Origin of the Liquid Hot Isostatic Pressing process
In the late 1980s, when the author was president of Metal Casting Technology, Inc. (MCT), a joint venture proccess development company between Hitchiner Mfg. Co., Inc. and General Motors, a new low cost casting process for titanium alloys was invented and later patented, US 5,299,619. All titanium castings required Hot Isostatic Pressing (HIP) to achieve good mechanical properties.
The conventional HIP process, which uses argon gas to apply high pressure for closing internal porosity, is very effective, but very dangerous and costly - too much so for the commercial applications anticipated for the new low cost casting process.
As a result of this need, the author devised an approach using mechanical means to pressurize a non-reactive molten salt, which in turn, pressurized the casting surface, closing interna1 porosity. This brief article describes some of the early work which led up to the patenting of the Liquid Hot Isostatic Pressing (LHIP) process as disclosed in US Patent 5,340,419.