Summary of the invention
The purpose of the present invention is to provide a kind of low rhenium corrosion and heat resistant long-life high-strength nickel based single-crystal high-temperature alloy and its
Heat treatment process, which has and the comparable mechanical behavior under high temperature of the typical high-strength single crystal alloy of the second generation, and has good
Hot corrosion resistance and chronic tissue stability.
To achieve the above object, the technical solution adopted in the present invention is as follows:
A kind of low rhenium corrosion and heat resistant long-life high-strength nickel based single-crystal high-temperature alloy, weight percentage, the alloy
Chemical component is as follows:
Cr:8.0~11.0%, Co:7.0~11.0%, Mo:0.1~0.5%, W:3.0~6.0%, Ta:4.0~
7.0%, Al:3.8~5.2%, Ti:0~3.0%, Re:1.0~3.0%, C:0~0.2%, remaining is Ni;Wherein: 6.0%
≤ Al+Ti≤8.0%, Al/Ti > 1.
The preferred chemical component of nickel-base high-temperature single crystal alloy of the present invention is following (wt.%):
Cr:9.0~10.0%, Co:8.0~10.0%, Mo:0.1~0.5%, W:3.5~5.0%, Ta:5.0~
6.5%, Al:4.0~5.0%, Ti:0.5~3.0%, Re:1.5~3.0%, C:0~0.1%, remaining is Ni;Wherein:
6.5%≤Al+Ti≤7.5%, Al/Ti > 1.
In nickel-base high-temperature single crystal alloy provided by the invention, the ingredient and mass percentage of impurity meet following requirements: O
≤ 0.003%, N≤0.0015%, S≤0.004%, P≤0.018%, Si≤0.2%, Pb≤0.0005%, Bi≤
0.00005%.
The Design of Chemical Composition of alloy (alloy designations are named as DD421) of the present invention is based primarily upon following reason:
Re is very effective solution strengthening element in high temperature alloy, and can reduce the body diffusion coefficient of other elements, is mentioned
The roughening activation energy of high γ ' phase, delays the growth rate of γ ' phase.Re also segregation forms elementide in γ matrix, hinders
Dislocation motion significantly improves the mechanical behavior under high temperature of alloy.More importantly for alloy of the present invention, the addition of Re element
Remarkable effect has been played to the raising of the hot corrosion resistance of alloy, and can overcome the disadvantages that the appropriate reduction confrontation of Cr element in this alloy
It is influenced brought by hot corrosion resistance.And Re element generates very the antioxygenic property of alloy, especially structure stability
Detrimental effect.In addition, abundance of the Re in the earth's crust is very low, it is lower than 0.001g/t, the reserves in China are more rare, therefore
On the basis of acquisition higher mechanical property and good hot corrosion resistance, it should which the use of Re element contains in alloy less as far as possible
Amount.Therefore, the content of Re is controlled 1.0~3.0% in this alloy.
Cr is the main element for improving nickel base superalloy hot corrosion resistance, Cr in traditional corrosion-resistant superalloy
Content is generally higher than 12% (mass fraction, similarly hereinafter), and to guarantee alloy in heat erosion environment, it is rotten to be capable of forming continuous heat resistanceheat resistant
Lose Cr2O3Protective film, but a large amount of additions of Cr will increase the precipitation tendency of TCP phase in alloy, and limiting Mo, W, Re etc., other are strong
Change the addition of element, this is also the main reason for current corrosion and heat resistant single crystal alloy mechanical behavior under high temperature is generally relatively low.The present invention
A possibility that alloy improves alloy hot corrosion resistance by addition Re element, and realization suitably reduces Cr content in alloy (8~
11%), both guaranteed the hot corrosion resistance of alloy, also for increase alloy in intensified element (Mo, W, Re, Ta) and γ ' formation
Element (Al, Ti, Ta) content provides possibility, improves alloy solid solution and strengthens and precipitation strength level.
Co can reduce the stacking fault energy of alloy substrate, and to the structure stability of alloy, there is also certain beneficial effect, Co
Added be conducive to heat treatment when alloying element homogenization, alloy heat treatment window, but excessively high Co content meeting can be expanded
Low-alloyed solid solubility temperature is dropped, and drops low-alloyed breaking strength and antioxygenic property.Therefore the high temperature power in order to guarantee alloy
Performance is learned, Co content is controlled 7~11%.
Mo, W are most important solution strengthening elements in high temperature alloy, especially Mo other than having solution strengthening effect,
It also can increase γ/γ ' mismatch, improve alloy high-temp mechanical property.However, being excessively added for Mo, W element will increase dramatically
The precipitation of TCP phase is inclined to, and the addition content of especially Mo element is more sensitive for the precipitation of TCP phase, in alloy development process
Middle discovery, when the addition content of Mo element is more than 1%, microstructure stability cannot obtain effective guarantee, when relatively short
Between heat exposure test after the TCP such as a large amount of μ and σ tissue is precipitated in alloy.Especially in heat erosion environment, Mo is easy to draw
Acid frit reaction is played, very detrimental effect is generated to the hot corrosion resistance of alloy.On the other hand, Mo, W in alloy are reduced
Content low-alloyed density can also drop, control alloy density will be extremely important for large size single crystal alloy vane material.Cause
This controls the content of Mo, W respectively in 0.5% and 6% or less.
Al, Ti are most important γ ' formation elements in nickel-base high-temperature single crystal alloy, generate important shadow to alloy elevated temperature strength
It rings.Al element can significantly improve the antioxygenic property of alloy, and Ti element may react to form stable solid-state vulcanization with S
Object, delays the formation of metal-metal sulphide liquid eutectic, to delay heat erosion reaction process, the heat resistanceheat resistant for improving alloy is rotten
Corrosion energy, but Ti element is unfavorable to the antioxygenic property of alloy, and casting of the Ti as extremely strong normal segregation element, to alloy
Performance is brought a negative impact, and the cancellation band of a large amount of eutectics carrys out great difficulty when for alloy solid solution heat treatment.In addition, in alloy
Al, Ti's is excessively added the structure stability that can significantly reduce alloy.Therefore, it is necessary to which the Al+Ti rationally controlled in alloy always contains
Amount and Ti/Al ratio.In general, the volume fraction of γ ' is higher in aero-engine single crystal turbine blade, γ '/γ mismatch also compared with
Greatly, thus alloy it is relatively short when mechanical behavior under high temperature it is higher.Compared to aero engine turbine blades, industry gas turbine
The military service period of turbo blade is longer, and total service life reaches 50000 hours, alloy it is long when mechanical behavior under high temperature for blade
Safety be on active service and service life it is more important.In general, second generation aero-engine single crystal blade material (such as Ren é N5,
CMSX-4 etc.) γ ' volume fraction (65~70%) with higher, and there is very high γ '/γ mismatch, lead to alloy
Microscopic structure and performance degradation rate are very fast, though lead to alloy short time high temperature mechanical property with higher, mechanical property when long
It can be even horizontal not as good as generation corrosion and heat resistant single crystal alloy.Therefore, develop it is a kind of have medium γ ' volume fraction (50~
60%), lower γ '/γ mismatch corrosion and heat resistant single crystal alloy for improve combustion engine blade it is long when mechanical behavior under high temperature and
Structure stability will have potentiality very much.Therefore, to guarantee that alloy has both good high-temperature oxidation resistance and corrosion and heat resistant
Can, at the same guarantee alloy it is long when tissue and stability, Al/Ti > 1 in this alloy, Al content control 3.8~5.2%,
Ti content controls the overall control in 0~3.0%, Al+Ti, two kinds of elements 6.0~8.0%.
Ta, which mainly passes through, increases γ ' phase amount, improves γ ' phase intensity and thermal stability to improve the elevated temperature strength of alloy,
Has the function of solution strengthening simultaneously.Ta is other than having the heat resistance for improving alloy, also for the corrosion and heat resistant for improving alloy
Performance and antioxygenic property generate positive effect.Other than above-mentioned effect, since Ta is in interdendritic segregation, it can also pass through tune
The density of mushy zone interdendritic liquid in whole directional solidification, reduce casting in freckle the defects of formability.In addition, Ta is not
The formation element of TCP phase, it is little compared to solution strengthening elements, the influences to microstructure stability such as Mo, W, Re.But it is excessively high to contain
The Ta of amount will lead to the eutectic too high levels in alloy, so that the heat treatment of alloy becomes very difficult.In conjunction with factors above, originally
Ta content in invention alloy is controlled 4.0~7.0%.
The intensity of inevitable low angle boundary in single crystal alloy can be strengthened by adding suitable C, improve the casting of alloy
Low-alloyed recrystallization tendency drops in performance, but excess C can reduce alloy initial melting temperature, reduce alloy heat treatment window, and right
The mechanical property and structure stability of alloy have an adverse effect.Therefore, the C content in alloy should control C:0~
0.2%.
Nickel-base high-temperature single crystal alloy of the present invention is using elements such as pure Ni, Cr, Co, W, Mo, Al, Ti, Ta, Re, C true
Melting in empty induction furnace, and the satisfactory master alloy of chemical component is poured into, then pass through apparatus for directional solidification (high rapid hardening again
Gu method or liquid metal cooling method) remelting, using spiral crystal selector or seed-grain method directional solidification at monocrystalline coupon, and suitable
Heat treating regime under be heat-treated.Heat treating regime carries out in accordance with the following steps:
(1) solution heat treatment: 1~4 hour is kept the temperature at 1240~1260 DEG C;Then raise temperature to 1270~1290 DEG C of heat preservations 2
~8 hours, then it is air-cooled to room temperature;Wherein solution heat treatment successively using being warming up to air-cooled effect after certain temperature twice
Be: low temperature is dissolved first, by low melting point phased soln, improves the initial melting temperature of alloy, is next used higher temperature solid solution, will be closed
The precipitated phases such as γ/γ ' eutectic are farthest dissolved in gold;
(2) high-temperature aging is heat-treated: being kept the temperature 2~6 hours at 1080~1160 DEG C, is then air-cooled to room temperature;
(3) low temperature aging is heat-treated: being kept the temperature 20~28 hours at 850~930 DEG C, is then air-cooled to room temperature.
Wherein, it is using the effect of high-temperature aging heat treatment after aging strengthening model successively uses low temperature aging to be heat-treated: logical
Different aging time and temperature are crossed, the size and shape of γ ' phase in alloy is adjusted, improves alloy mechanical property.
For prior art background, the present invention has developed a kind of low rhenium corrosion and heat resistant long-life high intensity nickel-based monocrystal high temperature
Alloy, hot corrosion resistance is suitable with M38 alloy, 1050 DEG C it is below at use temperature, mechanical behavior under high temperature is much higher than
First generation single crystal super alloy, reach or close to the high-strength single crystal alloy Ren é N5 of the second generation level.
Advantages of the present invention and beneficial effect are described as follows:
(1) compared with other existing nickel-base high-temperature single crystal alloys, alloy of the present invention has excellent hot corrosion resistance,
900 DEG C and 950 DEG C of hot corrosion resistances it is suitable with M38 alloy.
(2) enduring quality of alloy of the present invention is much higher than first generation corrosion and heat resistant single crystal alloy, high close to typical case's second generation
Strong single crystal super alloy is horizontal, and the average creep rupture life under the conditions of 982 DEG C/273MPa is close to 70h, 1038 DEG C/172MPa condition
Under average creep rupture life be more than 100h, the average life span under the conditions of 982 DEG C/172MPa is more than 1000h, therefore, the present invention close
Gold is high-strength corrosion and heat resistant single crystal super alloy.
(3) alloy of the present invention Long-term Aging tissue stabilization under the conditions of 900 DEG C and 1000 DEG C.