A method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy

Abstract

The present invention provides a method for preparing stable enamel layer grains on the surface of a nickel-based superalloy, belonging to the field of materials processing. The method prepares enamel layer grains on the surface of the nickel-based superalloy by rotary rolling the surface at a specific temperature, contact stress, time, and speed. The stable enamel layer grains formed on the surface of the nickel-based superalloy using the present method are thick, neatly arranged, have high hardness, and exhibit good wear resistance, thereby improving the wear resistance of the nickel-based superalloy surface.

Description

Technical Field

[0001] The invention belongs to the field of material processing, and in particular relates to a method for preparing stable enamel layer grains on the surface of a nickel-based high-temperature alloy. Background Art

[0002] Nickel-based high-temperature alloys are widely used in the manufacture of hot-end components in the fields of aerospace, ocean, and transportation due to their excellent high-temperature structural stability, corrosion resistance, and outstanding mechanical properties. However, nickel-based high-temperature alloys will inevitably encounter friction and wear problems when serving in the above-mentioned fields, which greatly reduces the performance and safety reliability of the workpiece. The application of surface strengthening technology can significantly broaden the application field of nickel-based high-temperature alloys, and can significantly improve their wear resistance and extend their service life. How to modify the surface of nickel-based high-temperature alloys through surface strengthening technology to improve their wear resistance has always been the concern of many researchers. At present, the surface strengthening technology to improve nickel-based high-temperature alloys is to form a coating, i.e., a protective layer, on the surface of the substrate with different mechanical properties from the substrate, thereby improving the surface wear resistance of nickel-based high-temperature alloys. However, these technologies basically have problems such as unstable strengthening layer, complex strengthening process, and high strengthening cost.

[0003] Therefore, exploring how to stabilize the surface of nickel-based high-temperature alloys while improving their surface wear resistance plays a vital role in the field of materials processing. Summary of the Invention

[0004] In response to the above-mentioned deficiencies in the prior art, the present invention provides a method for preparing stable enamel layer grains on the surface of a nickel-based high-temperature alloy. Based on the excellent wear resistance of the enamel layer grains, an enamel layer grain structure with neatly arranged grains, good stability and excellent wear resistance is prepared on the surface of the nickel-based high-temperature alloy, thereby improving the wear resistance of the nickel-based high-temperature alloy.

[0005] The present invention adopts the following technical solutions:

[0006] A method for preparing stable enamel layer grains on the surface of a nickel-based high-temperature alloy comprises the following steps:

[0007] (1) rolling, crystallization annealing, cutting, rough grinding and fine grinding the nickel-based high-temperature alloy;

[0008] (2) mechanically polishing and electrolytically polishing the nickel-based high-temperature alloy after fine grinding in step (1);

[0009] (3) The nickel-based high-temperature alloy polished in step (2) is oxidized and then subjected to rotary rolling processing to obtain a nickel-based high-temperature alloy with stable enamel layer grains on the surface.

[0010] Furthermore, in the above step (1), rolling is performed at room temperature for 4 to 8 times, preferably 6 times.

[0011] Furthermore, in the above step (1), the temperature of the recrystallization annealing is 850-1200° C., preferably 1050° C.; and the annealing time is 20-60 min, preferably 60 min.

[0012] Furthermore, in the above step (1), the surface is finely ground until the roughness reaches below 2.0 μm.

[0013] Furthermore, in the above step (2), the mechanical polishing is performed to a mirror surface, the polishing liquid temperature of the electrolytic polishing is 45 to 50° C., preferably 50° C., and the electrolytic polishing is performed until the surface has a metallic luster.

[0014] By adopting the above further technical solution, the beneficial effects of the present invention are:

[0015] There is a thicker deformation layer on the surface of the nickel-based high-temperature alloy sample with greater roughness. The deformation layer has high residual stress and strain. Due to the high defect density of the deformation layer, the oxidation of Cr or other elements in the nickel-based high-temperature alloy can be accelerated, thereby affecting the oxidation process of Ni and further affecting the formation of the enamel layer. After the above-mentioned rough grinding and fine grinding, mechanical polishing and then electrolytic polishing can remove the stress layer on the mechanically polished surface. The above operation is used to reduce the roughness of the nickel-based high-temperature alloy surface, which is beneficial to the subsequent oxidation of Ni and helps to form an enamel layer on the surface of the nickel-based high-temperature alloy.

[0016] Furthermore, in the above step (3), the oxidation is to heat the polished nickel-based high-temperature alloy to 500-800° C. and oxidize for 10-30 minutes, preferably to heat to 800° C. and oxidize for 30 minutes.

[0017] Furthermore, in the above step (3), a ball-end tool with a diameter of 9 to 10 mm is used for rolling.

[0018] The beneficial effects of adopting the above further technical solution are:

[0019] The reciprocating rolling and friction motion on the surface of nickel-based high-temperature alloys will cause opposite shear forces, which is not conducive to the formation of enamel layer grains with a certain regular arrangement. The sliding rotation rolling and friction motion cyclically acts on the surface of nickel-based high-temperature alloys, which will form regularly arranged enamel layer grains. The load determines the maximum contact stress between contacts. Taking the maximum Hertzian contact stress in the ball head tool-plate contact as an example, too much load will cause cutting action on the plate, and too small load cannot compact to form a dense enamel layer. Therefore, a ball head tool with a diameter of 9 to 10 mm is helpful in preparing an excellent enamel layer on the surface of nickel-based high-temperature alloys.

[0020] Furthermore, in the above step (3), the contact stress of the rolling is 2 to 3.36 GPa, the speed is 100 to 500 mm / s, the sliding rotation rolling temperature is 500-800°C, and the time is 10 to 30 min; preferably, the contact stress is 2.4 GPa, the speed is 100 mm / s, the sliding rotation rolling temperature is 500°C, and the time is 15 min.

[0021] The beneficial effects of adopting the above further technical solution are:

[0022] During the rolling process, temperature, speed and time play an important role in the formation of the enamel layer on the surface of the nickel-based high-temperature alloy. Increasing the temperature can accelerate the formation of the enamel layer, but too high a temperature will affect the mechanical properties of the enamel layer and accelerate its spalling and transfer. If the temperature is too low, the nickel-based high-temperature alloy will not oxidize, and then the enamel layer will not appear; speed has a decisive effect on frictional heat. Too high a speed will generate obvious frictional heat, which will affect the mechanical properties of the enamel layer, thereby reducing the wear resistance of the nickel-based high-temperature alloy surface; the length of time determines the formation process of the enamel layer. If the time is too short, the enamel layer formed is thinner, and if the time is too long, the enamel layer will cause fatigue, thereby initiating cracks and reducing its wear resistance. Therefore, the above-mentioned rolling parameters can better construct a stable enamel layer on the surface of the nickel-based high-temperature alloy.

[0023] The nickel-based high-temperature alloy having stable enamel layer grains on the surface is obtained by the method for preparing stable enamel layer grains on the surface of the nickel-based high-temperature alloy.

[0024] By adopting the above technical solution, the beneficial effects of the present invention are:

[0025] The present invention addresses the problem of insufficient wear resistance of nickel-based high-temperature alloys. Based on the excellent wear resistance of enamel layer grains, a ball-end tool is used to perform rotary rolling processing on the surface of the polished nickel-based high-temperature alloy at a certain temperature, contact stress, time and speed. The enamel layer grains with a smooth surface and no defects such as cracks, delamination and pits are prepared on the surface of the nickel-based high-temperature alloy. The surface structure of the enamel layer is a neatly arranged grain shape with a hardness of up to 655±15HV. The enamel layer structure has good friction reduction and wear resistance. The friction coefficient of Inconel625 alloy with enamel layer grains is reduced by 0.17 compared with Inconel625 alloy without enamel layer grains. It can be seen that the method of the present invention can improve the surface wear resistance of nickel-based high-temperature alloys. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the three-dimensional morphology of Inconel 625 alloy after polishing.

[0027] Figure 2 This is the SEM image of the enamel layer on the surface of Inconel 625 alloy.

[0028] Figure 3 This is a cross-sectional TEM image of the enamel layer grains on the surface of Inconel 625 alloy.

[0029] Figure 4 The grain morphology and composition distribution of the enamel layer in the cross section of Inconel 625 alloy, where (a) is the STEM image, (b) is the O element distribution, and (c) is the Ni element distribution.

[0030] Figure 5 Friction coefficient of Inconel 625 alloy at different temperatures before and after treatment. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are described below to facilitate understanding of the present invention by those skilled in the art. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the appended claims, these changes are obvious, and all inventions and creations utilizing the concepts of the present invention are protected.

[0032] Example 1

[0033] This embodiment provides a nickel-based high-temperature alloy having stable enamel layer grains on its surface. The specific operation steps are as follows:

[0034] (1) Select Inconel625 nickel-based high-temperature alloy ingots with smooth and clean surfaces, no quality defects such as cracks, pinholes, bubbles and inclusions, no defects such as deep shrinkage cavities, looseness, segregation, internal cracks and pores, and dense and uniform crystal structure, and homogenize the nickel-based high-temperature alloy ingots to obtain equiaxed crystals with good plasticity;

[0035] (2) rolling the homogenized nickel-based high-temperature alloy ingot obtained in step (1) six times to obtain a plate-like nickel-based high-temperature alloy Inconel 625;

[0036] (3) performing complete recrystallization annealing on the plate-like nickel-based high-temperature alloy Inconel 625 obtained in step (2) at a temperature of 1050° C. for 1 h to eliminate work hardening;

[0037] (4) using a wire electric discharge machine to cut the annealed Inconel 625 plate obtained in step (3) into discs with a diameter of 50 mm and a thickness of 3 mm;

[0038] (5) The Inconel 625 alloy disc obtained in step (4) is subjected to rough grinding and fine grinding on a grinding machine to achieve a fine grinding roughness Ra of less than 2.0 μm;

[0039] (6) The Inconel 625 alloy obtained in step (5) is mechanically polished to a mirror surface with a surface roughness of less than 0.05 μm. The three-dimensional morphology after polishing is as shown in FIG. Figure 1 As shown;

[0040] (7) electrolytically polishing the mechanically polished Inconel 625 alloy obtained in step (6) in a mixed solution of perchloric acid and alcohol, wherein the volume ratio of perchloric acid to alcohol is 1:9, and the alcohol is industrial alcohol, polishing until it has a significant metallic luster, achieving a smaller roughness of less than 0.05 μm, and removing the stress layer, and the polishing liquid temperature is 50°C;

[0041] (8) Using a high and low temperature heavy load friction and wear testing machine, heat the Inconel 625 alloy polished in step (7) to 800° C. and oxidize for 30 minutes;

[0042] (9) A silicon nitride ceramic ball with a diameter of 9.6 mm was used to perform rotational rolling on the oxidized Inconel 625 alloy under the conditions of a maximum Hertzian contact stress of 2.4 GPa, a rolling speed of 100 mm / s, and a time of 15 min to obtain an Inconel 625 alloy with stable enamel layer grains on the surface.

[0043] Example 2

[0044] This embodiment provides a nickel-based high-temperature alloy having stable enamel layer grains on its surface. The specific operation steps are as follows:

[0045] (1) Select Inconel625 nickel-based high-temperature alloy ingots with smooth and clean surfaces, no quality defects such as cracks, pinholes, bubbles and inclusions, no defects such as deep shrinkage cavities, looseness, segregation, internal cracks and pores, and dense and uniform crystal structure, and homogenize the nickel-based high-temperature alloy ingots to obtain equiaxed crystals with good plasticity;

[0046] (2) rolling the homogenized nickel-based high-temperature alloy ingot obtained in step (1) seven times to obtain a plate-like nickel-based high-temperature alloy Inconel 625;

[0047] (3) performing complete recrystallization annealing on the plate-like nickel-based high-temperature alloy Inconel 625 obtained in step (2) at 1000° C. for 1 h to eliminate work hardening;

[0048] (4) using a wire electric discharge machine to cut the annealed Inconel 625 plate obtained in step (3) into discs with a diameter of 50 mm and a thickness of 3 mm;

[0049] (5) The Inconel 625 alloy disc obtained in step (4) is subjected to rough grinding and fine grinding on a grinding machine to achieve a fine grinding roughness Ra of less than 2.0 μm;

[0050] (6) mechanically polishing the finely ground Inconel 625 alloy obtained in step (5) to a mirror finish with a surface roughness Ra of less than 0.05 μm;

[0051] (7) electrolytically polishing the mechanically polished Inconel 625 alloy obtained in step (6) in a mixed solution of perchloric acid and alcohol, wherein the volume ratio of perchloric acid to alcohol is 1:9, and the alcohol is industrial alcohol, polishing until it has a significant metallic luster, achieving a smaller roughness of less than 0.05 μm, and removing the stress layer, and the polishing liquid temperature is 50°C;

[0052] (8) Using a high and low temperature heavy load friction and wear testing machine, the Inconel 625 alloy polished in step (7) was heated to 700° C. and kept oxidized for 25 minutes;

[0053] (9) A silicon nitride ceramic ball with a diameter of 9.4 mm was used to perform rotational rolling on the oxidized Inconel 625 alloy under the conditions of a maximum Hertzian contact stress of 3 GPa, a rolling speed of 200 mm / s, and a time of 20 min to obtain an Inconel 625 alloy with a stable enamel layer grain on the surface.

[0054] Experimental Example 1

[0055] The Inconel 625 nickel-based high-temperature alloy having stable enamel layer grains on the surface prepared in Example 1 was tested as follows:

[0056] (1) The surface and cross section of the enamel layer in Example 1 were observed using SEM and FIB-TEM techniques, respectively. The results are as follows: Figure 2 and 3 shown.

[0057] Depend on Figure 2 and Figure 3 It can be seen that the enamel layer of Inconel 625 nickel-based high-temperature alloy has a smooth surface without defects such as cracks, steps and pits, and its microhardness is as high as 655±15HV. Through cross-sectional observation, it can be seen that the enamel layer has a nanocrystalline structure, with relatively large grains arranged neatly on the surface.

[0058] (2) The cross-sectional composition of the enamel layer of the Inconel625 nickel-based high-temperature alloy with stable enamel layer grains obtained in Example 1 was tested using STEM technology. Figure 4 shown.

[0059] Depend on Figure 4 It can be seen that the NiO phase constituting the enamel layer is densely distributed on the surface of Inconel 625 nickel-based high-temperature alloy.

[0060] Comparative Example 1

[0061] (1) The untreated Inconel 62 nickel-based superalloy and the Inconel 625 nickel-based superalloy with stable enamel layer grains on the surface obtained in Example 1 were tested and compared. The test results are as follows:

[0062] Friction and wear tests were conducted on the Inconel 625 nickel-based superalloy with an enamel layer structure in Example 1 and the untreated Inconel 625 nickel-based superalloy at 25°C, 200°C, 400°C, 500°C, 600°C and 800°C, with a sliding speed of 1m / s and a load of 20N. The average friction coefficient was as follows: Figure 5 The average friction coefficient values at each temperature are shown in the figure.

[0063] Depend on Figure 5 It can be seen that the average friction coefficient of the Inconel 625 nickel-based high-temperature alloy with stable enamel layer grains on the surface obtained in Example 1 is less than the average friction coefficient of the untreated Inconel 625 nickel-based alloy, specifically, the friction coefficient is reduced by 0.183 under 25°C friction conditions; the friction coefficient is reduced by 0.153 under 200°C friction conditions; the friction coefficient is reduced by 0.133 under 400°C friction conditions; the friction coefficient is reduced by 0.18 under 500°C friction conditions; the friction coefficient is reduced by 0.14 under 600°C friction conditions; the friction coefficient is reduced by 0.107 under 800°C friction conditions. It can be seen that the enamel layer structure formed on the surface of the nickel-based high-temperature alloy has good friction reduction and anti-wear effects.

[0064] (2) The friction coefficient of the Inconel 625 nickel-based high-temperature alloy with stable enamel layer grains on the surface obtained in Example 1 was compared with that of the alloy coated with a coating.

[0065] In "Wide Temperature Cyclic Tribological Behavior of Heat-treated NiAl-Bi2O3 Coating and Regeneration Mechanism of High and Low Temperature Lubrication Phase, Sun Huwei", the base material is S31008HEJIN (high chromium nickel austenitic stainless steel 06Cr25Ni20), and the coating material after heat treatment is NiAl-Bi2O3-Ar. It can be seen from the content 2.4 that the friction coefficient of the composite coating at room temperature, 400 and 800℃ is 0.46 at room temperature, with little change; the friction coefficient at 400℃ is 0.28; and the friction coefficient at 800℃ is 0.16.

[0066] And by Figure 5 It can be seen that the friction coefficient of the Inconel625 nickel-based superalloy surface with stable enamel layer grains obtained in Example 1 has reached 0.165 at a temperature of 400°C, and the friction coefficient at 800°C is 0.112. This shows that preparing an enamel layer grain structure with neatly arranged grains, good stability, and excellent wear resistance on the surface of a nickel-based superalloy can greatly reduce its friction coefficient and greatly improve the wear resistance of the nickel-based superalloy.

Claims

1. A method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy, characterized in that: The following steps are involved: (1) Rolling, crystallization annealing, cutting, rough grinding and fine grinding of nickel-based high-temperature alloys; (2) mechanically polishing and electrolytically polishing the nickel-based high-temperature alloy after fine grinding in step (1); (3) oxidizing the nickel-based high-temperature alloy polished in step (2) and then rolling it to obtain a nickel-based high-temperature alloy with stable enamel layer grains on the surface; In step (3), a ball-end tool with a diameter of 9 to 10 mm is used for rolling; the contact stress of rolling is 2 to 3.36 GPa, the speed is 100 to 500 mm / s, the sliding rotation rolling temperature is 500 to 800 °C, and the time is 10 to 30 min.

2. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: The rolling in the step (1) is performed 4 to 8 times at room temperature.

3. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: The temperature of the recrystallization annealing in step (1) is 850-1200°C, and the annealing time is 20-60 min.

4. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: In the step (1), the surface is finely ground until the roughness reaches below 2.0 μm.

5. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: In the step (2), the mechanical polishing is performed to a mirror surface, the polishing liquid temperature of the electrolytic polishing is 45-50°C, and the electrolytic polishing is performed to obtain a metallic luster.

6. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: The oxidation in step (3) is to heat the polished nickel-based high-temperature alloy to 500-800° C. and oxidize it for 10-30 minutes.

7. The method for preparing stable enamel layer grains on the surface of nickel-based high-temperature alloy according to claim 1, characterized in that: The contact stress of the rolling in step (3) is 2.4 GPa, the speed is 100 mm / s, the sliding rotation rolling temperature is 500°C, and the time is 15 min.

8. A nickel-based high-temperature alloy having stable enamel layer grains on its surface obtained by the method for preparing stable enamel layer grains on the surface of a nickel-based high-temperature alloy according to any one of claims 1 to 7.

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