Cold Spray Optimization via Residual Stress Measurement: A Behavioral Response To Seawater And Ultrasonic Consolidation Post-Treatment
Open Access
- Author:
- Brown, Robert
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 06, 2021
- Committee Members:
- Timothy Eden, Chair & Dissertation Advisor
Robert Campbell, Outside Unit & Field Member
Jeremy M. Schreiber, Special Member
Douglas Wolfe, Major Field Member
Albert Segall, Major Field Member
Albert Segall, Program Head/Chair - Keywords:
- Cold Spray
Residual Stress
Corrosion
Ultrasonic Consolidation
CuNi
Cr3C2-NiCr
Mechanical Properties
Microstructure - Abstract:
- The basis of this research explored cold spray in-situ measurement methods and provided a fundamental understanding of deposition characterization to develop and optimize process parameters. An in-situ beam curvature sensor was employed to investigate CuNi and Cr3C2-NiCr powder particle dynamics applied on a Cu-30Ni substrate and evaluated coating residual stress. The beam curvature technique directed material and component adjustments based on derived stress states to improve adhesion by 270%, hardness values increased by 18%, and porosity values decreased by 35%. Additionally, the beam curvature sensor identified unintentional process changes, which can be monitored for coating quality assurance and control. The optimized parameters were used for cold spray deposition of a 50:50 and 25:75 wt. % CuNi:Cr3C2-NiCr powder combination, each applied on a Cu-30Ni substrate, and exposed to six months of alternate immersion in natural seawater. Environmental effects due electrochemical kinetics demonstrated a reduction in adhesion of 25%, tensile stress decrease of 6%, and hardness loss of 7%. Optical micrograph revealed a 68% fracture of the as-cold sprayed Cr3C2-NiCr particles within the CuNi binding matrix. Despite the decline in mechanical properties, the deleterious effects would not preclude the coatings use as a dimensional restoration strategy. Cold spray coating properties were further improved, by applying ultrasonic consolidation as a post-treatment process upon a 50:50 and 25:75 wt. % CuNi:Cr3C2-NiCr metal matrix composite coating, each on a Cu-30Ni substrate. Mechanical properties saw an increase in tensile stress of 8%, adhesion value increase of 11%, and hardness value increase of 4%. However, optical micrographs revealed an additional 24% increase in fracture of the as-cold sprayed Cr3C2-NiCr particles due to the ultrasonic consolidation process. The benchmark results demonstrated ultrasonic consolidation post-treatment effectiveness, and the opportunity for future research.