The Effect of Deposition Conditions on Adhesion Strength of Ti and Ti6Al4V Cold Spray Splats
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JTTEE5 21:288–303 DOI: 10.1007/s11666-011-9720-3 1059-9630/$19.00 ASM International
The Effect of Deposition Conditions on Adhesion Strength of Ti and Ti6Al4V Cold Spray Splats Dina Goldbaum, J. Michael Shockley, Richard R. Chromik, Ahmad Rezaeian, Stephen Yue, Jean-Gabriel Legoux, and Eric Irissou (Submitted July 12, 2011; in revised form November 5, 2011) Cold spray is a complex process where many parameters have to be considered in order to achieve optimized material deposition and properties. In the cold spray process, deposition velocity influences the degree of material deformation and material adhesion. While most materials can be easily deposited at relatively low deposition velocity (700 m/s) that are only achievable with high gas pre-heat temperatures, the cohesive strength was higher than the splat adhesion strength. This is likely an effect of the gas jet heating the substrate and coating during deposition, leading to an enhancement to the metallurgical bonding. This hypothesis is further supported by a comparison between the cohesive strength and the data for splat adhesion strength on heated substrates. At velocities below 700 m/s, the splat adhesion strength on heated substrates is higher than the cohesive strength. At these velocities, the gas preheat temperature used for a coating is lower and temperature effects are reduced. Thus, a splat on pre-heated substrate at these velocities should have a stronger bond. For higher deposition velocities (>700 m/s), where gas jet heating is more significant, the cohesive strength and splat adhesion strength on heated substrates agree very well. In a previous study, we observed a similar correlation between cohesive strength and splat adhesion strength (Ref 25), but the comparison made here between Binder et al. (Ref 21) and our measurements of splat adhesion strength is the first time that both the effect of velocity and temperature have been correlated in this way for the coating and splat levels. Our splat adhesion test was shown to reveal trends for adhesion strength versus deposition velocity or temperature that are relevant to the bonding for a full coating, both between coating and substrate and cohesive strength within the coating. Also, the small scale precision of the method was useful for tracking the effects of particle size and position in the gas jet on the adhesion strength of splats. These are two variables that are known to have an effect, but are nearly impossible to measure experimentally
Peer-Reviewed
The adhesion strength of splats was found to vary with particle size and particle position in the deposition pass. Particle deposited at the center of the deposition pass and of smaller particle diameter showed superior adhesion strength when compared to the large particles or particles at the edge of the deposition pass. The extent of particle deformation measured in terms of splat flattening ratio, did not reflect well the degree of splat adhesion. The deformation of the substrate, on the other hand, was found to have a beneficial effe
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