Cobalt-based high-temperature alloy, key shaft and alloy preparation method for resisting adhesive wear

Abstract

The present invention discloses a cobalt-based high-temperature alloy, a key shaft, and a method for preparing the alloy that are resistant to adhesive wear, and belongs to the technical field of alloy processing. The present invention solves the problems in the prior art that cobalt-based high-temperature alloys are prone to forming banded structures, have poor wear resistance, and have large amounts of adhesive wear on friction pairs. The preparation method comprises: performing homogenization heat treatment on a cobalt-based alloy ingot; performing multi-directional forging on the cobalt-based alloy ingot that has undergone homogenization heat treatment to obtain a rod; performing secondary homogenization heat treatment on the rod; hot rolling the rod after the secondary homogenization heat treatment to obtain a rod; and performing finished product processing on the rod to obtain a cobalt-based high-temperature alloy rod with excellent adhesive wear resistance. The present invention can effectively eliminate the banded structure of the alloy through multi-directional forging and secondary homogenization heat treatment, obtain a uniform and fine grain structure and uniformly distributed carbides, improve the uniformity of the alloy structure, and at the same time improve the wear resistance of the alloy, especially reduce the amount of adhesive wear on the friction pair.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy processing, and in particular to a cobalt-based high-temperature alloy resistant to adhesive wear, a key shaft and a method for preparing the alloy. Background Art

[0002] The cobalt-based superalloy GH5605, with its excellent high-temperature mechanical properties and oxidation and corrosion resistance, can be used at temperatures up to 1000°C, finding important applications in aerospace engines, rocket engines, ships, and industrial gas turbines. Furthermore, due to the unique work-hardening properties of its cobalt-based solid solution, the alloy is also an ideal material for manufacturing key shafts, critical wear-resistant components in reactor control rod drive mechanisms. In control rod drive mechanisms, the key shafts slide in contact with Stellite cobalt-based alloy hooks, resulting in material wear during operation, primarily through adhesive wear.

[0003] However, if the friction pair formed by the key shaft and the Stellite cobalt-based alloy claw wears too much, there will be a risk of failure of the step-up and step-down operations of the control rod at the end of its service life, and there will also be a risk of excessive radioactivity of the reactor primary circuit coolant due to the activation of cobalt-containing wear debris.

[0004] Currently, the cobalt-based superalloy GH5605 is typically obtained by homogenizing, forging, rolling, and heat treating an ingot that has undergone vacuum induction melting and electroslag remelting. Due to its compositional characteristics, the GH5605 alloy produced using this method is prone to forming banded primary carbides and banded grains. This structure results in varying hardness and work hardening levels in different regions of the alloy, directly affecting its wear behavior when paired with a Stellite alloy. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a cobalt-based high-temperature alloy, a key shaft and an alloy preparation method that are resistant to adhesive wear, so as to solve the problems of existing cobalt-based high-temperature alloys such as easy formation of banded structure, poor wear resistance and large adhesive wear.

[0006] On the one hand, an embodiment of the present invention provides a method for preparing a cobalt-based high-temperature alloy that is resistant to adhesive wear, comprising: performing homogenization heat treatment on a cobalt-based alloy ingot; performing multi-directional forging on the cobalt-based alloy ingot that has undergone homogenization heat treatment to obtain a rod; performing secondary homogenization heat treatment on the rod; hot rolling the rod after the secondary homogenization heat treatment to obtain a rod; and performing finished product processing on the rod to obtain a cobalt-based high-temperature alloy rod that is resistant to adhesive wear.

[0007] Furthermore, the cobalt-based alloy ingot that has undergone homogenization heat treatment is subjected to multi-directional forging, including: upsetting and trimming the cobalt-based alloy ingot to obtain a forging blank; performing multi-fire multi-directional forging on the forging blank; and stretching the forging blank that has undergone multi-directional forging to obtain a rod blank.

[0008] Furthermore, the cobalt-based alloy ingot is upset in multiple passes along the axial direction; the upset ingot is forged and pressed into a square billet and chamfered to obtain a forged billet.

[0009] Furthermore, the forging blank is subjected to multiple-fire and multiple-group multi-directional forging, and the downward deformation amount in each direction in each group of multi-directional forging is 20-60%.

[0010] Furthermore, during the multi-fire multi-group multi-directional forging process, the heating temperature is 1150-1200°C, the holding time is greater than 2 hours, and the final forging temperature is greater than or equal to 900°C.

[0011] Furthermore, during the secondary homogenization heat treatment, the heat treatment temperature is 1180° C. to 1230° C., and the heat treatment time is 15 to 24 hours.

[0012] Furthermore, when the bar billet is hot rolled, the heating temperature is 1130-1180° C. and the holding time is greater than 1 hour.

[0013] Furthermore, the rods are subjected to finished product processing, including: performing a short-time primary solution heat treatment on the rods; performing a secondary solution heat treatment on the rods after the short-time primary solution heat treatment; and performing surface mechanical treatment on the rods after the solution heat treatment.

[0014] Furthermore, the rod is subjected to a short-term solid solution heat treatment, including: heating the rod to 1160-1190° C. and keeping the temperature for 0.1-0.3 h, with a heating rate greater than 20° C. / s during the heating process.

[0015] On the other hand, an embodiment of the present invention provides a cobalt-based high-temperature alloy that is resistant to adhesive wear, which is prepared using the method of the above embodiment and includes the following components: 0.06-0.12 wt.% C, 19.5-20.5 wt.% Cr, 9.5-10.5 wt.% Ni, 14.5-16 wt.% W, 1.2-1.8 wt.% Mn, 0.0015-0.0025 wt.% B, and the balance is Co.

[0016] On the other hand, an embodiment of the present invention further provides a key shaft for a control rod drive mechanism, which is made of the adhesive wear resistant cobalt-based high-temperature alloy of the above embodiment.

[0017] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0018] 1. The present invention combines multi-directional forging with secondary homogenization heat treatment, which can effectively eliminate the banded structure of the alloy, obtain a uniform and fine grain structure and uniformly distributed carbides, improve the uniformity of the alloy structure, and thus improve the wear resistance of the alloy, especially reduce the adhesive wear on the friction pair, and thus obtain a cobalt-based wear-resistant alloy bar with both mechanical properties and wear resistance.

[0019] 2. The present invention uses a short, primary solution heat treatment to simultaneously nucleate and recrystallize different energy storage structures within the alloy, ensuring uniform recrystallization of the grain structure. A secondary solution heat treatment then increases grain size, ensuring a suitable grain size and uniformly precipitating carbides, resulting in a cobalt-based wear-resistant alloy with uniform grain size and carbide distribution.

[0020] In the present invention, the above-mentioned technical solutions can be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages will become apparent from the description or be understood through practice of the present invention. The objectives and other advantages of the present invention can be achieved and obtained through the embodiments of the description and the contents particularly pointed out in the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0022] Figure 1 This is a microstructure photograph of the cobalt-based high-temperature alloy according to Example 1 of the present invention.

[0023] Figure 2 This is a microstructure photo of a cobalt-based high-temperature alloy in the prior art. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the present invention more apparent, exemplary embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. For the sake of clarity and conciseness, not all features of actual implementations are described in this specification.

[0025] It is also necessary to explain here that, in order to avoid obscuring the present invention due to unnecessary details, the accompanying drawings only show the device structure and / or processing steps that are closely related to the solution according to the present invention, while other details that are not closely related to the present invention are omitted.

[0026] An embodiment of the present invention provides a method for preparing a cobalt-based high-temperature alloy that resists adhesive wear, comprising the following steps:

[0027] Step S10, performing homogenization heat treatment on the cobalt-based alloy ingot;

[0028] Step S20, performing multi-directional forging on the cobalt-based alloy ingot that has undergone homogenization heat treatment to obtain a rod blank;

[0029] Step S30, performing a secondary homogenization heat treatment on the rod blank;

[0030] Step S40, hot rolling the bar blank after the secondary homogenization heat treatment to obtain a bar;

[0031] Step S50: performing finished product processing on the rod to obtain a cobalt-based high-temperature alloy rod that is resistant to adhesive wear.

[0032] In an embodiment of the present invention, the ingot is subjected to a homogenization heat treatment to uniformly diffuse the elements in the ingot, dissolve the primary carbides, eliminate segregation, and initially improve the uniformity of the alloy structure while reducing the local stress generated during the subsequent forging process. At this time, the ingot is repeatedly deformed in different directions through multi-directional forging. Compared with traditional forging methods, this method can break up and refine the grains within the alloy, thereby obtaining a finer grain size. It also makes the primary carbides that could not be dissolved during the initial homogenization heat treatment more evenly distributed, preventing the primary carbides from being distributed in a striped pattern along the deformation direction, laying the foundation for ultimately obtaining a uniform grain structure and improving wear resistance and mechanical property stability.

[0033] Through multi-directional forging, the structure of the ingot is greatly refined and uniform compared to before forging, which can greatly shorten the distance that the elements need to diffuse during the subsequent secondary homogenization heat treatment. At this time, through the secondary homogenization heat treatment, the elements can be diffused more evenly after a large amount of carbides are dissolved back, further improving the uniformity of the alloy structure and composition. In addition, before the finished product is heat treated, the carbide distribution, composition uniformity, deformation energy storage size and distribution in the alloy structure after hot rolling serve as the starting point of recrystallization, which has an important influence on the grain morphology after heat treatment. In order to ensure that a uniform grain structure is obtained, it is necessary to ensure the uniformity of the structure and composition as much as possible before the alloy is hot rolled. The embodiment of the present invention performs a secondary homogenization heat treatment on the rod before hot rolling, further improving the uniformity of the structure, facilitating the coordinated uniform deformation of each part during the later hot rolling process, creating good conditions for the carbides to be uniformly precipitated again during the subsequent hot rolling process, improving the adhesive wear resistance of the alloy, and ultimately obtaining a cobalt-based alloy with excellent wear resistance and mechanical properties.

[0034] The embodiments of the present invention combine multi-directional forging with secondary homogenization heat treatment, effectively eliminating the alloy's banded structure, resulting in a uniform, fine grain structure and evenly distributed carbides. This improves the uniformity of the alloy's structure, thereby enhancing the alloy's wear resistance. In particular, it can reduce adhesive wear on friction pairs, thereby producing a cobalt-based wear-resistant alloy bar with both mechanical properties and wear resistance. When applied to key shafts, it can effectively control the weight loss from adhesive wear caused by sliding friction with the Stellite alloy pair, thereby meeting the safety requirements for the use of cobalt-based deformed high-temperature wear-resistant alloys in control rod drive mechanisms.

[0035] The preparation method of the present invention is suitable for preparing cobalt-based wear-resistant alloy rods, such as GH5605 alloy small rods. The prepared GH5605 alloy small rods have a small adhesive wear amount and can be used in the key shaft of the control rod drive mechanism.

[0036] The diameter of the ingot that has undergone uniform heat treatment is 110 to 190 mm, and the height is 220 to 450 mm.

[0037] In some embodiments, the multi-directional forging of the cobalt-based alloy ingot in step S20 includes:

[0038] Step S21, upsetting and finishing the cobalt-based alloy ingot to obtain a forging blank;

[0039] Step S22, performing multi-fire multi-directional forging on the forging blank;

[0040] Step S23, stretching the forging blank after multi-directional forging to obtain a rod blank.

[0041] The embodiment of the present invention sequentially performs upsetting, multi-directional forging and drawing on a cobalt-based alloy ingot, thereby transforming the alloy material from an ingot into a forging billet, refining the grain structure, eliminating defects, and obtaining an alloy rod billet with a more uniform structure.

[0042] According to some embodiments of the present invention, in step S21, a cobalt-based alloy ingot is first upset in multiple passes along the axial direction; the upset ingot is then forged and shaped into a square billet and chamfered to obtain a forged billet. This embodiment facilitates subsequent multi-directional forging by upsetting and shaping the ingot into a square billet.

[0043] Specifically, in step S21, the ingot is heated to a temperature of 1150-1200°C for a holding time of more than 2 hours. After the holding time is completed, multiple upsetting passes are immediately performed, and then the ingot is shaped into a square billet by forging.

[0044] When upsetting the ingot in multiple passes along the axial direction, the deformation of each pass is controlled to be 10% to 20%, and the total upsetting deformation is controlled to be 45% to 60%. If the deformation of each pass is too low, the processing efficiency will be reduced; if the deformation of each pass is too high, the temperature of the surface where the ingot contacts the forging hammer will drop too much, which will affect the uniformity of deformation. A total upsetting deformation that is too small will also affect the processing efficiency. When the total upsetting deformation is too large, on the one hand, it will easily cause instability and cracking in the large deformation area on the outer surface of the ingot. On the other hand, it will cause the height-to-diameter ratio to be too large after changing direction during subsequent finishing, resulting in lateral bending and instability during forging. This embodiment controls the deformation within the above range, which can not only ensure processing efficiency, but also ensure deformation uniformity, and prevent instability and cracking on the outer surface of the ingot and lateral bending and instability during subsequent forging.

[0045] After upsetting the ingot, it is forged into a cube-like billet and chamfered to facilitate subsequent multi-directional forging. During the forging process, the amount of pressure per pass is controlled at 10 to 30 mm, and forging is performed with a small amount of deformation per pass, which can ensure both processing efficiency and deformation uniformity. It should be noted that during forging, the entire ingot has already undergone cooling and upsetting deformation, so the overall deformation per pass is smaller than that during upsetting.

[0046] In the embodiment of the present invention, after the ingot is trimmed into a square billet, chamfering is performed to avoid stress concentration and improve the microstructure. The chamfering range can be set to (10-20 mm)*45°.

[0047] According to some embodiments of the present invention, in step S22, the forging blank can be subjected to multiple fires and multiple groups of multi-directional forging, and the downward deformation in each direction in each group of multi-directional forging is controlled to be 20-60%. By controlling the deformation in each direction, the embodiments of the present invention can prevent the deformation from being too small, which is detrimental to the uniformity of the structure, and prevent the deformation from being too large, which may form carbide flow lines in a single direction that are difficult to eliminate later. At the same time, it can also prevent the excessive height-to-diameter ratio after reversing from causing lateral bending instability.

[0048] During multi-fire, multi-group, multi-directional forging, the billet is heated to a temperature of 1150-1200°C, held for more than 2 hours, and held at a final forging temperature of 900°C or higher. If the heating temperature is too low, the alloy cannot fully dynamically recrystallize, resulting in poor thermal deformation resistance, which can easily lead to uneven microstructure and even cracking when the temperature drops significantly. If the heating temperature is too high, excessive carbide resolubility and excessive grain coarsening can compromise further deformation uniformity. Setting the holding time to greater than 2 hours ensures consistent temperature throughout the billet. Furthermore, if the final forging temperature is too high, the total deformation per fire will be limited, affecting processing efficiency. If the final forging temperature is too low, the billet's deformation capacity will decrease, which can easily lead to cracking.

[0049] In some embodiments, in step S22, the forging blank may be subjected to 5-6 sets of multi-directional forging to fully forge the forging blank and improve the uniformity of the alloy structure. In step S22, the 5-6 sets of multi-directional forging may be completed in 1-2 passes to ensure that the final forging temperature is greater than or equal to 900°C to avoid a temperature drop that is too low and causes a decrease in the deformability of the forging blank.

[0050] Specifically, the forging billet, which has undergone roughing and finishing, is heated to 1150-1200°C and held at this temperature for more than 2 hours. After the holding period, the forging billet is subjected to multi-directional forging. In each set of multi-directional forging, the billet is forged in three mutually perpendicular directions, with multiple downward pressure passes in each direction. The deformation of each pass is controlled at 10%-20%. When the downward pressure deformation in one direction reaches 20-60%, the direction is reversed. After forging in three directions, a set of multi-directional forging is completed, and the forging billet is restored to a nearly cubic shape. This completes 5-6 sets of multi-directional forging. After the 5-6 sets of multi-directional forging are completed, a chamfer (10-20mm)*45° is applied.

[0051] If 5 to 6 groups of multi-directional forging are completed in 2 batches, the reheating temperature of the forged intermediate billet should be 1150 to 1200°C, and the holding time should be no less than 2 hours to ensure that the final forging temperature is no less than 900°C.

[0052] According to some embodiments of the present invention, in step S23, the forging blank is subjected to multi-pass drawing, with a heating temperature of 1150-1200°C, a holding time of greater than 2 hours, and a final forging temperature greater than or equal to 900°C. Furthermore, during the forging and drawing process, the deformation per pass can be controlled to 20%-40% to ensure deformation uniformity and processing efficiency.

[0053] Specifically, the forging blank can be forged and drawn into a bar with a diameter of 40-60 mm, which is then hot-rolled into small bars of the required size. The forging blank is forged and drawn over 2-4 heats to ensure the forging temperature is maintained, with the final forging temperature controlled to be no less than 900°C. During these 2-4 heats, the intermediate billet is reheated to a temperature of 1150-1200°C for a holding time of no less than 2 hours.

[0054] It should be noted that in step S20, the heating temperature can be kept consistent during upsetting, multi-directional forging, and drawing. This avoids frequent adjustments to the heating device temperature during the forging and blanking process, simplifying operation. Alternatively, during the final drawing cycle, the heating temperature can be slightly lower than that of the preceding cycles.

[0055] According to some embodiments of the present invention, in step S30, during the secondary homogenization heat treatment, the heat treatment temperature is 1180°C to 1230°C, and the heat treatment time is 15 to 24 hours. If the secondary heat homogenization temperature is too high, the grain boundary state of the alloy will deteriorate. Raising the temperature as much as possible within a safe temperature range is conducive to the re-dissolution of carbides and the rapid diffusion of elements. If the holding time is too short, the element diffusion is insufficient and the homogenization effect is poor; if the holding time is too long, the treatment efficiency is low and the cost is high.

[0056] In some embodiments, after multi-directional forging and secondary homogenization heat treatment, the rod blank is subjected to surface polarity treatment to remove defects such as oxide layers and cracks on the alloy surface. Specifically, the surface mechanical treatment can be performed by sandblasting and grinding.

[0057] According to some embodiments of the present invention, in step S40, when the bar blank is hot rolled, the bar blank is heated to a temperature of 1130-1180°C and held at this temperature for a time greater than 1 hour. In embodiments of the present invention, due to the rapid deformation rate during hot rolling, the bar blank undergoes a temperature increase during hot rolling. Therefore, the overall heating temperature during hot rolling is lower than that during forging. Furthermore, the hot deformation capacity of the forged bar blank is significantly improved, allowing processing at slightly lower temperatures. Furthermore, the slightly lower temperature also facilitates grain size control during subsequent heat treatment.

[0058] In some embodiments, when hot rolling the billet, the final rolling temperature is controlled at 900-1000° C., which is beneficial for controlling the uniformity of the structure and the grain size during the subsequent heat treatment process.

[0059] In some embodiments, the rod blank may be hot rolled in one to two passes to be hot rolled into a rod with a diameter of 8 to 10 mm, so as to be used in a control rod drive mechanism.

[0060] According to some embodiments of the present invention, the step S50 of processing the bar into finished products includes:

[0061] Step S51, performing a short-term solid solution heat treatment on the rod;

[0062] Step S52, performing a secondary solution heat treatment on the rod after the short primary solution heat treatment;

[0063] Step S53: performing surface mechanical treatment on the rod material after the solution heat treatment.

[0064] In the embodiment of the present invention, the rod is subjected to two solid solution heat treatments to recrystallize the cobalt-based alloy material and obtain a uniform and appropriate grain size, which is also beneficial to the uniform precipitation of carbides.

[0065] During hot rolling, energy storage differences may occur, leading to uneven grain growth during subsequent heat treatment. The present invention utilizes a short, single solution heat treatment to simultaneously nucleate and recrystallize structures with different energy storage within the alloy in a high-heat recrystallization environment, achieving uniform recrystallization and eliminating the uneven recrystallization caused by uneven energy storage during the initial hot rolling of the bar. Subsequently, a secondary solution heat treatment is performed to achieve uniform grain growth, ultimately yielding a cobalt-based alloy with an appropriately sized and uniformly distributed grain, thereby improving the alloy's wear resistance.

[0066] In some embodiments, the short-term single-solution heat treatment of the rod in step S51 includes heating the rod to 1160-1190° C. and holding the temperature for 0.1-0.3 hours, with a heating rate greater than 20° C. / s. Furthermore, water cooling is immediately performed after the holding temperature is completed.

[0067] Compared with traditional heat treatment, the embodiments of the present invention achieve simultaneous nucleation and recrystallization of different energy storage structures in the alloy by rapidly increasing the temperature and heating within the above-mentioned higher temperature range. At the same time, by limiting the holding time, it is beneficial to reduce the risk of grain growth and ensure that the grain structure is fine and uniform.

[0068] In some embodiments, in step S52, when the bar material undergoes a secondary solution heat treatment after a short primary solution heat treatment, the solution heat treatment temperature is 1120-1160° C., and the holding time is 1-4 hours. The embodiments of the present invention, by performing the final secondary solution heat treatment under the above-mentioned treatment conditions, can ensure that a suitable grain size is obtained, while uniformly precipitating a suitable amount of W and Cr carbides, thereby obtaining a cobalt-based wear-resistant alloy with uniform grain size and carbide distribution.

[0069] After the secondary solution heat treatment is completed, cooling is immediately performed, and the cooling method includes at least one of water cooling, air cooling, oil cooling and air cooling.

[0070] In step S53, the bar material that has undergone two solution heat treatments can be subjected to surface mechanical treatment by machining to remove the oxide scale and affected layer on the alloy surface, thereby obtaining a finished cobalt-based high-temperature alloy bar material. During the surface mechanical treatment, the amount of removal per side can be set to greater than 0.3 mm to ensure the quality of the finished bar material.

[0071] On the other hand, an embodiment of the present invention provides a cobalt-based high-temperature alloy that is resistant to adhesive wear, which is prepared using the method in the above embodiment and includes the following components: 0.06-0.12 wt.% C, 19.5-20.5 wt.% Cr, 9.5-10.5 wt.% Ni, 14.5-16 wt.% W, 1.2-1.8 wt.% Mn, 0.0015-0.0025 wt.% B, and the balance is Co.

[0072] Preferably, the composition of the cobalt-based high-temperature alloy includes: 0.09 wt.% C, 20 wt.% Cr, 10 wt.% Ni, 15.25 wt.% W, 1.5 wt.% Mn, 0.005 wt.% B, and the balance is Co.

[0073] Compared with the existing GH5605 alloy, the embodiments of the present invention take into account the corrosive environment in which the cobalt-based high-temperature alloy is used in the key shaft of the control rod drive mechanism, and strictly control the Fe content in the alloy to make the Fe content extremely low or even zero; at the same time, the added trace B element is concentrated at the grain boundaries in the alloy, which can reduce the grain boundary migration rate, facilitate the control of grain size during the preparation process, and ensure the uniformity of grain size.

[0074] In addition, embodiments of the present invention further provide a key shaft for a control rod drive mechanism, wherein the key shaft is made of the cobalt-based high-temperature alloy prepared by the preparation method of the above embodiment, or made of the cobalt-based high-temperature alloy with anti-adhesive wear of the above embodiment.

[0075] The cobalt-based high-temperature alloy and its preparation method of the present invention are described below with reference to specific embodiments.

[0076] Example 1

[0077] (1) Step S10: Homogenize the cobalt-based superalloy ingot. The ingot after homogenization heat treatment has a diameter of 150 mm and a height of 350 mm. The cobalt-based superalloy ingot has a composition comprising: 0.09 wt.% C, 20 wt.% Cr, 10 wt.% Ni, 15.25 wt.% W, 1.5 wt.% Mn, 0.002 wt.% B, and the balance being Co.

[0078] (2) Step S20, multi-directional forging:

[0079] S21, upsetting and shaping the homogenized heat-treated ingot into a square billet: After heating the ingot to 1180°C and holding it for 2.5 hours, upsetting is performed in multiple passes in the axial direction, with each pass deforming 10-20%, for a total upsetting deformation of 50%. Subsequently, the ingot is shaped into a nearly cubic billet using a small forging process with a reduction of 20 mm per pass, and chamfered to a 15 mm x 45° angle.

[0080] S22, the forging blank after upsetting and finishing is subjected to 6 sets of multi-directional forging in 2 batches. After each set of multi-directional forging is completed, the forging blank is restored to a substantially cubic billet. The specific process includes the following:

[0081] The first heating is at 1180℃ and the steel is taken out for forging after the holding time reaches 2.5h.

[0082] In the first group of multi-directional forging, multiple passes are performed in each direction, with each pass deformation of 10-20%. After the cumulative downward deformation in a single direction reaches 40%, the direction is reversed by 90° to complete the forging in three directions.

[0083] In the second group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0084] In the third group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0085] The second heating is carried out at a temperature of 1180°C. After holding for 2 hours, the steel is taken out and forged.

[0086] In the fourth group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0087] In the fifth group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0088] In the sixth group of multi-directional forging, the deformation per pass is 10-20%. After the cumulative deformation in a single direction reaches 40%, the direction is reversed by 90°.

[0089] After completing 6 sets of multi-directional forging, the forging blank is chamfered with a chamfer of 15mm*45°.

[0090] S23, the forging billet after multi-directional forging is forged and stretched to a rod billet with a diameter of 50 mm in two steps.

[0091] The first heating temperature is 1180℃, the holding time is 2.5h, and the deformation is 30%;

[0092] The second heating temperature is 1180℃, the holding time is 2h, and the deformation is 30%.

[0093] (3) Step S30, secondary homogenization heat treatment: The rod blank prepared by multi-directional forging is subjected to secondary homogenization heat treatment, the homogenization heat treatment temperature is 1200°C, and the homogenization heat treatment time is 15 hours; the surface of the rod blank that has undergone multi-directional forging and secondary homogenization heat treatment is mechanically treated by sandblasting and grinding wheel grinding to remove surface defects such as surface oxide scale and cracks.

[0094] (4) Step S40, hot rolling of the billet: The billet after the secondary homogenization heat treatment is rolled into a bar with a diameter of 9 mm in two passes. Specifically, the billet heating temperature of the two passes is 1150°C, and the final rolling temperature is 950°C.

[0095] (5) Step S50, bar finished product treatment: The bars obtained by hot rolling are subjected to finished product heat treatment and then surface treatment to obtain finished bars. The finished product heat treatment includes a short primary solution heat treatment and a secondary solution heat treatment.

[0096] S51, a short-term solid solution heat treatment is performed on the hot-rolled bar, with a heating rate greater than 20°C / s, a holding temperature of 1175°C, a holding time of 0.2h, and then the bar is taken out and water-cooled.

[0097] S52, the rod that has undergone the last solution heat treatment is subjected to a second solution heat treatment at a temperature of 1140°C for a holding time of 2.5 hours, and then taken out and water-cooled to obtain a wear-resistant alloy with uniform grain size and carbide distribution.

[0098] S53, the surface of the heat-treated bar is mechanically treated by machining to remove the surface oxide scale and the affected layer, with a single-side removal of 0.4mm.

[0099] Finally, a cobalt-based high-temperature alloy with resistance to adhesive wear was obtained. Adhesive wear test, hardness uniformity test and grain size test were carried out on the cobalt-based high-temperature alloy respectively:

[0100] (1) Room temperature ring-block wear weight loss: Adhesive wear tests were conducted in accordance with GB / T12444-2006 "Metallic Materials Wear Test Methods" with a load of 25 kg. GH5630A alloy was used as the friction pair. After 100,000 revolutions of wear, the weight loss of a φ40 (outer diameter) × φ16 (inner diameter) × 10 mm ring-shaped cobalt-based high-temperature alloy specimen was measured. The weight loss indicates wear resistance; the smaller the weight loss, the better the wear resistance. The initial weight of the ring specimen was 98 ± 0.5 g.

[0101] (2) Room temperature hardness uniformity test: The elongation of cobalt-based high-temperature alloy bars was tested in accordance with GB / T230.1-2018 "Rockwell hardness test for metallic materials - Part 1: Test method". The test points were distributed on the sample surface in a 3×3 matrix with a matrix range of no less than 20 mm × 20 mm. The hardness uniformity was evaluated by the maximum percentage of the hardness value of each measuring point deviating from the mean. The smaller the deviation ratio, the better the hardness uniformity of the alloy.

[0102] (3) Grain size testing: The grain size of cobalt-based high-temperature alloy bars is measured in accordance with GB / T6394 "Method for determination of average grain size of metals". The grain size range is formed by measuring the edge and center of the head, middle, and tail of the bar. The smaller the grain size range is, the more uniform the structure is, provided that the grain size range is not coarser than level 2.

[0103] Through the above tests, it can be found that the cobalt-based high-temperature alloy prepared in this embodiment has a weight loss of 0.043g due to wear, a maximum hardness deviation ratio of 3.5% from the mean, and a grain size range of 5.5 to 6.5. Figure 1 and Figure 2As shown, the carbides in the cobalt-based high-temperature alloy in the prior art are unevenly distributed and have obvious banded structures. In contrast, the alloy of this embodiment has no banded structure and the carbides are more evenly distributed.

[0104] Example 2

[0105] The difference from Example 1 lies in the forging process of step S20. Specifically, step S20 includes:

[0106] S21, upsetting and shaping the homogenized heat-treated ingot into a square billet: After heating the ingot to 1200°C and holding it for 2.5 hours, upsetting is performed in multiple passes in the axial direction, with each pass deforming 10-20%, for a total upsetting deformation of 45%. Subsequently, the ingot is shaped into a nearly cubic billet using a small forging process with a reduction of 30 mm per pass, and chamfered to a 10 mm x 45° angle.

[0107] S22, the forging blank after upsetting and finishing is divided into 5 groups of multi-directional forging in one batch. After each group of multi-directional forging is completed, the forging blank is restored to a square billet that is approximately cubic. The specific process includes the following:

[0108] The first heating is at 1200℃ and the steel is taken out for forging after holding for 3h.

[0109] In the first group of multi-directional forging, multiple passes are performed in each direction, with each pass deformation of 10-20%. After the cumulative downward deformation in a single direction reaches 60%, the direction is reversed by 90° to complete the forging in three directions.

[0110] In the second group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 50%.

[0111] In the third group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0112] In the fourth group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 40%.

[0113] In the fifth group of multi-directional forging, the deformation per pass is 10-20%, and the direction is reversed 90° after the cumulative downward deformation in a single direction reaches 25%.

[0114] After completing 5 sets of multi-directional forging, the forging blank is chamfered with a chamfer of 10mm*45°.

[0115] In step S23, the multi-directional forged billet is forged and stretched to a 40 mm diameter rod in two passes. Specifically, the first pass is heated to 1200°C, held for 3 hours, and has a deformation of 40%. The second pass is heated to 1150°C, held for 2 hours, and has a deformation of 20%.

[0116] The cobalt-based high-temperature alloy small bar obtained in this embodiment has a weight loss of 0.055g due to wear, a maximum hardness deviation ratio of 4.4% from the mean, a grain size range of 5.0 to 6.5, and no banded structure.

[0117] Example 3

[0118] In order to study the effect of heating temperature on alloy properties during forging, in step S20, the heating temperatures during the entire forging process are set to 1120°C, 1150°C, 1180°C, 1200°C and 1220°C, respectively, and the heating temperatures of each fire are kept consistent. The remaining steps and preparation conditions are the same as those in Example 1. The grain size range, mechanical properties and wear properties of the cobalt-based high-temperature alloy rod finally obtained are shown in Table 1. As shown in Table 1, when the forging temperature is too low (1120°C) or the forging temperature is too high (1220°C), the hardness uniformity and grain size uniformity of the cobalt-based high-temperature alloy are poor, resulting in a large weight loss due to wear, indicating that its anti-adhesive wear performance is poor.

[0119] Table 1 Performance test results of cobalt-based superalloys at different forging temperatures

[0120] Heating temperature 1120℃ 1150℃ 1180℃ 1200℃ 1220℃ Wear loss / g 0.075 0.047 0.043 0.049 0.064 Hardness uniformity / % 5.7 4.1 3.5 3.9 5.2 Grain size range / grade 5.0-8.0 5.0-7.0 5.5-6.5 4.5-6.0 3.5-6.0

[0121] Example 4

[0122] To investigate the effect of the secondary homogenization heat treatment conditions in step S30 on the alloy properties, the multidirectionally forged billets were subjected to secondary homogenization heat treatment at various treatment temperatures and treatment times. The remaining steps and preparation conditions were the same as in Example 1. The properties of the resulting cobalt-based superalloy bars are shown in Table 2. As shown in Table 2, when the secondary homogenization heat treatment temperature was too low (1150°C) or the treatment time was too short (12 hours), the hardness uniformity of the cobalt-based superalloy was poor, and the grain size range was large, resulting in greater wear weight loss. Meanwhile, higher treatment temperatures or longer treatment times improved the alloy's hardness uniformity, grain size uniformity, and wear resistance. However, when the treatment temperature was too high or the treatment time was too long, energy consumption was high, treatment efficiency was low, and performance improvements were not significant.

[0123] Table 2 Performance test results of alloys at different secondary homogenization heat treatment temperatures and times

[0124]

[0125] Example 5

[0126] To investigate the effects of different solution heat treatment conditions in step S50 on alloy properties, the hot-rolled bars were subjected to final heat treatment at various short-term primary solution heat treatment temperatures and various secondary solution heat treatment temperatures. The remaining steps and preparation conditions were the same as in Example 1. The grain size range, mechanical properties, and wear resistance of the resulting cobalt-based superalloy bars are shown in Table 3. As shown in Table 3, when the short-term primary solution heat treatment temperature is too low (1120°C), the cobalt-based superalloy exhibits a wider grain size range. When the temperature is too high (1220°C), the cobalt-based superalloy exhibits smaller grain sizes and larger grain sizes, resulting in greater wear weight loss. When the secondary solution heat treatment temperature is too low (1050°C) or too high (1200°C), the cobalt-based superalloy exhibits greater wear weight loss and poorer wear resistance.

[0127] Table 3 Performance test results of alloys under different solution heat treatment conditions

[0128]

[0129] Comparative Example 1

[0130] In order to explore the effect of secondary homogenization heat treatment on cobalt-based high-temperature alloys, compared with Example 1, the only difference is that the secondary homogenization heat treatment is not performed, and the other steps are the same.

[0131] The cobalt-based high-temperature alloy small bar prepared in this comparative example has a wear loss of 0.069 g, a maximum hardness deviation from the mean of 5.7%, a grain size range of 4.0 to 7.5, and the presence of a banded structure.

[0132] Comparative Example 2

[0133] In order to explore the effect of multi-directional forging on the cobalt-based high-temperature alloy, compared with Example 1, the only difference is that multi-directional forging is not used in step S20, and traditional forging method is used for forging, and the other steps are the same.

[0134] The cobalt-based high-temperature alloy small bar prepared in this comparative example has a wear loss of 0.067 g, a maximum hardness deviation from the mean of 5.8%, a grain size range of 4.0 to 7.5, and the presence of a banded structure.

[0135] Comparative Example 3

[0136] In order to explore the effect of the combination of multi-directional forging and secondary homogenization heat treatment on the cobalt-based high-temperature alloy, compared with Example 1, the difference is that multi-directional forging is not used in step S20, the traditional forging method is used for forging, and no secondary homogenization heat treatment is performed. The remaining steps are the same.

[0137] The cobalt-based high-temperature alloy small bar prepared in this comparative example has a wear loss of 0.077 g, a maximum hardness deviation from the mean of 6.1%, a grain size range of 4.0 to 8.0, and the presence of a banded structure.

[0138] Comparative Example 4

[0139] In order to explore the effect of a short-time single solution heat treatment on the properties of cobalt-based high-temperature alloys, compared with Example 1, the difference is that the rod is not subjected to a short-time single solution heat treatment, and the other steps are the same.

[0140] The cobalt-based high-temperature alloy small bar prepared in this comparative example has a wear loss of 0.063 g, a maximum hardness deviation from the mean of 5.4%, a grain size range of 5.0 to 8.0, and no banded structure.

[0141] Comparative Example 5

[0142] The composition of the cobalt-based superalloy ingot includes: 0.09 wt.% C, 20 wt.% Cr, 10 wt.% Ni, 15.25 wt.% W, 1.5 wt.% Mn, with the balance being Co. This comparative example differs from Example 1 in that the cobalt-based superalloy does not contain the element B. Testing of the cobalt-based superalloy bar produced in this comparative example showed a wear loss of 0.057 g, a maximum hardness deviation from the mean of 4.6%, and a grain size range of 4.5-7.0.

[0143] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a cobalt-based high-temperature alloy resistant to adhesive wear, characterized in that: include: homogenizing heat treatment of the cobalt-based alloy ingot; Performing multi-directional forging on the cobalt-based alloy ingot that has undergone homogenization heat treatment to obtain a rod blank; performing a secondary homogenization heat treatment on the rod blank; hot rolling the bar blank after the secondary homogenization heat treatment to obtain a bar; Performing a finished product treatment on the rod to obtain a cobalt-based high-temperature alloy rod that resists adhesive wear; The cobalt-based alloy ingot that has undergone homogenization heat treatment is subjected to multi-directional forging, comprising: Upsetting and finishing the cobalt-based alloy ingot to obtain a forging blank; Performing multi-fire multi-directional forging on the forging blank; The forging billet after multi-directional forging is stretched to obtain a rod billet; The cobalt-based alloy ingot is subjected to upsetting and blanking to obtain a forged billet, which comprises: upsetting the cobalt-based alloy ingot in multiple passes along the axial direction; then forging and blanking the upset ingot into a square billet and chamfering the billet to obtain a forged billet; the deformation amount of each pass during the forging process is generally smaller than the deformation amount of each pass during the upsetting process, and the range of the chamfer is within ; During the secondary homogenization heat treatment, the heat treatment temperature is 1180°C to 1230°C, and the heat treatment time is 15 to 24 hours; The bar is subjected to finished product processing, including: Performing a short-term solid solution heat treatment on the bar; Perform secondary solution heat treatment on the bars after a short time primary solution heat treatment; performing surface mechanical treatment on the bar after solution heat treatment; The bar is subjected to a short-term solid solution heat treatment, comprising: The rod is heated to 1160-1190° C. and kept at this temperature for 0.1-0.3 h, with a heating rate greater than 20° C. / s during the heating process; The composition of the cobalt-based high-temperature alloy is calculated by weight percentage: 0.06~0.12wt.%C, 19.5~20.5wt.%Cr, 9.5~10.5wt.%Ni, 14.5~16wt.%W, 1.2~1.8wt.%Mn, 0.0015~0.0025wt.%B, and the balance is Co.

2. The preparation method according to claim 1, characterized in that The forging blank is subjected to multi-fire multi-group multi-directional forging, and the downward deformation amount in each direction in each group of multi-directional forging is 20-60%.

3. The preparation method according to claim 2, characterized in that During the multi-fire, multi-group, multi-directional forging process, the heating temperature is 1150-1200° C., the holding time is greater than 2 hours, and the final forging temperature is greater than or equal to 900° C.

4. The preparation method according to any one of claims 1 to 3, characterized in that During the secondary homogenization heat treatment, the heat treatment temperature is 1180° C. to 1200° C., and the heat treatment time is 15 to 20 hours.

5. The method according to any one of claims 1 to 3, characterized in that When the bar billet is hot rolled, the heating temperature is 1130-1180° C. and the holding time is greater than 1 hour.

6. The preparation method according to claim 5, characterized in that The bar is subjected to a short-term solid solution heat treatment, comprising: The rod is heated to 1160-1175° C. and kept warm for 0.1-0.3 h, with a heating rate greater than 20° C. / s during the heating process.

7. A cobalt-based high-temperature alloy resistant to adhesive wear, characterized in that: Prepared by the method according to any one of claims 1 to 6, Includes the following ingredients: 0.06~0.12wt.%C, 19.5~20.5wt.%Cr, 9.5~10.5wt.%Ni, 14.5~16wt.%W, 1.2~1.8wt.%Mn, 0.0015~0.0025wt.%B, and the balance is Co.

8. A key shaft for a control rod drive mechanism, characterized in that: It is made of the cobalt-based high-temperature alloy with resistance to adhesive wear according to claim 7.

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