THE EFFECT OF COMPOSITION ON THE POROSITY, STRUCTURE, AND PROPERTIES OF NICKEL-TANTALUM, NICKEL-TANTALUM CARBIDE, AND NICKEL-TANTALUM-TANTALUM CARBIDE ALLOYS

A series of alloys has been produced from nickel powder, tantalum metal powder, and tantalum carbide powder, by powder-metallurgical techniques. A typical analysis of the powders is given.The effect of increasing additions of tantalum and tantalum carbide to nickel, both singly and in combination, has been investigated. The degree of residual porosity was shown to be a function of composition, compacting pressure, and sintering temperature. In addition, the effect of residual porosity on the hardness, density, and room-temperature properties of these alloys has been established. It is demonstrated that increased compacting pressures result in reduced porosity and improved high-temperature properties.The results of impact extrusion on the structure and properties of the nickel-tantalum-tantalum carbide alloys was also investigated. Impact extrusion reduces the level of porosity, as indicated by microstructure and density, and results in increased room-temperature properties and high-temperature properties in the case of the nickel-tantalum carbide alloys; the reverse is true for the high-temperature properties of the nickel-tantalum-tantalum carbide alloys.