Laser cladding metal powder, preparation method thereof and method for preparing wear-resistant and corrosion-resistant laser cladding layer on inner wall of hydraulic cylinder

Abstract

The application provides a laser cladding metal powder and a preparation method thereof and a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on an inner wall of a hydraulic cylinder, and relates to the technical field of alloy materials and surface engineering.The laser cladding metal powder provided by the application comprises the following components in mass percentage: Fe 431 76-85%, molybdenum 1.5-3%, tungsten carbide 10-15%, niobium carbide 2-3%, lanthanum oxide 1-2%, and cerium oxide 0.5-1%.The laser cladding metal powder obtained by designing the element components and the ratio of the element components has excellent wear resistance and corrosion resistance, and is more beneficial to the laser cladding process in terms of physical and chemical properties, so that the performance of the cladding layer is enhanced, the sensitivity of the cladding layer to thermal cracks is reduced, and the cladding efficiency is improved.The application provides a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on an inner wall of a hydraulic cylinder, which can effectively improve the wear resistance, corrosion resistance, reliability and service life of the inner wall of the hydraulic cylinder.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of alloy materials and surface engineering technology, and particularly relates to a laser cladding metal powder, a preparation method thereof and a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on an inner wall of a hydraulic cylinder. BACKGROUND

[0002] The hydraulic cylinder is an important component part of the blowout preventer and is an important safety device in oil drilling operations, which is used to prevent blowout accidents and ensure operation safety and environmental protection. The hydraulic cylinder is responsible for driving the closing and opening of the blowout preventer, and the hydraulic cylinder realizes the functions of shearing, sealing and opening and closing the gate of the blowout preventer through the hydraulic driving piston rod, and the wear resistance and corrosion resistance of the hydraulic cylinder directly affect the reliability and working efficiency of the equipment.

[0003] The base material of the hydraulic cylinder is 35CrMo steel, which cannot provide high corrosion resistance and high wear resistance. At present, a common solution on the market is to use laser cladding technology to clad a 316L stainless steel cladding layer on the inner wall of the hydraulic cylinder. Although the 316L cladding layer can meet the size repair and corrosion resistance of the inner wall of the hydraulic cylinder, the hardness of the 316L cladding layer is relatively low (HV250~290), and the wear resistance requirement of the hydraulic cylinder cannot be met. SUMMARY

[0004] Therefore, the present application aims to provide a laser cladding metal powder, a preparation method thereof and a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on an inner wall of a hydraulic cylinder. The laser cladding metal powder provided by the present application has excellent wear resistance and corrosion resistance.

[0005] In order to achieve the above-mentioned application purposes, the present application provides the following technical solutions:

[0006] The present application provides a laser cladding metal powder, which comprises the following components in mass percentage:

[0007] Fe431 76~85%, molybdenum 1.5~3%, tungsten carbide 10~15%, niobium carbide 2~3%, lanthanum oxide 1~2%, and cerium oxide 0.5~1%.

[0008] Preferably, the laser cladding metal powder comprises the following components in mass percentage: Fe431 77%, molybdenum 3%, tungsten carbide 15%, niobium carbide 2%, lanthanum oxide 2%, and cerium oxide 1%.

[0009] Preferably, the particle size of the laser cladding metal powder is 35~50µm.

[0010] The present application provides a preparation method of the laser cladding metal powder described in the above technical solutions, which comprises the following steps:

[0011] Mixing powders of Fe431, molybdenum, tungsten carbide, niobium carbide, lanthanum oxide and cerium oxide and then drying to obtain the laser cladding metal powder.

[0012] Preferably, the mixing is ball milling mixing, and an auxiliary agent is added during the ball milling mixing, and the auxiliary agent includes ethanol.

[0013] The application provides a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on an inner wall of a hydraulic cylinder.

[0014] The wear-resistant and corrosion-resistant laser cladding layer is obtained by performing super-high-speed laser cladding on the to-be-cladded part of the inner wall of the hydraulic cylinder, and the super-high-speed laser cladding is performed in a coaxial powder feeding mode and uses the laser cladding metal powder described in the above technical solution.

[0015] Preferably, before the super-high-speed laser cladding, the method further comprises: preheating the hydraulic cylinder after pre-treating the to-be-cladded part of the inner wall of the hydraulic cylinder, the pre-treating comprises sequentially performing machining and cleaning, and the preheating is performed at a temperature of 350 DEG C for 15 min.

[0016] Preferably, the super-high-speed laser cladding is performed under conditions including a laser power of 5500 W, a spot diameter of 0.8 mm, a powder feeding rate of 63 g / min, a scanning speed of 20 m / min, an overlapping rate of 75%, a cladding layer thickness of 0.8 mm and a protective gas flow rate of 19.5 L / min, and the super-high-speed laser cladding is performed in a left-right reciprocating symmetrical scanning path.

[0017] Preferably, during the super-high-speed laser cladding, the temperature between layers is kept at 200 DEG C.

[0018] Preferably, after the super-high-speed laser cladding, the method further comprises: after the obtained cladded sample is cooled to room temperature, sequentially performing first tempering treatment and second tempering treatment, the first tempering treatment is performed at a temperature of 300 DEG C for 2 h, and the second tempering treatment is performed at a temperature of 550 DEG C for 4 h.

[0019] The application provides a laser cladding metal powder, which comprises the following components in mass percentage: Fe431 76-85%, molybdenum 1.5-3%, tungsten carbide 10-15%, niobium carbide 2-3%, lanthanum oxide 1-2% and cerium oxide 0.5-1%.

[0020] In the present application, molybdenum, niobium carbide and tungsten carbide can enhance the hardness, wear resistance and corrosion resistance of the cladding layer, lanthanum and cerium elements can improve the fluidity of the molten pool and the grain size, and can significantly improve the crack resistance of the cladding layer. Through the design of the element composition and the ratio thereof, the cladding layer formed by the laser cladding metal powder obtained has excellent wear resistance and corrosion resistance, and is more beneficial to the laser cladding process in terms of physical and chemical properties, so that the performance of the cladding layer is enhanced, the thermal crack sensitivity of the cladding layer is reduced, and the cladding efficiency is improved.

[0021] The present application provides a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on the inner wall of a hydraulic cylinder. The present application adopts an ultra-high-speed laser cladding method, which has the characteristics of small heat input, high efficiency, strong cladding layer bonding force, high powder utilization rate and easy-to-control cladding layer thickness. The present application is suitable for both new product strengthening of the hydraulic cylinder and repair and remanufacturing of failed hydraulic cylinders, and can effectively improve the wear resistance, corrosion resistance, reliability and service life of the inner wall of the hydraulic cylinder.

[0022] Further, the present application optimizes the ultra-high-speed laser cladding process parameters, including: cladding process parameter control (laser power, scanning speed), heat input control (preheating before cladding, interlayer temperature maintenance during cladding), and path design optimization (left-right symmetrical step-by-step scanning path), to reduce the thermal stress of the hydraulic cylinder, prevent thermal deformation of the hydraulic cylinder, realize the strengthening or efficient repair of the easily damaged parts of the hydraulic cylinder, and thus improve the use reliability and production efficiency of the hydraulic cylinder. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The morphology diagram of the laser cladding metal powder obtained in Example 1;

[0024] Figure 2 The cross-sectional morphology diagram of the cladding layer prepared in Examples 1-2 and Comparative Examples 2-6;

[0025] Figure 3 The morphology diagram of the cladding layer after salt spray test of Examples 1-2 and Comparative Examples 1-5. DETAILED DESCRIPTION

[0026] The present application provides a laser cladding metal powder, which comprises the following components in mass percentage:

[0027] Fe431 76-85%, molybdenum 1.5-3%, tungsten carbide 10-15%, niobium carbide 2-3%, lanthanum oxide 1-2%, and cerium oxide 0.5-1%.

[0028] The laser cladding metal powder provided by the present application comprises Fe431 (431 stainless steel, corresponding to Chinese brand 1Cr17Ni2, martensitic stainless steel) 76-85%, which can be 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84% or 85%, preferably 77%. In the present application, the Fe431 is used as a tough matrix powder. When the content of the Fe431 is too high, the structure is more prone to ferrite / martensite, which is good in plasticity and toughness, but the hardness and wear resistance are reduced. When the content of the Fe431 is too low, the relative proportion of carbides and rare earth phases is high, the hardness and wear resistance are enhanced, but the layer brittleness is increased, and the crack sensitivity can be increased. The present application does not have special requirements for the Fe431, and commercially available products known to those skilled in the art can be used. In the embodiments of the present application, the Fe431 produced by Hebei Guifa Alloy Wear-resistant Material Co., Ltd. is used, and the composition is as follows in terms of mass percentage: carbon (C) 0.20%, silicon (Si) 0.5%, chromium (Cr) 16%, manganese (Mn) 1%, nickel (Ni) 1.5%, and the balance is iron.

[0029] The laser cladding metal powder provided by the present application comprises molybdenum (Mo) 1.5-3%, which can be 2%, 2.5% or 3%, preferably 3%. In the present application, when the content of the molybdenum is high, it is easier to form Mo2C and other carbides, thereby improving the hardness and wear resistance. When the content of the molybdenum is low, the main solid solution strengthening is improved, the tempering stability is improved, and the hardness improvement effect is not obvious.

[0030] The laser cladding metal powder provided by the present application comprises tungsten carbide (WC) 10-15%, which can be 10%, 11%, 12%, 13%, 14% or 15%, preferably 15%. In the present application, when the content of the tungsten carbide is too low, the hardness and wear resistance are limitedly improved.

[0031] The laser cladding metal powder provided by the present application comprises niobium carbide (NbC) 2-3%, which can be 2%, 2.5% or 3%, preferably 2%. In the present application, when the content of the niobium carbide is high, the number of hard points is increased, and the wear resistance is improved, but too much is prone to form continuous brittle network structure, thereby reducing the compactness of the layer.

[0032] The laser cladding metal powder provided by the present application comprises lanthanum oxide (La2O3) 1-2%, which can be 1%, 1.5% or 2%, preferably 2%. In the present application, the lanthanum oxide can refine the grains to improve the toughness and crack resistance, improve the fluidity of the molten pool, and improve the cladding forming quality. When the content of the lanthanum oxide is too low, the effects of refining the grains and improving the fluidity of the molten pool are not obvious.

[0033] The laser cladding metal powder provided by the present application contains cerium oxide (CeO2) 0.5-1% by mass, which can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, and preferably 1%. In the present application, the cerium oxide can play the role of purification, refinement and dispersion strengthening, and when its content is too low, the auxiliary refining and purification effect is not effective.

[0034] The laser cladding metal powder provided by the present application is an iron-based high-hardness alloy powder. In the present application, the addition of molybdenum element can form high-hardness molybdenum carbide (Mo2C) hard phase, enhancing the hardness and wear resistance of the cladding layer; the addition of niobium element can also form stable niobium oxide (Nb2O5), enhancing the oxidation resistance of the cladding layer; Mo element can promote the formation of a stable molybdenum-rich oxide film (such as MoO3, Cr-Mo-O) in the coating, improve the density of the passivation film, and inhibit local corrosion; when Mo coexists with Cr in the Fe431 powder, the pitting potential is increased, and the corrosion resistance stability is enhanced; meanwhile, the Mo element is solid-solved in the coating, the grains are refined, the microstructure is optimized, the accumulation of impurities at the grain boundaries is reduced, and the intergranular corrosion sensitivity is reduced; the addition of lanthanum and cerium elements improves the flowability and wettability, enhances the uniformity and bonding force of the cladding layer, and refines the grains, which can significantly reduce the risk of cracks in the cladding layer. In the present application, the main functions of tungsten carbide in laser cladding are: strengthening the particle phase, which is not easy to completely melt during laser cladding and usually exists in the form of particles or partial dissolution, forming a dispersedly distributed hard phase; grain refinement, the presence of tungsten carbide can act as a grain nucleation core to inhibit the coarsening of the matrix structure in the cladding layer, thereby refining the grains; formation of secondary carbides, part of the tungsten carbide will decompose into secondary hard carbides at high temperatures, which is equivalent to generating a strengthening phase outside the original particles, which can significantly improve the hardness and wear resistance of the cladding layer.

[0035] The present application can effectively reduce the generation of defects in the cladding layer on the basis of enhancing the wear resistance and corrosion resistance of the cladding layer through the design of the element components and their proportions.

[0036] In the present application, the particle size of the laser cladding metal powder is preferably 35-50 µm.

[0037] The present application provides a preparation method of the laser cladding metal powder described in the above technical solutions, which comprises the following steps:

[0038] The powders of Fe431, molybdenum, tungsten carbide, niobium carbide, lanthanum oxide and cerium oxide are mixed and then dried to obtain the laser cladding metal powder.

[0039] In the present application, the mixing is ball milling mixing, which is preferably carried out in a planetary ball mill. In the present application, the grinding balls used in the ball milling mixing preferably include large balls and small balls, the diameter of the large balls is preferably 10 mm, the diameter of the small balls is preferably 3-5 mm, and the mass ratio of the large balls to the small balls is preferably 7:3; the ball-to-material ratio of the ball milling mixing is preferably 10-15:1, and controlling the ball-to-material ratio is conducive to ensuring that the hard phase is fully broken and uniformly distributed. In the present application, the ball milling mixing is preferably stopped for 20 min after 1 h of mixing to prevent the powder from overheating and oxidizing, and the total time of the ball milling mixing (excluding the stopping time) is preferably 12 h. In the present application, an auxiliary agent is also preferably added during the ball milling mixing, and the auxiliary agent preferably includes ethanol, and the present application does not have special requirements for the amount of the auxiliary agent, and the amount used by those skilled in the art is known.

[0040] In the present application, after the ball milling mixing, the obtained powder is preferably sieved, and the sieving preferably uses a 300-mesh sieve; and the powder with a particle size of 35-50 µm is obtained after the sieving.

[0041] In the present application, the temperature of the drying is preferably 130°C, and the time is preferably 3 h, and the drying is preferably carried out in a constant-temperature drying box.

[0042] The present application provides a method for preparing a wear-resistant and corrosion-resistant laser cladding layer on the inner wall of a hydraulic cylinder, comprising the following steps:

[0043] The wear-resistant and corrosion-resistant laser cladding layer is obtained by performing ultra-high-speed laser cladding on the to-be-cladded part of the inner wall of the hydraulic cylinder; the ultra-high-speed laser cladding adopts a coaxial powder feeding mode, and the cladding powder used is the laser cladding metal powder according to the above technical solution.

[0044] In the present application, the inner wall of the hydraulic cylinder can be the inner wall of a blowout preventer hydraulic cylinder, and the base material is 35CrMo steel.

[0045] In the present application, before the ultra-high-speed laser cladding, the inner wall of the hydraulic cylinder to be cladded is preferably preheated after being pretreated. In the present application, the pretreatment preferably includes machining and cleaning in sequence; the machining is preferably performed by a lathe to remove the failure and oxidation layer of the part to be cladded; the cleaning preferably includes chemical cleaning with a weak acid solution and wiping with ethanol to remove rust, oil stains and impurities on the part to be cladded. Specifically, chemical cleaning with a weak acid solution can remove rust, and wiping with ethanol can remove oil stains. In the present application, the preheating temperature is preferably 350℃, and the holding time is preferably 15 min. The preheating is specifically performed by transferring the pretreated hydraulic cylinder to a preheating furnace for preheating. Then, the preheated hydraulic cylinder is transferred to an ultra-high-speed laser cladding device for ultra-high-speed laser cladding of the inner wall to be cladded. By preheating before cladding, the present application can reduce thermal stress and prevent cracking, and improve the adhesion of the cladding layer to the substrate.

[0046] In the present application, the conditions of the ultra-high-speed laser cladding preferably include a laser power of 5500W, a spot diameter of 0.8mm, a powder feeding rate of 63g / min, a scanning speed of 20m / min, an overlap rate of 75%, a cladding layer thickness of 0.8mm, and a protective gas flow rate of 19.5L / min. The protective gas is preferably argon. In the present application, the ultra-high-speed laser cladding preferably adopts a left-right reciprocating symmetrical scanning path. During the ultra-high-speed laser cladding, the interlayer temperature is preferably maintained at 200℃ to prevent cracking and avoid thermal stress caused by rapid cooling.

[0047] In the present application, after the ultra-high-speed laser cladding, the obtained cladded sample is preferably wrapped with an asbestos blanket for heat preservation, slowly cooled to room temperature, and then subjected to first and second tempering treatments in sequence. In the present application, the obtained cladded sample is immediately subjected to tempering treatment after being cooled to room temperature. In the present application, the first tempering treatment has a temperature of 300℃ and a holding time of 2h; the first tempering treatment is followed by furnace cooling, and then the second tempering treatment. In the present application, the second tempering treatment has a temperature of 550℃ and a holding time of 4h; the second tempering treatment is followed by furnace cooling. In the present application, the first tempering treatment functions to quickly diffuse and remove hydrogen after cladding, preventing cold cracking (delayed cracking); and the second tempering treatment functions to eliminate residual stress, stabilize the microstructure, and improve the toughness of the bonding zone. In the present application, the first tempering treatment is also referred to as low-temperature hydrogen elimination tempering, and the second tempering treatment is also referred to as medium-temperature tempering.

[0048] After the second tempering treatment, the hydraulic cylinder with the cladding layer is preferably subjected to mechanical processing for post-treatment, such as post-treatment with a grinding machine or other machining equipment, to meet the technical requirements of size, roughness, roundness and the like specified in the drawing.

[0049] At present, the plasma cladding technology and the plasma spraying technology are usually adopted for preparing the cladding layer on the inner wall of the hydraulic cylinder, wherein the plasma cladding technology has large heat input and is easy to cause the deformation of the inner wall part, the bonding of the coating prepared by the plasma spraying technology with the inner wall substrate of the hydraulic cylinder belongs to mechanical embedding, the bonding force of the coating cannot meet the requirement of the working condition of the hydraulic cylinder, and the thickness of the coating prepared by the plasma spraying technology is limited, and the effect is not ideal when the damage of the inner wall exceeds 0.5mm. The super-high-speed laser cladding technology is adopted in the present application, the laser has the characteristics of high directionality, high monochromaticity, high coherence and high energy density, is different from the conventional cladding process, and has the characteristics of small heat input, high efficiency, strong bonding force of the cladding layer, high powder utilization rate and easy control of the thickness of the cladding layer, and can reduce the post-processing cost of the cladding layer. The laser cladding layer prepared by the method of the present application can repair or remanufacture the damaged part of the inner wall of the hydraulic cylinder, can improve the corrosion resistance and wear resistance of the inner wall of the hydraulic cylinder, can enhance the service life and stability of the hydraulic cylinder, and can achieve the effect of reducing cost and increasing benefit. The method provided by the present application is suitable for the strengthening of new hydraulic cylinders and the repair and remanufacture of failed hydraulic cylinders, and further realizes the recycling of waste hydraulic cylinders, reduces the waste of resources, significantly reduces the production cost of enterprises, and has good industrial application prospect.

[0050] In order to further illustrate the present application, the laser cladding metal powder, the preparation method thereof and the method for preparing the wear-resistant and corrosion-resistant laser cladding layer on the inner wall of the hydraulic cylinder provided by the present application are described in detail below in combination with examples, but they cannot be understood as limiting the protection scope of the present application.

[0051] The metal powder Fe431 used in each embodiment is produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd., and the composition thereof is as follows in terms of mass percentage: carbon (C) 0.20%, silicon (Si) 0.5%, chromium (Cr) 16%, manganese (Mn) 1%, nickel (Ni) 1.5%, and the balance of iron.

[0052] Example 1

[0053] A laser cladding metal powder (iron-based high-hard alloy material) and a preparation method of the cladding layer thereof, for improving the surface hardness, wear resistance and corrosion resistance of the inner wall of the hydraulic cylinder.

[0054] A 35CrMo pipe material with a length of 100mm, a diameter of 80mm and a wall thickness of 10mm is selected as a substrate, and a cladding layer is prepared on the inner wall thereof, the material of the cladding layer is an iron-based high-hard alloy powder, and the particle size of the powder is 35-50µm. The powder raw material is selected from the metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd., and the thickness of the cladding layer is 0.8mm. The specific process is as follows:

[0055] Step 1: Preparation of iron-based high-hard alloy powder (laser cladding metal powder)

[0056] The composition of the cladding metal powder is as follows in terms of mass percentage: Fe 431.77%, molybdenum (Mo) 3%, tungsten carbide (WC) 15%, niobium carbide (NbC) 2%, lanthanum oxide (La2O3) 2%, and cerium oxide (CeO2) 1%. The corresponding mass of the alloy powder is weighed using an experimental balance, mechanically mixed for 12 hours using a planetary ball mill, the grinding balls are large balls with a diameter of 10 mm and small balls with a diameter of 5 mm (mass ratio of large balls to small balls is 7:3), the ball-to-material ratio is 15:1, the auxiliary agent is ethanol (addition amount is 35 mL / kg of powder), and the mixing is stopped for 20 minutes every 1 hour to prevent the powder from being overheated and oxidized. A 300-mesh screen is used for screening to obtain metal powder with a particle size of 35-50 µm. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130°C for 3 hours for standby.

[0057] Figure 1 The morphology of the laser cladding metal powder obtained in Example 1 can be seen, and the sphericity is high, most of the particles are spherical or approximately spherical, the surface is smooth, and part of the small particles add elements uniformly around the large particles, which is beneficial to the uniformity of the cladding layer structure.

[0058] Step 2: Pretreatment of substrate and cladding powder

[0059] The cladding part of the hydraulic cylinder is pretreated, and the lathe is used to remove the failure and oxide layer of the repaired part, and then the rust, oil stains and impurities of the repaired part are removed. Among them, the rust is eliminated by chemical cleaning method with weak acid solution, the oil stains are removed by wiping with ethanol, and finally the treated hydraulic cylinder is clamped on the lathe bed by using the clamp.

[0060] Step 3: Laser cladding of hydraulic cylinder

[0061] The surface of the repaired part of the hydraulic cylinder is repaired by ultra-high-speed laser cladding in a coaxial powder feeding mode, and the specific cladding process parameters are as follows: laser power is 5500W, spot diameter is 0.8mm, powder feeding rate is 63g / min, scanning speed is 20m / min, overlap rate is 75%, cladding layer thickness is 0.8mm, and protective gas flow is 19.5L / min. Left and right reciprocating symmetrical scanning path is adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding, the preheating temperature is 350°C (heat preservation for 15 minutes), the interlayer temperature is maintained at 200°C during cladding, and the cladding is completed by wrapping with asbestos blanket and slowly cooling to room temperature.

[0062] Step 4: Post-processing

[0063] After laser cladding, the part cooled to room temperature is immediately tempered for post-processing, first low-temperature hydrogen removal tempering, process 300°C, heat preservation time 2h, furnace cooling; then medium-temperature tempering, process 550°C, heat preservation 4h, and furnace cooling again.

[0064] Comparative Example 1

[0065] Take 35CrMo steel samples to test their hardness, friction and wear resistance, and corrosion resistance. The purpose is to compare the performance of the coating prepared in Example 1 and verify its improvement effect.

[0066] Select a 35CrMo sample block with a length of 10 mm, a width of 10 mm, and a height of 10 mm for sample preparation and performance testing. The specific steps are as follows:

[0067] Step 1: Inlay

[0068] Clean the sample to remove surface oil and surface impurities (cleaning reagent: ethanol). Use a hot inlay machine (phenolic resin) to inlay the sample for subsequent grinding and polishing and to protect the edge.

[0069] Step 2: Grinding

[0070] Use a grinding and polishing machine to prepare the sample. Use diamond sandpaper. From coarse to fine, grind (240#→400#→600#→800#→1200#→2000#→3000#), and rotate the sample 90° for each sandpaper change to ensure that the previous grinding mark is completely removed. Keep the water flowing to prevent tissue changes caused by heating.

[0071] Step 3: Polishing

[0072] Use the same polishing machine + polishing cloth + polishing agent (alumina suspension or diamond suspension) at a speed of 500 r / min for rough polishing and fine polishing. The polishing pressure should be moderate to prevent "ghosting" or "corrugated" surfaces.

[0073] Comparative Example 2

[0074] A kind of iron-based high-hardness alloy material and its cladding layer preparation method, the purpose is to compare the coating prepared in Example 1 and verify its performance improvement effect.

[0075] Select a 35CrMo pipe with a length of 100 mm, a diameter of 80 mm, and a wall thickness of 10 mm as the substrate. Process and prepare the cladding layer on the inner wall. The cladding layer material is Fe431 iron-based alloy powder with a particle size of 35-50 µm. The powder is Fe431 metal powder produced by Hebei Guifa Alloy Wear-resistant Material Co., Ltd. The cladding layer thickness is 1.2 mm. The specific steps are as follows:

[0076] Step 1: Iron-based high-hardness alloy powder preparation

[0077] Place the metal powder Fe431 in a constant temperature drying box at a preset temperature of 130°C for 3 hours for standby.

[0078] Step 2: Pretreatment of substrate and cladding powder

[0079] The hydraulic cylinder cladding site is pretreated, and the lathe is used to remove the failure and oxidation layer of the repaired site. Then the rust, oil stains and impurities on the repaired site are removed. Among them, the rust is eliminated by weak acid solution chemical cleaning method, the oil stains are removed by ethanol wiping method, and finally the treated hydraulic cylinder is clamped on the lathe bed by using the clamp.

[0080] Step 3: cladding layer preparation

[0081] The surface of the hydraulic cylinder to be repaired is repaired by super-speed laser cladding in a coaxial powder feeding mode. The specific cladding process parameters are as follows: laser power is 5500W, spot diameter is 0.8mm, powder feeding rate is 63g / min, scanning speed is 20m / min, overlap rate is 75%, cladding layer thickness is 0.8mm, and protective gas flow is 19.5L / min. Left and right reciprocating symmetric scanning path is adopted, the hydraulic cylinder is preheated before cladding, the preheating temperature is 350℃ (holding for 15min), the interlayer temperature is maintained at 200℃ during cladding, and the cladding is completed by wrapping with asbestos blanket and slowly cooling to room temperature.

[0082] Step 4: post-treatment

[0083] After laser cladding, the sample cooled to room temperature is immediately tempered after treatment, first low-temperature hydrogen removal tempering, process 300℃, holding time 2h, furnace cooling; then medium-temperature tempering, process 550℃, holding time 4h, furnace cooling again.

[0084] Comparative example 3

[0085] An iron-based high-hardness alloy material and a preparation method of a cladding layer thereof, the purpose is to compare the coating with different cladding process of example 1, and verify the performance improvement effect.

[0086] A 35CrMo pipe with a length of 100mm, a diameter of 80mm and a wall thickness of 10mm is selected as the substrate, and a cladding layer is prepared on the inner wall. The cladding layer material is iron-based high-hardness alloy powder with a particle size of 35-50μm. The powder raw material is selected from the metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd., and the cladding layer thickness is 0.8mm. The specific process is as follows:

[0087] Step 1: preparation of iron-based high-hardness alloy powder

[0088] The composition of the cladding metal powder is as follows in terms of mass percentage: Fe 431.77%, molybdenum (Mo) 3%, tungsten carbide (WC) 15%, niobium carbide (NbC) 2%, lanthanum oxide (La2O3) 2%, and cerium oxide (CeO2) 1%. The corresponding mass of alloy powder is weighed using an experimental balance, mechanically mixed for 12 hours using a planetary ball mill, the grinding balls are large balls with a diameter of 10 mm and small balls with a diameter of 5 mm (mass ratio of large balls to small balls is 7:3), the ball-to-material ratio is 15:1, the auxiliary agent is ethanol (addition amount is 35 mL / kg of powder), and the mixing is stopped for 20 minutes every 1 hour to prevent the powder from being overheated and oxidized. A 300-mesh screen is used for screening to obtain metal powder with a particle size of 35-50 µm. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130°C for 3 hours for standby.

[0089] Step 2: Pretreatment of substrate and cladding powder

[0090] The cladding part of the hydraulic cylinder is pretreated, and the lathe is used to remove the failure and oxide layer of the repaired part, and then the rust, oil stains and impurities of the repaired part are removed. Among them, the rust is eliminated by chemical cleaning with weak acid solution, the oil stains are removed by wiping with ethanol, and finally the treated hydraulic cylinder is clamped on the lathe bed using a clamp.

[0091] Step 3: Laser cladding of hydraulic cylinder

[0092] The surface of the repaired part of the hydraulic cylinder is repaired by high-speed laser cladding in a coaxial powder feeding mode, and the specific cladding process parameters are as follows: laser power is 4500W, spot diameter is 2mm, powder feeding rate is 53g / min, scanning speed is 15m / min, overlap rate is 75%, cladding layer thickness is 0.8mm, and protective gas flow is 19.5L / min. Left and right reciprocating symmetrical scanning path is adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding, the preheating temperature is 350°C (heat preservation for 15 minutes), the interlayer temperature is maintained at 200°C during cladding, and the cladding is completed after wrapping with asbestos blanket for slow cooling to room temperature.

[0093] Step 4: Post-treatment

[0094] After laser cladding, the sample is immediately tempered after being cooled to room temperature, first low-temperature hydrogen removal tempering, process 300°C, heat preservation time 2h; then medium-temperature tempering, process 550°C, heat preservation 4h, and then furnace cooling.

[0095] Comparative Example 4

[0096] An iron-based high-hardness alloy material and a preparation method of a cladding layer thereof, the purpose is to compare the coating with different cladding process in Example 1, and verify the performance improvement effect.

[0097] A 35CrMo pipe with a length of 100 mm, a diameter of 80 mm, and a wall thickness of 10 mm is selected as a substrate, and a cladding layer is processed on the inner wall thereof. The cladding layer material is a ferrous-based high-hardness alloy powder with a particle size of 35-50 µm. The powder raw material is a metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd. The cladding layer thickness is 0.8 mm. The specific process is as follows:

[0098] Step 1: Preparation of ferrous-based high-hardness alloy powder

[0099] The composition of the cladding metal powder is as follows in terms of mass percentage: Fe 431.77%, molybdenum (Mo) 3%, tungsten carbide (WC) 15%, niobium carbide (NbC) 2%, lanthanum oxide (La2O3) 2%, and cerium oxide (CeO2) 1%. The corresponding mass of alloy powder is weighed using a laboratory balance, and mechanical mixing is performed for 12 h using a planetary ball mill. The grinding balls are large balls with a diameter of 10 mm and small balls with a diameter of 5 mm (mass ratio of large balls to small balls is 7:3). The ball-to-material ratio is 15:1. Ethanol is used as an additive (addition amount is 35 mL / kg of powder). Mixing is performed for 1 h, followed by a 20 min pause to prevent overheating and oxidation of the powder. Screening is performed using a 300-mesh screen to obtain a metal powder with a particle size of 35-50 µm. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130°C for 3 h for standby use.

[0100] Step 2: Pretreatment of substrate and cladding powder

[0101] The cladding part of the hydraulic cylinder is pretreated. The lathe is used to remove the failure and oxidation layer of the repaired part, and then the rust, oil stains, and impurities on the repaired part are removed. The rust is removed by chemical cleaning with a weak acid solution, and the oil stains are removed by wiping with ethanol. Finally, the treated hydraulic cylinder is clamped on the lathe bed using a clamp.

[0102] Step 3: Laser cladding of hydraulic cylinder

[0103] The surface of the repaired part of the hydraulic cylinder is repaired by ultra-high-speed laser cladding in a coaxial powder feeding mode. The specific cladding process parameters are as follows: laser power is 5500 W, spot diameter is 0.8 mm, powder feeding rate is 73 g / min, scanning speed is 25 m / min, overlap rate is 75%, cladding layer thickness is 0.8 mm, and protective gas flow rate is 23.5 L / min. A left-right reciprocating symmetric scanning path is adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding at a temperature of 350°C (with a holding time of 15 min). The interlayer temperature is maintained at 200°C during the cladding process. After cladding, the hydraulic cylinder is wrapped with an asbestos blanket for slow cooling to room temperature.

[0104] Step 4: Post-processing

[0105] After laser cladding, the parts are immediately tempered after being cooled to room temperature, first low-temperature hydrogen removal tempering, process 300℃, holding time 2h, furnace cooling; then medium-temperature tempering, process 550℃, holding time 4h, furnace cooling again.

[0106] Example 2

[0107] A laser cladding metal powder (iron-based high-hardness alloy material) and a preparation method of a cladding layer thereof:

[0108] A 35CrMo pipe with a length of 100mm, a diameter of 80mm and a wall thickness of 10mm is selected as a substrate, and a cladding layer is prepared on the inner wall thereof. The cladding layer material is an iron-based high-hardness alloy powder with a particle size of 35-50µm. The powder raw material is a metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd. The cladding layer has a thickness of 0.8mm. The specific process is as follows:

[0109] Step 1: Preparation of iron-based high-hardness alloy powder (laser cladding metal powder)

[0110] The composition of the cladding metal powder is as follows in terms of mass percentage: Fe 431.85%, molybdenum (Mo) 1.5%, tungsten carbide (WC) 10%, niobium carbide (NbC) 2%, lanthanum oxide (La2O3) 1%, and cerium oxide (CeO2) 0.5%. The corresponding mass of alloy powder is weighed using a laboratory balance, and mechanical mixing is performed for 12h using a planetary ball mill. The grinding balls are large balls with a diameter of 10mm and small balls with a diameter of 5mm (mass ratio of large balls to small balls 7:3). The ball-to-material ratio is 15:1. Ethanol is used as an additive (addition amount 35mL / kg of powder). The powder is mixed for 1h and then stopped for 20min to prevent overheating and oxidation of the powder. A 300-mesh sieve is used for sieving, and the metal powder with a particle size of 35-50µm is obtained. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130℃ for 3h for standby.

[0111] Step 2: Pretreatment of substrate and cladding powder

[0112] The cladding part of the hydraulic cylinder is pretreated. The lathe is used to remove the failure and oxidation layer of the repaired part, and then the rust, oil stains and impurities of the repaired part are removed. The rust is removed by chemical cleaning with a weak acid solution, and the oil stains are removed by wiping with ethanol. Finally, the treated hydraulic cylinder is clamped on the lathe bed using a clamp.

[0113] Step 3: Laser cladding of hydraulic cylinder

[0114] The surface of the hydraulic cylinder to be repaired is repaired by super-speed laser cladding in a coaxial powder feeding mode. The specific cladding process parameters are as follows: laser power is 5500W, spot diameter is 0.8mm, powder feeding rate is 63g / min, scanning speed is 20m / min, overlap rate is 75%, cladding layer thickness is 0.8mm, and protective gas flow rate is 19.5L / min. Left and right reciprocating symmetric scanning paths are adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding at a temperature of 350℃ (for 15min), the interlayer temperature is maintained at 200℃ during the cladding process, and the cladding is completed by wrapping the stone wool blanket to slowly cool to room temperature.

[0115] Step 4: Post-treatment

[0116] After laser cladding, the sample is immediately tempered after being cooled to room temperature. First, low-temperature hydrogen removal tempering is performed at a process of 300℃ for 2h with furnace cooling; then, medium-temperature tempering is performed at a process of 550℃ for 4h with furnace cooling.

[0117] Comparative Example 5

[0118] An iron-based high-hardness alloy material and a preparation method of a cladding layer thereof are provided, which aims to compare the coating prepared by different powder ratio processes with Example 1 to verify the performance improvement effect.

[0119] A 35CrMo pipe with a length of 100mm, a diameter of 80mm and a wall thickness of 10mm is selected as the base body, and a cladding layer is prepared on the inner wall thereof. The material of the cladding layer is an iron-based high-hardness alloy powder with a particle size of 35-50µm. The powder raw material is a metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd., and the thickness of the cladding layer is 0.8mm. The specific process is as follows:

[0120] Step 1: Preparation of iron-based high-hardness alloy powder (laser cladding metal powder)

[0121] The composition of the cladding metal powder is as follows: Fe431 65%, molybdenum (Mo) 5%, tungsten carbide (WC) 20%, niobium carbide (NbC) 5%, lanthanum oxide (La2O3) 3%, and cerium oxide (CeO2) 2%. The corresponding mass of alloy powder is weighed using a laboratory balance, and mechanical mixing is performed for 12h using a planetary ball mill. The grinding balls are large balls with a diameter of 10mm and small balls with a diameter of 5mm (mass ratio of large balls to small balls is 7:3), the ball-to-material ratio is 15:1, and ethanol is used as an additive (addition amount is 35mL / kg of powder). Stop for 20min every 1h of mixing to prevent the powder from overheating and oxidizing. Screen the powder through a 300-mesh screen to obtain a metal powder with a particle size of 35-50µm. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130℃ for 3h for standby.

[0122] Step 2: Pretreatment of base material and cladding powder

[0123] The hydraulic cylinder cladding site is pretreated, and the lathe is used to remove the failure and oxidation layer of the repaired site. Then the rust, oil stains and impurities on the repaired site are removed. Among them, the rust is eliminated by weak acid solution chemical cleaning method, the oil stains are removed by ethanol wiping method, and finally the treated hydraulic cylinder is clamped on the lathe bed by using the clamp.

[0124] Step 3: Laser cladding of hydraulic cylinder

[0125] The surface of the hydraulic cylinder to be repaired is repaired by super-speed laser cladding in a coaxial powder feeding manner. The specific cladding process parameters are: laser power is 5500W, spot diameter is 0.8mm, powder feeding rate is 63g / min, scanning speed is 20m / min, overlap rate is 75%, cladding layer thickness is 0.8mm, and protective gas flow is 19.5L / min. Left and right reciprocating symmetric scanning path is adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding, the preheating temperature is 350℃ (heat preservation for 15min), the interlayer temperature is maintained at 200℃ during cladding, and the cladding is completed after the cladding is completed. The stone wool blanket is wrapped for slow cooling to room temperature.

[0126] Step 4: Post-processing

[0127] After laser cladding, the part cooled to room temperature is immediately tempered after treatment, first low-temperature hydrogen removal tempering, process 300℃, heat preservation time 2h, furnace cooling; then medium temperature tempering, process 550℃, heat preservation 4h, furnace cooling again.

[0128] Comparative example 6

[0129] An iron-based high-hardness alloy material and a preparation method of a cladding layer thereof, the purpose is to compare the coating with different powder ratio process of example 2, and verify the performance improvement effect.

[0130] Select 35CrMo pipe material with length of 100mm, diameter of 80mm and wall thickness of 10mm as base body, and process and prepare cladding layer on the inner wall. The cladding layer material is iron-based high-hardness alloy powder with particle size of 35-50µm. The powder raw material is selected from the metal powder produced by Hebei Gui Fa Alloy Wear-resistant Material Co., Ltd., and the cladding layer thickness is 0.8mm. The specific process is as follows:

[0131] Step 1: Preparation of iron-based high-hardness alloy powder (laser cladding metal powder)

[0132] The composition of the cladding metal powder is as follows in terms of mass percentage: Fe 431 80%, molybdenum (Mo) 5%, tungsten carbide (WC) 10%, niobium carbide (NbC) 5%, the corresponding mass of alloy powder is weighed by using an experimental balance, mechanical mixing is performed for 12 h by using a planetary ball mill, the grinding balls are large balls with a diameter of 10 mm + small balls with a diameter of 5 mm (mass ratio of large balls to small balls is 7:3), the ball-to-material ratio is 15:1, and ethanol is selected as an additive (addition amount is 35 mL / kg of powder), and the mixing is stopped for 20 min every 1 h to prevent the powder from being overheated and oxidized. Screening is performed by using a 300-mesh screen to obtain metal powder with a particle size of 35-50 µm. The pre-prepared powder is dried in a constant-temperature drying box at a preset temperature of 130℃ for 3 h for standby.

[0133] Step 2: Pretreatment of substrate and cladding powder

[0134] The cladding part of the hydraulic cylinder is pretreated, the lathe is used to remove the failure and oxide layer of the repaired part, and then the rust, oil stains and impurities of the repaired part are removed. Among them, the rust is eliminated by using a weak acid solution chemical cleaning method, the oil stains are removed by using an ethanol wiping method, and finally the treated hydraulic cylinder is clamped on the lathe bed by using a clamp.

[0135] Step 3: Laser cladding of hydraulic cylinder

[0136] The surface of the repaired part of the hydraulic cylinder is repaired by using the method of coaxial powder feeding, and the specific cladding process parameters are as follows: laser power is 5500 W, spot diameter is 0.8 mm, powder feeding rate is 63 g / min, scanning speed is 20 m / min, overlap rate is 75%, cladding layer thickness is 0.8 mm, and protective gas flow rate is 19.5 L / min. The left and right reciprocating symmetric scanning path is adopted to reduce local heat concentration. The hydraulic cylinder is preheated before cladding, the preheating temperature is 350℃ (heat preservation for 15 min), the interlayer temperature is maintained at 200℃ during cladding, and the cladding is completed by wrapping the asbestos blanket for slow cooling to room temperature.

[0137] Step 4: Post-treatment

[0138] After laser cladding, the part cooled to room temperature is immediately tempered for post-treatment, first low-temperature hydrogen elimination tempering, process 300℃, heat preservation time 2h, furnace cooling; then medium-temperature tempering, process 550℃, heat preservation 4h, again furnace cooling.

[0139] The cladding layer obtained in the examples and each comparative example is sampled, and the morphology, hardness and wear resistance performance are detected by using a metallographic microscope, a hardness tester and a friction and wear testing machine, and the specific detection methods are as follows:

[0140] (1) Vickers hardness test of cladding layer

[0141] The Vickers hardness of the cladding layer is measured by a digital Vickers hardness tester of HV-1000 type, and the experimental scale is selected as HV 0.2 , a diamond pyramid indenter, and the loading time is 5 s.

[0142] (2) Friction and wear test of the cladding layer

[0143] The friction and wear test of the cladding layer is carried out by using an SRV-4 type wear tester. The test adopts a ball-disc contact reciprocating motion form, and the friction pair is a GCr15 steel ball with a diameter of 10 mm. The test load is 20 N, the frequency is 10 Hz, the reciprocating stroke is 1 mm, the test time is 1 h, and the temperature is room temperature. After the wear test, the volume of the wear part is measured by using a laser confocal microscope.

[0144] (3) Salt spray test of the cladding layer

[0145] The salt spray test is carried out by using a LYW-075N multifunctional salt spray test box. The corrosion solution is a 5wt% NaCl solution with a pH value of 6.5-7.2, and the test time is 96 h. After the salt spray test, the corrosion condition of the sample is observed and recorded.

[0146] The detection results are as follows:

[0147] Figure 2 The cross-sectional morphology of the cladding layer prepared for Examples 1-2 and Comparative Examples 2-6 is shown. It can be seen that the cladding layers of Examples 1-2, Comparative Examples 2, 3, 4, and 6 are uniform and continuous, without macroscopic cracks, pores, and other defects. Comparative Example 5 has obvious defects such as thermal cracks.

[0148] Table 1 is a comparison of the hardness (HV) of the cladding layers of Examples 1-2 and Comparative Examples 1-6.

[0149] Table 1 is a comparison of the hardness of the cladding layers of Examples 1-2 and Comparative Examples 1-6

[0150]

[0151] As can be seen from the data in Table 1, the average hardness of the cladding layer of Example 1 is higher than that of the other comparative examples. By adjusting the element ratio, adding molybdenum (Mo) elements, niobium (Nb) elements, and tungsten carbide (WC), the hardness of the cladding layer of Example 1 is the highest, reaching 685.66 HV, which is 2.6 times that of the substrate 35CrMo. It is generally believed that the hardness value is one of the key indicators for measuring the wear resistance of the cladding layer. The hardness of the coating of Example 2 is improved less than that of Example 1 due to the lower content of hard phase. Although the hardness of the coating of Comparative Example 5 is improved significantly due to the high content of hard phase, the wettability of the cladding layer is reduced and the crack sensitivity of the cladding layer is increased due to the hard phase, resulting in uneven microstructure, cracks, and other defects in the cladding layer, and uneven hardness distribution of the cladding layer.

[0152] Table 2 is the wear volume comparison of the cladding layers of Examples 1-2 and Comparative Examples 1-6 after the friction and wear test under the dry friction condition.

[0153] Table 2 Wear volume comparison under dry friction condition

[0154]

[0155] As can be seen from Table 2, the wear volume of the cladding layer of Example 1 is smaller than that of the other comparative examples, indicating that the wear resistance of the cladding layer of Example 1 is better.

[0156] Figure 3 Fig. 3 is the morphology of the cladding layer of Examples 1-2 and Comparative Examples 1-5 after the salt spray test. It can be seen that the surfaces of Comparative Example 1 and Comparative Example 5 have serious corrosion phenomenon, and Examples 1-2 and Comparative Examples 2, 3 and 4 have no corrosion phenomenon. It indicates that the laser cladding coating of the present application can provide excellent corrosion resistance to the inner wall of the liquid cylinder.

[0157] The above description is only the preferred embodiments of the present application, and does not limit the present application in any form. It should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should be considered as the protection scope of the present application.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant laser cladding layer on the inner wall of a hydraulic cylinder, characterized in that, Includes the following steps: Ultra-high-speed laser cladding is performed on the inner wall of the hydraulic cylinder to obtain a wear-resistant and corrosion-resistant laser cladding layer. The ultra-high-speed laser cladding adopts a coaxial powder feeding method, and the cladding powder used is laser cladding metal powder, which is composed of the following components by mass percentage: The composition of Fe431 is as follows: 77% Fe431, 3% molybdenum, 15% tungsten carbide, 2% niobium carbide, 2% lanthanum oxide, and 1% cerium oxide. The Fe431 composition by mass percentage is: 0.20% carbon, 0.5% silicon, 16% chromium, 1% manganese, 1.5% nickel, with the balance being iron. The base material of the inner wall of the hydraulic cylinder is 35CrMo steel; the conditions for the ultra-high speed laser cladding include: laser power 5500W, spot diameter 0.8mm, powder feeding rate 63g / min, scanning speed 20m / min, overlap rate 75%, cladding layer thickness 0.8mm, and protective gas flow rate 19.5L / min; the ultra-high speed laser cladding adopts a left-right reciprocating symmetrical scanning path.

2. The method according to claim 1, characterized in that, The particle size of the laser-clad metal powder is 35~50µm.

3. The method according to claim 1, characterized in that, The method for preparing the laser cladding metal powder includes the following steps: The laser cladding metal powder is obtained by mixing powders of Fe431, molybdenum, tungsten carbide, niobium carbide, lanthanum oxide, and cerium oxide and then drying them.

4. The method according to claim 3, characterized in that, The mixing is ball milling; during ball milling, an auxiliary agent is added, including ethanol.

5. The method according to claim 1, characterized in that, Before performing ultra-high-speed laser cladding, the process also includes: pre-treating the part of the hydraulic cylinder to be clad on the inner wall and then preheating the hydraulic cylinder; the pre-treatment includes machining and cleaning in sequence; the preheating temperature is 350°C and the holding time is 15 minutes.

6. The method according to claim 1, characterized in that, During the ultra-high-speed laser cladding process, the interlayer temperature is maintained at 200℃.

7. The method according to claim 1, characterized in that, After the ultra-high-speed laser cladding, the sample is cooled to room temperature and then subjected to a first tempering treatment and a second tempering treatment in sequence. The temperature of the first tempering treatment is 300°C and the holding time is 2 hours. The temperature of the second tempering treatment is 550°C and the holding time is 4 hours.

Images