Optimization of Atmospheric Plasma Spray Process Parameters using a Design of Experiment for Alloy 625 coatings |
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Authors: | F Azarmi TW Coyle J Mostaghimi |
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Affiliation: | (1) Mechanical Engineering, University of Toronto, Center for Advanced Coating Technologies, 5 King’s College Road, Toronto, Canada, M5S 3G8 |
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Abstract: | Alloy 625 is a Ni-based superalloy which is often a good solution to surface engineering problems involving high temperature
corrosion, wear, and thermal degradation. Coatings of alloy 625 can be efficiently deposited by thermal spray methods such
as Air Plasma Spraying. As in all thermal spray processes, the final properties of the coatings are determined by the spraying
parameters. In the present study, a D-optimal experimental design was used to characterize the effects of the APS process
parameters on in-flight particle temperature and velocity, and on the oxide content and porosity in the coatings. These results
were used to create an empirical model to predict the optimum deposition conditions. A second set of coatings was then deposited
to test the model predictions. The optimum spraying conditions produced a coating with less than 4% oxide and less than 2.5%
porosity. The process parameters which exhibited the most important effects directly on the oxide content in the coating were
particle size, spray distance, and Ar flow rate. The parameters with the largest effects directly on porosity were spray distance,
particle size, and current. The particle size, current, and Ar flow rate have an influence on particle velocity and temperature
but spray distance did not have a significant effect on either of those characteristics. Thus, knowledge of the in-flight
particle characteristics alone was not sufficient to control the final microstructure. The oxidation index and the melting index incorporate all the parameters that were found to be significant in the statistical analyses and correlate well with the
measured oxide content and porosity in the coatings.
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Keywords: | coating optimization using DOE influence of spray parameters porosity of coatings APS coatings oxidation in APS coatings |
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