Hot Isostatic Pressure Healing of Navy Gun Metal Castings.

Abstract : The report summarizes the investigation of the use of Hot Isostatic Pressure (HIP) processing to heal defects in Navy Gun Metal castings. The effects of HIP processing temperature at 15,000-psi pressure on the mechanical properties, microstructure, and cast-in porosity in G-metal were investigated. HIP at temperatures between 1250 and 1500 F were found to practically eliminate porosity. Gas permeable porosity was eliminated in every case. Increases in yield strength of 14 percent, ultimate tensile strength of 37 percent, and elongation of 100 percent were obtained compared to as-cast properties. Dendritic segregation was reduced and second phase material redissolved as a result of HIP processing. The HIP conditions developed were applied to the processing of cast 4-in. flex connector bodies with generally similar results. (Modified author abstract)