Influence of the Powder Size Distribution on the Microstructure of Cold-Sprayed Copper Coatings Studied by X-ray Diffrac
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JTTEE5 16:610–618 DOI: 10.1007/s11666-007-9116-6 1059-9630/$19.00 ASM International
Influence of the Powder Size Distribution on the Microstructure of Cold-Sprayed Copper Coatings Studied by X-ray Diffraction T. Kairet, M. Degrez, F. Campana, and J.-P. Janssen (Submitted March 9, 2007; in revised form August 13, 2007) Two copper powders were deposited with CGT3000 cold-gas dynamic spray system on aluminum substrates. Mechanical properties have been studied using microhardness, nanoindentation, and bond strength measurements. The deposition efficiency has also been studied. The x-ray diffraction patterns allow the characterization of the microstructure such as grain size, strain in the coating, and dislocation densities. Both powders and coatings have been fully characterized. Three methods have been used to interpret the x-ray patterns: the Warren-Averbach method, the Hall-Williamson (H-W) method, and the modified H-W method. A comparison between the state of the powders before and after deposition will give an insight on the metallurgical processes that take place during the formation of the coating. The influence of the grain size distribution will also be discussed.
Keywords
cold-gas dynamic spraying, copper, HallWilliamson, Warren-Averbach, x-ray diffraction
1. Introduction The cold-gas dynamic spray process leads to the build up of a coating by accelerating fine powders (5–25 lm in diameter) to supersonic speeds in a Laval nozzle. The powder particles impact the surface with a speed ranging from 500 to 1200 m/s and bond to the surface when a critical value of impact speed is reached. During the impact, severe plastic deformation and high strain rates allow the formation of adiabatic shear bands at the interface between the impinging particle and the substrate. Several authors (Ref 1, 2) have linked the value of the critical speed for bonding to the onset of these adiabatic shear bands. Borchers et al. (Ref 3) have observed grain refinement and changes in the copper microstructure at the interface between grains. Fine elongated grains and possibly some recrystallized grains have also been identified. This article is an invited paper selected from presentations at the 2007 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Global Coating Solutions, Proceedings of the 2007 International Thermal Spray Conference, Beijing, China, May 1416, 2007, Basil R. Marple, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2007. T. Kairet and M. Degrez, Matie`re & Mate´riaux, Universite´ Libre de Bruxelles, Rue de lÕIndustrie 24, Nivelles, 1400, Belgium; and F. Campana and J.-P. Janssen, Advanced Coating, S.A., Liege, Belgium. Contact e-mail: [email protected].
610—Volume 16(5-6) Mid-December 2007
The powder size distribution will have a crucial importance on the quality of the coating. The process is essentially influenced by the kinetic energy transferred to the
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