In plasma spraying, a deposited layer is formed through the sequential build-up of splats. An FGM can be produced by depositing layers of sequentially varying compositions. Three processing methods exist for plasma spray processing of FGMs. These three methods can be broadly classified as follows:
Each technique has its own merits and limitations. For instance, when processing FGMs, using a single plasma torch, which are composed of materials that have large differences in melting points it is sometimes necessary to space powder injection ports at intervals downwind from the exit of the torch. Also, incorporating two or more torches-while allowing for the use of independent processing parameters-offers the ability to control particle trajectories through the plasma flame, and thus through thermal history and velocity. Process combinations offer a unique approach to creating novel microstructures.
The basic FGM fabrication apparatus requirement is that dissimilar materials (e.g., metal and ceramic with a large difference in density and melting point) should be homogeneously mixed in the desired portions on the planes normal to the thickness directions. Additionally, the desired compositional pattern should be achieved with good reproducibility in the heat flow direction.
Single Torch Assembly
Multiple Torch Assembly
Powder Injection Parameters
Gradient Types
Application to the Energy Sector
More Information of Plasma Spraying
Return to Plasma Processing of FGMs
last updated 5/20/96 by Dr. T. Jewett