US3355286A - Nickel base alloy - Google Patents

Description

United States Patent Ofiice ABSTRACT OF THE DISCLOSURE An alloy, 45% by Weight tungsten, 10% cobalt and remainder nickel having excellent fabricability, excellent 3,355,286 Patented Nov. 28, 1967 The alloy ingots are hammer forged at 2500 F. to bar shapes suitable for rolling. Heating for forging may be done in air. The forged bars are hot rolled or hot swaged to an intermediate size in the temperature range of 2200 to 2500 F. After solution annealing at 2000" F. to 2500 F. to remove any residual Work and homogenize the structure, the alloys are quenched or air cooled to room temperature and finish rolled or drawn to size cold. If the alloys are to be used in the annealed temper, they are solution annealed a second time after cold fabrication.

The alloys are readily worked hardened to high strengths by cold working. The tensile and impact prop erties of the Ni-45 W-lO Co alloy with various amounts of cold work are shown in Table I.

Table I TENSILE PROPERTIES AT 75 F. [0.2% Oiiset N i-45 W-lO 00] ductility and toughness and capable of being cold drawn to 50%.

The present invention relates to nickel based alloys and more particularly, to nickel based alloys containing tungsten and cobalt, and having the characteristics of excellent fabricability and great strength, as well as high ductility and toughness.

It has been found that the addition of cobalt to the commercial Ni-45 W alloy improves fabricability and oxidation characteristics during fabrication, suppresses the formation of WNi minimizes the formation of primary tungsten in the microstructure and improves weld ductility. In particular, the alloys of the present invention can be cold rolled and drawn more than 50 percent, and have very high tensile and yield strength, combined with excellent ductility (particularly with regard to reduction in area), and with impact toughness. The present alloys are readily weldable with resultant ductile welds.

The alloys of the present invention contain 45 weight percent tungsten, from 10 to weight percent cobalt, and the remainder nickel.

The alloys are prepared by induction melting under The tensile properties were measured on 0.100-inch diameter test samples machined from 0.156 inch square rods. Microim-pact properties were measured from subsize notched Izod samples machined from 0.156 inch square rods.

The presence of cobalt in the nickel-tungsten alloy clearly improves fabricability. Addition of 10 weight percent cobalt also retards the formation of low temperature precipitates which interfere with welding. The time for a V.H.N. hardness increase to occur on heating solution annealed alloys at 1600 F., the temperature of maximum instability, varies with cobalt content as shown in Table II.

Table II 30 Time for 30 V.H.N.

hardness increase Composition: at 1600 F.

Ni-45 W hours 0.15 Ni-45 W-lO C0 .do 3.5 Ni-45 W-20 Co do 0.2

Although it may be seen that 10 percent cobalt appears near the optimum amount for retarding instability during welding, larger amounts of cobalt are beneficial to the properties exhibited by the present alloys in the vacuum in a zirconite crucible. The alloys are made from annealed condition as shown by Table IH.

Table III TENSILE PROPERTIES AT 75 F. [0.2% Offset] Ultimate Yield Reduction Notch ed Composition Strength, Strength, Elongation, in Area, Impact Prop- K s.i. K s.i. percent percent erties at -40 Ni- W 177. 6 84. 9 31 28 34 Ni-45 W-10 Co 181. 5 76. 6 40 46 98 Ni-45 W-20 C0 179. 8 75. 4 48 68 123 high purity nickel, tungsten, and cobalt, and are melted and cast into ingots without difiiculty. Auxiliary additions to permit fabrication are unnecessary.

As may be seen, both the tensile ductility and the impact properties are improved by increasing the cobalt content of the Ni-45 W alloy. The Ni-45 W-20 Co alloy 3 shows greater than 98 inch pound impact properties after 25 percent cold working :as compared to 31 inch pounds for the Ni45 W-lO Co alloy.

It will be understood that modification and variations in the present invention may be effected without departing from the spirit and scope thereof.

What is claimed is:

An alloy consisting of essentially 45% by weight of tungsten, 10% cobalt and 45 nickel and characterized 4 References Cited UNITED STATES PATENTS 1,634,343 7/1927 Smith 75171 5 DAVID L. RECK, Primary Examiner.

HYLAND BIZOT, Examiner.

R. O. DEAN, Assistant Examiner.

by excellent fabricability, ductility and toughness, capable 10 of being cold rolled and drawn 50%.