High temperature light weight load bearing aerospace structures such as compressor fan blades for the front section of aircraft engines represent one of the primary areas of application for these difficult to synthesize materials. While companies such as 3M and GE Aircraft Engines have employed techniques such as conventional e-beam evaporation and plasma spraying to create CFR MMCs, each of these methods has drawbacks. Conventional e-beam evaporation suffers from low materials utilization efficiency, with significant quantities of the expensive metal matrix material ending up on the walls of the processing chamber instead of the fibers. To capture as much vapor as possible during its conventional e-beam processing, 3M uses intricate fiber manipulation systems. These fiber manipulation systems frequently break fibers, forcing the coating run to be terminated.
Plasma spray technology creates a rough surfaced, fiber containing plasma spray foil.
During the hot isostatic pressing cycle which presses these layers together, significant fiber fracture often degrades the properties of the resulting material. During each run, the fiber frame itself was covered with aluminum foil to ensure that metal deposition on it was not included in the weight change measurements. It should be noted that the deposition efficiency measured in this study is an average value over the entire surface area of the fibers. Instead, the main vapor stream crossed the primary carrier gas flow and passed between the e-beam gun and the top of the fiber array. Once the carrier gas flow was increased so that the vapor passed through the frame, deposition efficiencies increased dramatically.