GB/T 39192-2020Heat treatment of superalloy parts (English PDF)

3.1 Temperature equalization time

the time FROM when all the temperature control thermocouples reach the technique setting temperature TO the time that the core temperature of the workpiece reaches the lower limit temperature of the furnace temperature uniformity required by the technique setting temperature

3.2 Metallurgical transformation time

the time FROM when the temperature of the core of the workpiece reaches the lower limit temperature of the furnace temperature uniformity required by the technique setting temperature TO the time when the workpiece is out of the furnace

4.1.3 Vacuum furnace

4.1.3.1 The vacuum pressure of the vacuum furnace shall not be greater than 0.067Pa. The cold pressure rise rate shall not be greater than 1.33Pa/h. The determination method is in accordance with GB/T 10066.1.

4.1.3.2 When the vacuum furnace is heated by backfilling inert gas protection, the vacuum furnace shall be equipped with furnace gas pressure and dew point monitoring system. The dew point of the furnace atmosphere should not be higher than -51°C.

4.1.3.3 When the furnace temperature uniformity test is performed on the vacuum furnace, it shall be carried out at the lowest vacuum pressure used in the production of the workpiece. But it does not need to be lower than 1.3×10-3Pa.

4.1.3.4 Vacuum sensor, vacuum pressure display and recorder shall be calibrated regularly. It is recommended to conduct a comparison test on the vacuum measurement and recording system every six months. The maximum allowable error is ±0.5 orders of magnitude. See formula (1):

Where, Pa - Indicated value of vacuum sensor, vacuum pressure display and recorder; Pt - Indicated value of standard measuring equipment.

4.1.3.5 If the vacuum furnace is equipped with a dew point measuring device, it shall be calibrated regularly. The maximum allowable measurement error is ±5°C.

4.1.4 Inert gas furnace

4.1.4.1 During the furnace temperature uniformity test, the gas pressure in the furnace shall be consistent with the heat treatment of the workpiece.

4.1.4.2 The dew point of the atmosphere in the inert gas furnace shall not be higher than -51°C.

4.1.4.3 The dew point measurement system shall be calibrated regularly. The maximum allowable measurement error is ±5°C.

4.2 Cooling equipment

4.2.1 Quenching tank

evenly heated and cooled.

6.2 Loading to furnace

6.2.1 There shall be enough space between adjacent workpieces. Especially when stacking is used, it shall be ensured that the furnace gas can flow smoothly, evenly heat and cool on its inner and outer surfaces.

6.2.2 The workpiece shall be placed steadily on the rack, tray, frame or special fixture, so as to ensure that all the workpieces are in the effective heating zone.

6.2.3 When calculating the heat preservation time by loading a thermocouple, the thermocouple shall be inserted into the previously machined hole of the workpiece or equivalent test block. And the top of the thermocouple shall be in contact with the bottom of the hole. The gap between the hole and the thermocouple is sealed with ceramic fiber and so on. The bottom of the hole shall be located at the center of the largest section of the workpiece or equivalent test block. If an equivalent test block is used, its length shall be at least 3 times the maximum thickness.

6.3 Heating

6.3.1 For workpieces with large dimensions and complex shapes, it is recommended to use preheating or segmented heating when heating for solid solution treatment. The preheating temperature is generally 800°C~850°C.

When the solid solution treatment temperature is above 1000°C, generally use two or more section heating. For heat treatment with preheating or section heating, the workpiece shall be put into the furnace below the preheating temperature or the temperature of the low temperature section of the section heating.

6.3.2 When there is no preheating or segmented heating requirements, the workpiece shall be heated with the furnace in accordance with the process regulations or loaded into the furnace after the furnace temperature reaches the set temperature and is stable. If there is no specific stipulation, the method of heating to the warming furnace is preferred.

6.4 Heat preservation time

6.4.1 When the load thermocouple is not used to calculate the heat preservation time, the heat preservation time shall be calculated when the indicated temperature of all temperature-controlled thermocouples in the furnace reaches the process set temperature.

6.4.2 When calculating the heat preservation time by the load thermocouple, the heat preservation time shall be calculated from the time when all thermocouples (including temperature control, recording, alarm and protection thermocouples) reach the lower limit temperature of furnace temperature uniformity required by the process set temperature. If the load thermocouple is buried in the core of the workpiece or equivalent test block, the temperature equalization time shall be deducted from the heat preservation time given in Table 3~Table 5. Only keep the metallurgical transformation time. The calculation of temperature equalization time given in Table 3~Table 5 is only applicable to air resistance furnace and inert atmosphere furnace.

6.4.3 When the workpiece is stacked or the stack is used for multi-layer loading, the temperature equalization time shall be determined by the load thermocouple. When determining the temperature equalization time, the number of workpieces installed in the furnace shall be the actual maximum number of furnaces in the production.

6.4.4 Use at least 2 load thermocouples to measure the temperature equalization time. Fix a load thermocouple at the center of the workpiece or equivalent test block at the center of the middle layer. The other one is fixed at the core of the workpiece or equivalent test block at the low temperature of the heating furnace or the position closest to the low temperature. The location of the low temperature point shall be determined based on the results of the most recent furnace temperature uniformity test. The workpiece and the load thermocouple are heated according to the actual heating method used in the production (heating with the furnace, preheating, heating in segments or warmly loading to furnace). Record the time when the last temperature control thermocouple reaches the process set temperature and the time when all thermocouples (including temperature control, record, alarm and protection and load thermocouples) reach the lower limit temperature of furnace temperature uniformity required by the process set temperature. The time difference between the two is the temperature equalization time.

6.4.5 For vacuum heat treatment, the temperature equalization time of the workpiece shall be determined by the load thermocouple. If it is not possible to determine the temperature equalization time of the workpiece by installing a load thermocouple, take 2 times the temperature equalization time of air resistance furnace heating as the temperature equalization time of vacuum heating.

6.5 Partial pressure of vacuum heat treatment

When vacuum heat treatment is used, the vacuum working pressure shall generally not be greater than 0.133Pa. When the inflatable body is used, the partial pressure is controlled at 1.33Pa~13.3Pa.

6.6 Cooling

For a workpiece that uses oil cooling, polymer aqueous solution, water cooling, air cooling or air cooling, when the workpiece is cooled below 200°C, it is allowed to exit the groove, stop wind cooling or stop air cooling.

6.7 Recording

If there are no special regulations, the records and data preservation of the heat treatment process shall be implemented in accordance with the regulations of GB/T 32541.

7.1 Appearance

7.1.1 There shall be no defects such as cracks on the surface of the workpiece after heat treatment.

7.1.2 Slight yellowish oxidation is allowed on the surface of the workpiece after heat treatment in vacuum or inert atmosphere.

7.2 Metallographic inspection

7.2.1 The average grain size of the deformed superalloy is tested in accordance with the provisions of GB/T 6394 or special technical documents. The average grain size of the cast superalloy is tested in accordance with the provisions of GB/T 14999.7.

7.2.2 The inspection of the microstructure is carried out in accordance with the provisions of the special technical documents.

7.3 Mechanical properties

7.3.1 The hardness test is carried out in accordance with the provisions of GB/T 230.1 or GB/T 231.1.

7.3.2 The tensile properties at room temperature shall be carried out in accordance with the provisions of GB/T 228.1.

7.3.3 The high temperature tensile properties shall be carried out in accordance with the provisions of GB/T 228.2.

7.3.4 The durability and creep performance are carried out in accordance with the provisions of GB/T 2039. […]