACT FROM AUTHOR]