INTERNATIONAL JOURNAL OF MATERIALS SCIENCE AND ENGINEERING Volume 2, Nos. 1-2, January-December 2011, pp. 65-72 EFFECT OF NOZZLE GEOMETRY ON EXIT VELOCITY, TEMPRATURE AND PRESSURE FOR COLD SPRAY PROCESS Tarun Goyal 1, *, Prince Sharma 2 , R. S. Walia 3 & T. S. Sidhu 4 1, *Research Scholar, Punjab Technical Univeristy, Jallandhar. 2 Research Scholar, PEC University of Technology, Chandigarh. E-mail: prince2605530@gmail.com 3 Assistant Professor, PEC University of Technology, Chandigarh. E-mail: waliaravinder@yahoo.com 4 Director, SBSCET, Ferozepur. E-mail: tssidhu@rediffmail.com Abstract: In the cold spray process, powder particles are carried away at supersonic velocity by the carrier gas on passing through the nozzle. Bonding of the particles to the substrate resulting in coating is achieved by the kinetic energy of the powder particles rather than the thermal energy in most of the thermal spray processes. The impacting particles should have velocity higher than the critical velocity in order to form the coating. In this paper, ANSYS modelling is used to predict the velocity, temperature and pressure of the particles exiting the nozzle in the cold spray process. Comparison is made by selecting different nozzle geometry used in commercially available cold spray process. The aim of the research is to compare the velocity, temperature and pressure contours of the particles for chosen nozzle geometries which may be validated using experimental techniques of velocity measurement. The research will be useful in analyzing the coating deposition characteristics as it provides an estimate to whether the exiting particles will achieve a velocity higher than the critical velocity, an important characteristic to achieve coating by cold spray process. Keywords: Cold spray, Nozzle, Velocity, Coating.  International Science Press, ISSN: 0976-6243 * Corresponding Author: goyaltarun1@gmail.com, Tel: +91-172-2753289, Fax: +91-172-2745175 1. INTRODUCTION The phenomenon of cold gas-dynamic spraying (cold spray) was discovered in the early 1980s at the Institute of Theoretical and Applied Mechanics of the Siberian Branch of the Russian Academy of Sciences (ITAM of RAS) while studying models subjected to a supersonic two- phase flow (gas + solid particles) in a wind tunnel [1]. The fundamental concept of the cold spray (CS) process is that the coating is formed by a high-velocity flow of ‘‘cold” particles on a ‘‘cold” substrate. Cold spray process uses a high-pressure, high- velocity gas jet to impart the velocity for the coating particles. A high- pressure jet, preheated to compensate for the adiabatic cooling due to expansion, is expanded through a converging/diverging nozzle to form a supersonic gas jet. Powder particles, transported by a carrier gas, are injected into this gas jet. Momentum transfer from the supersonic gas jet to the particles results in high-velocity particle jet. These powder particles, on impact onto the substrate surface, plastically deform and form interlinking splats, resulting in a coating [2]. The cold spray process eliminates the harmful effects of high- temperature on coatings and substrates, which result into significant advantages like avoiding oxidation and undesirable phases, retaining properties of initial particulate material, conducting heat and electricity easily through the coatings and providing high density, high hardness and cold worked micro-structure [3]. There are currently two commercially available variants of the CGDS system namely: • Low pressure cold gas-dynamic spray (LPCGDS) • High pressure cold gas-dynamic spray (HPCGDS) The two main clear cut distinctions of the LPCGDS system from the HPCGDS system are; the utilization of low pressure gas (5-10 bars instead of 25-30 bars) and the radial injection of powder instead of axial injection. A schematic diagram for LPGDS is shown in Fig. 1. The accelerating gas (usually air or N 2 ) is injected at low pressure (5-10 bars) and preheated within the gas heater to temperatures up to about 400 0 C to optimize its aerodynamic properties. Solid powder particles are radially introduced downstream of the throat section of the Figure 1: A Typical LPCGDS Device [5]