Method for preparing crack-free equiaxed crystal cobalt alloy wear-resistant layer on surface of steel bar

Abstract

The invention relates to the field of metal surface engineering, and particularly discloses a method for preparing a crack-free isometric crystal cobalt alloy wear-resistant layer on the surface of a steel bar, which comprises the step of preparing an isometric crystal crack-free stellite 12 alloy layer on the surface of a stainless steel bar body by adopting a hot isostatic pressing method. The method comprises the following steps: firstly, putting a treated stainless steel rod body into a sheath, filling a gap between the wall of the sheath and the stainless steel rod body with atomized stellite 12 powder, compacting, additionally putting a pressing block above the rod body and the powder, carrying out hot isostatic pressing forming, and controlling the subsequent cooling rate to finally obtain a stellite 12 alloy layer on the surface of the stainless steel rod body. Through sheath design and hot isostatic pressing parameter selection, a stellite 12 alloy layer prepared through hot isostatic pressing is compact and free of cracks and other defects, the structure characteristic is converted into fine isometric crystals from dendrites, the surface hardness is improved, the abrasion performance is doubled, and preparation of the stellite 12 abrasion-resistant layer small in deformation, high in performance and free of cracks is achieved.

Description

Technical Field

[0001] This invention relates to the field of metal surface engineering technology, and more specifically, to a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar. Background Technology

[0002] Wear, as a form of material failure, causes significant economic losses. Therefore, employing surface protection technology to improve the wear resistance of workpiece surfaces, thereby extending their service life and reducing losses, has important practical value. Stellite 12 alloy, as a cobalt-based alloy, exhibits excellent wear resistance and is therefore frequently used for workpiece surface protection. In actual production, plasma arc welding is commonly used to prepare the alloy layer. However, the surface area requiring cladding on stainless steel components is often large, and due to performance requirements necessitating sufficient weld layer thickness, multi-layer cladding is often required in a single pass under processes such as plasma cladding. Under a large heat input, even austenitic stainless steels (18.0-20.0 μm / m·℃) with a coefficient of thermal expansion similar to Stellite 12 (13.3-15.5 μm / m·℃) exhibit considerable differences. This difference in thermal expansion coefficients results in significant thermal stress in the alloy layer during the welding process. Furthermore, Stellite 12 contains 1.45% carbon, a high carbon content that causes the formation of brittle and hard carbides during melting. This leads to significant thermal stress accumulation during welding, resulting in cracks in the alloy layer. Residual stress further contributes to cracking during subsequent cold working. Current technologies typically employ preheating before welding or slow cooling after welding to reduce cracking. However, insufficient preheating temperatures still result in cracking, while excessively high preheating temperatures reduce the hardness of the substrate. Post-weld heat treatment (such as stress-relief annealing) can partially eliminate residual stress, but its effectiveness in repairing existing microcracks is limited. Simultaneously, due to the rapid heating and cooling characteristics of plasma arc welding, the alloy layer near the substrate is not only diluted by the stainless steel but also develops coarse columnar crystals due to the high temperature gradient, reducing the alloy layer's service life. Controlling substrate deformation during welding is also a major challenge. These factors limit the application of Stellite 12 alloy in stainless steel workpieces.

[0003] Therefore, it is necessary to design a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar, in order to solve the problem that the alloy layer is prone to cracking due to the large thermal stress generated during the welding process in the traditional plasma arc welding method, and that it is also prone to cracking during subsequent cold working. Summary of the Invention

[0004] In view of this, the present invention proposes a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar, in order to solve the problem that the alloy layer is prone to cracking due to the large thermal stress generated during the welding process in the traditional plasma arc welding method, and is also prone to cracking during subsequent cold working.

[0005] This invention provides a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar, comprising the following preparation steps:

[0006] Pretreatment of stainless steel rods and Stellite 12 powder;

[0007] The stainless steel rod is placed in the sleeve, and the Stellite 12 powder is placed in the gap between the side wall of the sleeve and the stainless steel rod. The Stellite 12 powder is vibrated and compacted, and this process is repeated several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0008] Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, then cover it with the upper wall of the sleeve with the suction pipe, and weld the upper wall of the sleeve to the side wall of the sleeve to seal it.

[0009] The inside of the casing is evacuated by a vacuum tube, and then the vacuum tube is sealed before hot isostatic pressing is performed. The cooling rate is controlled, and a sample is taken after the process to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0010] Furthermore, the pretreatment involves cleaning the stainless steel rod with acetone or anhydrous ethanol and vacuum drying the Stellite 12 powder.

[0011] Furthermore, the vacuum drying temperature is 90-180℃, and the drying time is 4-10 hours.

[0012] Furthermore, after placing the stainless steel rod in the sleeve, the stainless steel rod is fixed to the outer wall of the sleeve by argon arc fixation.

[0013] Furthermore, the compaction pressure is 1-5 MPa.

[0014] Furthermore, the vacuuming process specifically involves: evacuating to a vacuum level of 1x10. -3 ~1x10 -4 After standing for 6-12 hours, vacuum up to 1x10⁻¹⁰ Pa. -3 ~1x10 -4 pa.

[0015] Furthermore, when sealing the extraction pipe, the extraction pipe is heated to red and then flattened. A section of the unflattened part away from the upper arm of the casing is cut off, and the cut is welded and sealed.

[0016] Furthermore, the heating temperature for hot isostatic pressing is 1000-1200℃, the pressure is 90-150MPa, and the heating time is 2-5 hours.

[0017] Furthermore, the hot isostatic pressing process specifically involves: raising the temperature of the cladding from room temperature to 500°C at a heating rate of 5–10°C / min and holding it at that temperature for 30 minutes; then raising the temperature to 900°C at a heating rate of 5–10°C / min and holding it at that temperature for 30 minutes; and finally raising the temperature to 1000–1200°C at a heating rate of 10°C / min and holding it at that temperature for 2–5 hours.

[0018] Furthermore, the cooling rate is 5°C / min, and the final cooling temperature is 160°C.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. Through innovative encapsulation design, pressure blocks and pressure rings are added inside the traditional encapsulation. During the degassing process, the pressure difference enables pre-forming before entering the furnace, resulting in a more compact alloy layer, while reducing the escape of powder during the degassing process.

[0021] 2. By using hot isostatic pressing, defects such as deformation and cracks under traditional cladding processes are controlled. At the same time, due to the characteristics of solid-state forming, there is no component segregation caused by different melting points of each component during fusion welding, which leads to unstable performance. After slow cooling, the microstructure is fine and uniform equiaxed crystals, and the hardness increases while the wear performance is improved by 44.5%.

[0022] 3. Using hot isostatic pressing to achieve near-net-shape forming of Stellite 12 can significantly reduce subsequent processing and material waste. This process is suitable for the industrial-scale mass production of a crack-free wear-resistant Stellite 12 coating on the surface of stainless steel bars. Attached Figure Description

[0023] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0024] Figure 1 A flowchart illustrating a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to an embodiment of the present invention;

[0025] Figure 2 This is a schematic diagram of a compaction scheme provided in an embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the encapsulation structure provided in an embodiment of the present invention;

[0027] Figure 4 This is a crack detection image of the Stellite 12 alloy layer, a comparative example of this invention.

[0028] Figure 5 These are microstructure images of Stellite 12 alloy layers from Example 1 and the comparative example of the present invention.

[0029] Figure 6 This is a comparison chart of the average hardness of the Stellite 12 alloy layer in Example 1 of the present invention and the comparative example.

[0030] Figure 7 This is a comparison chart of the friction and wear test results of Stellite 12 alloy layer in Example 1 of the present invention and the comparative example;

[0031] Figure 8 This is a microstructure diagram of the Stellite 12 alloy layer in Example 4 of the present invention.

[0032] In the diagram: 1-extraction pipe; 2-compression block; 3-compression ring; 4-Stali 12 powder; 5-outer wall of the casing; 6-stainless steel rod; 7-long compression cylinder. Detailed Implementation

[0033] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0034] In actual production, plasma arc welding is often used to prepare alloy layers. However, the surface area to be clad on stainless steel components is often large, and sufficient weld layer thickness is required due to performance requirements. This necessitates multi-layer cladding in a single pass under processes such as plasma cladding. Under such high heat input, even austenitic stainless steels (18.0-20.0 μm / m·℃) with a coefficient of thermal expansion similar to Stellite 12 (13.3-15.5 μm / m·℃) exhibit significant differences. This difference in coefficient of thermal expansion results in substantial thermal stress in the alloy layer during welding. Furthermore, Stellite 12 contains 1.45% carbon, which leads to the formation of brittle and hard carbides during melting. The accumulation of significant thermal stress during welding causes cracks in the alloy layer, and residual stress further contributes to cracking during subsequent cold working. Existing technologies typically employ preheating before welding or slow cooling after welding to reduce cracking. However, insufficient preheating temperature still makes cracking difficult to avoid, while excessively high preheating temperatures lead to a decrease in matrix hardness. Post-weld heat treatment (such as stress-relief annealing) can partially eliminate residual stress, but its effect on repairing existing microcracks is limited. Furthermore, due to the rapid heating and cooling characteristics of plasma arc welding, the alloy layer near the matrix is ​​not only diluted by the stainless steel but also develops coarse columnar crystals due to the high temperature gradient, reducing the service life of the alloy layer. In addition, controlling the deformation of the matrix during the welding process is also a major challenge. These factors limit the application of Stellite 12 alloy in stainless steel workpieces.

[0035] Therefore, it is necessary to design a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar, in order to solve the problem that the alloy layer is prone to cracking due to the large thermal stress generated during the welding process in the traditional plasma arc welding method, and that it is also prone to cracking during subsequent cold working.

[0036] like Figure 1 As shown in some embodiments of this application, a method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar includes the following preparation steps:

[0037] Pretreatment of stainless steel rods and Stellite 12 powder;

[0038] Place the stainless steel rod in the sleeve, place the Stellite 12 powder into the gap between the side wall of the sleeve and the stainless steel rod, vibrate and compact the Stellite 12 powder, repeat several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0039] Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, then cover it with the upper wall of the sleeve with the suction pipe, and weld the upper wall of the sleeve to the side wall of the sleeve to seal it.

[0040] The inside of the casing is evacuated by a vacuum tube, and after the vacuum tube is sealed, it is hot isostatically pressed and the cooling rate is controlled. After the process is completed, a sample is taken to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0041] Specifically, the stainless steel material of the stainless steel bar can be various types of stainless steel such as austenitic stainless steel, martensitic stainless steel, and ferritic stainless steel, and the shape is a bar with a diameter φ of 40 to 200 mm and a length L of 50 to 1400 mm.

[0042] Specifically, such as Figure 2 As shown, when the Sterizo 12 powder is first vibrated and then pressed, as... Figure 2 As shown, a long pressure cylinder is used for compaction.

[0043] Specifically, the sheath is made of 0.2–0.3 mm thick stainless steel, the extraction pipe is made of φ8–φ12 x 0.5–0.7 mm stainless steel tubing, the sheath is surrounded by TIG self-fusion welding, and the extraction pipe is welded to the sheath using TIG + wire feeding H08 welding. The sheath structure is as follows: Figure 3 As shown.

[0044] Specifically, TIG welding is used when sealing the upper wall of the sheath with the side wall of the sheath.

[0045] Specifically, Stellite 12 powder is prepared by gas atomization, with a particle size of 80-230 mesh. Its composition by mass percentage is: Cr 30%, W 8.5%, C 1.45%, Ni < 2%, Mo < 1%, Fe < 2%, Si < 2%, with the balance being Co and unavoidable impurities.

[0046] Specifically, such as Figure 2 As shown, Stellite 12 powder is compacted using a vibrator, and then the alloy powder is compacted using a pre-designed long pressure cylinder. This process is repeated multiple times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0047] Understandably, this invention, through innovative encapsulation design, adds pressure blocks and rings within the traditional encapsulation. During the degassing process, the pressure difference enables pre-forming before furnace entry, resulting in a denser alloy layer while reducing powder escape during degassing. Hot isostatic pressing (HIP) controls defects such as deformation and cracking inherent in traditional cladding processes. Furthermore, due to the characteristics of solid-state forming, it avoids the instability caused by component segregation due to different melting points during fusion welding. After slow cooling, the microstructure consists of fine, uniform equiaxed grains, increasing hardness and improving wear resistance by 44.5%. Using HIP to achieve near-net-shape forming of Stellite 12 significantly reduces subsequent processing and material waste. This process is suitable for the industrial-scale mass production of a crack-free wear-resistant Stellite 12 layer on the surface of stainless steel bars.

[0048] In some embodiments of this application, the pretreatment is as follows: cleaning the stainless steel rod with acetone or anhydrous ethanol; and vacuum drying the Stellite 12 powder.

[0049] In some embodiments of this application, the vacuum drying temperature is 90-180°C, and the drying time is 4-10 hours, with the drying temperature preferably being 180°C and the drying time preferably being 4 hours.

[0050] It is understandable that acetone or anhydrous ethanol is used to clean the surface of the processed stainless steel bars to remove oil and residual metal debris. Vacuum drying ensures that the powder is thoroughly dried.

[0051] In some embodiments of this application, after the stainless steel rod is placed in the sleeve, the stainless steel rod is fixed to the outer wall of the sleeve by argon arc fixation.

[0052] It is understandable that fixing the stainless steel rod to the outer wall of the sleeve by argon arc fixation can ensure that no displacement occurs during subsequent sleeve assembly.

[0053] In some embodiments of this application, the oxidation specifically involves mixing and stirring the lower layer of crude BDO with an oxidant to carry out the reaction.

[0054] In some embodiments of this application, the compaction pressure is 1-5 MPa, preferably 5 MPa.

[0055] In some embodiments of this application, the vacuuming process specifically involves: evacuating to a vacuum level of 1x10. -3 ~1x10 -4 After standing for 6-12 hours, vacuum up to 1x10⁻¹⁰ Pa. -3 ~1x10 -4 pa; preferably evacuated to 1x10 -4 After standing for 12 hours, vacuum up to 1x10⁻¹⁰. -4 pa.

[0056] In some embodiments of this application, when sealing the extraction tube, the extraction tube is heated to red and then flattened, a section of the unflattened part away from the upper arm of the casing is cut off, and the cut is welded and sealed.

[0057] Specifically, the exhaust pipe is heated to red by flame, flattened with hydraulic clamps to a length of 30mm, and then cut off at one end and sealed using TIG welding.

[0058] In some embodiments of this application, the heating temperature for hot isostatic pressing is 1000-1200℃, the pressure is 90-150MPa, and the heating time is 2-5 hours; the preferred heating temperature for hot isostatic pressing is 1100℃, the pressure is 120MPa, and the heating time is 2 hours.

[0059] In some embodiments of this application, the hot isostatic pressing is specifically performed as follows: the temperature of the cladding is increased from room temperature to 500°C at a heating rate of 5-10°C / min and held for 30 minutes; the temperature is then increased to 900°C at a heating rate of 5-10°C / min and held for 30 minutes; finally, the temperature is increased to 1000-1200°C at a heating rate of 10°C / min and held for 2-5 hours.

[0060] Preferably, the hot isostatic pressing process specifically involves: raising the temperature of the casing from room temperature to 500°C at a heating rate of 10°C / min and holding it at that temperature for 30 minutes; then raising the temperature to 900°C at a heating rate of 10°C / min and holding it at that temperature for 30 minutes; and finally raising the temperature to 1100°C at a heating rate of 10°C / min and holding it at that temperature for 2 hours.

[0061] In some embodiments of this application, the cooling rate is 5°C / min, and the final cooling temperature is 160°C.

[0062] Example 1

[0063] S1. The stainless steel material is 304 austenitic stainless steel, with a diameter φ of 50mm and a length L of 120mm. The composition of 304 stainless steel by mass percentage is: Cr 18-20%, Ni 10.5%, C 0.08%, Si 0.75%, Mn 2%, N 0.1%, with the balance being Fe and unavoidable impurities.

[0064] S2. Clean the surface of the stainless steel rod with anhydrous ethanol. Dry the Stellite 12 powder in a vacuum drying oven at 180°C for 4 hours. The Stellite 12 powder is prepared by gas atomization. The powder particle size is 80-230 mesh. Its composition by mass percentage is: Cr 30%, W 8.5%, C 1.45%, Ni < 2%, Mo < 1%, Fe < 2%, Si < 2%, with the balance being Co and unavoidable impurities.

[0065] S3. Place the stainless steel rod in the sleeve, fix the stainless steel rod to the outer wall of the sleeve by argon arc spot fixation, then first vibrate the Stellite 12 powder and then use a long pressure cylinder to compact it with a pressure of 5 MPa. Repeat this several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0066] S4. Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, and then cover it with the upper wall of the sleeve with the suction pipe. Connect and seal the upper wall of the sleeve with the side wall of the sleeve using TIG welding. The sleeve is made of 0.2mm thick stainless steel, and the suction pipe is made of φ8x0.5mm stainless steel pipe. The sleeve is TIG self-fusion welded around its perimeter, and the suction pipe and the sleeve are welded using TIG + wire feeding H08.

[0067] S5. Evacuate the inside of the casing to 1x10 using the vacuum tube. -4 Pa, let stand for 12 hours, then evacuate to 1x10 -4 After pa, heat the suction pipe to red, flatten it with hydraulic pliers to a length of 30mm, cut off one end and seal it with TIG welding.

[0068] S6. Under a pressure of 120 MPa, the sheath is heated. First, the sheath is heated from room temperature to 500°C at a heating rate of 10°C / min and held for 30 minutes. Then, the temperature is heated to 900°C at a heating rate of 10°C / min and held for 30 minutes. Finally, the temperature is heated to 1100°C at a heating rate of 10°C / min and held for 2 hours. After the heating is completed, the sheath is cooled to 160°C at a cooling rate of 5°C / min and a sample is taken to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0069] Example 2

[0070] S1. The stainless steel material is 304 austenitic stainless steel, with a diameter φ of 50mm and a length L of 120mm. The composition of 304 stainless steel by mass percentage is: Cr 18-20%, Ni 10.5%, C 0.08%, Si 0.75%, Mn 2%, N 0.1%, with the balance being Fe and unavoidable impurities.

[0071] S2. Clean the surface of the stainless steel rod with anhydrous ethanol. Dry the Stellite 12 powder in a vacuum drying oven at 90°C for 10 hours. The Stellite 12 powder is prepared by gas atomization. The powder particle size is 80-230 mesh. Its composition by mass percentage is: Cr 30%, W 8.5%, C 1.45%, Ni < 2%, Mo < 1%, Fe < 2%, Si < 2%, with the balance being Co and unavoidable impurities.

[0072] S3. Place the stainless steel rod in the sleeve, fix the stainless steel rod to the outer wall of the sleeve by argon arc fixation, then first vibrate the Stellite 12 powder and then use a long pressure cylinder to compact it with a pressure of 1 MPa. Repeat this process several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0073] S4. Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, and then cover it with the upper wall of the sleeve with the suction pipe. Connect and seal the upper wall of the sleeve with the side wall of the sleeve using TIG welding. The sleeve is made of 0.2mm thick stainless steel, and the suction pipe is made of φ8x0.5mm stainless steel pipe. The sleeve is TIG self-fusion welded around its perimeter, and the suction pipe and the sleeve are welded using TIG + wire feeding H08.

[0074] S5. Evacuate the inside of the casing to 1x10 using the vacuum tube. -3 Pa, let stand for 6 hours, then evacuate to 1x10 -3 After pa, heat the suction pipe to red, flatten it with hydraulic pliers to a length of 30mm, cut off one end and seal it with TIG welding.

[0075] S6. Under a pressure of 90 MPa, the sheath is heated. First, the sheath is heated from room temperature to 500°C at a heating rate of 5°C / min and held for 30 minutes. Then, the temperature is heated to 900°C at a heating rate of 5°C / min and held for 30 minutes. Finally, the temperature is heated to 1000°C at a heating rate of 10°C / min and held for 5 hours. After the heating is completed, the sheath is cooled to 160°C at a cooling rate of 5°C / min and a sample is taken to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0076] Example 3

[0077] S1. The stainless steel material is 304 austenitic stainless steel, with a diameter φ of 50mm and a length L of 120mm. The composition of 304 stainless steel by mass percentage is: Cr 18-20%, Ni 10.5%, C 0.08%, Si 0.75%, Mn 2%, N 0.1%, with the balance being Fe and unavoidable impurities.

[0078] S2. Clean the surface of the stainless steel rod with anhydrous ethanol. Dry the Stellite 12 powder in a vacuum drying oven at 180°C for 4 hours. The Stellite 12 powder is prepared by gas atomization. The powder particle size is 80-230 mesh. Its composition by mass percentage is: Cr 30%, W 8.5%, C 1.45%, Ni < 2%, Mo < 1%, Fe < 2%, Si < 2%, with the balance being Co and unavoidable impurities.

[0079] S3. Place the stainless steel rod in the sleeve, fix the stainless steel rod to the outer wall of the sleeve by argon arc spot fixation, then first vibrate the Stellite 12 powder and then use a long pressure cylinder to compact it with a pressure of 5 MPa. Repeat this several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0080] S4. Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, and then cover it with the upper wall of the sleeve with the suction pipe. Connect and seal the upper wall of the sleeve with the side wall of the sleeve using TIG welding. The sleeve is made of 0.2mm thick stainless steel, and the suction pipe is made of φ8x0.5mm stainless steel pipe. The sleeve is TIG self-fusion welded around its perimeter, and the suction pipe and the sleeve are welded using TIG + wire feeding H08.

[0081] S5. Evacuate the inside of the casing to 1x10 using the vacuum tube. -4 Pa, let stand for 12 hours, then evacuate to 1x10 -4 After pa, heat the suction pipe to red, flatten it with hydraulic pliers to a length of 30mm, cut off one end and seal it with TIG welding.

[0082] S6. Under a pressure of 150 MPa, the sheath is heated. First, the sheath is heated from room temperature to 500°C at a heating rate of 10°C / min and held for 30 minutes. Then, the temperature is heated to 900°C at a heating rate of 10°C / min and held for 30 minutes. Finally, the temperature is heated to 1200°C at a heating rate of 10°C / min and held for 2 hours. After the heating is completed, the sheath is cooled to 160°C at a cooling rate of 5°C / min and a sample is taken to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0083] Example 4

[0084] S1. The stainless steel material is 304 austenitic stainless steel, with a diameter φ of 100mm and a length L of 200mm. The composition of 304 stainless steel by mass percentage is: Cr 18-20%, Ni 10.5%, C 0.08%, Si 0.75%, Mn 2%, N 0.1%, with the balance being Fe and unavoidable impurities.

[0085] S2. Clean the surface of the stainless steel rod with anhydrous ethanol. Dry the Stellite 12 powder in a vacuum drying oven at 180°C for 4 hours. The Stellite 12 powder is prepared by gas atomization. The powder particle size is 80-230 mesh. Its composition by mass percentage is: Cr 30%, W 8.5%, C 1.45%, Ni < 2%, Mo < 1%, Fe < 2%, Si < 2%, with the balance being Co and unavoidable impurities.

[0086] S3. Place the stainless steel rod in the sleeve, fix the stainless steel rod to the outer wall of the sleeve by argon arc spot fixation, then first vibrate the Stellite 12 powder and then use a long pressure cylinder to compact it with a pressure of 5 MPa. Repeat this several times until the Stellite 12 powder is at the same height as the stainless steel rod.

[0087] S4. Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, and then cover it with the upper wall of the sleeve with the suction pipe. Connect and seal the upper wall of the sleeve with the side wall of the sleeve using TIG welding. The sleeve is made of 0.2mm thick stainless steel, and the suction pipe is made of φ8x0.5mm stainless steel pipe. The sleeve is TIG self-fusion welded around its perimeter, and the suction pipe and the sleeve are welded using TIG + wire feeding H08.

[0088] S5. Evacuate the inside of the casing to 1x10 using the vacuum tube. -4 Pa, let stand for 12 hours, then evacuate to 1x10 -4 After pa, heat the suction pipe to red, flatten it with hydraulic pliers to a length of 30mm, cut off one end and seal it with TIG welding.

[0089] S6. Under a pressure of 120 MPa, the sheath is heated. First, the temperature is increased from room temperature to 500°C at a heating rate of 10°C / min and held for 30 minutes. Then, the temperature is increased to 900°C at a heating rate of 10°C / min and held for 30 minutes. Finally, the temperature is increased to 1100°C at a heating rate of 10°C / min and held for 2 hours. After the process, samples are directly taken and air-cooled to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

[0090] Comparative Example

[0091] The stainless steel material is 304 austenitic stainless steel, with a diameter φ of 50mm and a length L of 120mm. The composition of 304 stainless steel by mass percentage is: Cr 18-20%, Ni 10.5%, C 0.08%, Si 0.75%, Mn 2%, N 0.1%, with the balance being Fe and unavoidable impurities.

[0092] The stainless steel rod body is coated with a wear-resistant layer of Stellite 12 alloy using a conventional plasma cladding process in the art.

[0093] Effect test

[0094] The Stellite 12 alloy wear-resistant layer prepared in Example 1 and the Stellite 12 alloy wear-resistant layer prepared in the comparative example were subjected to dye penetrant testing for defects in the alloy layer. Then, wire cutting samples were taken and the microstructure was observed using a scanning electron microscope. Finally, a friction and wear tester was used to test the wear performance.

[0095] Test results as follows Figure 4-6 As shown, Figure 5 In Figure a, the microstructure of the Stellite 12 alloy layer in Example 1 is shown, and in Figure b, the microstructure of the Stellite 12 alloy layer in the comparative example is shown. Figure 6 In the figure, a represents the average hardness of the Stellite 12 alloy layer in Example 1, and b represents the average hardness of the Stellite 12 alloy layer in the comparative example.

[0096] It is evident that plasma-clad Stellite 12 exhibits cracking, while the Stellite 12 alloy layer prepared by hot isostatic pressing (HIP) is dense and defect-free. Microstructural analysis reveals that plasma-clad Stellite 12 exhibits a typical dendritic structure with a size of 10–15 micrometers, while the HIP-prepared Stellite 12 structure consists of fine equiaxed crystals with a size of 1–5 micrometers. The hardness increased by 78 HV, an increase of 16%. The wear rate was 8.693E. -6 (mm3·N -1 ·m -1 Compared to plasma cladding's 1.567E -5 (mm3·N -1 ·m -1 The yield increased by 44.5%. However, after direct air cooling, the microstructure was not equiaxed grains, but retained the shape of lamellar and columnar grains.

[0097] Wear performance test results are as follows Figure 7 As shown, Figure 7 In Example 1, layer a represents the friction and wear test results of the Stellite 12 alloy layer, and layer b represents the friction and wear test results of the comparative Stellite 12 alloy layer. Figure 7 The test results are shown in Table 1, which shows the wear rate of the Stellite 12 alloy layer prepared using the same method.

[0098] Table 1. Wear rate of Stellite 12 alloy layers prepared by different methods

[0099]

[0100] It is evident that the Stellite 12 alloy wear-resistant layer formed by hot isostatic pressing in this invention exhibits significantly lower wear volume and wear rate in wear performance tests compared to the Stellite 12 alloy wear-resistant layer prepared by the traditional plasma cladding method.

[0101] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar, characterized in that, The preparation steps include the following: Pretreatment of stainless steel rods and Stellite 12 powder; The stainless steel rod is placed in the sleeve, and the Stellite 12 powder is placed in the gap between the side wall of the sleeve and the stainless steel rod. The Stellite 12 powder is vibrated and compacted, and this process is repeated several times until the Stellite 12 powder is at the same height as the stainless steel rod. Place a pressure ring and a pressure block on top of the Stellite 12 powder and the stainless steel rod, then cover it with the upper wall of the sleeve with the suction pipe, and weld the upper wall of the sleeve to the side wall of the sleeve to seal it. The inside of the casing is evacuated by a vacuum tube, and after the vacuum tube is sealed, it is hot isostatically pressed and the cooling rate is controlled. After the process is completed, a sample is taken to obtain a stainless steel rod with a Stellite 12 alloy wear-resistant layer on the surface.

2. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 1, characterized in that, The pretreatment is as follows: the stainless steel rod is cleaned with acetone or anhydrous ethanol; the Stellite 12 powder is vacuum dried.

3. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 2, characterized in that, The vacuum drying temperature is 90-180℃, and the drying time is 4-10 hours.

4. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 3, characterized in that, After placing the stainless steel rod in the sleeve, the stainless steel rod is fixed to the outer wall of the sleeve by argon arc tack fixing.

5. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 4, characterized in that, The compaction pressure is 1-5 MPa.

6. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 5, characterized in that, The vacuuming process specifically involves: evacuating to a vacuum level of 1x10. -3 ~1x10 -4 After standing for 6-12 hours, vacuum up to 1x10⁻¹⁰ Pa. -3 ~1x10 -4 pa.

7. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 6, characterized in that, When sealing the extraction tube, heat the extraction tube to red and flatten it, cut off the unflattened part away from the upper arm of the casing, and weld the cut end to seal it.

8. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 7, characterized in that, The heating temperature for hot isostatic pressing is 1000-1200℃, the pressure is 90-150MPa, and the heating time is 2-5 hours.

9. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 8, characterized in that, The hot isostatic pressing process specifically involves: raising the temperature of the cladding from room temperature to 500°C at a heating rate of 5–10°C / min and holding it at that temperature for 30 minutes; then raising the temperature to 900°C at a heating rate of 5–10°C / min and holding it at that temperature for 30 minutes; and finally raising the temperature to 1000–1200°C at a heating rate of 10°C / min and holding it at that temperature for 2–5 hours.

10. The method for preparing a crack-free equiaxed cobalt alloy wear-resistant layer on the surface of a steel bar according to claim 9, characterized in that, The cooling rate is 5°C / min, and the final cooling temperature is 160°C.

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