Residual, or locked-in internal, stresses are regions of misfit within a metal part or assembly that can cause distortion and fracture just as can the more obvious applied, or service, stresses. This chapter describes the fundamental facts about residual stresses and discusses the basic mechanisms of residual stress formation: thermal, transformational, mechanical, and chemical.

Temperature and deformation gradients developed in the course of manufacturing can have undesired effects on the microstructures along their path; the two most common being residual stress and distortion. This chapter discusses these manufacturing-related problems and how they can be minimized by heat treatments. It also provides information on residual stress evaluation and prediction techniques.

This article, prepared under the auspices of the ASM Thermal Spray Society Committees on Accepted Practices, describes a procedure for evaluating residual stresses in thermal spray coatings, which is an extension of the well-known layer removal method to include the Young’s modulus and Poisson’s ratio properties of the thermal spray coating material and the substrate. It presents questions and answers that were selected to introduce residual stresses in thermal spray coatings. The article describes equipment and the laboratory procedure for the modified layer removal method and provides the description of the residual stress specimen. It also describes the procedures for applying or installing bonded resistance strain gages, the dimensions of the test specimen, the procedure for removing layers, and the method for interpreting the data to evaluate residual stresses. The spreadsheet program, “ MLRM for Residual Stresses ,” is available as a supplement to this document.