CoCr alloys and methods for making same

摘要

A method of producing a forged part is described. The method includes the steps of: preparing an ingot consisting essentially of: Element Weight Percent C 0.00-0.35 Si 0.00-1.00 Cr 26.00-30.00 Mo 5.00-7.00 Ni 0.00-1.00 Fe 0.00-0.75 Mn 0.00-1.00 N 0.00-0.25 Co Balance (b) determining the ingot melting temperature; (c) determining the pouring temperature; (d) minimizing the difference between the pouring temperature and the mold temperature to no more than about 100° F.; (e) designing an investment casting preform geometry to achieve uniform reduction in all sections of the part; (f) preparing an investment mold; (g) molding the part by casting; (h) placing the part in a forging die; (i) subjecting the part to one or more forging hits at a forging preheat of between about 1700° F. and about 1800° F. to achieve a reduction of about 15% to about 20%; (j) vacuum annealing the part at between about 1800° F. and about 2400° F. for about 30 minutes to about 8 hours under a partial pressure of argon; (k) quenching the part to below about 1400° F. in about 5 minutes or less under a minimum of about 5 bars of argon; and (l) subjecting the part to one or more forging hits at between about 1200° F. and about 2200° F. to achieve a final about 3% to about 60% of reduction. The pouring temperature is preferably no more than about 100° F. from the ingot melting temperature. The investment mold has one or more gates. The forging die is designed to match the preform geometry to facilitate homogeneous percentage reduction in all areas and section thicknesses of the part.