Microstructure and Mechanical Properties of Low-Pressure Cold-Sprayed (LPCS) Coatings
- PDF / 511,485 Bytes
- 7 Pages / 593.972 x 792 pts Page_size
- 33 Downloads / 209 Views
eli Koivuluoto, Juha Lagerbom, Mikko Kylma¨lahti, and Petri Vuoristo (Submitted May 7, 2008; in revised form September 9, 2008) In low-pressure cold spraying, compressed air is used as a process gas. The most important process parameters are temperature and pressure. In the Low-Pressure Cold Spraying (LPCS) system in this study, the maximum preheating temperature is 650 °C and pressure is 9 bar. Powders used in LPCS process contain alumina with metallic powders; therefore LPCS is the method to spray soft metallic coatings with ceramic hard phase for different application areas, e.g., thick coatings and coatings for electrical and thermal conduction and corrosion protection applications. The aim of this study was to investigate microstructure, denseness, and mechanical properties of LPCS Cu, Ni, and Zn coatings. LPCS coatings seemed to be dense according to Scanning Electron Microscope (SEM) studies but corrosion tests were needed to identify the existence of porosity. Through-porosity was observed in structures of the LPCS coatings. Bond strengths of LPCS Cu and Zn coatings were found to be 20-30 MPa, and hardness was high indicating reinforcement and work hardening.
Keywords
copper, low-pressure cold spraying, mechanical properties, microstructure, nickel, zinc
1. Introduction Cold spraying was developed in the former Soviet Union in the 1980s. Cold spraying is regarded as the latest development in the thermal spray techniques. The process is based on the utilization of significantly lower process temperatures with high particle velocities than those in other thermal spray methods. A coating is formed when powder particles impact at high velocities (high kinetic energy) on the substrate, deform, and adhere to substrate or to other particles. Moreover, good bonding between the cold-sprayed powder particles needs a high degree of plastic deformation upon the particle impact (Ref 1, 2). In low-pressure cold spraying (LPCS), preheating temperatures of the process gas (air) are between room temperature This article is an invited paper selected from presentations at the 2008 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray Crossing Borders, Proceedings of the 2008 International Thermal Spray Conference, Maastricht, The Netherlands, June 2-4, 2008, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2008. Heli Koivuluoto, Juha Lagerbom, Mikko Kylma¨lahti, and Petri Vuoristo, Department of Materials Science, Tampere University of Technology, P.O. Box 589, 33101 Tampere, Finland. Contact e-mail: [email protected].
Journal of Thermal Spray Technology
(RT) and 650 °C, and pressures are between 5 and 9 bar. Typically, compressed air is used in this method as the process gas to spray powder mixtures (Ref 3). Particle velocities are reported to be approximately from 350 to 700 m/s in the low-pressure cold spray process (Ref 4). Irisso
Data Loading...
