Clean and environment-friendly method for laser cladding of wear-resistant material

Abstract

The invention provides a method for increasing the carbon content and the wear resistance of a laser cladding wear-resistant material in a clean and environment-friendly manner. An adhesive, alcohol and composite metal powder are fully mixed, the mixture is pre-laid on the surface of low-carbon steel after being dried, and laser is adopted as a heat source to melt the pre-laid composite metal powder, so that the composite metal powder is metallurgically bonded with a base material; the adhesive is decomposed under the action of a laser heat source to generate a carbon element, so that the carbon content of a cladding layer is increased, and the uniformity and stability of a structure are improved; compared with the mode that graphite is added into the composite metal powder for mixing, the mode can improve the working environment of workers, facilitates industrial production, can reduce dust pollution, is more environmentally friendly and facilitates environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of laser cladding surface strengthening, and in particular relates to a clean and environmentally friendly laser cladding wear-resistant material method. Background Art

[0002] Metal products are the most widely used parts in the world, with an annual consumption of up to one trillion US dollars. Many metal equipment parts such as bearings are subject to multiple damages such as impact, wear and corrosion, and wear is the most common and basic failure mode. Foreign data show that the proportion of mechanical parts damaged by wear is as high as 80%. In addition, due to the increasingly harsh working environment (high temperature, high humidity, high speed, heavy load, high salt spray, etc.), the problem of equipment system failure caused by rapid wear on the surface of metal components has become more prominent. Therefore, improving the wear resistance and corrosion resistance of metal components and extending their service life have always been an important research field in the global equipment manufacturing industry. Using a cladding method to clad wear-resistant metal powder particles containing carbides, silicides and borides on the surface of steel parts to prepare a wear-resistant coating is one of the common and effective means to improve the wear resistance of steel, among which carbides are more widely studied. The traditional method of increasing the carbon content of the cladding layer is to add graphite powder to the cladding metal powder. However, graphite powder is light in weight, which is not conducive to the uniformity and stability of the cladding layer. In addition, it produces a lot of dust during mixing, which is not conducive to environmental protection.

[0003] The wear resistance, hardness and friction coefficient of the cladding coating are key indicators to measure the wear resistance of the coating. Adding elements such as tungsten, molybdenum and vanadium to the cladding metal is a widely used method to improve the hardness of the cladding layer, but due to its high density, it is easy to sink to the bottom during the cladding process, resulting in poor wear resistance of the upper layer of the cladding. The cooling speed of laser cladding is fast and has little impact on the parent material. It can prevent the hard phases such as tungsten, molybdenum and vanadium added to the cladding metal from sinking to the bottom, ensure the uniformity and stability of the cladding layer, and improve its wear resistance. Laser cladding technology has obvious advantages over traditional surface strengthening technology. It has the advantages of high bonding strength between the cladding layer and the substrate, low dilution rate, fine grain structure, high degree of automation, and low pollution. Summary of the invention

[0004] In view of the background technology, the present invention aims to provide a method for increasing the metal carbon content of laser cladding wear-resistant materials in a clean and environmentally friendly manner, which solves the problems of low carbon content in the metal of the cladding layer during laser cladding using the pre-laying method, resulting in poor wear resistance and hardness; poor tissue uniformity and stability during the pre-laying cladding process; and high dust content of raw materials and harsh working environment during the metal powder preparation process, which is not conducive to industrialization.

[0005] To solve the above problems, the technical solution of the present invention is implemented as follows:

[0006] (1) Preparation of cladding metal powder: metal powder, micro-carbon ferrochrome powder and tungsten oxide powder are mixed. The above component powders are mixed, and 10-50% micro-carbon ferrochrome and an appropriate amount of tungsten oxide are added to NiCrBSi powder. The sample is placed in a ball mill, and alcohol and ball-milled particles are added. The mass ratio of powder, alcohol and ball-milled particles is 1:1:5; the ball milling time is 8-10 hours, and the powder is placed in a vacuum drying furnace at a drying temperature of 70-80°C until the alcohol is completely volatilized.

[0007] (2) Weigh a certain amount of stearic acid, add an appropriate amount of anhydrous ethanol, and dissolve it in a water bath. After it is fully dissolved, mix the ball-milled and dried composite metal powder in A with the dissolved stearic acid, with a mass fraction of stearic acid of 1-5%. Stir well, and then use a 300 μm sieve to granulate. Dry the sieved composite metal powder in a dry environment for later use.

[0008] (3) Use wire cutting to cut Q235 steel into 100×50×10mm samples, use sandpaper to polish the samples to remove surface rust and oxide layer, then use alcohol to clean the sample surface to remove oil and other impurities, and dry. Pre-lay the dried composite metal powder in B on the treated Q235 steel surface, with the size of length×width×thickness of 60mm×20mm×1mm, and lay two pieces of length×width

[0009] × 70mm×10mm×1mm thick thin steel plates are placed in parallel on the surface of the steel plate to be welded, with a parallel spacing of 20-30mm between the two plates, to form a pre-paving trough. Use an appropriate amount of anhydrous ethanol to moisten the granulated particles, and then spread them in the 20-30mm wide paving trough formed by the parallel thin plates, and use a pressing plate to compact the wet particles. The compacted pre-paved particles are left to stand for 5-10 minutes to allow the alcohol to completely evaporate, and the two thin steel plates outside the trough are removed, leaving a dry and compacted pre-paved layer on the surface of the steel plate to be welded.

[0010] (4) Use laser to clad the pre-laid layer, the power is 1000-1600W, and the laser moving speed is 15-25㎜ / S. During the laser cladding operation, Ar gas with a purity of 99.99% is blown in by side blowing to protect the pre-laid material in the cladding area, and the Ar gas flow rate is 20L / min. Adjust the laser cladding process parameters to form a layer of wear-resistant material with uniform structure and good performance on the surface of the substrate.

[0011] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0012] The adhesive in the pre-laying method is decomposed under heat source to produce carbon source, which increases the carbon content of the cladding layer and is clean and environmentally friendly. The laser cladding method can prevent tungsten and other materials in the cladding layer from sinking to the bottom, and increase the uniformity and stability of the cladding layer structure. The alternate-pass cladding method can reduce the mutual influence of adjacent passes, increase the flatness of the cladding layer, and improve the uniformity and stability of the structure. DETAILED DESCRIPTION

[0013] The present invention will be described in detail below. The exemplary embodiments and descriptions of the present invention are used to explain the present invention but are not intended to limit the present invention.

[0014] Implementation method 1:

[0015] A method for increasing the metal carbon content of a laser cladding layer in a clean and environmentally friendly manner, the preparation steps comprising:

[0016] Preparation of cladding metal powder, mixing NiCrBSi metal powder, micro-carbon ferrochrome powder and tungsten oxide powder, mixing the above component powders, configuring three different proportions, NiCrBSi + 10% WO 3 Sample ①, NiCrBSi+10%WO 3 Sample ② with 20% micro-carbon ferrochromium added to the powder, NiCrBSi+10% WO 3 Sample ③ without micro-carbon ferrochromium in the powder. Place in a ball mill, add alcohol and ball milled particles, the mass ratio of powder, alcohol, and ball milled particles is 1:1:5; ball milling time is 8h, put in a vacuum drying furnace, drying temperature is 75℃, until the anhydrous ethanol is completely volatilized.

[0017] A. Weigh a certain amount of stearic acid, add an appropriate amount of anhydrous ethanol, and dissolve it in a water bath.

[0018] After it is fully dissolved, the ball-milled and dried composite metal powder in A is mixed with the dissolved stearic acid, with a mass fraction of 3% stearic acid, and fully stirred. Then, a 300 μm sieve is used for granulation. The sieved composite metal powder is dried in a dry environment for later use.

[0019] B. Use wire cutting to cut Q235 steel into 100×50×10㎜ samples, use sandpaper to polish the samples to remove surface rust and oxide layer, then use anhydrous ethanol to clean the sample surface to remove oil and other impurities, and dry. Pre-lay the metal powder dried in B on the treated Q235 steel surface, with the material size of length×width×thickness of 60mm×20mm×1mm, and lay 2 pieces of length×width

[0020] × 70mm×10mm×1mm thick thin steel plates are placed in parallel on the surface of the steel plate to be welded, with a parallel spacing of 20mm between the two plates, forming a pre-paving trough. Use an appropriate amount of anhydrous ethanol to moisten the granulated particles, then spread them in the 20mm wide paving trough formed by the parallel thin plates, and use a pressing plate to compact the wetted particles. The compacted pre-paved particles are left to stand for 8 to 10 minutes to allow the alcohol to completely evaporate, and the two thin steel plates outside the trough are removed, leaving a dry and compacted pre-paved layer on the surface of the steel plate to be welded.

[0021] C. Use laser to clad the pre-laid layer, the laser power is 1000W, and the laser moving speed is 15mm

[0022] / S. During the laser cladding process, Ar gas with a purity of 99.99% was blown in by side blowing to protect the pre-laid materials in the cladding area. The Ar gas flow rate was 20L / min. Adjust the laser cladding process parameters.

[0023] A layer of wear-resistant material with uniform structure and good performance is formed on the surface of the substrate. D. A laser cladding composite coating is prepared by the above preparation method.

Claims

1. A method for increasing the carbon content of a laser cladding layer in a clean and environmentally friendly manner, characterized in that: The method comprises the following steps: (1) ball-milling the composite metal powder, adding 1%-5% of an organic binder to granulate the powder, and drying the powder; (2) wetting the granulated composite metal powder with alcohol, pre-laying the powder on the pre-treated surface of the substrate using a mold, and placing the powder in a drying oven for drying; (3) after the pre-laying layer is dried, scanning the powder with a laser; wherein the scanning in step (2) is that if the continuous cladding process is a cladding layer formed by continuously overlapping multiple layers of the first, second, third, fourth, and fifth layers, then the cladding is firstly cladding the first, third, and fifth layers, then pre-laying the layers, and finally cladding the second and fourth layers, and so on.

2. The method for preparing a laser cladding layer by carbonization according to claim 1, characterized in that: In this experiment, the composite metal powder is composed of NiCrBSi powder, micro-carbon ferrochrome powder and tungsten oxide powder. The composite metal powder includes but is not limited to this powder composition.

3. The method for preparing a laser cladding layer by carbonization according to claim 1, characterized in that: After being heated by the laser heat source, the adhesive can produce a clean carbon source to improve the uniformity and stability of the cladding layer structure.

4. The method for preparing a laser cladding layer by carbonization according to claim 1, characterized in that: Using alcohol for wetting, due to its volatility, can supplement the cladding, solve the problem of mutual influence between adjacent passes in the pre-laying method, and increase the uniformity and stability of the cladding layer.