Heat treatment method for realizing grain boundary serration in nickel-based superalloy forging

Abstract

The present disclosure provides a heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging, including introducing a serrated grain boundary into a microstructure of a nickel-based superalloy forging by using a heat treatment method for controlling a cooling rate; the heat treatment method for controlling cooling speed includes the following steps: step S1: holding the nickel-based superalloy forging for 0.5-4 h at 1,050-1,200° C.; step S2: cooling the nickel-based superalloy forging to 650-800° C. at a preset cooling rate, and holding for 1-8 h, where the preset cooling rate is 1-20° C/min; and step S3, taking out and cooling the nickel-based superalloy forging to room temperature with water. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging provided by the present disclosure can realize the grain boundary serration in the nickel-based superalloy forging.

Claims

1. A heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging, comprising introducing a serrated grain boundary into a microstructure of the nickel-based superalloy forging by using a heat treatment method for controlling a cooling rate, wherein the heat treatment method for controlling a cooling rate comprises the following steps: step S1: holding the nickel-based superalloy forging for 0.5-4 h at 1,050-1,200° C.; step S2: cooling the nickel-based superalloy forging to 650-800° C. at a preset cooling rate, and holding for 1-8 h, wherein the preset cooling rate is 1-20° C/min; and step S3: taking out and cooling the nickel-based superalloy forging to room temperature with water; wherein the nickel-based superalloy forging comprises the following components: Cr: 20.0-24.0% by weight, Co: 10.0-15.0% by weight, Mo: 8.0-10.0% by weight, Fe: ≤3.0% by weight, Mn: ≤1.0% by weight, Si: ≤1.0% by weight, Al: 0.8-1.5% by weight, Ti: ≤0.6% by weight, C: 0.05-0.15% by weight, and the balance being Ni.

2. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging according to claim 1, wherein a designation of the nickel-based superalloy forging is Inconel 617.

3. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging according to claim 1, wherein the heat treatment method for controlling a cooling rate is carried out in a heat treating furnace capable of controlling the cooling rate.

4. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging according to claim 1, wherein the heat treatment method for controlling a cooling rate promotes grain boundary segregation of Mo, Cr and C in the nickel-based superalloy forging during controlled cooling, produces plate-like M.sub.6C and M.sub.23C.sub.6 at the grain boundary, has a dragging effect on the migration of the grain boundary, and forms the serrated grain boundary between grains.

5. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging according to claim 1, wherein an average amplitude of the serrated grain boundary in the nickel-based superalloy forging is greater than 1 μm.

6. The heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging according to claim 1, wherein room temperature mechanical properties of the nickel-based superalloy forging are tested with reference to GB/T 228.1 Metallic Materials—Tensile Testing—Part 1: Method of Test at Room Temperature.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow chart of a heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging in the examples of the present disclosure.

DETAILED DESCRIPTION

(2) Preferred examples of the present disclosure are given and described below in detail with reference to FIG. 1, so that the functions and characteristics of the present disclosure can be better understood.

(3) As shown in FIG. 1, the examples of the present disclosure provides a heat treatment method for realizing grain boundary serration in a nickel-based superalloy forging, including introducing a serrated grain boundary into a microstructure of the nickel-based superalloy forging by using a heat treatment method for controlling a cooling rate; the heat treatment method for controlling a cooling rate includes the following steps: step S1: holding the nickel-based superalloy forging for 0.5-4 h at 1,050-1,200° C.; step S2: cooling the nickel-based superalloy forging after treatment to 650-800° C. at a preset cooling rate, and holding for 1-8 h, where the preset cooling rate is 1-20° C/min; and step S3: taking out and cooling the nickel-based superalloy forging to room temperature with water; where the nickel-based superalloy forging includes the following components: Cr: 20.0-24.0% by weight, Co: 10.0-15.0% by weight, Mo: 8.0-10.0% by weight, Fe: ≤3.0% by weight, Mn: ≤1.0% by weight, Si: ≤1.0% by weight, Al: 0.8-1.5% by weight, Ti: ≤0.6% by weight, C: 0.05-0.15% by weight, and the balance being Ni.

(4) A designation of the nickel-based superalloy forging is Inconel 617.

(5) The heat treatment method for controlling a cooling rate is carried out in a heat treating furnace capable of controlling the cooling rate.

(6) The heat treatment method for controlling a cooling rate promotes grain boundary segregation of Mo, Cr and C in the nickel-based superalloy forging during controlled cooling, produces plate-like M.sub.6C and M.sub.23C.sub.6 at the grain boundary, has a dragging effect on the migration of the grain boundary, and forms the serrated grain boundary between grains.

(7) An average amplitude of the serrated grain boundary in nickel-based superalloy forging is greater than 1 μm.

(8) Room temperature mechanical properties of the nickel-based superalloy forging are tested with reference to GB/T 228.1 Metallic Materials—Tensile Testing—Part 1: Method of Test at Room Temperature.

(9) Example 1:

(10) In the present example, the heat treatment for controlling a cooling rate (hereinafter referred to as: controlled cooling heat treatment) is conducted on the Inconel 617 nickel-based superalloy forging after forging and forming. Some straight random grain boundaries were transformed into serrated grain boundaries, and the average amplitude of the serrated grain boundary was 1 μm. A specific implementation process was as follows: 1. The Inconel 617 nickel-based superalloy forging after forging and forming was placed in a heat treating furnace, and held for 0.5-4 h (1 h in this example) at 1,050-1,200° C. (1,200° C. in this example). 2. The Inconel 617 nickel-based superalloy forging in step 1 was placed in the heat treating furnace, cooled to 650-800° C. (750° C. in this example) at a certain cooling rate of 1-20° C/min (10° C/min in this example), and held for 1-8 h (8 h in this example). 3. The Inconel 617 nickel-based superalloy forging in step 2 was taken out and cooled to room temperature with water. 4. Samples were cut from the Inconel 617 nickel-based superalloy after water cooling in step 3, and analyzed by scanning electron microscopy (SEM). Compared with conventional treatment (without controlled cooling heat treatment), some straight grain boundaries were transformed into serrated grain boundaries in the Inconel 617 nickel-based superalloy forging after the controlled cooling heat treatment, and M.sub.23C.sub.6 and M.sub.6C carbides were precipitated at the grain boundaries. The average amplitude of the serrated grain boundary was greater than 1 μm (the average amplitude in this example was 1.5 μm). 5. The Inconel 617 nickel-based superalloy forging treated by water cooling in step 3 was processed into M10 threaded rods, and the mechanical properties were tested with reference to GB/T 228.1 Metallic Materials—Tensile Testing—Part 1: Method of Test at Room Temperature. The results are shown in Table 1.

(11) After the Inconel 617 nickel-based superalloy forging in this example was subjected to the controlled cooling heat treatment (holding for 1 h at 1,200° C., cooling to 750° C. at a cooling rate of 10° C/min and holding for 8 h, taking out and cooling to room temperature with water), some straight grain boundaries were transformed into serrated grain boundaries. The average amplitude of the serrated grain boundary was 1.5 μm. The room temperature mechanical properties of the alloy were not influenced while introducing the serrated grain boundaries.

(12) Table 1. Mechanical properties of Inconel 617 nickel-based superalloy in the first controlled cooling heat treatment

(13) TABLE-US-00001 No. σ.sub.b/MPa σ.sub.0.2/MPa δ/% Controlled cooling process 1 800 312 60 Holding for 1 h at 1,200° C. 2 805 315 61 Cooling rate 10° C./min 3 803 316 61 750° C. Holding for 8 h Average 802.6 314.3 60.7 Water cooling

(14) Example 2:

(15) It was basically the same as Example 1. There were the following differences: the controlled cooling heat treatment process was holding for 1.5 h at 1,100° C., cooling to 700° C. at a cooling rate of 6° C/min, holding for 6 h, taking out and cooling to room temperature with water; and the average amplitude of the serrated grain boundary in the alloy was 1.1 μm.

(16) The Inconel 617 nickel-based superalloy with the same chemical composition as in Example 1 was used for controlled cooling heat treatment. The alloy was placed in a heat treating furnace, held for 1.5 hat 1,100° C., cooled to 700° C. at a cooling rate of 6° C/min, held for 6 h, taken out and cooled to room temperature with water. The grain boundary structure was analyzed by SEM, and the results showed that the average amplitude of the serrated grain boundary in the alloy was 1.1 μm. The Inconel 617 nickel-based superalloy forging after controlled cooling heat treatment was processed into M10 threaded rods, and the mechanical properties were tested with reference to GB/T 228.1 Metallic Materials—Tensile Testing—Part 1: Method after of Test at Room Temperature. The results are shown in Table 2.

(17) Table 2. Mechanical properties of Inconel 617 nickel-based superalloy in the second controlled cooling heat treatment

(18) TABLE-US-00002 No. σ.sub.b/MPa σ.sub.0.2/MPa δ/% Controlled cooling process 1 798 306 63 Holding for 1.5 h at 1,100° C. 2 794 304 62 Cooling rate 6° C./min 3 800 310 63 700° C. Holding for 6 h Average 797.3 306.7 62.7 Water cooling

(19) After the Inconel 617 nickel-based superalloy forging in this example was subjected to the controlled cooling heat treatment (holding for 1.5 h at 1,100° C., cooling to 700° C. at a cooling rate of 6° C/min and holding for 6 h, taking out and cooling to room temperature with water), some straight grain boundaries were transformed into serrated grain boundaries. The average amplitude of the serrated grain boundary was 1.1 μm. The room temperature mechanical properties of the alloy were not influenced while introducing the serrated grain boundaries.

(20) Example 3:

(21) It was basically the same as Example 1. There were the following differences: the controlled cooling heat treatment was holding for 1 h at 1,150° C., cooling to 650° C. at a cooling rate of 8° C/min, holding for 4 h, taking out and cooling to room temperature with water; and the average amplitude of the serrated grain boundary in the alloy was 1.2 μm.

(22) The Inconel 617 nickel-based superalloy with the same chemical composition as in Example 1 was used for controlled cooling heat treatment. The alloy was placed in a heat treating furnace, held for 1 h at 1,150° C., cooled to 650° C. at a cooling rate of 8° C/min, held for 4 h, taken out and cooled to room temperature with water. The grain boundary structure was analyzed by SEM, and the results showed that the average amplitude of the serrated grain boundary in the alloy was 1.2 μm. The Inconel 617 nickel-based superalloy forging after controlled cooling heat treatment was processed into M10 threaded rods, and the mechanical properties were tested with reference to GB/T 228.1 Metallic Materials—Tensile Testing—Part 1: Method after of Test at Room Temperature. The results are shown in Table 3.

(23) Table 3. Mechanical properties of Inconel 617 nickel-based superalloy in the third controlled cooling heat treatment

(24) TABLE-US-00003 No σ.sub.b/MPa σ.sub.0.2/MPa δ/% Controlled cooling process 1 796 306 64 Holding for 1 h at 1,150° C. 2 802 312 62 Cooling rate 8° C./min 3 800 308 63 650° C. Holding for 4 h Average 799.3 308.7 63 Water cooling

(25) After the Inconel 617 nickel-based superalloy forging in this example was subjected to the controlled cooling heat treatment (holding for 1 h at 1,150° C., cooling to 650° C. at a cooling rate of 8° C/min and holding for 4 h, taking out and cooling to room temperature with water), some straight grain boundaries were transformed into serrated grain boundaries. The average amplitude of the serrated grain boundary was 1.2 μm. The room temperature mechanical properties were not influenced while introducing the serrated grain boundaries.

(26) The results of the examples show that the objective of the present disclosure can be achieved within the range of the technical parameters of the technical solution of the present disclosure. Some straight grain boundaries of the forging are transformed into serrated grain boundaries, and room temperature mechanical properties are not influenced while introducing the serrated grain boundaries.

(27) The present disclosure has been described in detail above with reference to the accompanying drawings and examples, and those skilled in the art can make various modifications to the present disclosure according to the above description. Therefore, some details in the examples should not be construed as limiting the present disclosure, and the present disclosure will take the scope defined by the appended claims as the protection scope of the present disclosure.