Some properties of a fibre-reinforced nickel-base alloy

Abstract

Abstract Some improvement in tensile strength and creep-rupture strength has been demonstrated on reinforcing Nimocast 713C with 20 v/o of 0·050 in. diam. tungsten wire. A more significant enhancement in both strength and specific strength was achieved using tungsten-5% rhenium as the reinforcement. Theoretically, higher specific strength at elevated temperatures could be obtained by reinforcement with molybdenum or niobium alloys provided that suitable barrier coatings can be developed to prevent interaction between matrix and reinforcement. The fatigue properties of Nimocast 713C in tension-tension loading are not measurably influenced by reinforcement with 0·050 (or 0·040) in. diam. tungsten wire, in contrast to previous reports on composites of a nickel-base alloy plus 0·010 in. diam. wires. This behaviour is interpreted in terms of the relative effectiveness of the fibre arrays of given volume fraction in arresting the propagating fatigue cracks. A limited number of tests have shown that the composites are stable in thermal cycling conditions. Chemical interaction between matrix and reinforcement occurs to a degree which is considered acceptable on fibres of greater than 0·030 in. diam. The present data indicate that the choice of refractory metal wire diameter must be made on the basis of a compromise of fatigue strength, creep-rupture strength, and long term elevated temperature stability and the ability to retain alignment during infiltration. The feasibility of using extrusion as a fabrication technique has been demonstrated.