In situ measurement of residual stresses and elastic moduli in thermal sprayed coatings Part 1: apparatus and analysis

Mechanical properties, such as residual stress and Young's modulus, play a critical role in the synthesis and performance of thermally sprayed coatings. Thus, it is important to understand their evolution, the influence of processing parameters, and to be able to determine them accurately. The first part of this two-part paper presents a novel in situ curvature method for determination of stresses and Young's modulus of plasma sprayed coatings. The principle of the method is explained, details of the instrument are provided and the analytical procedure is described. The capabilities of the method are discussed in detail, namely the ability to observe the stress evolution during the entire spraying process, to separate the quenching and thermal stress contributions to final residual stress and to determine the Young's modulus of the coating. Brief examples of application are also included, and the potential for use of this method for process control of coating quality is addressed. In the second part, a case study for plasma sprayed molybdenum will be presented, focusing on the influence of the key processing parameters