A method of spraying an anti-stick coating on a roll surface

Abstract

The present application relates to the technical field of copper processing, and particularly relates to a spraying method of a roll surface anti-adhesion coating, which comprises the following steps: after cleaning the roll, performing sand blasting roughening treatment and cleaning, then preheating the roll to 80-90 DEG C; spraying a chromium alloy powder on the rotating roll surface to form a transition layer by using plasma spraying, and then tempering; preparing a composite powder comprising 70-80wt% ceramic phase powder, 20-30wt% anti-adhesion powder and 3-5wt% friction-reducing powder; performing axial gradient spraying of the composite powder on the surface of the transition layer by using plasma spraying, so as to obtain a functional layer which is thicker in the middle region than in the two end regions; performing gradient heat treatment on the roll under inert gas protection, and after cooling, performing grinding and polishing on the functional layer, so as to obtain a product; through reasonable material selection, gradient spraying process and appropriate heat treatment, the anti-copper adhesion performance, the bonding strength and the service life of the coating are effectively improved, so as to meet the use requirements of the roll for copper processing.

Description

Technical Field

[0001] This invention relates to the technical field of copper processing, and in particular to a method for spraying an anti-adhesion coating on the surface of a rolling mill roll. Background Technology

[0002] Copper and copper alloys have excellent ductility and fluidity. During cold rolling, under the action of high rolling force and frictional temperature rise, copper atoms tend to migrate to the surface of the rolls and form a firm adhesion, which is called roll sticking. Roll sticking can cause defects such as scratches, pits and copper nodules on the surface of copper materials. In severe cases, it is necessary to stop the machine to clean the rolls, which not only reduces the product qualification rate, but also reduces production efficiency and increases processing costs due to frequent machine stoppages.

[0003] In existing technologies, roll coatings prepared using plasma spraying have the following problems: Some plasma-sprayed coatings, due to the strong affinity of the selected spraying material for copper, result in significant adhesion between the roll surface and the copper material. During rolling, the copper easily sticks to the roll surface. Furthermore, the lack of effective anti-adhesion components in the coating further exacerbates the sticking problem. Additionally, some plasma-sprayed coatings have insufficient bonding with the roll substrate, leading to low bonding strength. Under the alternating stress during rolling, the coating is prone to cracking and peeling, severely affecting the roll's service life.

[0004] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the present invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0005] To solve the above-mentioned technical problems, the present invention provides a spraying method for an anti-adhesion coating on the surface of a roll. By selecting appropriate materials, using a gradient spraying process and appropriate heat treatment, the anti-copper adhesion performance, bonding strength and service life of the coating are effectively improved to meet the requirements of rolls used in copper processing.

[0006] The present invention provides a method for spraying an anti-adhesion coating on a roll surface, comprising:

[0007] After cleaning the rolls in step S1, the rolls are roughened by sandblasting and then preheated to 80-90°C. More specifically, the rolls in this step are plain rolls without any coating. Sandblasting roughens the rolls to form a mechanical anchoring structure that enhances the interfacial bonding force. Preheating to 80-90°C can improve the deposition activity and provide a clean and high-energy surface for subsequent spraying.

[0008] S2 employs plasma spraying to coat chromium-containing alloy powder onto the surface of a rotating roll to form a transition layer, followed by tempering. More specifically, plasma spraying allows for uniform deposition of the chromium-containing alloy, and the resulting α-Cr solid solution can regulate the coefficient of thermal expansion, filling the thermal mismatch between the roll substrate and the functional layer. Tempering eliminates residual stress from the spraying process and simultaneously generates a nano-Cr2O3 sealing film, which synergistically inhibits interfacial oxidation and significantly improves the bonding strength.

[0009] More specifically, the parameters for plasma spraying are: spraying power 30-40kW, plasma gas is Ar+H2, Ar flow rate 30-50L / min, H2 flow rate 3-8L / min, spraying distance 100-130mm, roller rotation speed 4-8r / min, and axial movement speed 80-120mm / min.

[0010] S3 prepares a composite powder comprising 70–80 wt% ceramic phase powder, 20–30 wt% anti-adhesion powder, and 3–5 wt% friction-reducing powder; more specifically, the preparation method of the composite powder is as follows:

[0011] Weigh the above substances according to the proportion, and ball mill them in a planetary ball mill at a speed of 200-300 r / min with anhydrous ethanol as the medium for 2-4 hours. After mixing evenly, dry and sieve.

[0012] S4 employs plasma spraying to apply composite powder in an axial gradient onto the transition layer surface, resulting in a functional layer that is thicker in the central region than at both ends. More specifically, the central region, as the main rolling zone, experiences more intense rolling forces and wear. The thicker coating increases the overall bending strength by increasing the material thickness. Simultaneously, the higher temperatures in the subsequent gradient heat treatment generate pre-stress in the central region to compensate for the stress during operation, enhancing its resistance to deformation. The rolling stress at both ends is lower, and the thinner coating avoids stress concentration caused by material redundancy, reducing the risk of cracking.

[0013] During the spraying process, the composite powder can be uniformly combined in a molten or semi-molten state, ensuring the synergistic distribution of the rigid skeleton of the ceramic phase, the anti-adhesion powder and the friction-reducing powder. This not only preserves the high hardness of the ceramic phase and the Cr2O3 passivation film formation potential of the anti-adhesion powder, but also allows MoS2 to uniformly fill the micropores.

[0014] More specifically, the parameters for plasma spraying are: spraying power 40-50kW, plasma gas is Ar+H2, Ar flow rate 30-50L / min, H2 flow rate 5-12L / min, spraying distance 100-150mm, and roller rotation speed 4-10r / min.

[0015] Under S5 inert gas protection, the rolls undergo gradient heat treatment, and after cooling, the functional layer is ground and polished to obtain the product. More specifically, in this step, the inert gas can significantly reduce the oxygen concentration in the environment, preventing MoS2 in the composite powder from being oxidized to MoO3 at high temperature due to excessive oxygen. At the same time, it avoids the excessive oxidation of elements such as Cr and Fe in the anti-adhesion powder to form a loose oxide layer, which would damage the density of the Cr2O3 passivation film. The trace oxygen retained in the low-oxygen environment can meet the requirements of the anti-adhesion powder to form a Cr2O3 passivation film during gradient heat treatment. The Cr2O3 film generated by the reaction of Cr with trace oxygen is dense and stable, which can block the diffusion and adhesion of copper atoms.

[0016] Metallurgical interlocking is formed by driving the diffusion of chromium from the transition layer to the functional layer through gradient heat treatment.

[0017] More specifically, polishing is performed until the surface roughness Ra is at most 0.1 μm.

[0018] As a preferred embodiment of the present invention, the chromium-containing alloy powder is one of NiCr, CoCrAlY or FeCrNi and ZrO2, wherein ZrO2 is partially stabilized zirconium oxide and accounts for 5-8 wt% of the chromium-containing alloy powder.

[0019] More specifically, NiCr, CoCrAlY, and FeCrNi are all high-chromium alloys that can stably form α-Cr solid solutions, regulating the coefficient of thermal expansion to compensate for the thermal mismatch between the roll steel matrix and the functional layer; the particle size of NiCr, CoCrAlY, or FeCrNi is 20-45μm, which is suitable for plasma spraying process, allowing the powder to fully melt and deposit uniformly during spraying, forming a transition layer of uniform thickness;

[0020] The ZrO2 added to the transition layer and the ZrO2 in the Al2O3-ZrO2 ceramic phase of the functional layer are both partially stabilized zirconia. The ZrO2 added to the transition layer has a particle size of 1-3 μm, which can be uniformly filled into NiCr, CoCrAlY or FeCrNi, improving dispersibility and providing more channels for subsequent chromium diffusion.

[0021] As a preferred embodiment of the present invention, the ceramic phase powder is an Al2O3-ZrO2 composite powder, wherein ZrO2 is partially stabilized zirconium oxide, and ZrO2 accounts for 25-35 wt% of the ceramic phase powder;

[0022] More specifically, Al2O3 provides basic wear resistance for the functional layer with its high hardness, resisting the scratching and wear during copper rolling. Partially stabilized ZrO2 absorbs stress through a controllable phase transformation toughening effect, making up for the brittle defects of ceramic materials, inhibiting crack propagation, and avoiding thermal shock cracking.

[0023] More specifically, the particle size of Al2O3 is 10-20μm. The skeleton formed by the composite of Al2O3 and ZrO2 can not only support the anti-adhesion powder and the friction-reducing powder, preventing the particles from falling off or being crushed under high pressure, but also work synergistically with the Cr2O3 passivation film formed by the anti-adhesion powder and the friction-reducing effect of MoS2. While ensuring wear resistance, it buffers rolling stress and reduces the impact of frictional heat, thereby enhancing the comprehensive performance of the functional layer. Combined with the metallurgical interlocking structure formed by the transition layer, it improves the overall stability of the coating.

[0024] More specifically, the ZrO2 particle size in the Al2O3-ZrO2 ceramic phase is 20-40 μm, and the ZrO2 composition forms a continuous gradient from the transition layer to the functional layer, avoiding stress concentration caused by abrupt changes in interface composition.

[0025] As a preferred embodiment of the present invention, the anti-adhesion powder is one of 316L stainless steel powder or 17-4PH powder with a Cr content >15wt%, and the particle size is 20-35μm.

[0026] More specifically, the high chromium content of 316L stainless steel powder and 17-4PH powder provides a sufficient Cr source for the formation of Cr2O3 passivation film during gradient heat treatment. The Cr2O3 passivation film has high chemical stability and weak affinity for copper, which can effectively block the diffusion and adhesion of copper atoms.

[0027] As a preferred embodiment of the present invention, the friction-reducing powder is MoS2 with a particle size of 2-5 μm;

[0028] More specifically, the ultrafine particle size of 2–5 μm can efficiently fill the micropores formed by the accumulation of ceramic phase skeleton, and remain stably inside the functional layer through mechanical anchoring, avoiding extrusion under high pressure rolling; the layered crystal structure of MoS2 can significantly reduce the coefficient of friction through shear slip, reduce the frictional heat between the roll and the copper material, thereby inhibiting the rupture of the Cr2O3 passivation film and thermal shock cracking of the ceramic phase caused by high temperature; at the same time, the soft properties of MoS2 complement the metallic phase plasticity of the anti-adhesion powder, and it is not easily crushed by high pressure under the support of the anti-adhesion powder, thus continuously playing a friction-reducing role.

[0029] As a preferred embodiment of the present invention, the middle region accounts for 70-80% of the roll body, the two end regions account for 15-20% of the roll body, and the remaining region is a transition region connecting the middle region and the two end regions, and the thickness of the functional layer gradually changes in the transition region.

[0030] More specifically, the middle section, as the main rolling zone, bears the most intense rolling force and frictional wear. A thicker coating is applied to the larger middle section to increase bending strength and, in conjunction with subsequent gradient heat treatment, generate pre-stress to compensate for working stress. The rolling loads at both ends are smaller, and a thinner coating with a moderate proportion can avoid stress concentration caused by material redundancy and reduce the risk of edge cracking. The thickness of the transition zone gradually changes, so that the coating performance and residual stress form a continuous transition, eliminating the interface abruptness caused by the division of the zones and avoiding the generation of stress concentration points.

[0031] As a preferred embodiment of the present invention, the gradient heat treatment method is as follows: holding at 200-250℃ for 1-2 hours, raising the temperature to 350-400℃ and holding for 1-2 hours, and then holding at 500-550℃ with gradient temperature control for 1-2 hours.

[0032] More specifically, the residual stress generated by spraying is slowly released at 200–250℃ to prevent the coating from cracking due to stress concentration; the initial diffusion of elements at the interface between the transition layer and the functional layer is promoted at 350–400℃; and at 500–550℃, the diffusion of chromium from the transition layer to the functional layer is driven to form a continuous concentration gradient to achieve metallurgical interlocking, while the anti-adhesion powder is promoted to form a dense Cr2O3 passivation film. At the same time, the gradient temperature control allows the central region to undergo sufficient phase transformation and diffusion.

[0033] As a preferred embodiment of the present invention, the gradient temperature control method is as follows: the temperature in the middle region is 10-20°C higher than that in the two end regions, and the temperature in the transition region changes gradually.

[0034] More specifically, the central region has a thicker functional layer and is the main rolling zone. The higher temperature in this region promotes more complete diffusion of chromium, forming a more continuous chromium concentration gradient to strengthen metallurgical interlocking. At the same time, it generates more pre-stress to compensate for the main stress during operation. The functional layers at both ends are thinner, and the lower temperature can avoid material embrittlement caused by excessive diffusion and reduce edge stress concentration. The temperature gradient in the transition region corresponds to the gradual change in the thickness of the functional layer, achieving a continuous transition in the degree of chromium diffusion and stress distribution. This avoids the generation of new stress concentration points due to abrupt temperature changes, thus enabling the gradient heat treatment and the gradient structure of the functional layer to work synergistically and improve the structural stability of the functional layer.

[0035] As a preferred embodiment of the present invention, the thickness of the transition layer is 30-50 μm, the thickness of the functional layer in the two end regions is 80-100 μm, the thickness of the functional layer in the middle region is 120-140 μm, and the thickness of the functional layer in the transition region gradually changes.

[0036] More specifically, the thickness of the transition layer is controlled at 30-50μm, which can provide sufficient space for the α-Cr solid solution formed by chromium alloy powder, adjust the difference in thermal expansion coefficients with the roll steel substrate and ceramic functional layer, and generate a complete Cr2O3 sealing film in the layer and on the surface through tempering treatment, effectively inhibiting interface oxidation.

[0037] The functional layer thickness at both ends is 80-100μm. The lower limit of 80μm can meet the basic wear resistance requirements and ensure that the two ends have a certain structural strength to resist edge friction. The upper limit of 100μm avoids material redundancy by moderately thinning the layer and reduces stress abrupt changes caused by excessive thickness difference between the two ends and the middle area.

[0038] The thickness of the functional layer in the middle region is 120-140 μm. The lower limit of 120 μm increases the overall bending strength by increasing the material thickness, providing sufficient structural support to resist the severe pressure and wear during rolling. The upper limit of 140 μm, on the basis of increased thickness, is combined with high-temperature gradient heat treatment to promote the formation of more Cr2O3 passivation film and enhance the surface anti-adhesion performance.

[0039] As a preferred embodiment of the present invention, the tempering method is as follows: tempering at 300-350°C for 1-2 hours in an inert atmosphere.

[0040] More specifically, an inert atmosphere can prevent the transition layer from being over-oxidized and contaminated during tempering, allowing chromium to participate in the formation of the Cr2O3 film in a directional manner; the temperature range of 300-350℃ can activate the diffusion of chromium in chromium-containing alloys, promote the uniform precipitation of nano-sized Cr2O3 particles in the layer and on the surface, forming a dense sealing film to block the penetration of corrosive media, and also avoid excessively high temperatures that could lead to coarse grains in the transition layer or a decrease in the bonding force with the substrate.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows: The transition layer serves as a connecting layer between the roll steel substrate and the ceramic functional layer. The α-Cr solid solution formed by chromium and ZrO2 regulate the coefficient of thermal expansion, filling the thermal mismatch difference between the roll steel substrate and the ceramic functional layer. Combined with the nano-Cr2O3 sealing film generated by sandblasting anchoring and tempering, it synergistically inhibits interface oxidation, thereby greatly improving the bonding strength. Furthermore, the micro-grain boundary network formed by ZrO2 added to the transition layer provides a rapid migration channel for chromium, driving chromium to diffuse directionally into the functional layer to promote the formation of a continuous Cr2O3 passivation film, blocking the penetration path of copper atoms. With the help of the cross-scale lattice connection and phase transformation volume expansion effect of ZrO2 in the functional layer, a pre-compression stress field is formed in the interface region, which simultaneously improves the bonding strength and anti-stripping ability.

[0042] In the functional layer, the ceramic phase powder forms a rigid skeleton, resisting copper wear through high hardness and the toughening effect of ZrO2 phase transformation. Its micropores are filled with MoS2 lubricant and mechanically anchor high-chromium stainless steel anti-adhesion powder. The anti-adhesion powder forms a low surface energy Cr2O3 passivation film under the activation of rolling heat to block the diffusion and adhesion of copper atoms. At the same time, the plastic deformation of the metallic phase buffers the stress and supports the soft MoS2 particles to prevent high pressure crushing. MoS2 greatly reduces the friction coefficient through layered shear slip, significantly inhibiting the Cr2O3 film rupture and ceramic phase thermal shock cracking caused by frictional heat.

[0043] Due to the concentration difference of chromium between the transition layer and the functional layer, gradient heat treatment drives the chromium in the transition layer to diffuse directionally into the functional layer, forming a continuous chromium concentration gradient and realizing interlayer metallurgical interlocking. At the same time, the Cr2O3 film in the transition layer and the Cr2O3 generated in situ by the stainless steel in the functional layer are seamlessly connected to form an inert barrier, completely blocking the cross-layer penetration of copper atoms.

[0044] Based on the stress distribution characteristics of the rolls, the thickened coating in the middle improves the bending strength while matching the high-temperature treatment to generate pre-compression stress to compensate for the working stress; the thinning design at the edges avoids stress concentration, and the synchronous stepped cooling prevents embrittlement; the gradual transition zone realizes the continuous distribution of residual stress, which makes the overall anti-peeling performance of the coating leap forward. Attached Figure Description

[0045] Figure 1 This is a schematic flowchart of a method for spraying an anti-adhesion coating on the surface of a roll according to the present invention. Detailed Implementation

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0048] The sources of materials in the specific implementation are shown in the table below:

[0049] Table 1: Sources of Materials

[0050]

[0051]

[0052] The rolls used in the embodiments and comparative examples are all rolled steel with a diameter of 300 mm and a length of 1200 mm. The material is GCr15 bearing steel and there is no coating on the surface.

[0053] Both the examples and comparative examples underwent the following tests:

[0054] (a) Copper adhesion amount: Simulating actual rolling conditions, after continuously rolling 50km of copper strip, the copper adhesion amount on the surface of the functional layer of the roll was determined by inductively coupled plasma mass spectrometry. The specific method is as follows: the roll surface is pretreated to ensure that the test area is clean and free of interference. Several representative test points are selected, and the adhesion on the surface of the functional layer is scraped or dissolved with a special tool. The collected samples are then subjected to specific chemical treatment and introduced into the inductively coupled plasma mass spectrometer for analysis.

[0055] (b) Functional layer bond strength test: Refer to ASTM C633-13 "Standard Test Method for Adhesion or Bond Strength of Thermally Sprayed Coatings" and use the tensile peel test. The specific method is as follows: use high-strength structural adhesive to bond the surface of the functional layer of the sample to the tension bar of the tensile fixture, cure for 24 hours, fix the sample on the universal testing machine, apply axial tensile force at a tensile speed of 5 mm / min until the functional layer peels off, and record the maximum tensile force value; Bond strength = maximum tensile force / coating bonding area (unit: MPa).

[0056] (c) Hardness test of the middle part of the roll: According to GB / T4340.1-2009 "Metallic materials Vickers hardness test - Part 1: Test method", a microhardness tester (load 100g, holding pressure 15s) was used to test 5 points in the middle part of the functional layer and the average value was taken (unit: HV).

[0057] Example 1

[0058] A method for spraying an anti-adhesion coating on a roll surface includes the following steps:

[0059] S1 roll pretreatment:

[0060] The surface of the roll was ultrasonically cleaned with anhydrous ethanol for 30 minutes to remove oil and impurities. After drying, a smooth roll was obtained.

[0061] The surface of the roll is sandblasted and cleaned using 80-mesh brown corundum sand under a pressure of 0.5 MPa to form a surface structure with a roughness of 5-8 μm.

[0062] The sandblasted roll is placed in a heating furnace and heated to 85°C at a rate of 5°C / min, and held at that temperature for 30 min.

[0063] S2 is used to prepare the transition layer:

[0064] Atmospheric plasma spraying equipment is used, with a spraying power of 35kW, plasma gas of Ar+H2, Ar flow rate of 40L / min, H2 flow rate of 5L / min, spraying distance of 120mm, roller rotation speed of 5r / min, and axial movement speed of 100mm / min.

[0065] The transition layer is a composite powder of NiCr alloy powder and ZrO2, wherein ZrO2 is 8wt% Y2O3 partially stabilized zirconium oxide, accounting for 6wt% of the total mass of the composite powder, and the remaining 94wt% is NiCr alloy powder, wherein the Cr content is 25wt% and the Ni content is 75wt%, the particle size of NiCr alloy powder is 30μm, and the particle size of ZrO2 is 2μm.

[0066] A transition layer with a thickness of 40 μm is uniformly deposited on the surface of the roll using the above plasma spraying parameters.

[0067] The rolls for depositing the transition layer were placed in an argon-protected furnace and heated to 320°C at a rate of 10°C / min, held at that temperature for 1.5 hours, and then cooled to room temperature with the furnace.

[0068] S3 preparation of composite powder:

[0069] Raw material ratio: 75wt% ceramic phase powder, 22wt% anti-adhesion powder, 3wt% friction-reducing powder;

[0070] Ceramic phase powder: Al2O3-ZrO2 composite powder (Al2O3 accounts for 70wt%, ZrO2 accounts for 30wt%, and ZrO2 is 8wt% Y2O3 partially stabilized zirconia), with Al2O3 particle size of 15μm and ZrO2 particle size of 30μm;

[0071] Anti-adhesion powder: 316L stainless steel powder, with a Cr content of 18wt% and a particle size of 25μm;

[0072] Friction-reducing powder: MoS2 powder, particle size 3μm.

[0073] The above raw materials were added to a planetary ball mill, anhydrous ethanol was used as the medium, the solid-liquid ratio was 1:1, the ball milling speed was 250 r / min, and the ball milling time was 3 h. After mixing, the mixture was dried in an oven at 80℃ and passed through a 500-mesh sieve to obtain composite powder.

[0074] S4 functional layer spraying:

[0075] Atmospheric plasma spraying equipment was used, with the following parameters: spraying power 45kW, plasma gas Ar+H2, Ar flow rate 40L / min, H2 flow rate 8L / min, spraying distance 130mm, and roller rotation speed 5r / min.

[0076] The composite powder from step S3 is fed into the flame through a powder feeder at a powder feeding rate of 50g / min, and axially gradient sprayed on the surface of the transition layer to form a continuous functional layer.

[0077] The final rolls obtained are as follows:

[0078] Central region: accounting for 70%, located in the 200-1040mm section of the roller body, with a coating thickness of 130μm;

[0079] Both ends: each accounting for 11.7%, located in the 0-140mm and 1080-1200mm sections of the roller body, with a coating thickness of 90μm;

[0080] Transition region: each accounts for 3.3%, located in the 140-200mm and 1040-1080mm segments, with the thickness gradually changing from 90μm to 130μm.

[0081] S5 gradient heat treatment and post-treatment:

[0082] Place the rolls in an argon-protected furnace and process them according to the following steps:

[0083] First stage: Increase the temperature to 220℃ at a rate of 5℃ / min and hold for 1.5 hours;

[0084] Second stage: Continue to raise the temperature to 380℃ and keep it warm for 1.5 hours;

[0085] The third stage: the temperature is raised to 500-550℃ with gradient temperature control, with the central area at 530℃, the two end areas at 515℃, and the transition area changing linearly with position, and the temperature is maintained for 1.5 hours.

[0086] Cooling: Cool to room temperature with the furnace.

[0087] The functional layer of the cooled roll is ground and polished, and the final thickness of the functional layer is: 120μm in the middle, 80μm at both ends, with a gradual transition area and a surface roughness Ra0.1μm.

[0088] Example 2

[0089] Unlike Example 1, the raw material for the transition layer in Example 2 is a composite powder of CoCrAlY alloy powder and ZrO2. The ZrO2 is 8wt% Y2O3 partially stabilized zirconium oxide, accounting for 7wt% of the total mass of the transition layer, and the remaining 93wt% is CoCrAlY alloy, with Cr content of 30wt%, Co content of 60wt%, Al content of 10wt%, and Y content of 5wt%. The particle size of the CoCrAlY alloy powder is 30-40μm, and the particle size of ZrO2 is 1.5μm.

[0090] Example 3

[0091] Unlike Example 1, the ratio of the composite powder was changed as follows:

[0092] Raw material ratio: 70wt% ceramic phase powder, 27wt% anti-adhesion powder, 3wt% friction-reducing powder;

[0093] Ceramic phase powder: Al2O3-ZrO2 composite powder (Al2O3 accounts for 75wt%, ZrO2 accounts for 25wt%, ZrO2 is 8wt% Y2O3 partially stabilized zirconia), Al2O3 particle size is 18μm, ZrO2 particle size is 30μm;

[0094] Anti-adhesion powder: 316L stainless steel powder, with a Cr content of 18wt% and a particle size of 30μm;

[0095] Friction-reducing powder: MoS2 powder, particle size 2.6μm.

[0096] The rolls obtained in Examples 1-3 were all subjected to tests (a)-(c), and the results are shown in Table 2:

[0097] Table 2 Test results of Examples 1-3

[0098] Example 1 Example 2 Example 3 <![CDATA[Copper adhesion amount (mg / m 2 )]]> 3.2 4.5 2.8 Functional layer bonding strength (MPa) 68 65 72 Hardness (HV) at the center of the roll 860 850 880

[0099] Examples 1-3 all performed well. The transition layer, through the α-Cr solid solution formed by the chromium alloy, regulates the coefficient of thermal expansion. Combined with the nano-Cr2O3 sealing film generated by tempering and the chromium diffusion driven by gradient heat treatment, a stable metallurgical interlocking structure is constructed, which greatly improves the bonding strength of the functional layer. The rigid skeleton formed by the ceramic phase powder in the functional layer provides a high hardness foundation. The phase transformation toughening effect of ZrO2 balances hardness and toughness. The Cr2O3 passivation film generated by the anti-adhesion powder and the friction reduction effect of MoS2 work together to effectively block the diffusion of copper atoms, keeping the amount of copper adhesion at an extremely low level. At the same time, the setting of axial gradient thickness and the gradual transition zone realize the continuous distribution of stress, further ensuring the stability of the overall performance of the coating.

[0100] Comparative Example 1:

[0101] Unlike Example 1, the transition layer preparation step is omitted, and the functional layer is directly sprayed onto the pretreated roll surface.

[0102] Comparative Example 2:

[0103] Unlike Example 1, the functional layer composite powder does not contain 316L stainless steel powder, but is replaced by ceramic phase powder in the same proportion.

[0104] Comparative Example 3:

[0105] Unlike Example 1, the gradient heat treatment in step S5 was omitted, and the temperature was maintained at a single temperature of 380°C for 4.5 hours.

[0106] The rolls obtained from Comparative Examples 1 to 3 were all subjected to tests (a)-(c), and the results are shown in Table 3:

[0107] Table 3 Test results of Comparative Examples 1-3

[0108] Comparative Example 1 Comparative Example 2 Comparative Example 3 <![CDATA[Copper adhesion amount (mg / m 2 )]]> 163 502 95 Functional layer bonding strength (MPa) 19 23 42 Hardness (HV) at the center of the roll 845 980 840

[0109] Comparative Example 1 omitted the transition layer preparation step and directly sprayed the functional layer onto the pretreated roll surface. This resulted in the inability to control the coefficient of thermal expansion through the formation of α-Cr solid solution by the chromium-containing alloy of the transition layer. It also lacked the nano-Cr2O3 sealing film generated by tempering and the metallurgical interlocking structure brought about by the diffusion of chromium. This caused the bonding between the functional layer and the roll substrate to lose its buffering and anchoring effect. The internal stress caused by the difference in thermal expansion could not be relieved, which led to a significant decrease in the bonding strength of the functional layer. At the same time, without the sealing protection of the transition layer, the surface of the functional layer was prone to micro-defects due to loose bonding. Copper atoms were more likely to adhere and diffuse, ultimately resulting in a significant increase in the amount of copper adhesion.

[0110] Comparative Example 2, due to the absence of 316L stainless steel powder in the functional layer composite powder and its substitution with ceramic phase powder, lost the Cr2O3 passivation film generated by the anti-adhesion powder. This passivation film, which could synergistically block copper atom diffusion with the friction-reducing effect of MoS2, resulted in a sharp decrease in anti-adhesion ability without it, leading to a significant increase in copper adhesion. Furthermore, although increasing the proportion of ceramic phase may slightly increase hardness, the lack of the toughness buffer of the metallic phase increases the brittleness of the functional layer, making the bonding interface prone to cracking due to stress concentration, thus reducing the bonding strength of the functional layer.

[0111] Comparative Example 3, by omitting gradient heat treatment and using only a single temperature holding at 380℃, cannot achieve gradient temperature-controlled directional diffusion of chromium, making it difficult to construct a stable metallurgical interlocking structure, resulting in a decrease in the bonding strength of the functional layer. At the same time, single-temperature treatment cannot achieve continuous stress distribution like gradient heat treatment, and stress concentration is easily generated inside the coating due to uneven temperature field, affecting the overall stability. Furthermore, the lack of precise control over the formation of oxide film at each stage during gradient heating results in insufficient integrity and density of the Cr2O3 passivation film, weakened anti-copper adhesion ability, and ultimately an increase in copper adhesion.

[0112] Comparative Example 4:

[0113] Unlike Example 1, the transition layer uses NiCr alloy powder and no ZrO2 is added.

[0114] The rolls obtained in Comparative Example 4 were all tested in (a)-(c), and the results are shown in Table 4:

[0115] Table 4 shows the test results for Comparative Example 4 and Example 1.

[0116]

[0117]

[0118] In Comparative Example 4, the absence of ZrO2 in the transition layer resulted in a lack of fine grain boundary network formed by ZrO2, leading to a decrease in the diffusion efficiency of chromium into the functional layer. This resulted in insufficient continuity of the Cr2O3 passivation film in the functional layer, making it easier for copper atoms to penetrate and adhere, thus increasing the copper adhesion amount to 42 mg / m. 2 Meanwhile, the lack of cross-scale lattice connection and synergistic regulation of thermal expansion coefficient between ZrO2 and functional layer ZrO2 leads to increased thermal mismatch stress between transition layer and functional layer, and the bonding strength drops to 48 MPa. Although it is better than Comparative Example 1 without transition layer due to the basic role of retaining NiCr alloy transition layer, it is significantly worse than Example 1 with added ZrO2, highlighting the key role of ZrO2 in improving anti-adhesion and bonding strength.

[0119] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method of spraying an anti-adhesive coating on a roll surface, characterized in that, The application relates to a method for preparing a roller for a rolling mill. The roller is preheated to 80-90 DEG C after sand blasting roughening treatment and cleaning; A transition layer is formed on the surface of the rotating roller by spraying a chromium-containing alloy powder on the surface of the roller by plasma spraying, and the transition layer is tempered; A composite powder is prepared, which comprises 70-80 wt% ceramic phase powder, 20-30 wt% anti-adhesion powder and 3-5 wt% friction-reducing powder; The composite powder is sprayed on the surface of the transition layer by axial gradient spraying to obtain a functional layer with a thicker middle region than two end regions; The roller is subjected to gradient heat treatment under inert gas protection, and the functional layer is ground and polished after cooling to obtain a product; The chromium-containing alloy powder is one of NiCr, CoCrAlY or FeCrNi and ZrO2, wherein ZrO2 is partially stabilized zirconia, and the content of ZrO2 in the chromium-containing alloy powder is 5-8 wt%; The ceramic phase powder is Al2O3-ZrO2 composite powder, wherein ZrO2 is partially stabilized zirconia; The anti-adhesion powder is one of 316L stainless steel powder with a Cr content of more than 15 wt% or 17-4PH powder, and the particle size is 20-35 mu m; The friction-reducing powder is MoS2 with a particle size of 2-5 mu m; The method of the gradient heat treatment is as follows: heat preservation at 200-250 DEG C for 1-2 h, heating to 350-400 DEG C for 1-2 h, and then gradient temperature control at 500-550 DEG C for 1-2 h; the method of the gradient temperature control is that the temperature of the middle region is 10-20 DEG C higher than that of the two end regions, and the temperature of the transition region gradually changes.

2. The method of claim 1, wherein the method is characterized by, The middle region accounts for 70-80% of the roller body, the two end regions account for 15-20% of the roller body, and the rest is a transition region connecting the middle region and the two end regions, and the thickness of the functional layer gradually changes in the transition region.

3. The method of claim 2, wherein the coating is applied by spraying. The thickness of the transition layer is 30-50 mu m, the thickness of the functional layer in the two end regions is 80-100 mu m, the thickness of the functional layer in the middle region is 120-140 mu m, and the thickness of the functional layer in the transition region gradually changes.

4. The method of claim 1, wherein the roll surface anti-adhesion coating is applied by spraying. The method of the tempering is as follows: tempering treatment at 300-350 DEG C for 1-2 h in an inert atmosphere.

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