CN103341586B - Method for achieving forming of GH4738 nickel-base superalloy turbine discs - Google Patents

Abstract

The invention discloses a method for achieving forming of GH4738 nickel-base superalloy turbine discs, and relates to a method for preparing the GH4738 nickel-base superalloy turbine discs. The method aims at solving the problems that an existing technology for preparing the GH4738 nickel-base superalloy turbine discs is complex and low in efficiency, and cannot achieve the purposes that the turbine discs are good in quality, even in grain distribution and free of surface crack. The method for achieving forming of the GH4738 nickel-base superalloy turbine discs comprises the following steps: adopting a compound insulation method with a sheath and insulation cotton, carrying out double-firing-number heating, upsetting and die forging, and carrying out solidifying solution and double aging processing at the subsolid solution temperature. By means of the method, the GH4738 nickel-base superalloy turbine discs with different diameter dimensions and disc thicknesses can be prepared. The method can be applied to preparation of nickel-base superalloy turbine discs in the field of petrochemical engineering and aerospace, and preparation of other disc forge pieces used under the high temperature condition.

Description

A method for forming GH4738 nickel-based superalloy turbine disk

technical field

The invention relates to the field of turbine disc forming of nickel-based deformed superalloy, which is used for long-term use at around 720°C, and requires high temperature strength, long-lasting creep, fatigue and crack growth rate under severe stress conditions. A method for forming a nickel-based superalloy turbine disk.

Background technique

In the field of petrochemical industry, the flue gas turbine developed by using the thermal energy of refinery tail gas to generate electricity is a product with great market prospects at home and abroad, which has created huge benefits for the development of the national economy; at the same time, aerospace engines urgently need turbines that can withstand high temperatures and high strength. Disk parts, whether it is a key turbine disk part used in a flue gas turbine or an aerospace engine, the important material for manufacturing the high-temperature hot end part is mainly GH4738 nickel-based superalloy. The alloy is a domestic precipitation-hardening nickel-based deformation superalloy, also known as GH864 alloy, which is generally used for a long time at around 720 °C. The alloy is mainly strengthened by the γ' phase and grain boundary carbides. It has a certain ability to resist high temperature oxidation and hot corrosion. One of the biggest advantages is that it has a good high temperature toughness matching; therefore, this alloy has always been used in the manufacture of aerospace One of the main materials of turbine disks and turbine blades in engines and power machinery [Semiatin S L, Fagin P N, Glavicic M G, et al. Deformation behavior of Waspaloy at hot-working temperatures. Scripta Materialia ., 2004, 50: 625; Yao Zhihao, Zhang Maicang, Dong Jianxin. Stress rupture fracture model and microstructure evolution for Waspaloy[J]. Metallurgical and Materials Transactions A , DOI: 10.1007/s11661-013-1660-8, 2013;];

As a typical hard-to-deform high-temperature alloy, GH4738 alloy has high alloying degree, high deformation resistance, and narrow deformable temperature, so it is very difficult to form during hot working; Cracks, severe mixed crystals, and excessive grain size will cause the turbine disk to be scrapped, resulting in huge economic losses, and even damage to operating equipment and casualties. The control of the hot working process has an important influence on the grain size of the alloy and the distribution and morphology of the carbides at the grain boundary. If the forging temperature is too high, the grains will be coarse, and even the filming phenomenon at the alloy grain boundary will occur; if the forging temperature is too low, It will cause forging cracks in the alloy disc. Improper temperature control will inevitably have a greater impact on tissue performance. At the same time, the deformation rate, deformation amount and insulation measures can also have an important impact on the alloy structure. [Yao Zhihao, Dong Jianxin, Zhang Maicang. Control and prediction of microstructure during hot deformation of GH738 superalloy I. Construction of microstructure evolution model[J]. Acta Metallica Sinica , 47(12): 1581-1590, 2011; Yao Zhihao, Wang Qiuyu, Zhang Maicang, Dong Jianxin. Control and prediction of microstructure during hot deformation of GH738 superalloy II. Validation and application of microstructure evolution model[J]. W P, Radavich J F, Couts W H. Effect of hot work on the properties of Waspaloy [J]. Metallurgical Transactions . 1970, 1: 2623~2630;]; The impact of process control is more necessary and important. Reasonable selection of forging temperature and deformation rate is of great significance to the precise control of the GH4738 alloy structure; in addition, accurate control of the deformation will enable the turbine disc to obtain sufficient recrystallization; although, the static recrystallization of the subsequent high-temperature solution treatment can affect the grain The grain size is adjusted to a certain extent, but it will not significantly reduce the overall grain size of the disc forging, so the control of deformation is also the basis and premise for obtaining high-quality forgings; Uniformity or re-dissolution and precipitation of carbides will adversely affect the grain boundary, resulting in undesirable structures such as mixed crystals, grain boundary phase film formation, and abnormal grain growth, resulting in decreased mechanical properties and unstable properties of the alloy The degree increases. Studies have shown that the follow-up heat treatment system also plays an important role in the improvement of alloy properties [Yao Zhihao, Dong Jianxin, Zhang Maicang, et al. Correlation between microstructure and mechanical properties of GH864 alloy. Rare Metal Materials and Engineering , 2010, 39( 9): 1565; Guimaraes A A, Jonas J J .Recrystallization and aging effects associated with the high temperature deformation of Waspaloy and Inconel 718 [J]. Metallurgical Transactions A . 1981, A12: 1655-1666; Yao Zhihao, Dong Jianxin, Zhang Maicang, Yu Qiuying, Zheng Lei. Effect of solid solution temperature on microstructure and properties of GH864 alloy used in cigarette machine blades [J]. Journal of Materials Heat Treatment , 32(7): 44-50, 2011]; at present, in the actual production of GH4738 alloy, due to the deformation process Cracks and unqualified microstructures of turbine disks often occur due to control, and it is urgent to study the key forming process of this alloy turbine disk.

Contents of the invention

The purpose of the present invention is to solve the existing problems of complex process, low efficiency and difficulty in obtaining high-quality, uniform grain size distribution and no surface cracks in the preparation of GH4738 nickel-based superalloy turbine discs. Therefore, a control process for forging and forming of GH4738 alloy turbine disk is proposed, in order to obtain GH4738 nickel-based superalloy turbine disk that can meet the standard requirements of mechanical properties.

The invention relates to a GH4738 nickel-based superalloy material, the composition of which is: C: 0.02-0.08; Al: 1.2-1.6; Ti: 2.75-3.25; Co: 12.0-15.0; Cr: 18.0-21.0; Mo: 3.5- 5.0; Fe≤2.0; S≤0.001; P≤0.005; Ni balance, the main strengthening phases in this alloy are spherical γ' phase, M ₂₃ C ₆ and MC phase.

The technical scheme of the present invention is: a kind of method for realizing the forming of GH4738 nickel-based superalloy turbine disc, which specifically includes the following steps:

step 1.

1) Hard wrap the regular cylindrical rod blank:

First of all, choose a regular cylindrical alloy rod blank, the initial average grain size of the rod blank is less than 170μm, use thermal insulation cotton to wrap the selected cylindrical alloy rod blank coated with lubricant firmly, and then use the cut thickness A 0.5-1mm stainless steel plate is hard-wrapped on the outside of the insulation cotton, and the joint is welded firmly;

2) Heating the wrapped bar material:

Put the sheathed bar in the effective area of the electric furnace, pad it with refractory bricks below, control the heating temperature of the electric furnace at 1060-1120°C, and connect the external armored couple to the K-type electric couple as required;

3) Upsetting cake process:

a. When the billet has fully reached the set temperature, the sheathed bar is quickly transferred to the flat anvil of the press after it is released from the furnace, and a layer of thermal insulation cotton is laid on the lower flat anvil. The bar is placed in the middle of the flat anvil, and the transfer time is controlled within 1min Within the mold temperature is not lower than 350 ℃;

b. The press is pressed according to the preset pressing mode. Firstly, the height dimension is pressed and deformed by 30-40%, and the pressure is kept for 30s. Finally, the height dimension is upset to 40-50% of the original undeformed bar height, and the deformation The speed is controlled at 5-10mm/s;

c. Remove the biscuit, remove the outer jacket, place it in a sand pit to cool in air, and set aside;

Step 2:

The cake blank obtained in step 1 is subjected to the following die forging process control: a. First, the cake blank is hard-coated as shown in step 1); b. The packaged cake blank is placed in the effective area of the electric furnace, Use refractory bricks to pad it up below, and control the heating temperature at 1060-1120°C; c. The external armored couple is connected to a K-type galvanic couple as required,

d. After adjusting the preheated mold on the press, use water lubricant to lubricate the mold cavity to ensure that the mold temperature is above 350°C;

e. After the die forging blank has fully reached the set temperature, the cake blank is quickly transferred to the press mold after being released from the furnace, and the cake blank is placed in the middle of the mold, and the transfer time is controlled within 1 minute;

f. The press presses according to the pre-set pressing mode, and the deformation rate is controlled at 5-10mm/s; the final compressible deformation should be controlled at 55-75% of the height of the original cake. After forging, immediately remove the forging and remove the outer crust Set of materials, placed in the bunker for air cooling, spare;

Step 3:

The die forging disc obtained in step 2 is subjected to heat treatment control under sub-solution conditions. The heat treatment temperature should be controlled at 1000-1040°C for 4-8 hours, then air-cooled or oil-cooled, and then double-aging treatment is carried out at a temperature of 700- Hold at 900°C for 1-16 hours for air cooling, cool at 60°C/min to the second stage of aging, hold at 650-800°C for 6-24 hours, and carry out air cooling to obtain a formed GH4738 nickel-based superalloy turbine disk.

The GH4738 nickel-based superalloy turbine disc is forged by the above method, which is suitable for manufacturing hot end components such as the GH4738 alloy turbine disc for aerospace engines and flue gas turbines.

The present invention has the advantage that:

(1) This invention proposes a GH4738 nickel-based superalloy turbine disc forming method. Compared with other discs with the same composition, the prepared disc has no cracks, good grain structure and better high temperature mechanical properties.

(2) A method for forming GH4738 nickel-based superalloy turbine disc proposed by the present invention can obtain better mechanical properties under the same forging conditions in terms of heat treatment optimization.

The beneficial effect of the present invention is: the GH4738 turbine disc controlled by the forging forming method is then subjected to appropriate solid solution and aging heat treatment, and the optimization of temperature and time is ensured. The finally obtained heat-treated GH4738 alloy has a good structure, relatively uniform grain size and intermittent distribution of grain boundary carbides; the test results of tensile properties and durability show that the turbine disc forming method of the GH4738 nickel-based superalloy realized through this invention The performance of the disk parts exceeds the requirements of the technical conditions, and at the same time, the fluctuation of the alloy performance is reduced, which ensures the stable operation of the high-temperature operating turbine disk components.

Description of drawings

Fig. 1 is the initial grain structure of the original bar in Example 1 of the present invention.

Fig. 2 is the grain structure at R/2 of the forged turbine disk in Example 1 of the present invention.

Fig. 3 is the distribution state of the strengthening phase after the heat treatment of the forged turbine disk in Example 1.

detailed description

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

Carry out actual forging production verification based on the best thermal processing process control principles obtained above, for example: now forging GH4738 alloy rods for a certain type of turbine disc;

Embodiment 1: This embodiment proposes a method for forming a GH4738 nickel-based superalloy turbine disk, and obtains better performance, which is characterized in that it specifically includes the following steps:

step 1:

1) The regular Φ110mm×260mm cylindrical rod blank is hard-coated, the initial grain size is 150μm, and the actual composition of the selected GH4738 alloy is measured as C: 0.06; Al: 1.42; Ti: 3.15; Co: 13.5; Cr: 20.0; Mo: 4.1; Ni balance. a. First wrap the bar firmly with thermal insulation cotton; b. Then use a cut stainless steel plate (thickness 0.8mm) to hard wrap the outer side of the thermal insulation cotton, and weld the connection firmly.

2) Heating the sheathed bar: a. Put the bar in the effective area of the electric furnace, pad it with refractory bricks below, and control the heating temperature at 1080°C; b. Connect the external armored couple to the K type as required galvanic couple.

3) Upsetting cake process: a. After the billet has completely reached the set temperature, the sheathed bar is quickly transferred to the flat anvil of the press after being released from the oven, and a layer of insulation cotton is laid on the lower flat anvil, and the bar is placed in the middle of the anvil The transfer time is controlled within 1min, and the mold temperature is not lower than 350°C; b. Press the press according to the preset pressing mode, first press the height dimension to 30% of the height of the undeformed bar, hold the pressure for 30s, and then press the height dimension Upsetting is 50% of the initial undeformed height, and the deformation rate is controlled at 10mm/s. c. Remove the cake base, remove the outer jacket, and place it in a sand pit for air cooling; the sundries and oxide scales on the surface of the cake base must be cleaned;

Step 2:

The cake base obtained in step 1 is controlled by the die forging process as follows: a. First, the cake base is hard-coated as shown in 1); b. The wrapped cake base is placed in the effective area of the electric furnace, and the refractory Pad it up with bricks, and control the heating temperature at 1080°C; c. Connect the external armored couple to the K-type couple as required; d. After adjusting the preheated mold on the press, lubricate the mold cavity with water lubricant , to ensure that the temperature is above 350°C; e. After the die forging billet reaches the set temperature completely, the cake billet is quickly transferred to the press mold after being released from the furnace, and the cake billet is placed in the middle of the mold, and the transfer time is controlled within 1min; f. The press is pressed according to the preset pressing mode, and the deformation rate is controlled at 10mm/s. The final compressible deformation should be controlled at 65% of the height of the original cake to ensure sufficient deformation for recrystallization, reduce the average grain size, and improve the overall strength of the disc. After forging, remove the forging immediately and remove the outer sheath material. Placed in a bunker for air cooling;

Step 3:

The die forging disc obtained in step 2 is subjected to heat treatment control under sub-solid solution conditions. The heat treatment temperature should be controlled at 1020°C for 4 hours, oil cooling, and then double aging treatment. /min cooling to the second stage of aging, at a temperature of 760 ° C for 16 hours, and air cooling.

Figure 1 shows the initial grain structure of the bar, and Figure 2 shows the grain structure at R/2 of the forged turbine disk. It can be seen that the grain structure of the forging is relatively uniform, and there is no mixed crystal phenomenon, as shown in Figure 3 Shown is the strengthening phase distribution state after heat treatment of the turbine disk;

Table 1-Table 3 shows the mechanical properties of the forged turbine disk. The performance indicators of the alloy were measured by sampling the R/2 part of the turbine disk in the chord direction; it can be found that the tensile properties and durability performance at room temperature and high temperature are far Exceeding the requirements of technical conditions, the room temperature tensile performance strength has increased by about 40% compared with the standard value, while the plastic elongation and area reduction rate have increased by more than 1 times; at the same time, the durability of the forged alloy has been improved most obviously, and its durability is the standard Value more than 5 times, thereby, illustrate that the performance of the turbine disc produced by forging of the present invention has a larger performance margin;

Table 1 Tensile properties at room temperature

Table 2 High temperature tensile properties

Table 3 Persistence performance

Embodiment 2: This embodiment proposes a method for realizing the forming of a GH4738 nickel-based superalloy turbine disk, and obtains better performance, which is characterized in that it specifically includes the following steps:

step 1:

1) The regular Φ102mm×270mm cylindrical rod blank is hard-coated, the initial grain size is 160μm, and the actual composition of the selected GH4738 alloy is measured as C: 0.04; Al: 1.39; Ti: 3.05; Co: 13.3; Cr: 19.8; Mo: 4.05; Ni balance. a. First wrap the bar firmly with thermal insulation cotton; b. Then use a cut stainless steel plate (thickness 0.8mm) to hard wrap the outer side of the thermal insulation cotton, and weld the connection firmly.

2) Heat the sheathed bar: a. Put the bar in the effective area of the electric furnace, pad it with refractory bricks below, and control the heating temperature at 1060°C; b. Connect the external armored couple to the K type as required galvanic couple.

3) Upsetting cake process: a. After the billet has fully reached the set temperature, the sheathed bar is quickly transferred to the flat anvil of the press after being released from the oven, and a layer of insulation cotton is laid on the lower flat anvil, and the bar is placed in the middle of the flat anvil as much as possible , the transfer time is controlled within 1min, and the mold temperature is not lower than 350°C; b. Press the press according to the preset pressing mode, first press 40% of the height dimension, hold the pressure for 30s, and then upset the height dimension without deformation initially 40% of the bar height, the deformation rate is controlled at 5mm/s. c. Remove the cake base, remove the outer jacket, and place it in a sand pit for air cooling; the sundries and scales on the surface of the cake base must be cleaned.

Step 2:

The cake base obtained in step 1 is controlled by the die forging process as follows: a. First, the cake base is hard-coated as shown in 1); b. The wrapped cake base is placed in the effective area of the electric furnace, and the refractory Pad it up with bricks, and control the heating temperature at 1060°C; c. Connect the external armor couple to the K-type couple as required; d. After adjusting the preheated mold on the press, lubricate the mold chamber with water lubricant , to ensure that the temperature is above 350°C; e. After the die forging billet reaches the set temperature completely, the cake billet is quickly transferred to the press mold after being released from the furnace, and the cake billet is placed in the middle of the mold, and the transfer time is controlled within 1min; f. The press is pressed according to the preset pressing mode, and the deformation rate is controlled at 10mm/s. The final compressible deformation should be controlled at 65% of the height of the original cake to ensure sufficient deformation for recrystallization, reduce the average grain size, and improve the overall strength of the disc. After forging, remove the forging immediately and remove the outer sheath material. Placed in a bunker for air cooling;

Step 3:

The die forging disc obtained in step 2 is subjected to heat treatment control under sub-solution conditions. The heat treatment temperature should be controlled at 1040 ° C for 6 hours, oil cooling, and then double aging treatment. /min cooling to the second stage of aging, at a temperature of 700 ° C for 24 hours, air cooling.

After testing, the room temperature, high temperature tensile properties and durability properties all meet the technical requirements.

Example 3:

This embodiment proposes a method to realize the forming of GH4738 nickel-based superalloy turbine disc, and obtains better performance. The difference between the forming process and Example 1 lies in step (2): the cake base obtained in step 1 is subjected to the following die forging process Control: a. Firstly, hard wrap the biscuit as shown in 1); b. Put the wrapped biscuit in the effective area of the electric furnace, pad it with refractory bricks below, and control the heating temperature at 1080°C ; c. Connect the external armored couple as required, K-type galvanic couple; d. After adjusting the preheated mold on the press, use water lubricant to lubricate the mold chamber to ensure that the temperature is above 350°C; e. After the forging billet reaches the set temperature completely, the cake is quickly transferred to the mold of the press after being released from the furnace, and the cake is placed in the middle of the mold, and the transfer time is controlled within 1 minute; f. The press presses according to the preset pressing mode, The deformation rate is controlled at 7mm/s. The final compressible deformation should be controlled at 65% of the height of the original cake to ensure sufficient deformation for recrystallization, reduce the average grain size, and improve the overall strength of the disc. After forging, remove the forging immediately and remove the outer sheath material. Placed in the bunker for air cooling; other steps are exactly the same as in Example 1.

Example 4:

This embodiment proposes a key forming method to realize the GH4738 nickel-based superalloy turbine disc, and obtains better performance. The difference between the forming process and Example 1 lies in step (3): the die-forged disc obtained in step 2 is sub-formed. For heat treatment control under solid solution conditions, the solution heat treatment temperature should be controlled at 1020°C for 5 hours of oil cooling, and then double aging treatment, the temperature is 845°C for 4 hours for air cooling, and the second stage of aging is cooled at 60°C/min. Insulated at 760°C for 16 hours and air-cooled. After testing, the tensile properties at room temperature, high temperature and durability all meet the technical requirements. Other steps are identical to Example 1.

Example 5:

This embodiment proposes a key forming method to realize the GH4738 nickel-based superalloy turbine disk, and obtains better performance. The difference between the forming process and Example 1 lies in step (1): the regular Φ620mm×1230mm cylindrical rod blank is processed Hard sheath, the initial grain size is 120μm, and the measured actual composition of the selected GH4738 alloy is C: 0.03; Al: 1.49; Ti: 3.25; Co: 13.02; Cr: 19.07; Mo: 4.44; Ni balance . a. First, use thermal insulation cotton to wrap the bar firmly; b. Then use a cut stainless steel plate (thickness 0.8mm) to hard wrap the outer side of the thermal insulation cotton, and weld the connection firmly;

Step (3): Control the heat treatment of the die-forged disc obtained in step 2 under sub-solution conditions. The heat treatment temperature should be controlled at 1030°C for 5 hours and air-cooled, and then perform double aging treatment. The temperature should be 845°C for 5 hours and then air-cooled , cooled at 60°C/min to the second stage of aging, and then air-cooled at a temperature of 760°C for 16 hours. Other steps are identical to Example 1. After testing, the room temperature, high temperature tensile properties and durability properties all meet the technical requirements.

Based on the above analysis, using the key process control of the turbine disk forming and proper heat treatment of the turbine disk in the present invention, satisfactory structure and performance data will be obtained, meeting and exceeding the requirements of the technical conditions.

Claims (2)

1. realize a GH4738 nickel base superalloy turbine disk manufacturing process, it is characterized in that, specifically comprise the following steps:

Step 1:

1) the cylindrical bar blank of rule is carried out Hard Roll cover:

First, choose the cylindrical alloy bar blank of rule, the initial average grain size of rod blank is less than 170 μm, heat-preservation cotton is adopted to be wrapped up securely by the cylindrical alloy bar blank chosen coating lubricant, be that the corrosion resistant plate of 0.5-1mm carries out Hard Roll cover outside described heat-preservation cotton again with the thickness cut, and junction is welded;

2) bar that jacket is good is heated:

Be placed on by the bar that jacket is good in electric furnace effective coverage, paved below with refractory brick, heating by electric cooker temperature controls at 1060-1120 DEG C, and external armour is even connects K type galvanic couple on request;

3) upsetting cake technique:

A. after blank reaches design temperature completely, be transported to rapidly on press flat anvil after being come out of the stove by the bar of jacket, lower flat anvil paving one layer of heat preservation is cotton, and bar is placed on flat anvil centre position, and transhipment time controling is within 1min, and mold temperature is not less than 350 DEG C;

B. press is suppressed by the compacting pattern pre-set, and first height dimension is suppressed deflection 30-40%, pressurize 30s, finally again by height dimension jumping-up to the 40-50% not being out of shape at first bar height, rate of deformation controls at 5-10mm/s;

C. take off biscuit, remove outside jacket, be placed on sand pit hollow cold, for subsequent use;

Step 2:

Biscuit step 1 obtained carries out following contour forging technique control: a. first as shown in step 1) method by as described in biscuit carry out Hard Roll cover; B. be placed in electric furnace effective coverage by the biscuit that jacket is good, paved with refractory brick below, heating and temperature control is at 1060-1120 DEG C; C. external armour is even connects K type galvanic couple on request;

D. after being adjusted on press by preheated mould, use aqua lubricant lubrication impression, ensure that mold temperature is more than 350 DEG C;

E. after die forging blank reaches design temperature completely, biscuit is transported to rapidly on press die after coming out of the stove, and biscuit is placed on mould centre position, and transhipment time controling is within 1min;

F. press is suppressed by the compacting pattern pre-set, and rate of deformation controls at 5-10mm/s; Finally can suppress deflection should control, at the 55-75% of former biscuit height, after forging, to take off forging immediately, remove outside sheath material, be placed on sand pit hollow cold, for subsequent use;

Step 3:

Die forging diskware step 2 obtained carries out the Heat Treatment Control under sub-solid solution condition, heat treatment temperature should control within 4-8 hour, to carry out air cooling or oil cooling 1000-1040 DEG C of insulation, then double aging process is carried out, temperature is that 700-900 DEG C of insulation 1-16h carries out air cooling, second stage timeliness is cooled to 60 DEG C/min, be 650-800 DEG C in temperature and be incubated 6-24h, air cooling carries out, and obtains the shaping GH4738 nickel base superalloy turbine disk.

2. a GH4738 nickel base superalloy turbine disk for method process as claimed in claim 1, this GH4738 nickel base superalloy turbine disk is applicable to the turbine diskware manufacturing Aero-Space engine, flue gas turbine expander.