Study of the Effect of Thickness on the Residual Stress Profile of a Cold Spray Coating by Finite Element Analysis Felipe Torres, Ruben Fernandez Faculty of Physical and Mathematical Science, University of Chile, Santiago, Chile felipe.torres.c@ug.uchile.cl, +56974577762 Abstract The understanding of residual stress is of critical importance in the cold spray and thermal spray processes. It has a direct effect on the integrity of the coating related to the adhesion strength, fatigue life, and can lead to undesired effects such as the delamination of the coating. In cold spray, several investigations have evaluated the impact of the residual stress on the coatings, and it is generally accepted that cold spray coatings follow a similar profile to those obtained in the shot peening process. Although the measurement of residual stresses gives fundamental insight into the process, the estimation of such stresses considering the deposition of each layer by numerical methods has not been extensively studied. This work proposes a method for analyzing the evolution of residual stress on a cold spray coating, both on the coating and the substrate, as a function of the deposited layers, using Finite Element Analysis (FEA). The evolution of the residual stress profile with the coating thickness was obtained along the transverse direction. The results were compared to experimental and numerical data from previous studies. The influence of the deposition of each layer on the residual stress profile has been discussed. Introduction Cold spray is an additive manufacturing process based on the deposition of solid-state powder particles by high-velocity impacts. Particles are accelerated by injection into a high- velocity stream of expanding gas and are impacted against a substrate. In the impact, particles undergo high plastic deformation and an increase in temperature, generating internal residual stresses on the material. This phenomenon has an influence on the properties of the coatings. Residual stress is an important aspect that can affect the integrity and durability of the coatings. Tensile residual stress can cause delamination and peeling. This case has been found on thermal spray coatings and can be explained by the solidification and consequent cooling to room temperature of the successively deposited layers [1–4]. On the other hand, compressive residual stress is beneficial for the coatings and can improve the fatigue life [1,5–9]. Many studies have reported that cold spray coatings exhibit a beneficial compressive residual stress [3,6,10–16]. These studies mainly explain this phenomenon with the peening effect caused by the impact of the particles against the substrate. Previous research has tried to predict the residual stress profile on cold spray coatings by numerical and analytical methods [3,10,11]. Ghelichi et al. [11] deposited pure aluminum and Al7075 powders on an Al5052 substrate. They implemented a numerical and an analytical model to study the annealing effect of the gas temperature on the residual stress of the substrate. The authors obtained a good agreement with experimental data. Shayegan et al. [10] tried to predict the effect of several deposition parameters on the residual stress profile for the substrate. They simulated aluminum particles impacting a magnesium AZ31B substrate. The study examined the effect of particle velocity, diameter, shape, angle of impact, and the friction coefficient on the residual stress profile generated on the substrate. Luzin et al. [3] measured the residual stress on coatings of different materials and fitted the residual stress profiles of the coating and the substrate with the Tsui and Clyne analytical model[17]. Although residual stress can be measured and fitted to numerical and analytical models, the evolution of the residual stress profile on the coatings and the substrate as a function of the deposited layers is not easily predicted. In this study, a numerical analysis of residual stress in an aluminum cold spray coating is implemented. The analysis is done on both the substrate and the coating. For this purpose, a new methodology is proposed, in which the deposited layers and the substrate, both of aluminum, are considered as a single solid. The behavior of the residual stress profile is examined for 16 deposited layers. The thermal expansion effect is not considered in this work. Numerical model The numerical method in this work is divided into two parts, impacts modeling, and layering modeling. The first part (impacts) simulates the cold spray process of aluminum particles over an aluminum substrate. This part is divided, in turn, into two steps. The first step was focused on modeling the impact of 325 particles without considering the bonding of the particles. This step had the objective of extracting the residual stress induced on a substrate of aluminum solely by the impacts. The second step was focused on the impact and deposition of 25 particles over a substrate with the same characteristics as the previous simulation. This step was done to extract the residual stress induced on one layer due to deposition. Finally, the Thermal Spray 2021: Proceedings from the International Thermal Spray Conference May 24–28, 2021 F. Azarmi, X. Chen, J. Cizek, C. Cojocaru, B. Jodoin, H. Koivuluoto, Y. Lau, R. Fernandez, O. Ozdemir, H. Salami Jazi, and F. Toma, editors DOI: 10.31399/asm.cp.itsc2021p0261 Copyright © 2021 ASM International® All rights reserved. www.asminternational.org 261 Downloaded from http://dl.asminternational.org/itsc/proceedings-pdf/ITSC 2021/83881/261/487853/itsc2021p0261.pdf by guest on 22 September 2021