Abstract—In this article, using finite element analysis (FEA) and an X-ray diffractometer (XRD), cold-sprayed titanium particles on a steel substrate is investigated in term of cooling time and the development of residual strains. Three cooling-down models of sprayed particles after deposition stage are simulated and discussed: the first model (m1) considers conduction effect to the substrate only, the second model (m2) considers both conduction as well as convection effect to the environment, and the third model (m3) which is the same as the second model but with the substrate heated to a near particle temperature before spraying. Thereafter, residual strains developed in the third model is compared with the experimental measurement of residual strains, which involved a Bruker D8 Advance Diffractometer using CuKa radiation (40kV, 40mA) monochromatised with a graphite sample monochromator. For deposition conditions of this study, a good correlation was found to exist between the FEA results and XRD measurements of residual strains. Keywords—cold gas dynamic spray, X-ray diffraction, explicit finite element analysis, residual strain, titanium, particle impact, deformation behavior. I. INTRODUCTION ECHNOLOGICAL advantages of titanium make this material attractive for a range of applications including aviation, sports, medical devices, and automotive industry. However, application of titanium is limited due to the high costs for producing and machining; where cost for titanium is approximately ten times more than steel. Improvement in fabrication process for titanium is fundamental for more cost effective titanium products in the future. Cold spray technology offers a cost-effective alternative for a wide range of products including titanium. In this technology, titanium particles in a carrier gas are accelerated under high pressure and temperature using a De Laval type nozzle to supersonic velocity (~500-1000 m/s) [1]. The impact of particles to substrate results in plastic deformation and bonding, which create coatings. Compared with other spray technologies, cold spray process temperatures during the impact is generally below the melting temperature of particles. This, under certain conditions, has the potential to produce an T. D. Phan is with Swinburne University of Technology, Hawthorn, Vic. 3122, Australia (e-mail: Dphan@swin.edu.au). Dr S. H. Zahiri is with CSIRO Manufacturing and Materials Technology, Gate 5, Normanby Road, Clayton, Vic. 3168, Australia (e-mail: Saden.Zahiri@csiro.au). Prof S. H Masood is with Swinburne University of Technology, Hawthorn, Vic 3122, Australia (e-mail: SMasood@swin.edu.au). Dr M. Jahedi is with CSIRO Manufacturing and Materials Technology, Gate 5, Normanby Road, Clayton, Vic. 3168, Australia (e-mail: Mahnaz.Jahedi@csiro.au). Finite element method allows high velocity impact behavior of particles to be simulated and visualised. It helps to investigate the effects of varying coating conditions to the characteristics of sprayed titanium parts. Recently, Zhang, Li and Liao [3] have modelled the impact and deformation behaviors of spray particle. The reported numerical results have indicated that the flattening ratio of particles increases with the increase in particle impact velocity, which is comparable to other published work [4, 5]. The finite element method can also be applied to determine residual strains in coatings [6, 7], which is an important parameter in a cold spray process because failure of coating due to residual strains is a serious problem like cracking. Predicting the development of residual strains can also help to avoid strain-induced failures. Ghafouri-Azar et. al. [8] investigated the effect of varying both substrate and coating temperature on development of residual strain. In their study, a high velocity oxy-fuel torch was used to deposit coating of both stainless steel and tungsten carbide cobalt alloy on a stainless steel substrate. In addition, measurement of residual strain by X-ray diffraction (XRD), which is a non-destructive method, has been widely used to investigate the development of residual stress and strain by several researchers [7, 8]. In the measurement process, mono-chromised X-ray is diffracted following Bragg´s law [9]: n.λ = d.sin(2θ) (1) where n = order of magnitude, λ = X-rays wavelength, d = lattice spacing and 2θ = diffraction angle. Any strain in the material causes the planes in the crystal lattice to change and a tilt in reflected beam occurs from the original with a slightly different angle. A diffraction peak is made up of many peaks from different sub-grains. Their shape depends on crystal size, and their position on the local micro- strain [10]. For example, shifted planes create smaller diffraction peaks around the original one resulting in so called “X-ray Line Broadening”. All single peaks together solve in the measured diffraction peak [11]. In this study, cold-sprayed titanium particles on a steel substrate are analysed in term of cooling time and developed residual strains using the finite element analysis (FEA) and X- ray diffractometer (XRD) measurement. Three types of cooling-down models of sprayed particles after deposition Thanh-Duoc Phan, Saden H. Zahiri, S. H. Masood, Mahnaz Jahedi Finite Element Analysis of Cooling Time and Residual Strains in Cold Spray Deposited Titanium Particles T oxygen free deposit [2]. World Academy of Science, Engineering and Technology International Journal of Materials and Metallurgical Engineering Vol:6, No:8, 2012 805 International Scholarly and Scientific Research & Innovation 6(8) 2012 scholar.waset.org/1307-6892/10481 International Science Index, Materials and Metallurgical Engineering Vol:6, No:8, 2012 waset.org/Publication/10481