Laser cladding wear-resistant coating for furnace roller surface and preparation method of laser cladding wear-resistant coating

Abstract

The invention provides a laser cladding wear-resistant coating for the surface of a furnace roller and a preparation method of the laser cladding wear-resistant coating, and belongs to the field of coatings. The preparation method comprises the following steps: preheating a pretreated furnace roller matrix to 400-500 DEG C; on the basis of a laser gradient cladding method, a bottom coating, a middle coating and a surface coating are sequentially deposited on the surface of a furnace roller base body, slow cooling is conducted under the protective atmosphere, and a composite coating is obtained; the wear-resistant coating is obtained through strengthening treatment; the raw materials of the bottom coating comprise first cobalt-based alloy powder and a first strengthening phase; the first strengthening phase is titanium carbide TiC; the raw materials of the middle coating comprise second cobalt-based alloy powder and a second strengthening phase; the second strengthening phase is hafnium carbide HfC or tantalum carbide TaC; the surface coating comprises the following raw materials: third cobalt-based alloy powder, a third strengthening phase and an additive; the third strengthening phase comprises hafnium carbide HfC and rare earth oxide; and the additive adopts boron carbide B4C. The prepared coating breaks through the high-temperature limit of 1400 DEG C, the high-temperature hardness and wear resistance are remarkably improved, and the problem of thermal stress cracking is solved.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, and specifically relates to a laser cladding wear-resistant coating for furnace roller surfaces and its preparation method. Background Technology

[0002] High-temperature furnace rollers, commonly referred to simply as furnace rollers or heating furnace rollers, are rotating components installed inside continuous industrial heating furnaces (such as annealing furnaces, quenching furnaces, steel rolling furnaces, glass kilns, etc.) to support and transport workpieces under high-temperature conditions. They are made of rigid, high-temperature-resistant rollers. The working environment of furnace rollers is extremely harsh (typically 800℃~1000℃, or even higher), therefore their surfaces require special treatment to resist high temperatures and maintain high-temperature strength and wear resistance. Coating is one of the most widely used and reliable surface treatment methods.

[0003] Cobalt-based alloy coatings have become representative of furnace roll surface coatings due to their excellent high-temperature performance, resistance to high-temperature oxidation and hot corrosion, and good resistance to thermal fatigue. However, with the development of industrial manufacturing needs, the manufacture of some special material products requires higher temperature environments (such as above 1400℃). Studies have found that the wear life of coatings is significantly shortened at around 1400℃. Summary of the Invention

[0004] In view of this, the present invention provides a laser cladding wear-resistant coating for the surface of furnace rollers and a method for preparing the same, aiming to solve at least one technical problem in the background art.

[0005] This invention is implemented as follows: This invention provides a method for preparing a laser cladding wear-resistant coating for the surface of furnace rollers, the method comprising the following steps: The pretreated furnace roller substrate is preheated to 400℃~500℃; Based on the laser gradient cladding method, the raw materials for the base coating, the intermediate coating, and the top coating are sequentially deposited on the surface of the furnace roller substrate and slowly cooled under a protective atmosphere to obtain a composite coating. The composite coating is strengthened to obtain a wear-resistant coating; The raw materials for the base coating include a first cobalt-based alloy powder and a first reinforcing phase; the first reinforcing phase is titanium carbide (TiC). The raw materials for the intermediate coating include a second cobalt-based alloy powder and a second reinforcing phase; the second reinforcing phase is hafnium carbide (HfC) or tantalum carbide (TaC). The raw materials for the surface coating include a third cobalt-based alloy powder, a third reinforcing phase, and additives; the third reinforcing phase includes hafnium carbide (HfC) and rare earth oxides; the rare earth oxides are selected from yttrium oxide (Y2O3) or lanthanum oxide (La2O3); the additives are boron carbide (B4C).

[0006] Further, the first cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 25%~35% Ni, 20%~25% Cr, 13%~16% W, with the balance being Co; the amount of the first reinforcing phase is 8wt%~12wt% of the first cobalt-based alloy powder.

[0007] Furthermore, the second cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 20%~30% Ni, 20%~25% Cr, 18%~22% W, 5%~8% Mo, 2%~5% Al, with the balance being Co; the amount of the second reinforcing phase is 13wt%~17wt% of the second cobalt-based alloy powder.

[0008] Further, the third cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 18%~24% Ni, 18%~22% Cr, 18%~24% W, 6%~10% Mo, 3%~7% Al, 0.3%~0.6% Y, with the balance being Co; the amounts of hafnium carbide (HfC) and rare earth oxides in the third reinforcing phase are 18wt%~22wt% and 5wt%~8wt% of the third cobalt-based alloy powder, respectively; and the amount of additives is 2wt%~4wt% of the third cobalt-based alloy powder.

[0009] Furthermore, the steps of the laser gradient cladding method specifically include: The raw material for the base coating is deposited on the surface of the furnace roller substrate by laser cladding and cooled to below 200°C to form the base coating. The raw material for the intermediate coating is deposited on the base coating by laser cladding and then cooled to below 200°C to form the intermediate coating. The raw material for the surface coating is deposited onto the intermediate coating using laser cladding to form the surface coating. The material is transferred into a preheated argon-protected furnace and cooled to room temperature at a rate of ≤50℃ / h to form a composite coating. When preparing the intermediate and top coatings using the laser gradient cladding method, the laser power is 4000W~4500W, and a rectangular spot is used.

[0010] Furthermore, the strengthening process includes laser shock peening and ultrasonic rolling.

[0011] Furthermore, the conditions for laser shock enhancement include: pulse energy = 5J~10J, spot size Ø = 1mm~5mm, overlap rate = 40%~60%, and number of shocks = 2~5.

[0012] Furthermore, the conditions for ultrasonic rolling include: ultrasonic frequency = 15kHz~25kHz, static pressure 300N~500N, rolling times = 2~5 times; feed speed = 0.05mm / r~0.15mm / r; and the surface roughness Ra after ultrasonic rolling ≤ 0.2μm.

[0013] Furthermore, the strengthening treatment also includes surface machining, which is performed before laser shock strengthening to make the surface roughness Ra ≤ 3.2 μm.

[0014] The second aspect of the present invention provides a laser cladding wear-resistant coating obtained by the method for preparing the laser cladding wear-resistant coating for the surface of furnace rollers.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention employs a three-layer cladding coating that is metallurgically bonded to the furnace roller body, breaking through the 1400℃ high-temperature limit through an ultra-high temperature ceramic-high entropy alloy composite system; in-situ reaction reinforcement technology significantly improves high-temperature hardness and wear resistance; the functionally graded coating structure features a three-layer gradient design that balances bonding strength and surface properties, solving the problem of thermal stress cracking. The composite post-treatment process, combining laser shock peening and ultrasonic rolling, synergistically enhances fatigue resistance. 2. The laser cladding wear-resistant coating for furnace rollers prepared by this invention has excellent wear resistance, high temperature resistance, high hardness and fatigue resistance. Under application conditions of 1400℃, the service life of the coating of this invention is more than 3 times that of conventional coated furnace rollers. Its application has good economic and social benefits. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the laser cladding wear-resistant coating of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0018] A method for preparing a laser cladding wear-resistant coating for furnace roller surface, comprising steps S1-S3.

[0019] S1. Preheat the pretreated furnace roller substrate to 400℃~500℃.

[0020] In specific implementation, the furnace roll base is made of forged H13 die steel conforming to GB / T 1299-2014 standard (tempered hardness 48HRC-52 HRC); the pretreatment steps specifically include: (1) Turning: Leave a 3.0mm allowance on one side of the working surface (for cladding coating).

[0021] (2) Surface cleaning: sandblasting (white corundum sand, 60 mesh, surface roughness Ra=6.3μm).

[0022] (3) Clean with acetone for 15 minutes to remove oil stains.

[0023] (4) Non-destructive testing: Magnetic particle testing confirmed that there were no cracks or pore defects.

[0024] S2. Based on the laser gradient cladding method, the raw materials for the base coating, the intermediate coating, and the top coating are sequentially deposited on the surface of the furnace roller substrate and slowly cooled under a protective atmosphere to obtain a composite coating.

[0025] The raw materials for the base coating include a first cobalt-based alloy powder and a first reinforcing phase; the first reinforcing phase is titanium carbide (TiC) (3μm-20μm); the first cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 25%~35% Ni, 20%~25% Cr, 13%~16% W, with the balance being Co; the amount of the first reinforcing phase is 8wt%~12wt% of the first cobalt-based alloy powder. The function of the base layer is to ensure metallurgical bonding with the H13 matrix.

[0026] The intermediate coating is made from a second cobalt-based alloy powder and a second reinforcing phase (3μm-20μm). The second reinforcing phase is hafnium carbide (HfC) or tantalum carbide (TaC). The second cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 20%~30% Ni, 20%~25% Cr, 18%~22% W, 5%~8% Mo, 2%~5% Al, with the balance being Co. The amount of the second reinforcing phase is 13wt%~17wt% of the second cobalt-based alloy powder. The intermediate layer serves to transition thermal stress.

[0027] The raw materials for the surface coating include a third cobalt-based alloy powder, a third reinforcing phase, and additives. The third reinforcing phase includes hafnium carbide (HfC) (3μm-20μm) and rare earth oxides (0.5μm-2μm). The rare earth oxides are selected from yttrium oxide (Y₂O₃) or lanthanum oxide (La₂O₃). The additives are boron carbide (B₄C) (1μm-5μm). The third cobalt-based alloy powder contains the following elements in weight percentage: 0.05%~0.15% C, 18%~24% Ni, 18%~22% Cr, 18%~24% W, 6%~10% Mo, 3%~7% Al, 0.3%~0.6% Y, with the balance being Co. The amounts of hafnium carbide (HfC) and rare earth oxides in the third reinforcing phase are 18wt%~22wt% and 5wt%~8wt% of the third cobalt-based alloy powder, respectively. The amount of additives is 2wt%~4wt% of the third cobalt-based alloy powder. The surface layer is designed to resist wear and corrosion at 1400℃.

[0028] The reinforcing phase in the raw materials of the intermediate coating and the top coating is replaced by hafnium carbide HfC (melting point 3140℃) or TaC (melting point 3880℃), which have higher thermal stability and oxidation resistance above 1400℃.

[0029] Rare earth oxides are added to the raw materials of the surface coating: 5%~8% Y2O3 or La2O3 (particle size 0.5~2μm) are introduced to inhibit high-temperature grain growth by pinning grain boundaries and improve the thermal shock resistance of the coating. In addition, the W content of the second cobalt-based alloy powder and the third cobalt-based alloy powder are increased to 18%~22% and 18%~24% respectively, and 5%~8% and 6%~10% Mo are added respectively (to improve high-temperature strength), and Al is increased to 2%~5% and 4%~6% to promote the formation of a dense Al2O3 oxide film. In addition, 0.3%~0.6% Y is added to the raw materials of the surface coating to purify grain boundaries and improve the adhesion of the oxide film.

[0030] The coating of this invention employs an ultra-high temperature ceramic-high entropy alloy composite system. The topcoat and intermediate coatings utilize an optimized high entropy alloy of HfC / TaC + Al2O3 + refractory elements, breaking the 1400℃ high-temperature limit. The topcoat achieves in-situ reaction enhancement, generating ultra-hard borides through the addition of B4C, significantly improving high-temperature hardness and wear resistance. The functionally graded coating structure of this invention, consisting of a base coat, intermediate coat, and topcoat, balances bonding strength and surface properties through a three-layer gradient design, solving the problem of thermal stress cracking.

[0031] The specific steps of the laser gradient cladding method include: S21. The raw material for the base coating is deposited on the surface of the furnace roller substrate using laser cladding, and then cooled to below 200°C to form the base coating. The conditions for laser cladding include: a laser power of 3500W~4000W, and the use of a circular laser spot. A dual-channel powder feeder is used to separately deliver the first cobalt-based alloy powder and the first reinforcing phase.

[0032] S22. The raw material for the intermediate coating is deposited on the base coating using laser cladding, and then cooled to below 200°C to form the intermediate coating. A dual-channel powder feeder is used to deliver the second cobalt-based alloy powder and the second reinforcing phase, respectively. The laser power is 4000W~4500W, and a rectangular spot is used.

[0033] S23. The raw material for the surface coating is deposited onto the intermediate coating using laser cladding to form the surface coating; a dual-channel powder feeder is used to separately deliver the third cobalt-based alloy powder and the mixture of the third reinforcing phase and additives. The laser power is 4000W~4500W, and a rectangular spot is used.

[0034] When preparing intermediate and top coatings, increasing laser power ensures that the high-melting-point strengthening phase is fully melted, and using rectangular laser spots instead of circular laser spots improves energy uniformity.

[0035] S24. Transfer the material into a preheated argon-protected furnace and cool it to room temperature at ≤50℃ / h to form a composite coating with a total thickness of 3.0mm±0.2mm.

[0036] In practice, preheating the furnace roller substrate (400℃~500℃) and slow cooling after cladding (argon atmosphere furnace) can effectively prevent cracking.

[0037] A dual-channel powder feeder is used to separately deliver cobalt-based alloy powder and reinforcing phase / additive, and the ratio is adjusted in real time. For example, the flow rate of ceramic phase (reinforcing phase / additive) is increased for surface coating.

[0038] S3. Strengthen the composite coating to obtain a wear-resistant coating.

[0039] After composite processing, the surface is strengthened by laser shock peening (LSP) and ultrasonic rolling to introduce residual compressive stress (>800 MPa) into the surface layer, which inhibits the propagation of high-temperature fatigue cracks.

[0040] In practice, the enhanced processing includes the following steps: S31. Surface machining: such as turning, to achieve a surface roughness Ra≤3.2μm.

[0041] S32. Laser Shock Enhancement (LSP): The conditions for laser shock enhancement include: pulse energy = 5J~10J, spot size Ø = 1mm~5mm, overlap rate = 40%~60%, and number of shocks = 2~5.

[0042] S33. Ultrasonic rolling: The conditions for ultrasonic rolling include: ultrasonic frequency = 15kHz~25kHz, static pressure 300N~500N, rolling times = 2~5 times; feed speed = 0.05mm / r~0.15mm / r; and the surface roughness Ra after ultrasonic rolling ≤ 0.2μm.

[0043] The structure of the laser cladding wear-resistant coating used on the surface of furnace rollers is as follows: Figure 1 As shown, it includes a furnace roller substrate 1 and a base coating 2, an intermediate coating 3 and a top coating 4 sequentially covering the surface of the furnace roller substrate 1.

[0044] Example 1 A method for preparing a laser cladding wear-resistant coating for furnace roller surface, comprising steps S1-S3.

[0045] S1. Preparation of furnace roller substrate Forged H13 die steel conforming to GB / T 1299-2014 standard (tempered hardness 48-52 HRC) was selected as the furnace roll base. First, it was machined to leave a 3.0mm allowance on each side of the working surface (for cladding coating). Then, it was sandblasted (white corundum sand, 60 mesh) to clean the surface, so that the surface roughness Ra=6.3μm. Then, it was ultrasonically cleaned with acetone for 15 minutes to remove oil stains. Finally, non-destructive testing was performed, and magnetic particle testing was used to confirm that there were no cracks or porosity defects.

[0046] The furnace roller substrate after the above treatment is heated to 450℃±20℃ by laser non-focus scanning (infrared temperature measurement monitoring).

[0047] S2, laser cladding gradient coating The raw materials (i.e., coatings) for the primer, intermediate coating, and topcoat were prepared according to the proportions in Table 1. The weight percentages of the reinforcing phase and additives were based on the corresponding cobalt-based alloy powder. The cobalt-based alloy powder was first mixed in a three-dimensional powder mixer for 12 hours (45 rpm, argon protection), then dried at 120°C for 2 hours, and stored in a sealed container (humidity <10% RH).

[0048] Table 1

[0049] The cobalt-based alloy powder and ceramic powder (reinforcing phase, reinforcing phase + additives) in the raw materials for each coating are placed in a dual-channel gas-carrying powder feeder (with independent control of metal / ceramic powder flow rate). An IPG fiber laser (wavelength 1064nm, power range 0W-6000W) is used to perform laser gradient cladding on the preheated furnace roller substrate according to the parameters in Table 2. First, a base coating (1 layer, approximately 1.0mm thick) is clad and cooled to below 200℃; then an intermediate coating (1 layer, approximately 1.0mm thick) is clad and cooled to below 200℃; finally, a top coating (1 layer, approximately 1.0mm thick) is clad, for a total thickness of 3.0mm ± 0.2mm. After melting, slow cooling is performed: the material is transferred to an argon-protected furnace (preheated to 300℃) and cooled to room temperature at a rate of ≤50℃ / h.

[0050] Table 2

[0051] S3, Enhancement Processing (1) Turning; finish turning the coating to a final thickness of 2.5 mm (surface roughness Ra≤3.2 μm).

[0052] (2) Laser shock peening (LSP); Equipment: Nd:YAG pulsed laser (wavelength 1064nm, pulse width 8ns).

[0053] Parameters: Pulse energy 8J, spot size Ø3mm, overlap rate 50%, 3 impacts (water curtain protection).

[0054] Effect: Introduces residual compressive stress >800 MPa.

[0055] (3) Ultrasonic rolling (USR); Parameters: ultrasonic frequency 20kHz, static pressure 400N, rolling 3 times (feed speed 0.1mm / r).

[0056] Results: Surface roughness was reduced to Ra≤0.2μm, and hardness was increased by 15%.

[0057] Example 2 The difference between this embodiment and Embodiment 1 is that the raw materials for the base coating, intermediate coating, and top coating are adjusted as shown in Table 3, while the other conditions and steps are the same as in Embodiment 1.

[0058] Table 3

[0059] Example 3 The difference between this embodiment and Embodiment 1 is that the raw materials for the base coating, intermediate coating, and top coating are adjusted as shown in Table 4, while the other conditions and steps are the same as in Embodiment 1.

[0060] Table 4

[0061] Example 4 The difference between this embodiment and Embodiment 1 is that HfC in the raw materials of the intermediate coating and the top coating is replaced with TaC, while the other conditions and steps are the same as in Embodiment 1.

[0062] Example 5 The difference between this embodiment and Embodiment 1 is that the Y2O3 in the raw material of the surface coating is replaced with La2O3, while the other conditions and steps are the same as in Embodiment 1.

[0063] Comparative Example 1 The difference between this comparative example and Example 1 is that the reinforcing phase HfC in the raw materials of the intermediate coating and the top coating is replaced with TiC, so that the reinforcing phase is the same as that of the base coating. All other conditions and steps are the same as in Example 1.

[0064] Comparative Example 2 The difference between this comparative example and Example 1 is that the rare earth oxide Y2O3 in the raw material of the surface coating is removed, while the other conditions and steps are the same as in Example 1.

[0065] Comparative Example 3 The difference between this comparative example and Example 1 is that additive B4C was removed from the raw materials of the surface coating, while the other conditions and steps are the same as in Example 1.

[0066] Comparative Example 4 The difference between this comparative example and Example 1 is that the base layer is removed, forming a wear-resistant coating composed of an intermediate coating and a top layer. All other conditions and steps are the same as in Example 1.

[0067] Comparative Example 5 The difference between this comparative example and Example 1 is that the intermediate coating is removed, forming a wear-resistant coating composed of a base coating and a top coating. All other conditions and steps are the same as in Example 1.

[0068] Comparative Example 6 The difference between this comparative example and Example 1 is that the top coating layer is removed, forming a wear-resistant coating composed of a base coating layer and an intermediate coating layer. All other conditions and steps are the same as in Example 1.

[0069] Comparative Example 7 The difference between this comparative example and Example 1 is that the laser shock strengthening process in the strengthening treatment is removed, while the other conditions and steps are the same as in Example 1.

[0070] Comparative Example 8 The difference between this comparative example and Example 1 is that the ultrasonic rolling process in the strengthening treatment is removed, while the other conditions and steps are the same as in Example 1.

[0071] The wear-resistant coating samples prepared in Examples 1 to 5 and Comparative Examples 1 to 8 were subjected to performance tests, including high-temperature hardness, high-temperature oxidation rate, high-temperature wear resistance, thermal shock resistance, and maximum applicable temperature at 1400℃. Meanwhile, the substrate without any coating was used as a blank control. The results are shown in Table 5.

[0072] (1) Test method / standard for high temperature hardness: The high temperature Vickers hardness tester (model HTV-PHS30, Shimadzu, Japan) was used. The test was conducted after holding the test at 1400℃ for 30 minutes under argon protection. The load was 1kg and the pressure was held for 15s. The average value of 5 points was taken. The data is in the form of average value ± standard deviation.

[0073] (2) Test method / standard for high temperature wear resistance: According to GB / T 12444-2006, a high temperature rotary wear tester (model MMS-2B) was used, with Al2O3 ceramic balls (Ø6mm) as the grinding material, a load of 20N, a rotation speed of 200r / min, and a wear time of 60min. The wear volume loss (mm) was recorded. 3 Repeat the process for 5 groups and calculate the mean. The data is expressed as mean ± standard deviation.

[0074] (3) Test method / standard for high-temperature oxidation rate: According to GB / T 13303-91, the sample is placed in a muffle furnace at 1400℃ for static oxidation for 100h, the change in mass per unit area before and after oxidation is measured, and the oxidation rate (mg / cm²) is calculated. 2 (h), repeat 5 groups and calculate the mean, which is in the form of mean ± standard deviation.

[0075] (4) Test method / standard for thermal shock resistance: According to HB 7269-96, the sample is kept at 1400℃ for 5 min and then quickly quenched in water (20℃). The cycle is repeated until the coating cracks or peels off, and the number of cycles is recorded.

[0076] (5) Test method / standard for the maximum applicable temperature: The step heating method is adopted. After each 50°C increase, the coating hardness and bonding strength are tested until the hardness decreases by more than 20% or peeling occurs. This temperature is recorded as the maximum applicable temperature.

[0077] Table 5

[0078] Table 5 shows that the coatings obtained in Examples 1 to 5 of the present invention break through the high temperature limit of 1400℃, significantly improve high temperature hardness and wear resistance, and solve the problem of thermal stress cracking.

[0079] Compared to Example 1, replacing the HfC in the intermediate and surface layers with TiC in Comparative Example 1 resulted in a decrease of approximately 24% in high-temperature hardness, an increase of approximately 85% in high-temperature oxidation rate, a decrease of approximately 68% in wear resistance, a reduction of approximately 56% in the number of thermal shock cycles, and a decrease in the maximum applicable temperature of approximately 230°C. This indicates that TiC lacks sufficient thermal stability and oxidation resistance above 1400°C, and cannot meet the requirements for ultra-high temperature service.

[0080] Compared with Example 1, after removing the surface Y2O3, the high-temperature oxidation rate increased by about 56% and the number of thermal shock cycles decreased by about 40% in Comparative Example 2. This indicates that rare earth oxides have a significant effect on pinning grain boundaries and improving the oxide film. After removal, the coating’s resistance to high-temperature oxidation and thermal shock is significantly reduced.

[0081] Compared with Example 1, after removing the surface layer of B4C, the high-temperature hardness decreased by about 14% and the wear resistance decreased by about 62%, indicating that the HfB2 superhard phase generated by the in-situ reaction of B4C and HfC is the key to improving the surface hardness and wear resistance.

[0082] Compared with Example 1, Comparative Example 4 showed that the coating bond strength with the substrate was extremely poor after the bottom layer was removed. It peeled off after only 5 thermal shocks and could not form a complete coating structure. This indicates that the bottom layer plays an irreplaceable role in ensuring the metallurgical bond between the coating and the substrate and in relieving thermal stress.

[0083] Compared with Example 1, Comparative Example 5 showed that after removing the intermediate layer, the number of thermal shock cycles decreased by about 64% and the maximum applicable temperature decreased by about 160°C. This indicates that the intermediate layer, as a thermal stress transition layer, can effectively alleviate the difference in thermal expansion coefficients between the surface layer and the bottom layer. Without the intermediate layer, the coating is prone to thermal stress cracking.

[0084] Compared with Example 1, Comparative Example 6 showed a significant decrease in high-temperature hardness and wear resistance after the surface layer was removed, and the maximum applicable temperature decreased by about 200°C. This indicates that the surface layer, as a functional layer that directly contacts the high-temperature wear environment, is the core component of the ultra-high temperature ceramic-high entropy alloy composite system that breaks through the 1400°C limit.

[0085] Compared with Example 1, Comparative Example 7 showed that the number of thermal shock cycles decreased by about 36% after laser shock strengthening was removed, indicating that the residual compressive stress introduced by laser shock strengthening can effectively suppress the initiation and propagation of high-temperature fatigue cracks.

[0086] Compared with Example 1, Comparative Example 8 showed that after removing ultrasonic rolling, the surface roughness increased (Ra≈0.8μm), the high-temperature wear resistance decreased slightly, and the number of thermal shock cycles decreased by about 20%. This indicates that ultrasonic rolling can not only improve the surface finish, but also further improve the fatigue resistance of the coating through surface nano-sizing.

[0087] In summary, this invention, through a three-layer gradient structure design of "base coating (TiC+Co-based alloy) + intermediate coating (HfC / TaC+Co-based alloy) + top coating (HfC+rare earth oxides+B4C+Co-based alloy)," combined with laser shock peening and ultrasonic rolling composite post-treatment, achieves a synergistic improvement in the coating's high hardness, high wear resistance, high thermal shock resistance, and high oxidation resistance at high temperatures above 1400℃. The service life is more than three times longer than conventional coatings, demonstrating significant industrial application value.

[0088] To verify the effect of additive B4C in the coating on the coating strengthening effect, the mechanical properties of the coating sample prepared in Example 1 were tested and compared with those of Comparative Example 3 without B4C. The results are shown in Table 6, where the data are in the form of mean ± standard deviation.

[0089] The tests include: microhardness, fracture toughness, and bond strength.

[0090] (1) Microhardness test method: Vickers microhardness tester (model HV-1000) was used with a load of 0.5 kg and a holding pressure of 15 s. Ten points were randomly selected on the coating surface for measurement.

[0091] (2) Fracture toughness test method: The fracture toughness was determined by indentation method, and the K_IC value was calculated according to the Anstis formula. The measurement was repeated 10 times.

[0092] (3) Bond strength test method: The coating bond strength test was carried out according to ASTM C633 standard, and the test was repeated 10 times.

[0093] Table 6

[0094] As shown in Table 6, compared with Comparative Example 3 (without B4C), the coating of Example 1 exhibits an increase in microhardness of approximately 16%, fracture toughness of approximately 25%, and bonding strength of approximately 16%. This indicates that the addition of B4C significantly improves the overall mechanical properties of the coating. This is because, under the high-temperature conditions of laser cladding, B4C participates in the in-situ reaction and forms a high-hardness boride phase, while simultaneously promoting the dispersed distribution of the reinforcing phase in the matrix, thereby improving the coating's hardness and crack resistance. Furthermore, boron (B) can play a reinforcing role at grain boundaries, increasing grain boundary bonding strength and further enhancing the overall mechanical properties of the coating. These results demonstrate that the addition of B4C can effectively strengthen the coating structure and significantly improve its wear resistance and crack resistance.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a laser-clad wear-resistant coating for the surface of a furnace roller, characterized in that, The preparation method includes the following steps: The pretreated furnace roller substrate is preheated to 400℃~500℃; Based on the laser gradient cladding method, the raw materials for the base coating, the intermediate coating, and the top coating are sequentially deposited on the surface of the furnace roller substrate and slowly cooled under a protective atmosphere to obtain a composite coating. The composite coating is strengthened to obtain a wear-resistant coating; The raw materials for the base coating include a first cobalt-based alloy powder and a first reinforcing phase; the first reinforcing phase is titanium carbide (TiC). The raw materials for the intermediate coating include a second cobalt-based alloy powder and a second reinforcing phase; the second reinforcing phase is hafnium carbide (HfC) or tantalum carbide (TaC). The raw materials for the surface coating include a third cobalt-based alloy powder, a third reinforcing phase, and additives; the third reinforcing phase includes hafnium carbide (HfC) and rare earth oxides; the rare earth oxides are selected from yttrium oxide (Y2O3) or lanthanum oxide (La2O3); the additives are boron carbide (B4C).

2. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 1, characterized in that, The first cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 25%~35% Ni, 20%~25% Cr, 13%~16% W, with the balance being Co; the amount of the first reinforcing phase is 8wt%~12wt% of the first cobalt-based alloy powder.

3. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 1, characterized in that, The second cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 20%~30% Ni, 20%~25% Cr, 18%~22% W, 5%~8% Mo, 2%~5% Al, with the balance being Co; the amount of the second reinforcing phase is 13wt%~17wt% of the second cobalt-based alloy powder.

4. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 1, characterized in that, The third cobalt-based alloy powder comprises the following elements by weight percentage: 0.05%~0.15% C, 18%~24% Ni, 18%~22% Cr, 18%~24% W, 6%~10% Mo, 3%~7% Al, 0.3%~0.6% Y, with the balance being Co; the amounts of hafnium carbide (HfC) and rare earth oxides in the third reinforcing phase are 18wt%~22wt% and 5wt%~8wt% of the third cobalt-based alloy powder, respectively; the amount of additives is 2wt%~4wt% of the third cobalt-based alloy powder.

5. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 1, characterized in that, The specific steps of the laser gradient cladding method include: The raw material for the base coating is deposited on the surface of the furnace roller substrate by laser cladding and cooled to below 200°C to form the base coating. The raw material for the intermediate coating is deposited on the base coating by laser cladding and then cooled to below 200°C to form the intermediate coating. The raw material for the surface coating is deposited onto the intermediate coating using laser cladding to form the surface coating. The material is transferred into a preheated argon-protected furnace and cooled to room temperature at a rate of ≤50℃ / h to form a composite coating. When preparing the intermediate and top coatings using the laser gradient cladding method, the laser power is 4000W~4500W, and a rectangular spot is used.

6. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 1, characterized in that, The strengthening process includes laser shock peening and ultrasonic rolling.

7. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 6, characterized in that, The conditions for laser shock peening include: pulse energy = 5J~10J, spot size Ø = 1mm~5mm, overlap rate = 40%~60%, and number of shocks = 2~5.

8. The method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 6, characterized in that, The conditions for ultrasonic rolling include: ultrasonic frequency = 15kHz~25kHz, static pressure 300N~500N, rolling times = 2~5 times; feed speed = 0.05mm / r~0.15mm / r; and the surface roughness Ra after ultrasonic rolling ≤ 0.2μm.

9. A method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to claim 6, characterized in that, The strengthening process also includes surface machining, which makes the surface roughness Ra ≤ 3.2 μm before laser shock strengthening.

10. The laser cladding wear-resistant coating obtained by the method for preparing a laser cladding wear-resistant coating for the surface of a furnace roller according to any one of claims 1 to 9.

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