阅读说明：本技术 一种降低镍基高温合金涡轮盘热应力的方法 (Method for reducing thermal stress of nickel-based superalloy turbine disk ) 是由 瞿宗宏 宋嘉明 罗成 白瑞敏 郑作赟 黄椿森 赖运金 王庆相 梁书锦 于 2019-09-30 设计创作，主要内容包括：本发明公开了一种降低镍基高温合金涡轮盘热应力的方法,具体按以下步骤进行：步骤1,制备表面平整的镍基高温合金涡轮盘毛坯,然后对镍基高温合金涡轮盘毛坯进行喷砂处理；步骤2,对步骤1中得到的镍基高温合金涡轮盘毛坯进行预热,然后使用超音速火焰法,在镍基高温合金涡轮盘毛坯表面喷涂不锈钢涂层；步骤3,将步骤2中得到的镍基高温合金涡轮盘毛坯进行固溶处理,得到镍基高温合金涡轮盘,本发明降低了镍基高温合金热处理过程中产生的热应力,降低热处理过程中的淬火开裂风险,提高了坯料的组织均匀性。(The invention discloses a method for reducing the thermal stress of a nickel-based superalloy turbine disk, which comprises the following steps: step 1, preparing a nickel-based superalloy turbine disc blank with a smooth surface, and then performing sand blasting on the nickel-based superalloy turbine disc blank; step 2, preheating the nickel-based superalloy turbine disc blank obtained in the step 1, and spraying a stainless steel coating on the surface of the nickel-based superalloy turbine disc blank by using a supersonic flame method; and 3, carrying out solution treatment on the nickel-based superalloy turbine disc blank obtained in the step 2 to obtain the nickel-based superalloy turbine disc.)

1. A method for reducing the thermal stress of a nickel-based superalloy turbine disk is characterized by comprising the following steps:

step 1, preparing a nickel-based superalloy turbine disc blank with a smooth surface, and then performing sand blasting on the nickel-based superalloy turbine disc blank;

step 2, preheating the nickel-based superalloy turbine disc blank obtained in the step 1, and spraying a stainless steel coating on the surface of the nickel-based superalloy turbine disc blank by using a supersonic flame method;

and 3, carrying out solution treatment on the nickel-based superalloy turbine disc blank obtained in the step 2 to obtain the nickel-based superalloy turbine disc.

2. The method for reducing the thermal stress of the nickel-based superalloy turbine disk according to claim 1, wherein in the step 2, the preheating temperature is 300-400 ℃, and the spraying speed of a spray gun is 800-1700 m/s.

3. The method for reducing the thermal stress of the nickel-based superalloy turbine disk according to claim 1, wherein in the step 2, the thickness of the coating on the surface of the nickel-based superalloy turbine disk blank is 6-7 mm.

4. The method for reducing the thermal stress of the nickel-based superalloy turbine disc as claimed in claim 1, wherein the step 3 is specifically that the sprayed nickel-based superalloy turbine disc blank is placed in a heat treatment furnace, heated for 4-5 hours and then kept warm, and then the nickel-based superalloy turbine disc blank is taken out and placed in air to be cooled to room temperature.

5. The method for reducing the thermal stress of the nickel-based superalloy turbine disk according to claim 4, wherein in the step 3, the heating temperature is 1100-1200 ℃, and the holding time is 5-6 hours.

Technical Field

The invention belongs to the technical field of high-temperature alloy preparation, and relates to a method for reducing thermal stress of a nickel-based high-temperature alloy turbine disc.

Background

High temperature alloys generally refer to a class of metallic materials that have high oxidation and corrosion resistance at service temperatures above 600 ℃ and that can be used for long periods of time under certain stress conditions. The nickel-based superalloy has excellent high-temperature strength and high-temperature creep resistance, excellent oxidation resistance and hot corrosion resistance, higher mechanical fatigue resistance and thermal fatigue resistance, and good structural stability at high temperature, so that the nickel-based superalloy is widely applied to the fields of hot end parts of gas turbine engines and the like. The nickel-base superalloy mainly performs precipitation strengthening by using a precipitation strengthening phase gamma 'phase, and the quantity, size, shape and distribution of the gamma' phase have great influence on the performance of the nickel-base superalloy. After the nickel-based superalloy is prepared into a blank, the number, size, morphology and distribution of gamma' phases need to be adjusted through heat treatment so as to obtain ideal alloy structure and performance.

The heat treatment of the nickel-based high-temperature alloy is divided into solution treatment and aging treatment, the cooling process after the solution treatment is also called quenching, the higher the quenching rate is, the finer the gamma' phase precipitated in the alloy structure is, and the higher the alloy strength is. However, the temperature of the surface of the blank is rapidly reduced due to the high cooling rate, the temperature inside the blank is high, a large temperature gradient is formed in the whole blank, and the temperature gradient causes different expansion and contraction of different parts of the blank, so that thermal stress is formed.

The existence of thermal stress has an important influence on the nickel-based superalloy process and performance: in the heat treatment process, when the thermal stress is greater than the tensile strength of the material, the blank can be quenched and cracked, so that the blank is scrapped; the thermal stress or the residual stress is converted after the blank is cooled to room temperature, and the blank is deformed after being processed by the residual stress, so that the part does not meet the size requirement and is finally scrapped; the difference of the temperature gradient causes the difference of tissues at different positions of the blank, and further causes the difference of mechanical properties of different parts of the blank. Therefore, the method for reducing the heat treatment thermal stress of the nickel-based high-temperature alloy is researched, the processing and the service performance of the nickel-based high-temperature alloy can be effectively improved, and a new process is provided for the heat treatment of the nickel-based high-temperature alloy.

Disclosure of Invention

The invention aims to provide a method for reducing the thermal stress of a nickel-based superalloy turbine disk, which can reduce the thermal stress in heat treatment.

The technical scheme adopted by the invention is that the method for reducing the thermal stress of the nickel-based superalloy turbine disc specifically comprises the following steps:

step 1, preparing a nickel-based superalloy turbine disc blank with a smooth surface, and then performing sand blasting on the nickel-based superalloy turbine disc blank;

step 2, preheating the nickel-based superalloy turbine disc blank obtained in the step 1, and spraying a stainless steel coating on the surface of the nickel-based superalloy turbine disc blank by using a supersonic flame method;

and 3, carrying out solution treatment on the nickel-based superalloy turbine disc blank obtained in the step 2 to obtain the nickel-based superalloy turbine disc.

In the step 2, the preheating temperature is 300-400 ℃, and the spraying speed of the spray gun is 800-1700 m/s.

In the step 2, the thickness of the coating on the surface of the nickel-based superalloy turbine disc blank is 6-7 mm.

And 3, specifically, placing the sprayed nickel-based superalloy turbine disc blank in a heat treatment furnace, heating for 4-5 hours, preserving heat, taking out the nickel-based superalloy turbine disc blank, and placing in air to cool to room temperature.

In the step 3, the heating temperature is 1100-1200 ℃, and the heat preservation time is 5-6 h.

The invention has the advantages of reducing the thermal stress generated in the heat treatment process of the nickel-based high-temperature alloy, reducing the quenching cracking risk in the heat treatment process, reducing the residual stress of the blank after the heat treatment, improving the tissue uniformity of the blank, reducing the internal temperature gradient of the blank by the coating, reducing the precipitation size difference of each part and the mechanical property difference of different parts of the blank.

Drawings

FIG. 1 is a schematic structural view of a nickel-base superalloy turbine disk in a method of reducing thermal stress of the turbine disk of the present invention;

FIG. 2 is a graph of temperature change for an uncoated nickel-base superalloy turbine disk;

FIG. 3 is a graph of temperature change for a coated nickel-base superalloy turbine disk;

FIG. 4 is a nickel-base superalloy turbine disk residual stress profile;

FIG. 5 is a topographical view of the uncoated gamma prime phase of the surface of a nickel-base superalloy turbine disk blank;

FIG. 6 is a topographical view of a nickel-base superalloy turbine disk blank having a coating gamma prime phase on the surface.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

A method for reducing the thermal stress of a nickel-based superalloy turbine disk specifically comprises the following steps:

step 1, preparing a nickel-based superalloy turbine disc blank with a smooth surface, and then performing sand blasting on the nickel-based superalloy turbine disc blank;

step 2, preheating the nickel-based superalloy turbine disc blank obtained in the step 1, and spraying a stainless steel coating on the surface of the nickel-based superalloy turbine disc blank by using a supersonic flame method;

and 3, carrying out solution treatment on the nickel-based superalloy turbine disc blank obtained in the step 2 to obtain the nickel-based superalloy turbine disc.

In the step 2, the preheating temperature is 300-400 ℃, and the spraying speed of the spray gun is 800-1700 m/s.

In the step 2, the thickness of the coating on the surface of the nickel-based superalloy turbine disc blank is 6-7 mm.

And 3, specifically, placing the sprayed nickel-based superalloy turbine disc blank in a heat treatment furnace, heating for 4-5 hours, preserving heat, taking out the nickel-based superalloy turbine disc blank, and placing in air to cool to room temperature.

In the step 3, the heating temperature is 1100-1200 ℃, and the heat preservation time is 5-6 h.

The nickel-based superalloy turbine disc prepared by the method is selected to perform a contrast test with a nickel-based superalloy turbine disc prepared by a traditional method:

temperature thermocouples are inserted into a position 1 and a position 2 shown in fig. 1 to monitor the cooling process of the nickel-based superalloy turbine disc blank, the temperature change of the nickel-based superalloy turbine disc without the coating is shown in fig. 2, the temperature change of the nickel-based superalloy turbine disc with the coating prepared by the invention is shown in fig. 3, and as can be seen by comparing fig. 2 and fig. 3, the temperature difference between the position 1 and the position 2 in fig. 2 is large, which indicates that a large temperature gradient exists in the turbine disc blank to generate a large thermal stress, so that the turbine disc blank has a cracking risk, and the temperature difference between the position 1 and the position 2 in fig. 3 does not exist basically, which indicates that the temperature in the turbine disc blank is uniform, the thermal stress is small, and the risk of cracking of the turbine disc blank is greatly reduced.

In the stress measurement position shown in fig. 1, the residual stress of the nickel-based superalloy turbine disc blank is measured by a deep hole method, fig. 4 is a residual stress distribution diagram of the nickel-based superalloy turbine disc blank, and as can be seen from fig. 4, when no coating is formed, the maximum residual stress of the turbine disc blank reaches 600MPa, and when a coating is formed, the residual stress level of the turbine disc blank is obviously reduced and is less than 250 MPa.

Fig. 5 shows the appearance of the gamma ' phase after the heat treatment without a coating on the surface of the nickel-based superalloy turbine disk blank, and it can be seen from the figure that the gamma ' phase at the position 1 is fine, the gamma ' phase at the position 2 is coarse, the appearance difference is large, and it can be seen that the structure of the nickel-based superalloy turbine disk blank without a coating is uneven after the heat treatment.

Fig. 6 shows the appearance of the γ ' phase after heat treatment of the nickel-based superalloy turbine disk blank with a coating on the surface, and it can be seen from the figure that the appearance and the size of the γ ' phase at the position 1 and the γ ' phase at the position 2 are equivalent, and it can be seen that the coated nickel-based superalloy turbine disk blank has a uniform tissue after heat treatment.

The reaction mechanism of the method for reducing the thermal stress of the nickel-based superalloy turbine disk is as follows: when the solid solution temperature (about 1150-1220 ℃) of the nickel-based high-temperature alloy is reached, the stainless steel coating on the surface layer of the blank is subjected to oxidation reaction to generate an oxide layer (the thickness of the oxide layer is about 1-2 mm, and the components of the oxide layer are mainly ferric oxide and chromium oxide), when the temperature is higher than 1000 ℃, the thermal conductivity of the oxide is 5-10W/(m DEG C), and the thermal conductivity of the nickel-based high-temperature alloy matrix is higher than 30W/(m DEG C). Therefore, the thermal sprayed coating has a heat insulation effect on the blank substrate, and the region of the nickel-based high-temperature alloy substrate close to the surface is not easy to rapidly dissipate heat in the cooling process, so that the temperature field of the nickel-based high-temperature alloy substrate is more uniform. Under a uniform temperature field, the expansion and contraction difference of different parts of the blank is small, and the thermal stress is obviously reduced, so that the quenching cracking risk is reduced, and the residual stress after heat treatment is also obviously reduced.

In the quenching and cooling process of the nickel-based superalloy, the surface of the blank is subjected to the largest tensile stress, so that the crack defects mostly originate from the surface. The existence of the stainless steel coating protects the surface of the nickel-based high-temperature alloy, is not easy to oxidize, provides conditions for crack initiation, and further reduces the risk of quenching cracking.