Influence of Impact Angle and Gas Temperature on Mechanical Properties of Titanium Cold Spray Deposits
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JTTEE5 20:234–242 DOI: 10.1007/s11666-010-9557-1 1059-9630/$19.00 ASM International
Influence of Impact Angle and Gas Temperature on Mechanical Properties of Titanium Cold Spray Deposits K. Binder, J. Gottschalk, M. Kollenda, F. Ga¨rtner, and T. Klassen (Submitted June 1, 2010; in revised form August 27, 2010) Titanium coatings have a high potential for various applications and can be produced in high quality by cold spraying. In this contribution, the two major challenges are addressed: (i) optimizing mechanical properties by systematic variation of process parameters, and (ii) evaluating the influence of the spray angle with respect to complex geometries. High deposition efficiencies of more than 95% can be obtained and the coatings show very low porosities as well as high tensile strength of over 450 MPa by using nitrogen as process gas. The influence of process conditions on the mechanical properties is discussed on the basis of single impact morphologies, coating microstructures, tubular coating tensile, as well as shear tests.
Keywords
coating-substrate interaction, cold gas dynamic spraying, influence of spray parameters
1. Introduction Due to the hexagonal closed packed (hcp) structure, plastic deformation of titanium (Ti) is limited and shaping processes like rolling (760-815 C) and forging (815900 C) have to be performed at sufficiently high temperatures and/or require subsequent annealing steps, and all these have to be performed in inert environments (Ref 1-3). Therefore, less costly routes for processing more complex shapes are requested by industry. Cold spraying is a promising technique for producing thick coatings with near-bulk properties. Metal particles are accelerated toward a substrate and deposited at the desired spot. Bonding of particles is facilitated by shear instabilities that occur during impact due to the plastic deformation under high strain rates (Ref 4-6). Because process temperatures (T) are comparatively low This article is an invited paper selected from presentations at the 2010 International Thermal Spray Conference and has been expanded from the original presentation. It is simultaneously published in Thermal Spray: Global Solutions for Future Applications, Proceedings of the 2010 International Thermal Spray Conference, Singapore, May 3-5, 2010, Basil R. Marple, Arvind Agarwal, Margaret M. Hyland, Yuk-Chiu Lau, Chang-Jiu Li, Rogerio S. Lima, and Ghislain Montavon, Ed., ASM International, Materials Park, OH, 2011. K. Binder, J. Gottschalk, M. Kollenda, F. Ga¨rtner, and T. Klassen, Helmut Schmidt University, University of the Federal Armed Forces, Hamburg, Germany. Contact e-mail: [email protected].
234—Volume 20(1-2) January 2011
(£1000 C) and processing times are typically shorter than about 1 ms, contamination by interstitial impurities like oxygen or nitrogen can be minimized. Several attempts were made to produce Ti-coatings or freestanding parts by cold spraying (Ref 7-12). Due to the limited deformability of Ti, so far costly helium had to be used to obtain s
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