US3362816A - Cobalt alloy - Google Patents

Description

United States Patent 3,362,816 COBALT ALLOY Heinrich Winter, Eschborn, Taunus, and Horst Kiupel,

Langen, Germany, assiguors to the Federal Republic of Germany as represented by the Secretary of Defense, Bonn, Germany N0 Drawing. Filed June 19, 1964, Ser. No. 376,582 Claims priority, application Germany, June 22, 1963,

2 Claims. (Cl. 75-171) Percent by weight Cobalt 55 Chromium 20 Tungsten 15 Nickel Our investigations concerning the incorporation of a hard temperature stable finely dispersed phase into an alloy of said type as matrix had the surprising result that a considerable improvement of the high temperature strength is attained when zirconium and boron, in an atomic proportion of about 1:2, corresponding to the compound ZrB are added to the melt in a total amount of up to about 12, preferably 1.5 to 3 percent by Weight of the alloy.

Already 0.5% by weight of such a Zr+2B addition to the base alloy produces a considerable increase of the high temperature properties. At 800 C. the hardness HV 5 increased from 98 to 134 kg./Inm. (The HV values designate the Vickers hardness, the numbers 5 etc, referring to the load in kg. applied for the test, in accordance with the ofiicial German testing standards, published as DIN 50133.)

Percent by Weight Cobalt 55 Chromium 20 Tungsten Nickel 5 Molybdenum 5 In such alloys, the malleability even increases up to an addition of 2% ZrB while also the strength characteristics at high temperatures show a strong increase. Above said limit, the malleability decreases again but even with an addition of 12% ZrB the alloy is not yet completely embrittled.

An alloy of the character described, containing 5% Mo and 1.5% ZrB tested in the cast state, had at room temperature an HV 30 of 357 kg/mm. and at 800 C. an HV 5 of 262 kg./mm.

It is surprising that forming the alloy and subsequent annealing for several hours at temperatures up to and exceeding 900 C. does not produce a decrease of the strength properties at room temperature but a further increase. The following values were measured at an alloy containing 5% Mo and 1.5% ZrB reduced by 50%.

HV 30 at room temperature 550 HV 5 at 800 C. 374 HV 30 after 3 hours annealing at 900 C. at room temperature 625 At the same time, the strength properties up to temperatures exceeding 1000 C. Were considerably increased. Particularly at temperatures about 900 C., the novel alloys have better high temperature characteristics than the hardenable nickel base superalloys. In said alloys, the phases producing the hardening in the nickel-solid solution, such as Ni Al or Ni Ti, dissolve at temperatures slightly above 1000 C. so that the upper temperature limit for using the known nickel base superalloys may only just exceed 900 C.

The novel alloys are very well suited for hard facing machine parts subjected to high temperatures. Due to the high strength characteristics at high temperatures and its ductility, the molybdenum containing alloy can be directly used for the manufacture of turbine blades and vanes.

We claim:

1. A cobalt base alloy consisting essentially of, 5 to 10 percent of nickel, by weight, from about 15 to about 30 percent of chromium, 10 to 20 percent of tungsten, 5 to 10 percent of nickel, and about 0.5 to 3 percent of zirconium boride ZrB the balance being cobalt.

2. The alloys as claimed in claim 1 wherein nickel is replaced partially by molybdenum.

References Cited UNITED STATES PATENTS 2,126,742 8/1938 Golyer 2,126,743 8/1938 Golyer 75 171 2,126,745 8/1938 Golyer 75-171 2,126,749 8/1938 Golyer 75-170 2,309,371 1/1943 Wissler 75-171 2,704,250 3/1955 Payson 75-171 DAVID L. RECK, Primary Examiner. HYLAND BIZOT, RICHARD O. DEAN, Examiners.

Claims (1)

1. A COBALT BASE ALLOY CONSISTING ESSENTIALLY OF, 5 TO 10 PERCENT OF NICKEL, BY WEIGHT, FROM ABOUT 15 TO ABOUT 30 PERCENT OF CHROMIUM, 10 TO 20 PERCENT OF TUNGSTEN, 5 TO 10 PERCENT OF NICKEL, AND ABOUT 0.5 TO 3 PERCENT OF ZIRCONIUM BORIDE ZRB2, THE BALANCE BEING COBALT.