DE1259101B - High temperature resistant, dispersion hardened cobalt alloy - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

C22c

German class: 40 b -19/04

Number: 1259 101

File number: W 34747 VI a / 40 b

Filing date: June 22, 1963

Opening day: January 18, 1968

The invention relates to a highly heat-resistant, dispersion-hardened one Cobalt alloy.

It has long been known to add small amounts of boron and zirconium to modern cobalt superalloys, since it is known that these additives in the cobalt superalloys are only positive, but practical never make a negative impression.

Such superalloys are e.g. B. the American alloys J 1650 (0.02 percent by weight B) and SM 302 (0.005 weight percent B).

The information in US Pat. No. 2,996,379 is practically of the same order of magnitude. The outermost upper limit that can be justified is 0.2 for the component boron and 0.2 for the component Zirconium 1.0 percent by weight given. That the previous inventor was concerned with his statements the components boron and zirconium has moved completely within the framework of the usual, it follows that that at no point in the patent is there any connection between the additions boron and zirconium with regard to the values achieved with the alloy proposed by him.

The invention was based on the object of producing highly heat-resistant, dispersion-hardened cobalt alloys. As a high-temperature cobalt alloy, an alloy is known that consists of approximately

55% cobalt,
20% chromium,
15% tungsten and 10% nickel

consists.

The attempts to incorporate a hard, temperature-stable, finely dispersed phase in such an alloy as a matrix showed that, surprisingly, there was a considerable increase in the heat resistance properties can be achieved when an alloy based on cobalt with 15 to 30 weight percent chromium, 1.0 to 20 percent by weight tungsten and 5 to 15 percent by weight nickel additions of zirconium and boron, for example in an atomic ratio of 1: 2 in the amount of 1.5 to 12 percent by weight.

Already 0.5 percent by weight of such a Zr J-B additive to the starting alloy cause a considerable increase in the high-temperature strength values. Thus, the hot hardness HV is 5 at a temperature of 800 ⁰ C instead of 98 (without the addition) already 134kp / mm ^2. As the proportion of zirconium boride increases, the deformability of the alloy decreases. This is disadvantageous for a number of applications for the alloy.

Highly heat-resistant, dispersion-hardened
Cobalt alloy

Applicant:

Federal Republic of Germany,
represented by the Federal Minister of
Defense,
ίο 5300 Bonn, Ermekeilstr. 27

Named as inventor:
Dr. Heinrich Winter, 6236 Eschborn;
Horst Kiupel, 6070 Langen

It has been found, quite unexpectedly, that the decrease in deformability does not occur when the Zirconium boride is contained in a starting alloy in which the nickel is partially or completely replaced by molybdenum is replaced, for example from

55% cobalt,

20% chromium,

15% tungsten,

5% nickel and

5% molybdenum

consists.

It was found that the deformability even increases up to an addition of 2% Zi ^- B ₂ , although at the same time the high temperature strength of the new alloy increases significantly. Above this limit, the deformability decreases again, but the alloy is not yet completely embrittled _{even with an addition of 12% ZrB 2.}

The following values were measured (alloy as above with 5% Mo and 1.5% ZrB ₂ in the as-cast state):

HV 30 at room temperature 357 kp / mm ²

HV 5 at 800 ⁰ C 262 kp / mm ²

A deformation of this alloy and subsequent annealing for several hours at temperatures up to more than 900 ° C. surprisingly does not result in a decrease in the strength properties at room temperature, but rather a further increase. The following values were measured (alloy with 5% Mo and 1.5% ZrB ₂ , 50% deformed):

HV 30 at room temperature 550 kp / mm ²

HV 5 at 800 ⁰ C 374 kp / mm ²

HV 30 after several hours of annealing
at 900 ⁰ C 625 kp / mm ²

709 719/557

At the same time, the heat resistance properties were significantly increased up to temperatures of over 1000 ° C. The alloys according to the invention were found to be superior to the known age-hardenable nickel-based superalloys in terms of their high-temperature strength, especially at temperatures above 900.degree. In the latter case, the hardening phases in the nickel solid solution, such as Ni ₃ Al, dissolve at temperatures a little above 1000 ° C, so that the highest application temperature of the known nickel-based superalloys can only just exceed 900 ° C.

3% ZrB ₂ hot hardness values were at 800 ° C of about 420 kgf / mm ^2, 9% ZrB _2, those of about kp / mm ² achieved.

The following high-temperature strength values in the base alloy (called M 1)

55% cobalt,
20% chromium,
15% tungsten,
5% nickel,
5% molybdenum

with an addition of 1.5 and 2.5% ZrB ₂ - the cobalt content was reduced by this amount - the following measurements continued to be made:

alloy State ff _B / 800 ° C
kp / mm ² (5 ₆ / 8OO ° C
% M 1 + 1.5% ZrB ₈
M 1 + 2.5% ZrB ₂ Forged and rolled at 1050 ° C
forged at 1050 ° C
As-cast state
As-cast state
(5 hours 800 ⁰ C + 50 hours 730 ° C) 68.7
63.0
50.0
70.3 56
14th
6th
6th

In the 100-hour creep test at 815 ° C., a value of 36 kp / mm ^{2 was determined} for the alloy M1 + 2.5% ZrB ₂ in the as-cast state. This value exceeds all values of currently known cobalt-based superalloys.

The alloys according to the invention are particularly suitable for armoring at high temperatures stressed machine parts. Because of the high heat resistance and ductility of the molybdenum-containing Alloy can be used to make turbine blades directly.

Claims (2)

Patent claims: 1. High-temperature, dispersion-hardened cobalt alloy, consisting of 15 to 30% chromium, 10 to 20% tungsten, 5 to 15% nickel, zirconium and boron approximately in an atomic ratio of 1: 2 in the amount of 1.5 to 12%, the rest cobalt. 2. Alloy according to claim 1, in which the nickel is wholly or partially replaced by molybdenum is. Considered publications:
U.S. Patent No. 2,996,379. 709 719/357 1.68 © Bundesdruckerei Berlin