RU2640118C1 - Cobalt-based wear-resistant alloy - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention can be used to repair and strengthen wind turbine blades of aircraft gas turbine engines with working temperature at least 1000°C. The cobalt based alloy contains, wt %: chromium 22-27, tungsten 7-10, nickel 5-12, carbon 1-1.8, silicon 0.1-1, titanium 1-2, at least one rare earth metal from the group comprising cerium, lanthanum and yttrium, 0.01-0.2; zirconium or hafnium, 1-2; the rest is cobalt.EFFECT: alloy is characterized by high working temperature, low friction coefficient, low wear rate and linear wear at working temperatures.2 tbl, 5 ex

Description

The invention relates to the field of metallurgy, in particular to cobalt-based alloys intended for repair and hardening of turbine blades of turbines of modern aircraft gas turbine engines (GTE) with operating temperatures of at least 1000 ° C.

The resource of a gas turbine engine is largely determined by the reliability of the gas turbine, the working blades of which are one of the most loaded parts that are exposed to prolonged exposure to high-temperature gas flow and operate in difficult conditions. Therefore, the blades are made of the most high-temperature, expensive alloys based on nickel and cobalt ("superalloys"). However, despite the high heat resistance, “superalloys” under the turbine operating conditions are prone to corrosion, high-temperature oxidation and erosion. In addition, the working blades wear out as a result of the contact interaction of the ends with the stator elements and the constant contact of the retaining shelves of the adjacent blades in the wheel.

The material for hardening retaining shelves and repair of blades should have high wear resistance, high strength characteristics, resistance to high temperature oxidation and corrosion, high weldability and low tendency to crack formation. All these requirements are more satisfied by cobalt-based alloys with carbide and / or intermetallic hardening.

To increase the wear resistance of friction parts, including parts and components of aircraft gas turbine engines operating under difficult loading conditions at temperatures of at least 1000 ° C, alloys based on Co-Cr-WC and Co-Cr-Mo-Si systems are mainly used, differing in various type of hardening cobalt matrix. An increase in the wear resistance of alloys based on the Co-Cr-Mo-Si system occurs due to the formation of a large number of strong Laves phases in the structure, which are released in cobalt alloys due to the addition of molybdenum and silicon.

Alloys based on the Co-Cr-W-C system are characterized by high wear resistance.

Known alloy disclosed in US Pat. US No. 4353742 A, 12/10/1982, the following chemical composition, wt.%:

cobalt and / or nickel and / or iron 50-70 chromium 27-35 molybdenum and / or tungsten 5-15 carbon and / or boron 0.3-2.25 silicon and / or manganese 0-3 copper 0-5

The disadvantage of this alloy of this group is phase instability and a decrease in strength and wear resistance at high temperatures (above 900 ° C).

A number of alloys based on the Co-Cr-Mo-Si system are known having the Tribaloy trademark (US Pat. B2 dated February 8, 2005).

In US Pat. US No. 6852176 B2, 02/08/2005 disclosed an alloy based on cobalt of the following chemical composition, wt.%:

chromium 13-16 molybdenum 20-30 silicon 2.2-3.2 cobalt rest

Wear-resistant alloys of this group are characterized by high resistance to corrosion at extremely high temperatures (above 1000 ° C), however, they have low ductility and higher wear rate when working with friction pair elements made of one alloy, in comparison with the known alloys based on the Co- Cr-WC, the wear resistance of which is ensured by the precipitation of carbides of various compositions in the cobalt matrix of the alloy.

Known alloy based on cobalt, disclosed in US Pat. CN No. 102168211 B, 05/15/2013, of the following chemical composition, wt.%:

cobalt 39-41 chromium 27-30 nickel 14-18 tungsten 2-5 silicon 0.5-2 manganese 0.5-1.5 carbon 0.05-0.2 cerium 0.02-0.2 iron rest

The disadvantage of this alloy is the low wear resistance due to the insufficient content of refractory elements (low tungsten content, the absence of molybdenum), forming solid solution hardening and providing increased wear resistance of the alloy.

Known heat-resistant weldable alloy on a cobalt basis, disclosed in US Pat. RU No. 2283361 C1, 09/10/2006, which can be used for the manufacture of flame tubes of combustion chambers, flame stabilizers and other hot gas turbine engine assemblies. The alloy contains, wt.%:

chromium 24-34 nickel 20-35 tungsten 7-14 molybdenum 0.5-5 titanium 1.3-3.5 carbon 0.01-0.06 nitrogen 0.3-3 lanthanum 0.003-0.1 magnesium 0.003-0.08 boron 0.0003-0.008 cerium 0.0003-0.06 cobalt rest

The disadvantages of this alloy are low tribological characteristics that narrow the scope of its application.

Known wear-resistant and corrosion-resistant cobalt alloy for friction parts, disclosed in US Pat. US No. 7754143 B2, 07/13/2010, of the following composition, wt.%:

carbon 0.5-1.2 silicon 0.6-2.1 chromium 17.0-24 iron 27.0-32 tungsten 1.4-20 molybdenum 3.8-9.7 nickel no more than 1 cobalt rest

The wear resistance of the alloy is achieved due to the formation of up to 50% eutectic phases in the structure, hardening the matrix from a solid solution based on αFe-αCo. The alloy also has high strength, but insufficient ductility and heat resistance at temperatures above 1000 ° C, due to the low ductility of the emitted eutectic phases.

Known wear-resistant alloy on a cobalt basis, disclosed in US Pat. US No. 4765955 A, 08/23/1988, characterized in the content of aluminum, which in combination with chromium increases the resistance of the alloy to high temperature oxidation. The alloy has the following composition, wt.%:

carbon 0.5-3.5 silicon 0.1-3 chromium 10-37 tungsten 0.1-17 molybdenum 0,1-10 titanium 0.01-4.5 aluminum 0.01-5.5 cobalt rest

The disadvantage of the alloy is its low operating temperature (up to 800-900 ° C), due to a decrease in wear resistance and heat resistance at higher temperatures, which may be affected by the non-optimal ratio of elements.

The closest analogue of the proposed alloy is an alloy based on the cobalt-chromium system disclosed in Pat. GB No. 778359 A, 07/03/1957, the following chemical composition, wt.%:

chromium 20-35 molybdenum and / or tungsten 3-15 carbon 0.25-3 boron 0.1-4 nickel and / or iron 1.0-25 cobalt not less than 25 silicon up to 5

The disadvantage of the prototype alloy is the high coefficient of friction during operation of the elements of friction pairs made of this alloy, for example, the contact pads of the retaining shelves of the blades of a turbine engine turbine.

The technical task of the invention is to develop a composition of a wear-resistant cobalt-based alloy, operable at high temperatures and dynamic contact loading, the use of which, for example, for hardening the retaining shelves of GTE turbine blades will significantly reduce the wear of the contact areas of the shelves and increase the resource of the blades.

The technical result of the invention is to increase the operating temperature to 1100 ° C, reduce the coefficient of friction, as well as provide low values of the intensity of wear and linear wear at operating temperatures.

To achieve the technical result, an alloy based on cobalt containing chromium, tungsten, nickel, carbon, silicon and cobalt is proposed, while it additionally contains titanium, at least one rare-earth metal from the group consisting of cerium, lanthanum and yttrium, and zirconium or hafnium, in the following ratio of components, wt.%:

chromium 22-27 tungsten 7-10 nickel 5-12 carbon 1-1.8 silicon 0.1-1 titanium 1-2 cerium and / or lanthanum and / or yttrium 0.01-0.2 zirconium or hafnium 1-2 cobalt rest

The present invention proposes, by introducing into the composition of the cobalt-based alloy carbide-forming elements of zirconium or hafnium in an amount of from 1.0 to 2.0 wt.% And titanium in an amount of from 1 to 2 wt.% To increase the wear resistance of the alloy due to the formation of various carbides composition having high hardness. It was found that the introduction of the indicated alloying carbide-forming elements into the composition of the cobalt alloy in combination with the carbide-forming elements present in the prototype alloy (carbon, chromium, tungsten) at a given ratio of components allows to increase wear resistance, reduce the wear rate and linear wear of parts of friction pairs made from an alloy of the same composition, operating under dynamic vibrocontact loading.

The introduction of at least one rare-earth metal from the group consisting of cerium, lanthanum and yttrium in a given amount helps to modify the alloy structure by stabilizing the Cr ₂ O ₃ compound formed on the surface of the alloy. It also contributes to an increase in the working temperature of the cobalt-based alloy and a decrease in the coefficient of friction.

Examples of carrying out the invention.

In vacuum induction furnaces, several castings were smelted using both pure charge materials and waste from our own production. Metal spillage was carried out in metal forms (steel pipes).

The compositions of the proposed alloy (examples 1-4) and prototype alloy (example 5) are shown in table 1.

Next, we tested tribological characteristics (friction coefficient, linear wear, wear rate) at a temperature of 1100 ° C. The test time was 2 hours 8 minutes (10 ⁵ cycles), the counterbody was a “type I finger” from the cobalt alloy under study, the “plate” was samples from the same alloy, the load was 10 N, the industrial oscillation frequency of the instruments was 13 Hz, the oscillation amplitude - 500 μm, the calculated load in the contact zone was ~ 327 MPa.

Tribological characteristics of the proposed alloy and prototype alloy are shown in table 2.

From table 2 it can be seen that the proposed alloy has a friction coefficient reduced by 27.0-27.5% compared with the prototype, as well as low values of linear wear and wear rate at a test temperature of 1100 ° C. At the same time, these indicators are not possible to measure at the indicated temperature for the prototype alloy with a lower working temperature due to its destruction. Thus, we can conclude that the proposed alloy has an increased operating temperature of 100 ° C relative to the prototype.

Using the proposed alloy will improve the resource and reliability of aircraft products.

Claims (2)

A cobalt-based alloy containing chromium, tungsten, nickel, carbon, silicon and cobalt, characterized in that it further comprises titanium, at least one rare earth metal from the group consisting of cerium, lanthanum and yttrium, and zirconium or hafnium, in the following the ratio of components, wt.%: chromium  22-27 tungsten 7-10 nickel 5-12 carbon 1-1.8 silicon 0.1-1 titanium 1-2 at least one rare earth metal from the group including cerium, lanthanum and yttrium 0.01-0.2 zirconium or hafnium 1-2 cobalt rest