阅读说明：本技术 一种保持镍基高温合金强度的多次钎焊及热处理工艺 (Multi-brazing and heat treatment process for maintaining strength of nickel-based high-temperature alloy ) 是由 郑磊 刘红亮 赵鑫 董建 孟晔 于 2021-07-16 设计创作，主要内容包括：本发明涉及一种保持镍基高温合金强度的多次钎焊及热处理工艺,具体工艺包括：多次真空钎焊循环(焊前清理、装配定位、预置钎料、真空钎焊)以及焊后时效处理。其中钎焊保温温度处于合金γ′相完全回溶温度点附近,且钎焊保温时间较短,使得多次钎焊循环之后合金内部的γ′相不会发生明显的粗化。焊后冷却阶段采用通氩气快冷,同时搭配空冷的方法,冷却速率较快；直接时效处理后合金内部γ′相的分布弥散均匀,使得处理后合金本体的强度得以保持。本发明所述方法同时解决了镍基高温合金需多次钎焊的工艺难题以及真空钎焊热处理之后合金强度下降的技术难题,极具推广和应用价值。(The invention relates to a multi-brazing and heat treatment process for keeping the strength of a nickel-based high-temperature alloy, which comprises the following specific steps of: multiple vacuum brazing cycles (cleaning before welding, assembling and positioning, presetting brazing filler metal, vacuum brazing) and aging treatment after welding. The brazing heat preservation temperature is near the complete re-dissolution temperature point of the gamma 'phase of the alloy, and the brazing heat preservation time is short, so that the gamma' phase in the alloy can not be obviously coarsened after multiple brazing cycles. In the post-welding cooling stage, the argon is introduced for quick cooling, and an air cooling method is adopted, so that the cooling rate is high; the distribution and dispersion of the gamma' phase in the alloy after direct aging treatment are uniform, so that the strength of the treated alloy body can be maintained. The method simultaneously solves the technical problems that the nickel-based high-temperature alloy needs to be brazed for multiple times and the alloy strength is reduced after the vacuum brazing heat treatment, and has great popularization and application values.)

1. A multi-brazing and heat treatment process for maintaining the strength of a nickel-based superalloy is characterized by comprising the following steps of:

step one, preparing before welding:

removing oxide skin covering on the surface of the alloy part by adopting a mechanical processing method to expose an alloy matrix, and removing oil stains and other impurities on the surface by using an ultrasonic cleaning method; assembling, positioning and presetting brazing filler metal;

step two, vacuum brazing:

placing the alloy part to be brazed and assembled in a vacuum brazing furnace for brazing circulation, wherein the brazing heat preservation temperature is 1010-1060 ℃, the heat preservation time is 8-20min, and the pressure in the furnace is not more than 10^-3Pa, introducing high-purity argon after brazing, quickly cooling to below 600 ℃, and discharging the alloy part out of the furnace for air cooling;

step three, supplementary brazing:

the operations of the first step and the second step are repeated for 1-3 times in sequence to finish multiple brazing treatment;

step four, aging treatment after welding:

and (3) placing the alloy part subjected to the brazing treatment in a heat treatment furnace, heating to 750-780 ℃, preserving heat for 10-14h for aging treatment, and taking out and air-cooling to room temperature.

2. The multiple brazing and heat treatment process for maintaining the strength of the ni-based superalloy as claimed in claim 1, wherein the brazing filler metal in the first step has a melting point of 970-.

3. The multiple brazing and heat treatment process for maintaining the strength of a nickel-base superalloy as in claim 1, wherein the heating furnace in the second step and the fourth step has a temperature rise rate of 10-25 ℃/min.

4. The multiple brazing and heat treatment process for maintaining the strength of the nickel-base superalloy as claimed in claim 1, wherein the cooling rate of the alloy part is not less than 100 ℃/min when argon is introduced for cooling in the second step.

5. The multiple brazing and heat treatment process for maintaining the strength of a nickel-base superalloy as claimed in claim 1, wherein the alloy is a GH4738 nickel-base superalloy, and the alloy comprises the following main components in percentage by mass: 0.03-0.10% of carbon, 18-21% of chromium, 12-15% of cobalt, 3.5-5% of molybdenum, 2.75-3.25% of titanium, 1.2-1.6% of aluminum, 0.003-0.01% of boron, 0.02-0.12% of zirconium and the balance of nickel.

Technical Field

The invention belongs to the technical field of heat treatment of nickel-based high-temperature alloy, and particularly relates to a multi-brazing and heat treatment process for keeping the strength of the nickel-based high-temperature alloy.

Technical Field

The development of the high-temperature alloy is closely related to the development of an aeroengine, has good high-temperature strength and oxidation and corrosion resistance, and is an irreplaceable key material for modern national defense construction and national economic development. At present, the dosage of the high-temperature alloy accounts for more than half of the dosage of the high-temperature alloy in advanced aeroengines, wherein the dosage of the high-temperature alloy with nickel base is the highest. The polycrystalline nickel-based high-temperature alloy is commonly used for manufacturing key parts of engines such as turbine discs and the like, is required to stably work in severe environments with high temperature and high stress, and provides high requirements for the strength of the alloy.

With the development and application of nickel-based high-temperature alloys, the related processing technology is receiving attention. The nickel-based high-temperature alloy is a typical difficult-to-machine material, and the shape of a nickel-based high-temperature alloy part is mostly irregular, and the geometric shape of some parts is composed of straight lines, circular arcs, special-shaped holes and the like, so that the shape is complex, and the research on the high-precision nickel-based high-temperature alloy machining method with high efficiency and low cost is more and more focused by people.

The processing methods commonly used from raw materials to finished products of the nickel-based superalloy component comprise rolling, forging, turning, welding and the like, each processing method has respective difficulties, and particularly in the aspect of welding technology, a welding joint is required to have high strength under a high-temperature condition, and the influence on the structure and the performance of an alloy base metal in the welding process is required to be accurately controlled. The nickel-based high-temperature alloy contains a large amount of alloy elements such as Al, Ti, Ta, W, Co and the like, when the nickel-based high-temperature alloy is processed by adopting a conventional welding method such as arc welding, submerged arc welding, plasma arc welding and the like, the welding difficulty is high, a larger welding stress is easily generated after welding to cause the cracking of a welding seam, and fine recrystallized grains formed by local melting and cooling of a base metal in the welding process also have a larger influence on the alloy performance; although the effective connection of the nickel-based high-temperature alloy can be realized by the instantaneous liquid phase diffusion welding, the heat preservation time is generally more than ten hours, the assembly precision before the welding is strictly controlled, the efficiency is low, the cost is high, and the process applicability is poor. The vacuum brazing is to use a metal material with a melting point lower than that of the base material as a brazing filler metal, heat the brazing filler metal in a vacuum furnace to melt the brazing filler metal, wet a welding seam and fill a joint gap to achieve the purpose of connection. The vacuum brazing has the advantages of short heat preservation time, small deformation of an alloy body after welding, smooth and attractive joint and the like, and has become an important research direction of a high-performance processing method of the nickel-based high-temperature alloy.

In the actual production process, the alloy part cannot be quickly taken out of the furnace after the vacuum brazing is finished, so that the cooling rate of the alloy is low, the subsequent continuous application of a standard aging treatment process can cause the size of a gamma 'strengthening phase precipitated in the alloy to be overlarge, the strengthening effect of the gamma' strengthening phase is reduced, and the alloy part has the risk of unqualified strength. In addition, due to the reasons of pre-welding assembly, fluctuation of welding parameters and the like, obvious welding defects are formed in a welding seam area sometimes, and repair welding needs to be carried out in order to guarantee the service safety of alloy parts and avoid economic loss caused by scrapped parts. In the service process, the strength value of the welding seam area is weak, and the cracked welding seam also needs to be brazed again. Therefore, there is a need to develop a multi-brazing and heat treatment process that can maintain the strength of the nickel-base superalloy.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a multi-brazing and heat treatment process for maintaining the strength of the nickel-based high-temperature alloy, and simultaneously solves the technical problems of multi-brazing and alloy strength reduction after vacuum brazing heat treatment.

In order to realize the purpose, the invention adopts the following technical scheme to realize the purpose:

the multiple brazing and heat treatment process for maintaining the strength of the nickel-based superalloy comprises the following steps of:

step one, preparing before welding:

removing scales and other coverings on the surface of the alloy part by adopting a mechanical processing method to expose an alloy matrix, and removing oil stains and other impurities on the surface by adopting an ultrasonic cleaning method; assembling, positioning and presetting brazing filler metal;

step two, vacuum brazing:

placing the alloy part to be brazed and assembled in a vacuum brazing furnace for brazing circulation, wherein the brazing heat preservation temperature is 1010-1060 ℃, the heat preservation time is 8-20min, and the pressure in the furnace is not more than 10^-3Pa, introducing high-purity argon after brazing, quickly cooling to below 600 ℃, and discharging the alloy part out of the furnace for air cooling;

step three, supplementary brazing:

the operations of the first step and the second step are repeated for 1-3 times in sequence to finish multiple brazing treatment;

step four, aging treatment after welding:

and (3) placing the alloy part subjected to the brazing treatment in a heat treatment furnace, heating to 750-780 ℃, preserving heat for 10-14h for aging treatment, and taking out and air-cooling to room temperature.

Further, the melting point of the brazing filler metal in the first step is 970-980 ℃.

Further, the heating rate of the heating furnace in the second step and the fourth step is 10-25 ℃/min.

Further, when argon is introduced for cooling in the second step, the cooling rate of the alloy part is not lower than 100 ℃/min.

Further, the alloy is GH4738 nickel-based high-temperature alloy, and comprises the following main components in percentage by mass: 0.03-0.10% of carbon, 18-21% of chromium, 12-15% of cobalt, 3.5-5% of molybdenum, 2.75-3.25% of titanium, 1.2-1.6% of aluminum, 0.003-0.01% of boron, 0.02-0.12% of zirconium and the balance of nickel.

Compared with the prior art, the invention has the following beneficial effects:

the invention selects the proper brazing filler metal to ensure that the brazing heat preservation temperature is close to the complete re-dissolution temperature point of the gamma 'phase of the nickel-based high-temperature alloy, and the brazing heat preservation time is shorter, so that the residual gamma' phase in the alloy can not be obviously coarsened after multiple brazing cycles. On the premise of ensuring the uniform structure of a soldered joint, the cooling speed of the soldered alloy part is obviously increased compared with that of the traditional soldered alloy part by adopting a method of firstly introducing argon for quick cooling and then discharging from a furnace for air cooling in the cooling stage; the aging stage after the brazing cycle cancels the stabilizing treatment in the traditional double aging process, and adopts a direct aging treatment method, so that the distribution of the gamma' phase in the obtained alloy is dispersed and uniform, and the strength of the treated alloy body is kept, wherein the tensile strength at room temperature is about 1340MPa, and the yield strength is about 915 MPa. The method simultaneously solves the technical problems that the nickel-based high-temperature alloy needs to be brazed for multiple times and the alloy strength is reduced after the vacuum brazing heat treatment, and has great popularization and application values.

Drawings

FIG. 1 is a photograph of the structure of the weld zone after vacuum brazing and aging treatment in example 1.

Detailed Description

The multiple brazing and heat treatment process for maintaining the strength of the nickel-based high-temperature alloy comprises the following steps of: and placing the prepared alloy component to be brazed and assembled into a vacuum brazing furnace for brazing circulation for 2-4 times, and then heating to the temperature of 750-780 ℃ for aging treatment for 10-14 h. For practical application objects, the alloy part is made of GH4738 nickel-base superalloy, and the alloy part mainly comprises the following components in percentage by mass: 0.03-0.10% of carbon, 18-21% of chromium, 12-15% of cobalt, 3.5-5% of molybdenum, 2.75-3.25% of titanium, 1.2-1.6% of aluminum, 0.003-0.01% of boron, 0.02-0.12% of zirconium and the balance of nickel.

The GH4738 alloy is a precipitation hardening type deformation high-temperature alloy, the strengthening mode is mainly precipitation strengthening, and a spherical gamma' phase distributed in the interior of crystal grains after heat treatment is a main strengthening phase. The standard aging treatment process of the GH4738 alloy comprises the following steps: stabilizing at 845 ℃ for 4h and aging at 760 ℃ for 16 h. However, for the alloy after vacuum brazing treatment, a large amount of gamma ' phase is distributed in the alloy, and if the matrix is subjected to stabilization treatment at 845 ℃, the gamma ' phase in the crystal can grow rapidly, so that the precipitation strengthening effect of the gamma ' phase is reduced.

In order to obtain a better precipitation strengthening effect, maintain the strength of the alloy and meet the requirement of performing supplementary brazing on the alloy part, the invention preferably adopts the following scheme: firstly, a brazing filler metal with a melting point of 970-. And secondly, adopting a method of introducing argon gas for quick cooling to below 600 ℃, and then discharging from the furnace for air cooling, on the premise of ensuring the uniform structure of the soldered joint, improving the cooling rate of the welded alloy part, and inhibiting the growth of the gamma' phase in the cooling stage. And thirdly, the aging treatment stage adopts a direct aging method, so that the stabilization treatment at higher temperature is avoided, and the growth amplitude of the gamma' phase in the aging treatment stage is reduced. Fourthly, after the alloy part is placed into the furnace, the temperature rise rate is controlled within the range of 10-25 ℃/min, and therefore the effect of uniform heating is better achieved.

The feasibility of the scheme of the application is verified by the following test modes: choose to useThe GH4738 sample of (a) simulates an alloy component that is vacuum brazed, and has the specific composition shown in table 1.

Table 1 GH4738 alloy compositions used in the examples and comparative examples

Composition (I)	C	Cr	Co	Mo	Ti	Al	B	Zr	Ni
										Content (wt.)	0.06	19.68	13.89	4.09	3.25	1.32	0.006	0.08	Balance of

The present invention will be described in more detail with reference to the accompanying drawings and examples, which are not intended to limit the present invention.

Examples

Example 1

The brazing method of the GH4738 alloy comprises the following steps:

the method comprises the following steps: removing scales and other coverings on the surface of the alloy part by adopting a mechanical processing method to expose an alloy matrix, and removing oil stains and other impurities on the surface by adopting an ultrasonic cleaning method; assembling, positioning and presetting brazing filler metal, wherein the melting point of the brazing filler metal is 970-980 ℃;

step two: placing the alloy parts to be brazed and assembled in a vacuum brazing furnace for brazing circulation, raising the temperature to 1030 ℃ at the speed of 15 ℃/min, keeping the temperature for 15min, and keeping the pressure in the furnace to be not more than 10^-3Pa, introducing high-purity argon after brazingRapidly cooling to below 600 ℃ at the speed of 110-;

step three: the operation of the first step and the operation of the second step are repeated for 2 times in sequence, and multiple brazing treatments are completed;

step four: and (3) placing the alloy part subjected to the brazing treatment in a heat treatment furnace, heating to 760 ℃ at the speed of 15 ℃/min, preserving heat for 12 hours for aging treatment, and taking out and air-cooling to room temperature.

The implementation results are as follows: when the welded joint after brazing is observed by using an optical lens, as shown in fig. 1, it can be seen that the interface bonding between the weld and the base metal is good, and no obvious welding defect exists.

Example 2

The brazing method of the GH4738 alloy comprises the following steps:

the method comprises the following steps: removing scales and other coverings on the surface of the alloy part by adopting a mechanical processing method to expose an alloy matrix, and removing oil stains and other impurities on the surface by adopting an ultrasonic cleaning method; assembling, positioning and presetting brazing filler metal, wherein the melting point of the brazing filler metal is 970-980 ℃;

step two: placing the alloy component to be brazed and assembled in a vacuum brazing furnace for brazing circulation, raising the temperature at the speed of 20 ℃/min to the brazing heat preservation temperature of 1020 ℃, keeping the temperature for 10min, and keeping the pressure in the furnace to be not more than 10^-3Pa, introducing high-purity argon after brazing, rapidly cooling to below 600 ℃ at the speed of 100-120 ℃/min, and taking the alloy part out of the furnace for air cooling;

step three: repeating the operation of the first step and the operation of the second step for 3 times in sequence to finish multiple brazing treatment;

step four: and (3) placing the alloy part subjected to the brazing treatment in a heat treatment furnace, heating to 750 ℃ at the speed of 20 ℃/min, preserving heat for 13h for aging treatment, and taking out and air-cooling to room temperature.

Comparative example 1

The brazing method of the GH4738 alloy comprises the following steps:

the method comprises the following steps: removing scales and other coverings on the surface of the alloy part by adopting a mechanical processing method to expose an alloy matrix, and removing oil stains and other impurities on the surface by adopting an ultrasonic cleaning method; assembling, positioning and presetting brazing filler metal;

step two: placing the alloy component to be brazed and assembled in a vacuum brazing furnace for brazing circulation, raising the temperature at the speed of 20 ℃/min to the brazing heat preservation temperature of 1000 ℃, keeping the temperature for 25min, and keeping the pressure in the furnace to be not more than 10^-3Pa, cooling the alloy part to 900 ℃ along with the furnace after brazing, introducing high-purity argon, cooling to below 100 ℃ at the speed of 40-60 ℃/min, and then discharging the alloy part from the furnace for air cooling;

step three: and (3) placing the alloy part subjected to brazing treatment in a heat treatment furnace, heating to 845 ℃ at the speed of 25 ℃/min, preserving heat for 4 hours for stabilization treatment, taking out and air-cooling to room temperature, heating to 760 ℃ at the speed of 25 ℃/min, preserving heat for 16 hours for aging treatment, and taking out and air-cooling to room temperature.

Performance detection

The GH4738 alloys after brazing and aging treatment of examples 1-2 and comparative example 1 were subjected to tensile tests at room temperature, and the results are shown in Table 2.

TABLE 2 tensile test results for GH4738 alloy at room temperature

Comparative example 1 in table 2 is the mechanical properties of GH4738 alloy measured after conventional vacuum brazing and aging treatment. Compared with the traditional vacuum brazing and aging process, the strength of the GH4738 alloy treated by the process is obviously improved, and the strength of the alloy reaches the strength of the alloy in a standard state. That is, the strength of the alloy is maintained after multiple vacuum brazing cycles and aging. The method simultaneously solves the technical problems that the nickel-based high-temperature alloy needs to be brazed for multiple times and the alloy strength is reduced after the vacuum brazing heat treatment, and has great popularization and application values.