Plasma-spraying is a process in which a high-temperature ionized gas jet is used to melt and accelerate micron-sized metal, ceramic, or alloy particles to build protective coatings on industrial machine components. Fundamental studies have focused on the fragmentation of the high-speed (~200 m/s) molten particles, which results in reduced mechanical strength of the final coating. High-speed particles (~40 µm diameter) were plasma-sprayed onto glass and metal held at either room temperature or at 400°C. Photographs of the splats, during spreading, were captured by using a fast CCD camera. A rapid two-color pyrometer was used to collect thermal radiation from the particles during flight and spreading to follow the evolution of their temperature. Particles that impacted the surface at room temperature disintegrated, leaving a small central solidified core on the substrate. On a surface held at 400°C, there was no fragmentation and a circular, disk-like splat remained. It was found that particles on heated surfaces had cooling rates that were significantly larger than those on non-heated surfaces, suggesting that splat-substrate contact was improved. Mathematical models were developed to show that the splat-surface contact area was significantly lower on non-heated surfaces, while the thermal contact resistance was more than an order of magnitude larger than on heated surfaces. It was concluded that the reduced splat-surface contact and increased thermal contact resistance was due primarily to vaporized adsorbates at the splat-substrate interface.
From these fundamental studies, the research program will be ready to conduct other studies with greater industrial applicability. Government of Alberta funding has been secured to study the application of nanostructured ceramics to combat wear, erosion, and corrosion in equipment in the oil sands and forestry sectors. Other projects will involve the novel fabrication of thermocouples by cold-gas dynamic spraying for application in forest fires, as well as the fabrication of solid oxide fuel cells by combined thermal spraying processes. Fundamental engineering research will still be an important component of the research program. The presentation will detail plans to develop advanced heat transfer models and experiments to estimate the temperature distribution in substrates during thermal spray deposition and the thermal diffusivity of thermal-sprayed coatings.
About the Speaker
Dr. André McDonald received his BSME (cum laude) from the City College of New York (CCNY) in 2001, where he was the Dupont Mechanical Engineering Distinguished Graduate and won the Peggy Benline, Eliza Ford, and ALCOA awards. He was awarded his MSME from that same institution in 2002. He received his Ph.D. from the University of Toronto in 2007, followed by a short post-doctoral fellowship at the Industrial Materials Institute - National Research Council Canada (IMI-NRC) in Boucherville, Québec. He has three years of work experience as a mechanical design engineer in the area of environmental control (HVAC) and heat transfer. He is currently a registered Professional Engineer in the province of Alberta.
Dr. McDonald’s research experience is broad. He has conducted studies in modeling mass transfer in bone at the Mount Sinai School of Medicine in New York City, micro-heat exchanger design at the City College of New York, and visualization and analysis of the spreading of plasma-sprayed particles at the University of Toronto/IMI–NRC. These studies have resulted in 7 peer-reviewed journal articles, 12 conference articles, and several awards including the International Thermal Spray Conference and Exposition Best Paper Award and 1st Place in the Canadian Society for Mechanical Engineering (CSME) Forum’s Graduate Student Presentation Competition.
| Date |
Wednesday, January 9th, 2008 |
| Location |
U of A Faculty Club
11435 Saskatchewan Drive |
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| Time |
Social Hour: 5:30 – 6:30 pm
Dinner: 6:30 – 7:30 pm
Presentation: 7:30
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| Costs |
Members: $20.00 Guests: $25.00
Student Members: $10.00 Student Guests: $15.00 |
| RSVP |
Use our electronic reservation tool by 4pm, Monday, January 7, 2008. |
