Method of heat treatment of products from heat-resistant nickel alloy of grades “хн73мбтю” (“эи”698), “хн73мбтю-вд” (“эи”698-“вд"), “хн71мбтю” (“эи698п”)

Abstract

FIELD: heat treatment of heat-resistant nickel alloys.SUBSTANCE: heat treatment of products made of heat-resistant nickel alloy of grades “ХН73МБТЮ” (“ЭИ”698), “ХН73МБТЮ-ВД” (“ЭИ”698-“ВД”), “ХН71МБТЮ” (“ЭИ698П”). The method of heat treatment of products made of heat-resistant nickel alloy ЭИ698 includes combined hardening and one- or two-stage aging. Combined hardening is carried out according to the following mode: heating to a temperature in the range of 1070-1130 °C, holding for 7-9 hours and cooling with the furnace to a temperature of 980-1030 °C, holding for 0.5-4 hours, hardening in air. Cooling with the furnace from the temperature of the upper hardening stage to the temperature of the lower stage is carried out at a rate ensured by the thermal equipment when changing the temperature setting. One- or two-stage aging is carried out according to the following modes: at a temperature of 775 °C with exposure for 16 hours and cooling in air or at a temperature of 775±10 °C with holding for 16 hours, cooling in air, then at a temperature of 700±10 °C with holding for 16-24 hours and air cooling.EFFECT: reduction in the time for heat treatment, the elimination of interoperational actions between the first and second hardening while obtaining the required set of properties of products made of heat-resistant nickel alloy “ЭИ”698.1 cl, 1 tbl, 1 ex

Description

[0001] The invention relates to the field of heat treatment of metals and alloys, namely to the heat treatment of products made of heat-resistant nickel alloy grades KhN73MBTYu (EI698), KhN73MBTYu-VD (EI698-VD), KhN71MTBYu (EI698P) - hereinafter the combined name EI698 is used.

[0002] A method for heat treatment of products made of heat-resistant nickel alloy EI698 is proposed, which includes two stages: the first stage (hardening) is heating to a temperature in the range of 1070°C - 1130°C, holding and cooling with a furnace to a temperature of 980°C - 1030°C, then hardening in air, the second stage is one- or two-stage aging.

[0003] The technical result is a reduction in the time for heat treatment, the elimination of interoperational actions between the first and second hardening while obtaining the required set of properties for products made of heat-resistant nickel alloy EI698.

[0004] A method is known (Aviation materials: reference book. Vol. 3 “Heat-resistant steels and alloys. Alloys based on refractory metals” Moscow: ONTI, 1989, 567 p. - p. 384) for heat treatment of heat-resistant nickel alloy EI698, which includes:

[0005] First hardening at a temperature of 1100°C - 1120°C, holding for 8 hours, cooling in air;

[0006] Second hardening at a temperature of 1000°C ± 10°C, holding for 4 hours, cooling in air;

[0007] Aging at 775°C ± 10°C, holding for 16 hours, air cooling; Second aging at 700°C ± 10°C, holding for 16-24 hours, air cooling, or aging in one of the modes:

[0008] 1. 800°C, holding for 16 hours, air cooling;

[0009] 2. 750°C, holding for 8 hours, air cooling +650°C, holding for 16-20 hours, air cooling;

[0010] 3. 775°C, holding for 16 hours, air cooling +700°C, holding for 16-20 hours, air cooling (Maslenkov S.B. Heat-resistant steels and alloys. Handbook. Moscow, Metallurgy. 1983. 192 p. - p. 121).

[0011] The disadvantage of this heat treatment method is the need for two quenching stages. Between the first and second stages, time is required for cooling after the first stage, intermediate storage of the workpieces before the second stage, organizing the second stage of quenching, including maintaining the necessary records, and heating the charge in the second stage from room temperature (heat treatment shop temperature) to the second quenching temperature.

[0012] Another well-known method of heat treatment of heat-resistant nickel alloy EI698 is described in the work of Vlasov O.N., Korneev N.N., Eremenko V.I., Lomberg B.S., Subbotin A.M., Gorokhov V.P. Optimization of heat treatment modes of deformed semi-finished products from medium-alloy heat-resistant nickel alloys / Metal Science and Heat Treatment of Metals. 1993. No. 1. Pp. 31-34. It proposes to adjust the second stage of hardening depending on the content of aluminum, titanium and niobium in a specific melt of EI698 alloy. In this case, it is proposed that if the total content of aluminum, titanium and niobium is greater than 8.21, the second hardening should be carried out from a temperature of 1010°C, and if the sum of aluminum, titanium and niobium is less than or equal to 8.21, from a temperature of 990°C.

[0013] The disadvantages of this method of heat treatment include the above-mentioned disadvantage of the first known method, as well as a number of other disadvantages:

[0014] - the need to calculate the content of aluminum, titanium and niobium in each smelt;

[0015] - leveling the effect of adjusting the second quenching temperature when using industrial furnaces, most of which have a temperature tolerance of ± 10°C, which reduces the choice of temperatures between 990°C and 1010°C to a temperature of 1000°C ± 10°C.

[0016] The technical objective of the proposed invention is to ensure the required set of properties for EI698 alloy products no lower than those achieved by the standard two-quench process, while reducing the overall quenching time. An additional objective of the invention is to reduce energy consumption for heat treatment of EI698 alloy products and eliminate the need for interoperational steps between the first and second quenching processes.

[0017] The stated problem is solved by combining the first and second hardening into one cycle in such a way that the temperature and holding time from the first hardening are taken into the combined cycle, the temperature and reduced holding time from the second, and the transition from the first to the second temperature is carried out without cooling the charge, at the speed provided by the furnace equipment.

[0018] The difference from known methods in the invention is that instead of the first and second hardening, a single hardening is carried out in a combined mode, while the transition between the temperatures of the first and second stages in the combined cycle is carried out at a speed ensured by the thermal equipment when the temperature task is shifted from the temperature of the upper stage to the temperature of the lower stage.

[0019] The proposed heat treatment method involves loading a batch of EI698 alloy blanks into a furnace at room temperature, either preheated to no more than 900°C or the first-stage hardening temperature. After heating the charge to the first-stage hardening temperature, it is held for 7-9 hours. The furnace temperature is then adjusted to the second-stage hardening temperature. The time required for this adjustment is not specified, so the furnace reaches the set temperature as quickly as its technical capabilities allow. After the charge reaches the second-stage hardening temperature, it is held for 0.5-4 hours. The charge is then removed from the furnace and cooled either in still air or by forced cooling using industrial fans or air cooling systems of any design.After cooling the charge, it undergoes one- or two-stage aging according to the following modes:

[0020] 775°C holding for 16 hours air cooling, or

[0021] 775°C ± 10°C, holding for 16 hours, air cooling, then 700°C ± 10°C, holding for 16-24 hours, air cooling.

[0022] Example

[0023] The blanks for the production of samples were heat treated according to the proposed method:

[0024] - Hardening at 1110°C, holding for 8 hours, then cooling in a furnace to 1000°C, holding for 0.5 hours, cooling in air;

[0025] - Aging at 775°C, holding for 16 hours, air cooling.

[0026] For the experiment, we used a melt that had passed acceptance tests for compliance with regulatory documentation in the established volume using the first known method (Aviation materials: reference book. Vol. 3 “Heat-resistant steels and alloys. Alloys based on refractory metals” Moscow: ONTI, 1989, 567 pp. - p. 384).

[0027] Tensile test specimens were made from heat-treated blanks to determine mechanical properties, impact toughness, and long-term strength. Tensile tests to determine mechanical properties were conducted in accordance with GOST 1497-2023 using a UTS 101 structural materials testing machine. Impact toughness (KCU) tests were conducted in accordance with GOST 9454-2025 using a TSCM-300 pendulum impact tester. Long-term strength tests were conducted on a UTS 1300 creep and long-term strength testing machine. Each test type was conducted on two specimens. The test results are presented in Table 1.

[0028]

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