Method of manufacturing a workpiece of any given cross-sectional dimensions from an oxide-dispersion-hardened nickel-based superalloy with directional coarse columnar crystals

A method of manufacturing a workpiece of any given cross-sectional dimensions from an oxide-dispersion-hardened nickel-based superalloy with directional coarse columnar crystals set with their longitudinal axis at right angles to the cross-sectional area, wherein, at least two workpiece parts consisting of the material quoted and available in the zone heat treated coarse crystalline condition are mechanically fine machined by milling and grinding to produce bonding surfaces on at least one side of each containing the longitudinal axis of the columnar crystals and are subsequently heat-treated in the temperature range from 50.degree. to 100.degree. C. below the recrystallization temperature for 0.5 to 6 hours to remove the stresses and structural perturbations introduced by cold working during the machining, wherein further the workpiece parts are joined together at the mutually corresponding bonding surfaces and are subjected to a diffusion bonding process by means of hot isostatic presssing in such a way that the workpiece parts are initially brought to 600.degree. C. under a pressure p.sub.K of not more than 5 MPa and are then heat-treated at a heating rate of not more than 2.degree. C./min to at least a critical temperature T.sub.K, above which no further cold working occurs and, subsequently, the pressure being slowly increased at a rate of not more than 1 MPa/min to a p.sub.max of 100 to 300 MPa with simultaneous heating at 2.degree. C./min up to a diffusion bonding temperature T.sub.D of 0.degree. to 50.degree. C. below the recrystallization temperature and wherein this condition retained for 1 to 24 hours and the workpiece bonded in this way is cooled to room temperature.