DE2062776A1 - Cobalt alloy - Google Patents

Description

l6. Dec. I97O

Gzy / goe CABOT CORPORATION

Cobalt alloy.

The invention relates to a cobalt alloy, in particular one that contains cobalt, chromium, tungsten and nickel along with relatively small amounts of lanthanum and relatively large amounts of carbon. the Alloys according to the invention are characterized by excellent abrasion resistance and resistance to oxidation at high temperatures, together with excellent mechanical properties. high Temperatures.

Heretofore, certain cobalt alloys have been used extensively at high temperatures. In general they were satisfactory except that in some Cases in comparison with nickel alloys did not have sufficient resistance to oxidation. Cobalt alloys with a low content of carbon and a content of smaller amounts of lanthanum, as described in US Pat. No. 31418, III have a significantly improved resistance to oxidation. Eh would mean progress

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Find cobalt alloys that have increased abrasion resistance and an oxidation resistance at high Have temperatures «

The aim of the invention is. a cobalt alloy with improved Oxidation resistance and improved abrasion resistance at elevated temperatures,

Other objects of the invention will become apparent from the description emerged.

The cobalt invention! Alloys are characterized in that they essentially l8 to 35% chromium, 3 to 18% tungsten., Up to 10% iron, 0, k to 1.3% carbon, 1 to JO% nickel, 0, Contains 2 to 1.2 silicon, 0.02 to 0.12 % lanthanum, up to 10 % tantalum, the remainder cobalt.

The preferred alloys of this type with optimal abrasion resistance contain 25 to 32 % chromium, 3 to 8 % tungsten, up to 5 % iron, 0.7 to 1.3 % carbon, 1 to 10 % nickel, 0.2 to 1, 2 % silicon, 0.02 to 0.12 % lanthanum, up to 10 % tantalum, the rest cobalt «

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Alloys of the type described with optimum breaking strength and ■ tensile strength, together with excellent abrasion resistance, contain: 18 to 24 % chromium, 6 to 18 % tungsten, up to 10 % iron, 0.4 to 0.7% holilensioff, 10 to 30% % Nickel, 0.2 to 1.2 silicon, 0.02 to 0 _; 12 % lanthanum, up to 10 % tantalum, the rest cobalt.

In addition to the constituents mentioned, the alloys may contain other components in lesser amounts include random · For example, zirconium in amounts up to about 2%, vanadium in amounts up to about 2%, boron in amounts up to about 0.02%, manganese in Amounts up to about 2) 6, titanium and aluminum in amounts up to about 4%, niobium in amounts up to about 2 % »

It was also found that a proportionate low lanthanum content and a relatively high one Carbon content has a noticeable resistance to oxidation and abrasion resistance at high temperatures cause"

It was also found that other rare earth metals can be present together with lanthanum, as they are present in mischmetal together with lanthanum, without

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is adversely affected by the improved resistance to oxidation β However, these other rare earth metals together should not exceed the lanthanum content, otherwise veins and non-metallic inclusions will form in the alloy, which impair the weldability and lead to weld seams of poor strength. For the production of alloys that are to be welded, lanthanum is therefore preferably added in practically elemental form. The amount of lanthanum should in all cases exceed the total amount of the other rare earth metals. For the preparation of alloys which are not to be welded, for example, one _o can lanthanum by conventional methods, in the form of misch metal, elemental lanthanum or lanthanum-containing alloys, add.

Table I shows various compositions of alloys. These alloys had melted down poured into cast pieces of about 90 to 110 kg, in the heat processed into sheets, 10 to 15 minutes at 1150 Annealed to 1230 C and then quenched. The additives on Lanthanum had the specified heights.

Samples of alloys of Table i in the form of sheets with edge lengths from 19 χ 19 mm and thicknesses from 1.5 to 3.2 mm were tested for their resistance to oxidation. The results are included in Table II.

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The tests for resistance to oxidation were carried out as follows.

1 »The samples became pieces with particle diameters

of 0.125 now wed.
2. The surfaces and weights of the samples were determined.

3ο The samples were 1095 or II50 C with flowing air

ο
in an amount of 4.4 l / cm of the furnace cross-section

treated four times per hour for 25 hours each. The swatches were cooled to room temperature between each treatment.
4β The samples were cooled in air.

5. The samples were descaled in a salt bath.

6. The descaled samples were carefully weighed and the weight loss calculated.

7. The penetration depth, calculated over a year, was calculated according to the following formula:

Weight loss

density

Surface of the

Pattern

Hours / year 100 hours

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Φ H H Φ

O +> O) P. +> O η Φ W. m φ « Φ φ pi ΙΛ « • Η ΙΛ CM CM

η)

U
N 0.21 0.21 I. 1 CCJ VO
O
O ■ VO
O
O ■ • Η
W. VO
O VO
cn
O VO
CN
O vO
CN
O CQ in
ο
O in
O
O ZOO ¹ Zoo' O O O O cn
• Η cn
•H O O ο O r-i T-I CN
in CN
in CN CN a cn cn CM Oi CN CN •H TH ο O O th
tH φ
Cs. 1.20 1.20 O
CO
CM 2.8o m
CN in
CN VO VO VO vO in in CO CO CO
cn OO
cn CM
CM CM
CM Os
CM ON
CM

CQ O Q

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Tabel

II

Oxidation rate in mm per year

alloy

1095 ° C

1150 ⁰ C

A B C D

0.5 ** 2 _v o8 0.38

0.64

Table II shows that the alloys of the invention A and C with one lanthanum content and one proportionate high carbon content, excellent resistance to oxidation, compared to alloys B and D that do not contain lanthanum.

Table III shows that an alloy according to the invention in addition to the improved resistance to oxidation, it also has excellent mechanical properties high temperatures.

Tabel III strain
1095 ° C alloy 0.2?
tensile strenght
1095 ° C fracture
strength
1095 ° C 78.3 % A. 480 kg / cm ² 1100 kg / cm ²

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An alloy of Composition A in cast form had at. a temperature of 980 C a breaking life YOU ^ 202 hours with a load of 910 kg / cm and an elongation of about 14 % "

Further tests were carried out to determine the abrasion resistance of an alloy according to the invention. A cast cylindrical sample of alloy C was placed under a contact pressure of 7 kg / cm against a flat one fixed pattern of the same alloy rotates. During the test, the samples had a temperature of 760 C. Rotation was continued for 8 hours at a constant speed of 160 cm / min Circumference of the cylindrical pattern "

The abrasion on the rotating sample was 1.45 microns / 10 m Distance «The abrasion for a composition D alloy under the same conditions was 2.31 microns / 1000 m.

- / ■

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Claims (1)

_ 9 claims 1. Cobalt alloy with increased resistance to oxidation at elevated temperatures, characterized in that it consists essentially of 18 to 35 % chromium, 3 to 18 % tungsten, up to 10 % iron, 0.4 to 1.3 % carbon, 1 to 30 % Nickel, 0.2 to 1.2 % silicon, 0.02 to 0.12 % lanthanum, up to 10 % tantalum, the remainder cobalt 2. Alloy according to claim I _9, characterized in that it consists essentially of 25 to 32 % chromium, 3 to 8 % tungsten, up to 5 % iron, 0.7 to 1.3% carbon, 1 to 10 % Nickel, 0.2 to 1.2 % silicon, 0.02 to 0.12 % lanthanum, up to 10 % tantalum, the remainder cobalt. 3 »Alloy according to claim 1, characterized in that it consists essentially of 18 to 24 % chromium, 6 to 8 % tungsten, up to 10 % iron, 0.4 to 0.7 % carbon, 10 to 30.94 nickel, 0.2 to 1.2 % silicon, 0.02 to 0.12 % lanthanum, up to 10 % tantalum, the remainder cobalt, consists ο 109826/1197