Instrumented indentation methods for measurement of residual stresses in thin films/coatings: a review

Residual stresses can be easily generated during the manufacturing of thin films/coatings due to deformation mismatches. The presence of residual stress may induce issues such as premature cracking and shedding, ultimately affecting the mechanical performance and service life of these materials. Consequently, measurement of residual stresses in thin films/coatings is of great importance to ensure their reliability in applications. Instrumented indentation, as a sophisticated micro/nano scale testing technique, proves highly effective for measuring residual stress in thin films/coatings due to its exceptional resolution and non-destructive characteristics. This review provides a comprehensive discussion and summary on the current instrumented indentation models for determination of residual stresses, including their advantages and limitations. Furthermore, the trends for future development and possible challenges were also given. For the current models, challenges mainly originate from preparing stress-free thin film/coating samples as reference samples, determining the directionality of non-equibiaxial residual stresses, as well as eliminating the influence of substrates on the measurement accuracy. Thus, there is an increasing demand to establish an instrumented indentation model capable of decoupling substrate effects and accurately measuring non-equibiaxial residual stresses in thin films/coatings without using reference samples.