Wear-resistant coating for inner wall of blast furnace and preparation method of wear-resistant coating

Abstract

The invention discloses a blast furnace inner wall wear-resistant coating and a preparation method thereof, and belongs to the technical field of metallurgical equipment protection. The coating is composed of nickel powder, chromium powder, molybdenum powder, niobium powder, boron powder, silicon powder, tungsten carbide powder, two innovative reinforcement phases, core-shell structure tungsten carbide boron nitride nanocapsules, yttrium-chromium-aluminum-nitrogen-oxygen high-entropy nanocrystals and yttrium oxide. The preparation process comprises the following steps: firstly, carrying out sand blasting and cleaning pretreatment on the inner wall of a blast furnace, then uniformly mixing and drying the powder mixture, cladding the powder mixture on the surface of the inner wall under the condition of controlling the temperature of a matrix by adopting a laser cladding technology, and finally, carrying out annealing treatment to obtain the compact coating. According to the method, two uniquely designed compounds are introduced, so that the wear resistance and thermal shock resistance of the coating at high temperature and the bonding strength of the coating and a matrix are remarkably improved, the service life of the inner wall of the blast furnace under harsh working conditions is effectively prolonged, and the key problem that the coating is easy to wear and peel off in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metallurgical equipment protection, and particularly relates to a blast furnace inner wall wear-resistant coating and a preparation method thereof. BACKGROUND

[0002] As the core smelting equipment of modern steel industry, the inner wall of the blast furnace is long-term operated in extremely harsh working conditions. In the continuous high-temperature environment, the inner wall surface not only has to withstand the mechanical scouring and impact of solid furnace charges such as coke and ore, but also is exposed to the chemical corrosion and abrasion of high-speed dust-containing coal gas. This multi-factor coupled damage effect makes the inner wall of the blast furnace, especially the area above the tuyere, one of the highest risk failure parts in the entire structure. The premature damage of the inner lining not only leads to production interruption and maintenance cost surge, but also can cause safety accidents, directly affecting the stability and economy of the blast furnace operation. Therefore, how to effectively improve the durability of the inner wall of the blast furnace and develop high-performance protection technology that can resist complex failure mechanisms has always been a key technical problem to be solved in the metallurgical industry.

[0003] At present, the protection of the inner wall of the blast furnace in the industry mainly relies on surface strengthening technology, among which the most widely used is the metal-based wear-resistant coating prepared by thermal spraying or laser cladding and the lining of refractory materials. Although the traditional nickel-based or cobalt-based alloy coating has certain high-temperature resistance and wear resistance, its limitations are exposed when dealing with long-term and severe thermal mechanical fatigue of the blast furnace. The hard reinforcing phase in this coating is prone to adverse interfacial reactions with the metal binder phase at high temperatures, leading to particle dissolution or the formation of brittle phases, resulting in a sharp decline in wear resistance. On the other hand, although ceramic coatings have excellent hardness, their inherent intrinsic brittleness makes them extremely sensitive to thermal shock and mechanical impact, and cracks are easily generated and propagated, eventually leading to large-area peeling of the coating. In addition, whether using physical unblocking methods such as air cannons and bin wall vibrators or mechanical modifications such as spiralization of the bin structure, only temporary relief or local improvement of the problem can be achieved, and the root cause of material freezing and bin wall wear cannot be fundamentally blocked. The existing single reinforcing phase coating system is difficult to achieve synergistic optimization in terms of high-temperature hardness, toughness, thermal shock resistance and bonding strength with the substrate, and often compromises one for the other, which is the core bottleneck of the current technology.

[0004] In summary, the existing blast furnace inner wall protection technology has the fundamental problem that the design of the coating material system fails to achieve coordinated adaptability to complex working conditions. The main problems are as follows: the chemical instability of traditional reinforcing phases at high temperatures leads to insufficient wear resistance; the physical properties of the components in the coating and the interface between the coating and the substrate are not matched, which causes weak interface bonding and stress concentration; the material system lacks a dissipation mechanism for thermal shock load, and has poor anti-peeling ability. These defects together make it difficult for the existing protection scheme to meet the demand for long-term, high-efficiency and safe operation of the blast furnace. Therefore, the industry is in urgent need of a new coating design concept and material system that can break through the shackles of existing technology, develop a high-performance wear-resistant coating that integrates ultra-high wear resistance, excellent toughness, excellent thermal shock resistance and firm interface bonding through innovation of material composition and fine control of structure, and thus provide reliable technical support for the long-term and stable operation of the blast furnace. SUMMARY

[0005] The purpose of the present application is to provide a blast furnace inner wall wear-resistant coating and a preparation method thereof, which solves the technical problems of the existing blast furnace inner wall, such as high-temperature dissolution and oxidation of hard phases in traditional wear-resistant coatings, insufficient toughness leading to easy cracking, and weak interface bonding leading to easy peeling under high-temperature, material scouring and thermal shock conditions.

[0006] The present application achieves the above-mentioned purpose by the following technical solutions: A preparation method of a blast furnace inner wall wear-resistant coating, comprising the following steps: S1, sandblasting treatment is performed on the surface of the blast furnace inner wall, brown corundum sand is used, the cleanliness of the surface of the blast furnace inner wall reaches Sa3.0 level, the roughness reaches Ra 40 μm, then the surface is ultrasonically cleaned with acetone and ethanol and dried to obtain a pretreated blast furnace inner wall surface; nickel powder, chromium powder, molybdenum powder, niobium powder, boron powder, silicon powder, tungsten carbide powder, core-shell structure tungsten carbide / boron nitride nanocapsule, yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal and yttrium oxide powder are mixed in a mixer to obtain a mixed powder; S2, the mixed powder is vacuum dried at 140-160℃, and then laser cladding is performed on the pretreated surface of the blast furnace inner wall using a laser; during the cladding process, the surface temperature of the blast furnace inner wall is controlled at 250-300℃ by an auxiliary cooling system; after the cladding is completed, the surface coating of the blast furnace inner wall is annealed, heated to 640-660℃ under argon protection, and then cooled to room temperature in the furnace.

[0007] In the present application, the preparation of the wear-resistant coating on the inner wall of the blast furnace is a process of surface metallurgy realized by laser cladding technology, and its mechanism involves the complex coupling of multiple stages such as rapid melting, physical and chemical reactions, and solidification crystallization. The whole process starts from the interaction of laser beam and powder and substrate. When the high-energy-density laser beam scans the mixed powder layer prepositioned or synchronously delivered, the light energy is quickly absorbed and converted into heat energy, causing the powder particles and the substrate surface layer to melt instantaneously, forming a tiny molten pool. In this molten pool, a series of key physical and chemical changes occur: the nickel-chromium alloy powder is first melted to form a liquid metal binder phase; the tungsten carbide powder partially dissolves in the molten nickel matrix, changing the composition of the melt; and the two key nanomaterials, the core-shell structure tungsten carbide boron nitride nanocapsule and yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal, maintain their solid-state structure as much as possible and disperse uniformly in the molten pool as strengthening phases. Among them, the boron nitride shell effectively protects the internal tungsten carbide core, preventing its excessive dissolution and loss of carbon elements; and the high-entropy nanocrystal, due to its high thermal stability, can still maintain its nanoscale and stable chemical composition in the high-temperature melt, becoming the core of heterogeneous nucleation in the solidification process, effectively refining the microstructure of the coating. Subsequently, after the laser beam moves away, the molten pool begins to rapidly solidify. This is a rapid cooling process far from equilibrium, and the metal elements in the melt use the dissolved tungsten carbide and niobium, molybdenum, etc. as strengthening sources to precipitate various complex carbide and boride hard phases, together with the unmelted tungsten carbide particles and the two nanometer reinforcing phases to form a multi-scale reinforcing network, which is firmly bonded together by the rapidly solidified nickel-based solid solution. At the same time, the yttrium oxide and the yttrium element in the high-entropy nanocrystal are enriched at the solid-liquid interface, reducing the interfacial energy of the solidification front through adsorption effect, refining the dendrites, and improving the wettability of the melt to the substrate and reinforcing phase, thereby realizing the firm metallurgical bonding between the coating and the substrate, rather than simple mechanical bonding. Finally, through precise annealing treatment, the internal stress generated in the coating during rapid solidification is effectively eliminated, part of the metastable phase is transformed into stable phase, the organization becomes more uniform and stable, the crack sensitivity is significantly reduced, and finally the coating becomes a dense, uniform, high internal bonding strength and firmly bonded to the substrate metal matrix composite system, which exhibits extraordinary wear resistance, thermal shock resistance and high-temperature oxidation resistance.

[0008] According to the preferred embodiment of the present application, in step S1, the mixing time is 6-8h.

[0009] According to the preferred embodiment of the present application, in step S2, the holding time is 2-4h.

[0010] According to the preferred embodiment of the present application, the preparation method of the core-shell structure tungsten carbide / boron nitride nanocapsule comprises: A1, placing tungsten carbide powder in a fluidized bed chemical vapor deposition reactor, and raising the bed temperature to 840-860 DEG C under the protection of argon; mixing borane-ammonia complex with ammonia gas and then feeding into the reactor to deposit a BN shell layer on the surface of WC; A2, after the deposition is completed, cooling to room temperature under the protection of argon.

[0011] In the present application, the core of the preparation of the core-shell structure tungsten carbide / boron nitride nanocapsule lies in that a complete, dense and firmly bonded boron nitride shell layer is grown in situ on the surface of the previously prepared tungsten carbide core particle by using chemical vapor deposition technology. The reaction mechanism starts from the accurate delivery and thermal decomposition of the precursor. The borane-ammonia complex is fed into a high-temperature reactor together with excess ammonia gas. After reaching the set temperature, the borane-ammonia complex molecules absorb energy, and their molecular structure becomes unstable, and chemical bonds such as ammonia boron bonds are broken, releasing active intermediate species containing boron and nitrogen. These active boron and nitrogen atoms or groups, together with the active nitrogen atoms generated by the pyrolysis of the simultaneously fed ammonia gas, constitute the film-forming "building blocks" diffused in the gas phase. Subsequently, these highly active boron and nitrogen atoms or groups are transported to the surface of the suspended tungsten carbide particles by diffusion and are adsorbed thereon. Under the catalytic action of the heterogeneous nucleation substrate provided by the tungsten carbide particles, the adsorbed boron and nitrogen atoms are orderly arranged and bonded according to the crystal structure of boron nitride (usually amorphous or turbulent layer structure), gradually nucleate and grow laterally, and finally connect to form a complete coating layer. In this process, ammonia not only participates in the reaction as a nitrogen source, but also provides a reducing atmosphere that effectively prevents the oxidation of the tungsten carbide core at high temperature. The strong covalent bond structure and dense characteristics of the formed boron nitride shell layer enable it to act as an ideal diffusion barrier under the extreme high-temperature environment of subsequent laser cladding, effectively blocking the element interdiffusion between the molten nickel-based alloy binder phase and the tungsten carbide core, thereby avoiding the generation of brittle intermetallic compounds. At the same time, its excellent high-temperature stability also ensures that the tungsten carbide core is immune to dissolution and instability, perfectly combining the hard and wear-resistant properties of the core with the high-temperature resistance and corrosion resistance of the shell layer.

[0012] According to the preferred embodiment of the present application, the molar ratio of borane-ammonia complex to ammonia gas is 1:15.

[0013] According to the preferred embodiment of the present application, the time for depositing the BN shell layer on the surface of WC is 90-120 min.

[0014] According to the preferred embodiment of the present application, the preparation method of the yttrium chromium aluminum nitrogen-oxygen high-entropy nanocrystal comprises: B1, placing metal powders of Y, Cr and Al in a ball mill together with anhydrous ethanol and zirconium oxide grinding balls, and ball milling under argon protection to obtain Y-Cr-Al amorphous pre-alloy slurry; drying the Y-Cr-Al amorphous pre-alloy slurry in a vacuum drying box at 58-62°C to obtain pre-alloy powder; B2, placing the pre-alloy powder in a tube furnace, heating to 1080-1120°C under a nitrogen atmosphere, and holding to obtain Y-Cr-Al-N nitride high-entropy phase powder; cooling the Y-Cr-Al-N nitride high-entropy phase powder to 500-600°C under a nitrogen atmosphere, then introducing nitrogen-oxygen mixed gas, holding, and then cooling to room temperature under a nitrogen atmosphere.

[0015] In the present application, the synthesis of yttrium chromium aluminum oxynitride high-entropy nanocrystalline is a multi-step solid-phase reaction process based on the design concept of high-entropy alloy, and the core mechanism is to use extremely high configuration entropy to drive and stabilize the formation of single-phase solid solution. The preparation process first realizes the atomic-level uniform mixing and alloying of elements through high-energy mechanical ball milling. After mixing yttrium, chromium and aluminum metal powder in equal molar ratio and high-energy ball milling for a long time, the violent collision between the milling balls and the powder produces a huge energy, which on the one hand constantly breaks and cold-welds the powder particles, making them finer; on the other hand, the severe plastic deformation introduces high-density crystal defects into the powder and significantly increases the energy storage of the system, which greatly reduces the activation energy of the solid-state diffusion reaction between elements, and finally promotes the mutual solid solution of three kinds of atoms to form a composition-uniform amorphous or nanocrystalline pre-alloy powder, which lays a uniform composition foundation for the subsequent formation of high-entropy phase. Subsequently, the pre-alloy powder is subjected to high-temperature nitriding treatment in a pure nitrogen atmosphere. At high temperature, nitrogen molecules decompose to form active nitrogen atoms, which diffuse into the loose structure of the amorphous pre-alloy and react with yttrium, chromium, aluminum and other metal atoms to form metal nitrides. Due to the high-entropy effect, i.e. the high mixing entropy generated by multiple main element elements occupying lattice sites, it is enough to offset the small positive value of the mixing enthalpy between different nitrides, thereby driving these nitrides to mutually solidify and form a single face-centered cubic or body-centered cubic structure of nitride high-entropy phase, rather than a simple mixture of multiple nitrides. Finally, a controllable low concentration of oxygen is introduced at a lower temperature for oxidation treatment. At this time, oxygen does not react with all metal elements to form independent oxide phases, but selectively enters the high-entropy nitride lattice formed in the form of solid solution, partially replacing the position of nitrogen atoms or occupying interstitial positions, forming a more complex oxynitride high-entropy solid solution. The rare earth yttrium element will preferentially segregate at the grain boundaries due to its strong affinity for oxygen, which can not only purify the grain boundaries and improve the bonding force, but also further stabilize the nanocrystalline structure. Finally, a structure-stable, composition-uniform yttrium chromium aluminum oxynitride high-entropy nanocrystalline is obtained, which can play a significant role in fine-grain strengthening, solid solution strengthening and improving oxidation resistance in the coating.

[0016] According to the preferred embodiment of the present application, in step B1, the molar ratio of Y, Cr and Al is 1:1:1.

[0017] According to the preferred embodiment of the present application, in step B2, the holding time is 4-6h; the content of oxygen in the nitrogen-oxygen mixed gas is 1.5-2.5%.

[0018] The application further provides the blast furnace inner wall wear-resistant coating prepared by the preparation method of the blast furnace inner wall wear-resistant coating, which comprises the following raw materials in parts by weight: 55-65 parts by weight of nickel powder; 15-20 parts by weight of chromium powder; 5-8 parts by weight of molybdenum powder; 2-4 parts by weight of niobium powder; 1-2 parts by weight of boron powder; 0.5-1.5 parts by weight of silicon powder; 3-6 parts by weight of tungsten carbide powder; 4-8 parts by weight of core-shell structure tungsten carbide / boron nitride nanocapsule; 2-5 parts by weight of yttrium chromium aluminum oxynitride high-entropy nanocrystal; and 0.5-1.5 parts by weight of yttrium oxide.

[0019] The application has the following beneficial effects: The blast furnace inner wall wear-resistant coating and the preparation method thereof have the following advantages.

[0020] Firstly, the application realizes a major breakthrough in the high-temperature wear resistance and structural stability of the coating. By introducing the self-designed core-shell structure tungsten carbide / boron nitride nanocapsule as the core reinforcing phase, the coating exhibits excellent wear resistance under high-temperature service conditions. The unique core-shell configuration of the nanocapsule enables the hard core to continuously provide efficient wear resistance support, and the dense boron nitride shell layer wrapped outside acts as a "protective armor", effectively preventing the erosion and dissolution of the hard phase by molten metal under high-temperature conditions, and inhibiting the occurrence of harmful interfacial reactions, thereby long-term maintaining the hardness and integrity of the coating. On the other hand, the introduction of yttrium chromium aluminum oxynitride high-entropy nanocrystal improves the thermal stability of the coating from the intrinsic material. This multi-component oxynitride ceramic phase utilizes its high-entropy effect to form a stable solid solution structure at the atomic scale, greatly inhibiting the grain coarsening and phase transformation under high temperature, so that the coating can still maintain fine-grained structure and stable mechanical properties under long-term high-temperature environment. The synergistic effect of the two innovative compounds significantly reduces the wear rate of the coating when facing the high-speed solid material erosion in the blast furnace, and the service life is doubled.

[0021] Secondly, the coating of the present application exhibits excellent thermal shock resistance, toughness and interface bonding strength, solving the key problem of easy peeling of traditional coatings. The boron nitride shell in the core-shell structure not only provides protection, but also effectively passivates the micro-crack tip due to its good lubricity and moderate elastic modulus, thereby absorbing and releasing the huge thermal stress generated in the rapid cooling and heating process of the coating, thereby significantly improving the thermal fatigue resistance. As a strengthening phase, the multi-principal-element characteristic of high-entropy nanocrystalline leads to serious lattice distortion, which hinders dislocation movement on the one hand, and produces toughening effect; on the other hand, the more coordinated thermal expansion coefficient between it and the metal binder phase reduces the interface stress concentration. More importantly, in the process of laser cladding, the activity of rare earth yttrium element greatly improves the wettability between the molten coating and the substrate, promotes the firm metallurgical bonding, and makes the bonding strength of the coating reach an unprecedented high level. The common contribution of the three ensures that the coating is not easy to produce cracks and peel off under harsh thermal cycle conditions, and the reliability is greatly improved.

[0022] Finally, the present application realizes the leap-forward improvement of the comprehensive performance of the coating and the synergistic effect between the components through the optimized overall formula and preparation process. The composite system formed by the nickel-chromium alloy as the binder phase, the fusion of the conventional tungsten carbide, two new types of nano-enhanced phases and rare earth oxides forms a multi-scale and multi-mechanism strengthening network. The process combination of laser cladding and subsequent precision heat treatment ensures that the coating has a dense structure, few defects and controllable residual stress. The finally obtained coating not only has high hardness and good wear resistance, but also has sufficient toughness, firm bonding and thermal shock resistance, fully meeting all the harsh requirements of the inner wall of the blast furnace for protective materials. The successful implementation of the technical scheme provides a solid technical guarantee for the long-term and efficient operation of the blast furnace, marking a new step for the blast furnace lining protection technology. DETAILED DESCRIPTION

[0023] It is necessary to point out here that the following detailed description is only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Those skilled in the art can make some non-essential improvements and adjustments to the present application according to the above application content.

[0024] The main related equipment and material suppliers are as follows: The nickel powder is purchased from Hunan Bohu New Material Co., Ltd.

[0025] The chromium powder is purchased from Nangong City Kejin Welding Material Co., Ltd.

[0026] The molybdenum powder is purchased from Baoji Funokang Industry Co., Ltd.

[0027] The niobium powder is purchased from Baoji Funokang Industry Co., Ltd.

[0028] The boron powder was purchased from Baoji Funokang Industry Co., Ltd.

[0029] The silicon powder was purchased from Guangdong Chuanguo High-tech Material Co., Ltd.

[0030] The tungsten carbide powder was purchased from Anhui Keyun Nanometer Technology Co., Ltd.

[0031] The laser was purchased from Changzhou Ruishasi Laser Technology Co., Ltd.

[0032] The borane-ammonia complex was purchased from Zhengzhou Alpha Chemical Co., Ltd.

[0033] The Y was purchased from Baoji Funokang Industry Co., Ltd.

[0034] The Cr was purchased from Nangong City Kejin Welding Material Co., Ltd. Example

[0035] Preparation of core-shell structured tungsten carbide boron nitride nanocapsules: 100 g of tungsten carbide powder was placed in a fluidized bed chemical vapor deposition reactor, and the bed temperature was raised to 850 °C under argon protection; 5 g of borane ammonia complex was mixed with 75 g of ammonia gas and introduced into the reactor at a flow rate of 500 mL / min to deposit a boron nitride shell on the surface of the tungsten carbide, with a deposition time of 110 min; after the deposition was completed, the temperature was cooled to 25 °C under argon protection. Preparation of yttrium-chromium-aluminum oxynitride high-entropy nanocrystals: 33 g of yttrium powder, 33 g of chromium powder, and 33 g of aluminum powder were placed in a ball mill together with 200 mL of anhydrous ethanol and 500 g of zirconia grinding balls under argon protection, and ball-milled at 450 r / min for 48 h to obtain a yttrium-chromium-aluminum amorphous pre-alloy slurry; the slurry was dried in a vacuum drying oven at 60 °C for 12 h to obtain a pre-alloy powder; the pre-alloy powder was placed in a tube furnace and heated to 1100 °C at a rate of 10 °C / min under a nitrogen gas flow of 200 mL / min, and held for 3 h to obtain yttrium-chromium-aluminum nitride high-entropy phase powder; the powder was cooled to 550 °C under nitrogen protection, then a nitrogen-oxygen mixture containing 2% oxygen was introduced, and held for 1 h, followed by cooling to 25 °C under nitrogen protection. Preparation of a wear-resistant coating on the inner wall of a blast furnace: The inner wall of the blast furnace was sandblasted using 24-mesh brown corundum sand to achieve a surface cleanliness of Sa3.0 and a roughness of Ra40 μm, then ultrasonically cleaned with acetone and ethanol for 20 min each and dried at 80 °C; 600 g of nickel powder, 180 g of chromium powder, 60 g of molybdenum powder, 30 g of niobium powder, 15 g of boron powder, 10 g of silicon powder, 50 g of tungsten carbide powder, 60 g of core-shell structured tungsten carbide boron nitride nanocapsules, 35 g of yttrium-chromium-aluminum oxynitride high-entropy nanocrystals, and 10 g of yttria powder were placed in a three-dimensional mixer and mixed at 30 r / min for 6 h; the mixed powder was vacuum dried at 150 °C for 3 h; a 3.5 kW semiconductor laser was used for laser cladding on the pretreated substrate surface, with a spot diameter of 3 mm, a scanning speed of 8 mm / s, an overlap rate of 40%, a powder feeding rate of 25 g / min, and a protective gas of 15 L / min of high-purity argon; the substrate temperature was controlled at 280 °C by an auxiliary cooling system; after cladding, the coating was annealed by heating to 650 °C at a rate of 5 °C / min under argon protection, holding for 3 h, and then cooling to 25 °C in the furnace. Example

[0036] The preparation method is the same as that in Example 1, except that the core-shell structured tungsten carbide boron nitride nanocapsule is prepared as follows: 100 g of tungsten carbide powder is placed in a fluidized bed and heated to 845°C under argon protection; 5 g of borane ammonia complex and 75 g of ammonia gas are introduced into the reactor at a flow rate of 500 mL / min, and the deposition time is 100 min; after the deposition is completed, it is cooled to 25°C. The yttrium chromium aluminum oxynitride high-entropy nanocrystal is prepared as follows: 33 g of yttrium powder, 33 g of chromium powder, and 33 g of aluminum powder are respectively mixed with 200 mL of anhydrous ethanol and 500 g of zirconium oxide grinding balls for 48 h to obtain a slurry; the slurry is dried at 60°C under vacuum for 12 h; the pre-alloyed powder is heated to 1080°C at a rate of 10°C / min under a nitrogen flow of 200 mL / min, and held for 4 h; the powder is cooled to 500°C under nitrogen protection, and then a nitrogen-oxygen mixed gas containing 1.5% oxygen is introduced, and held for 1.5 h, and then cooled to 25°C. The blast furnace inner wall wear-resistant coating is prepared as follows: the surface of the blast furnace inner wall is sandblasted to reach Sa3.0 and Ra40μm, ultrasonically cleaned with acetone and ethanol, and dried; 550 g of nickel powder, 150 g of chromium powder, 50 g of molybdenum powder, 20 g of niobium powder, 10 g of boron powder, 5 g of silicon powder, 30 g of tungsten carbide powder, 40 g of core-shell structured tungsten carbide boron nitride nanocapsule, 20 g of yttrium chromium aluminum oxynitride high-entropy nanocrystal, and 5 g of yttrium oxide powder are three-dimensionally mixed for 6 h; the mixed powder is dried at 140°C under vacuum for 3 h; a 3.5 kW laser is used for cladding, and the substrate temperature is controlled at 250°C; after cladding is completed, it is heated to 640°C at a rate of 5°C / min under argon protection, held for 2 h, and cooled in the furnace. Example

[0037] The preparation method is the same as that in Example 1, except that the core-shell structured tungsten carbide boron nitride nanocapsule is prepared as follows: 100 g of tungsten carbide powder is placed in a fluidized bed and heated to 860°C under argon protection; 5 g of borane ammonia complex and 75 g of ammonia gas are introduced into the reactor at a flow rate of 500 mL / min, and the deposition time is 120 min; after the deposition is completed, it is cooled to 25°C. The yttrium chromium aluminum oxynitride high-entropy nanocrystal is prepared as follows: 33 g of yttrium powder, 33 g of chromium powder, and 33 g of aluminum powder are respectively ball milled with 200 mL of anhydrous ethanol and 500 g of zirconium oxide grinding balls for 48 h; the slurry is dried at 60°C under vacuum for 12 h; the pre-alloyed powder is heated to 1120°C at a rate of 10°C / min under a nitrogen flow of 200 mL / min, and is kept for 2 h; the powder is cooled to 600°C under nitrogen protection, and then a nitrogen-oxygen mixed gas containing 2.5% oxygen is introduced, and is kept for 0.5 h, and then cooled to 25°C. The blast furnace inner wall wear-resistant coating is prepared as follows: the surface of the blast furnace inner wall is sand blasted to reach Sa3.0 and Ra40μm, and is ultrasonically cleaned with acetone and ethanol and dried; 650 g of nickel powder, 200 g of chromium powder, 80 g of molybdenum powder, 40 g of niobium powder, 20 g of boron powder, 15 g of silicon powder, 60 g of tungsten carbide powder, 80 g of core-shell structured tungsten carbide boron nitride nanocapsule, 50 g of yttrium chromium aluminum oxynitride high-entropy nanocrystal, and 15 g of yttrium oxide powder are three-dimensionally mixed for 6 h; the mixed powder is dried at 160°C under vacuum for 3 h; a 3.5 kW laser is used for cladding, and the substrate temperature is controlled at 300°C; after the cladding is completed, it is heated to 660°C at a rate of 5°C / min under argon protection, kept for 4 h, and cooled in the furnace.

[0038] Comparative Example 1 The preparation method is the same as that in Example 1, except that the blast furnace inner wall wear-resistant coating is prepared as follows: the surface of the blast furnace inner wall is sand blasted to reach Sa3.0 and Ra40μm, and is ultrasonically cleaned with acetone and ethanol and dried; 600 g of nickel powder, 180 g of chromium powder, 60 g of molybdenum powder, 30 g of niobium powder, 15 g of boron powder, 10 g of silicon powder, 145 g of tungsten carbide powder, and 10 g of yttrium oxide powder are three-dimensionally mixed for 6 h; the mixed powder is dried at 150°C under vacuum for 3 h; a 3.5 kW laser is used for cladding, and the substrate temperature is controlled at 280°C; after the cladding is completed, it is heated to 650°C at a rate of 5°C / min under argon protection, kept for 3 h, and cooled in the furnace.

[0039] Comparative Example 2 The preparation method is the same as that of Example 1, except that the preparation of the blast furnace inner wall wear-resistant coating is as follows: the surface of the blast furnace inner wall is sandblasted to reach Sa3.0 level and Ra40μm, ultrasonic cleaned with acetone and ethanol, and dried; 600g of nickel powder, 180g of chromium powder, 60g of molybdenum powder, 30g of niobium powder, 15g of boron powder, 10g of silicon powder, 110g of tungsten carbide powder, 60g of core-shell structure tungsten carbide boron nitride nanocapsule, and 10g of yttrium oxide powder are three-dimensionally mixed for 6h; the mixed powder is vacuum dried at 150℃ for 3h; a 3.5kW laser is used for cladding, and the substrate temperature is controlled at 280℃; after cladding, the temperature is raised to 650℃ at a rate of 5℃ / min under argon protection, and held for 3h, and the furnace is cooled down.

[0040] Comparative Example 3 The preparation method is the same as that of Example 1, except that the preparation of the blast furnace inner wall wear-resistant coating is as follows: the surface of the blast furnace inner wall is sandblasted to reach Sa3.0 level and Ra40μm, ultrasonic cleaned with acetone and ethanol, and dried; 600g of nickel powder, 180g of chromium powder, 60g of molybdenum powder, 30g of niobium powder, 15g of boron powder, 10g of silicon powder, 85g of tungsten carbide powder, 35g of yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal, and 10g of yttrium oxide powder are three-dimensionally mixed for 6h; the mixed powder is vacuum dried at 150℃ for 3h; a 3.5kW laser is used for cladding, and the substrate temperature is controlled at 280℃; after cladding, the temperature is raised to 650℃ at a rate of 5℃ / min under argon protection, and held for 3h, and the furnace is cooled down.

[0041] Performance test and result analysis According to the existing national and industry standards, the following methods are used to test the performance of the single crystal copper new materials prepared in Examples 1-3 and Comparative Examples 1-3: high temperature wear test uses a ball-on-disc wear tester, the coating sample is processed into a disc with a diameter of 30mm and a thickness of 5mm, an alumina ceramic ball with a diameter of 6mm is used as the grinding ball, the test conditions are temperature 600℃, load 20N, sliding speed 0.2m / s, and total sliding distance 1000m, the wear volume is measured by a surface profilometer and the wear rate is calculated; thermal shock performance test places the coating sample in an 800℃ muffle furnace for 10min, then quickly immerses it in 20℃ water for quenching, and the cycle is repeated until the coating appears obvious cracks or peeling, and the cycle number is recorded; bonding strength test uses the tensile method according to the standard, the coating sample and the counterpart are bonded by high-temperature structural adhesive, and the bonding strength is calculated by tensile testing to break on a universal testing machine at a speed of 1mm / min; high temperature oxidation test places the coating sample in a 900℃ muffle furnace for continuous heating for 100h, and the sample is taken out and weighed every 24h, and the oxidation weight gain per unit area is calculated; microhardness test uses a Vickers hardness tester, load 500g, holding time 15s, and the average value of 10 points of each sample is taken.

[0042] Table 1: Performance test results of each example and comparative example As can be seen from Table 1, the examples 1-3 effectively solve the key technical problems of traditional wear-resistant coatings by synergistically applying the core-shell structure tungsten carbide boron nitride nanocapsule and yttrium chromium aluminum oxynitride high-entropy nanocrystal. In terms of high-temperature dissolved oxidation resistance, the oxidation weight gain of the examples is only 1.75-1.92 mg / cm2, which is much lower than 4.35 mg / cm2 of the comparative example 1, which is due to the double protection mechanism of the isolation and protection of the boron nitride shell on the tungsten carbide core and the stable oxynitride structure of the high-entropy nanocrystal. In terms of improving toughness and cracking resistance, the thermal shock cycle of the examples reaches 25-28 times, which is significantly higher than 12 times of the comparative example 1, which is because the stress buffering effect of the core-shell structure and the fine-grain strengthening effect of the high-entropy nanocrystal synergistically improve the thermal fatigue resistance of the coating. In terms of enhancing the interface bonding and anti-peeling, the bonding strength of the examples reaches 65.5-68.2 MPa, which is about 50% higher than 44.3 MPa of the comparative example 1, which is due to the combined effect of the purification strengthening effect of rare earth elements in the high-entropy nanocrystal on the interface and the improvement of the wettability of the core-shell structure. It is particularly worth noting that the comparative examples 2 and 3 only use one modified compound, and their performance is better than that of the comparative example 1 but significantly worse than that of the examples, which confirms that the synergistic effect of the two compounds is indispensable. Finally, the microhardness of the examples reaches 795-815 HV0.5, and the high-temperature wear rate is as low as 2.1-2.4 x 10-5 mm3 / N·m, which fully verifies the significant effect of the technical scheme of the present application in solving the key technical problems of hard phase high-temperature dissolution, coating brittle cracking and weak interface bonding.

[0043] The above-described examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the present patent. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of protection of the present application.

Claims

1. A method for preparing a wear resistant coating for the inner wall of a blast furnace, characterized by the steps of Comprising: S1, sandblasting treatment is carried out on the inner wall surface of the blast furnace, brown corundum sand is used, the cleanliness of the inner wall surface of the blast furnace reaches Sa 3.0 level, the roughness reaches Ra 40 mu m, then ultrasonic cleaning is carried out with acetone and ethanol and drying, and the pretreated inner wall surface of the blast furnace is obtained; nickel powder, chromium powder, molybdenum powder, niobium powder, boron powder, silicon powder, tungsten carbide powder, core-shell structure tungsten carbide / boron nitride nanocapsule, yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal and yttrium oxide powder are mixed in a mixer to obtain mixed powder; S2, the mixed powder is vacuum dried at 140-160 DEG C, and then laser cladding is carried out on the pretreated inner wall surface of the blast furnace using a laser; during the cladding process, the temperature of the inner wall surface of the blast furnace is controlled at 250-300 DEG C through an auxiliary cooling system; after the cladding is completed, the inner wall surface coating of the blast furnace is annealed, heated to 640-660 DEG C under argon protection, and then cooled to room temperature in the furnace.

2. The method of claim 1, wherein the method further comprises: In step S1, the mixing time is 6-8 h.

3. The method of claim 1, wherein the method further comprises: In step S2, the holding time is 2-4 h.

4. The method of claim 1, wherein the method further comprises: The preparation method of the core-shell structure tungsten carbide / boron nitride nanocapsule comprises: A1, tungsten carbide powder is placed in a fluidized bed chemical vapor deposition reactor, the bed temperature is raised to 840-860 DEG C under argon protection, and BN shell deposition is carried out on the WC surface after the mixture of borane-ammonia complex and ammonia gas is introduced into the reactor; A2, after the deposition is completed, cooling is carried out to room temperature under argon protection.

5. The method of claim 4, wherein the method further comprises: The molar ratio of borane-ammonia complex to ammonia gas is 1:

15.

6. The method of claim 4, wherein the method further comprises: The time for BN shell deposition on the WC surface is 90-120 min.

7. The method of claim 1, wherein the method further comprises: The preparation method of the yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal comprises: B1, metal powders of Y, Cr and Al are placed in a ball mill together with anhydrous ethanol and zirconia grinding balls under argon protection to obtain Y-Cr-Al amorphous pre-alloy slurry; the Y-Cr-Al amorphous pre-alloy slurry is dried in a vacuum drying box at 58-62 DEG C to obtain pre-alloy powder; B2, the pre-alloy powder is placed in a tube furnace, heated to 1080-1120 DEG C under a nitrogen atmosphere, and then cooled to 500-600 DEG C under nitrogen protection, and then nitrogen-oxygen mixed gas is introduced, and then cooled to room temperature under nitrogen protection.

8. The method of claim 7, wherein the method further comprises the step of: In step B1, the molar ratio of Y, Cr and Al is 1:1:

1.

9. The method of claim 7, wherein the method further comprises: In step B2, the holding time is 4-6 h; the content of oxygen in the nitrogen-oxygen mixed gas is 1.5-2.5%.

10. A furnace inner wall wear resistant coating produced according to the method of producing a furnace inner wall wear resistant coating according to any one of claims 1 to 9, characterized in that The raw materials include the following weight parts: nickel powder 55-65 parts by weight; chromium powder 15-20 parts by weight; molybdenum powder 5-8 parts by weight; niobium powder 2-4 parts by weight; boron powder 1-2 parts by weight; silicon powder 0.5-1.5 parts by weight; tungsten carbide powder 3-6 parts by weight; core-shell structure tungsten carbide / boron nitride nanocapsule 4-8 parts by weight; yttrium chromium aluminum nitrogen oxygen high-entropy nanocrystal 2-5 parts by weight; yttrium oxide 0.5-1.5 parts by weight.