British license for the*molecular bonding of aluminum to steel by means of the AI-Fin process. Primary object of the study is the development of a rapid, economical method of manufacturing compressor stator assemblies. Wellworthy is licensed by the A1-Fin Division of the Fairchild Engine and Airplane Corporation, developer of the patented molecular bonding process.
Bright drawn steel strip is used for the airfoil section. The strip, which can be obtained to extremely close dimensions from the mills, is cropped to length and--by means of the A1-Fin process--an aluminum alloy root is bonded to it. The alloy used is selected for its corrosion resistance and strength. The immediate advantage of the method is that it provides a means of manufacturing compressor stator blades with a root section that is readily machineable--hence less expensive.
In addition, development is foreseen of compressor stator blade units in segments containing a number of blades or even complete stage rings with blade sections made integral by bonding in of the drawn airfoil strip steel. Cost and weight advantages are foreseen as resulting from such construction.
Extensive testing has proved the strength of the A1-Fin aluminum-to-steel bond. The A1-Fin bond has a tensile strength of approximately 15,000 psi. Tensile tests at elevated temperatures show that the bond retains its strength at temperatures at least as high as the 600 to 700 degrees F encountered in compressors. The bond is vibration proof and is leakproof to hot oil and diatomic gases under high pressures.
Pure aluminum and any of the common casting alloys such as 43, 142, 195, 355,356, Almag 35, Frontier 40E, etc., which have much higher tensile strength than pure aluminum, can be bonded to cast iron, "Ni-resist", carbon, alloy, stainless, inconel and the nimonic series. It is possible to heat treat after bonding, in some cases, to obtain desired physical properties.
Besides applications such as that being investigated by Wellworthy, the AI-Fin process is being used extensively for such things as aluminum-finned steel cylinder barrels, steel-backed aluminum bearings, bi-metallic pistons with ferrous ring carriers, aluminum gears with bonded-ifl-steel hubs, lightweight aluminum housings with steel or iron bearing retainers, bi-metallic automotive brake drums, etc.