阅读说明：本技术 一种利用激光技术再制造最小流量阀密封面的功能层合金材料及封面的制备方法 (Functional layer alloy material for remanufacturing minimum flow valve sealing surface by utilizing laser technology and preparation method of cover ) 是由 王晓航 陈海涛 董思远 于 2021-08-18 设计创作，主要内容包括：本发明涉及激光熔覆和表面工程技术领域,本发明涉及一种通过激光熔覆技术进行阀门密封面表层强化层的再制造,获得比传统镀硬铬使用寿命更久的密封表面。一种除鳞线上的喷射阀密封面的表层材料强化方法,具体包括以下步骤：清理、混合、熔覆、预制送粉、热处理。本发明提供了一种全新的喷射阀阀芯表面强化方法。镀铬的通常有效厚度仅有4-5μm,很难做到20μm以上的高质量镀铬层。而这种方法可以制作出更厚的强化表面,厚度至少可以达到1mm以上,可以有效延长表面被破坏的时间。通过该方法制作出的表面起到比镀铬层持久的防护作用达到提高产品整体使用寿命的作用。(The invention relates to the technical field of laser cladding and surface engineering, in particular to a method for remanufacturing a reinforced layer on the surface layer of a valve sealing surface by a laser cladding technology to obtain a sealing surface with longer service life than the traditional hard chromium plating. A surface layer material strengthening method for an injection valve sealing surface on a descaling line specifically comprises the following steps: cleaning, mixing, cladding, prefabricating and feeding powder and carrying out heat treatment. The invention provides a novel method for strengthening the surface of a valve core of an injection valve. The typical effective thickness of chromium plating is only 4-5 μm, and it is difficult to achieve high quality chromium coatings of 20 μm or more. The method can manufacture a thicker strengthened surface, the thickness can reach at least more than 1mm, and the time for damaging the surface can be effectively prolonged. The surface manufactured by the method plays a lasting protection role compared with a chromium coating, and the whole service life of the product is prolonged.)

1. The functional layer alloy material for remanufacturing the sealing surface of the minimum flow valve by utilizing the laser technology is characterized by comprising the following components in percentage by mass: 28-29% of Cr, 1.42-1.43% of C, 0.5-1.5% of Mn, less than or equal to 3.0% of Ni, less than or equal to 1.1% of Mo, less than or equal to 2.0% of Si, 8.1-8.4% of W, less than or equal to 3.0% of Fe, and the balance of Co.

2. A method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology is characterized by comprising the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent;

step 2, adopting prefabricated powder feeding, feeding the powder to the front of a molten layer through a powder pipe, and feeding the powder into a molten pool through rotation of a valve; if the size of the workpiece is too small, the powder can be directly fed into the molten pool in an air-borne powder feeding mode;

step 3, laser cladding;

step 4, performing powder feeding on the powder, wherein the powder feeding amount is 12-14 g/min, and the thickness of the melting layer is controlled to be 1-1.2 mm, so that the melting layer can meet the product performance requirement;

and 5, grinding the cladding surface to a designed size, wherein the surface roughness is Ra0.8.

3. The method for remanufacturing a sealing surface of a minimum flow valve by using a laser technology as claimed in claim 2, wherein the cladding parameter in the step 3 is 2600W to 2800W, and the cladding linear speed is controlled to be 800mm/min to 1000 mm/min.

Technical Field

The invention relates to the technical field of laser cladding and surface engineering, in particular to a method for preparing a functional layer alloy material and a cover for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology, and a sealing surface with longer service life than the conventional welding strengthening method is obtained.

Background

The minimum flow control valve of a motor feed pump in a thermal power plant often has the phenomena of valve core decompression sleeve cracking, valve blocking and internal leakage caused by damage of a sealing surface. The main causes of these phenomena are: firstly, the operation under high static pressure causes metal creep of the material, and finally the bushing is suddenly cracked; secondly, the high-pressure water flow flows through the narrow opening at the opening moment of the valve to cause erosion and abrasion to the sealing surface; and thirdly, the surface of the valve core is further damaged by flash evaporation and cavitation caused by the opened valve, so that the service life of the valve core assembly is influenced.

At present, the surface of the valve core is usually repaired by adopting a way of overlaying stellite alloy in China. During repair, overheating of the substrate caused by the welding process can cause transformation of the hardened precipitation phase of the substrate and thereby reduce the hardness of the substrate, and high dilution rates can also alter the composition of the metallic structure, leading to the formation of deleterious phases and ultimately affecting the useful life of the part. Because of these disadvantages, the build-up valve cartridge is typically repaired repeatedly every half year of operation. The existing welding technology can introduce a large amount of impurities into a sealing surface due to violent reaction, and the quality is seriously influenced. Even with MIG welding, the degree of densification of the obtained structure is much lower than that of the laser-formed structure.

Disclosure of Invention

In view of the problems in the prior art, the invention aims to provide a method for preparing a functional layer alloy material and a cover for remanufacturing a sealing surface of a minimum flow valve by using a laser technology. Due to the rapid fusing characteristic of laser, a sealing material structure which is denser than the existing welding structure can be formed, and a functional layer with high purity can be formed under the protection of inert gas.

In order to achieve the above purpose, the invention adopts the following technical scheme.

A functional layer alloy material for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology comprises the following components in percentage by mass: 28-29% of Cr, 1.42-1.43% of C, 0.5-1.5% of Mn, less than or equal to 3.0% of Ni, less than or equal to 1.1% of Mo, less than or equal to 2.0% of Si, 8.1-8.4% of W, less than or equal to 3.0% of Fe, and the balance of Co.

A method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology specifically comprises the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent.

And 2, adopting prefabricated powder feeding, feeding the powder to the front of the molten layer through a powder pipe, and feeding the powder into the molten pool through rotation of a valve. If the size of the workpiece is too small, the powder can also be fed directly into the melt pool by airborne powder feeding.

And 3, controlling the laser cladding power between 2600W and 2800W, and controlling the cladding linear speed between 800mm/min and 1000 mm/min.

And 4, performing powder feeding on the powder, wherein the powder feeding amount is 12-14 g/min, and the thickness of the melting layer is controlled to be 1-1.2 mm, so that the melting layer can meet the product performance requirement.

And 5, grinding the cladding surface to a designed size, wherein the surface roughness is Ra0.8.

Compared with the prior art, the invention has the following beneficial effects.

The invention relates to a method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology, which adopts the laser cladding technology to replace the prior surfacing welding (TIG welding or MIG welding repair method), wherein the laser cladding technology is used for cladding alloy powder at the sealing surface by laser to manufacture a new high-performance sealing surface. Due to the rapid fusing characteristic of laser, a sealing material structure which is denser than the existing welding structure can be formed, and a functional layer with high purity can be formed under the protection of inert gas.

At present, the minimum flow valve manufactured by Copes-Vulcan (CV) of foreign companies has generally accepted in the industry as having high performance quality. The service life of CV manufactured valves is usually 2-3 times that of domestic repaired valves. Through analysis, the valve sealing surface is subjected to MIG welding, and a compact functional layer is formed by strictly controlling process parameters. However, even such a structure is still sparse in its degree of densification compared to a laser-formed structure, as shown in fig. 1 (a). The sealing surface prepared by the method for remanufacturing the sealing surface of the minimum flow valve by utilizing the laser technology has a fine organization structure, is beneficial to distributing strengthening phases in a metal structure more uniformly, and can more effectively prevent the expansion of fatigue cracks. These characteristics will be beneficial to improve the fatigue resistance, creep resistance, erosion resistance and the like of the material on the whole, thereby prolonging the service life of the product.

Drawings

FIG. 1 is a metallographic structure comparison graph of a CV valve sealing surface and a laser cladding sealing surface provided by the invention under the same multiplying power. (a. the metallographic structure of the sealing surface of the American CV company; b. the metallographic structure of the laser cladding sealing surface).

FIG. 2 is an orthogonal test of the different compositional proportions of cobalt-based materials.

FIG. 3 shows the hardness of the sample under different ratios and process conditions of the cobalt-based material 2.

Detailed Description

The invention is described in detail below with reference to the figures and the specific embodiments. It will be readily understood by those skilled in the art that the following descriptions are only exemplary of the preferred embodiments of the present invention, and are not intended to limit the present invention, and any modifications, equivalents, improvements, etc. made within the spirit and principle of the present invention should be included in the scope of the present invention.

1. And (4) screening and testing the components and the dosage of the functional layer alloy material.

The existing stellite material is modified before laser cladding, and a material which has better fusion welding performance and is more suitable for laser cladding is redesigned. The selection of the material components is to slightly adjust the proportion of chemical components on the basis of the existing mature cobalt-based material, and then to screen out the components meeting the laser cladding requirements by a comparative experiment. After (FIG. 2), the internal tissues were cut to observe the presence of pores, defects, and inclusions. And finally, recording all chemical element component ratios meeting the quality requirements. Finally, the components of the alloy are 28-29% of Cr, 1.42-1.43% of C, 0.5-1.5% of Mn, less than or equal to 3.0% of Ni, less than or equal to 1.1% of Mo, less than or equal to 2.0% of Si, 8.1-8.4% of W, less than or equal to 3.0% of Fe, and the weight ratio of Co: and (4) the balance.

The cobalt-based material has good fatigue resistance and abrasion resistance, and has good weldability. Wherein, the cobalt element can effectively improve the cavitation resistance of the product. C can form a strengthening phase in the cladding process, and is mainly carbide MC. The content of C can avoid the formed MC particles from influencing the strengthening effect too much, and can form finer and more dispersed carbide to play a better strengthening role. High chromium levels form alkali metal sulfate (e.g., Na) resistance at the alloy surface₂SO₄Corroded Cr₂O₃A protective layer). The higher chromium content of the nickel-based alloy can compensate for the weak oxidation resistance of the cobalt-based alloy compared with the nickel-based alloy. The addition of Mn, Ni, Mo and other elements can further improve the overall corrosion resistance and abrasion resistance of the material, and the weldability of the powder enables laser cladding forming to be possible.

2. A screening test of key process parameters of a method for remanufacturing a minimum flow valve sealing surface by utilizing a laser technology is disclosed.

After the proper material components are determined, proper technological parameters are designed, mainly including laser power and cladding linear speed. Each component was clad using the same 3-4 processes (fig. 3). The samples were cut out of cross-sectional samples by wire cutting and the vickers hardness of the cross-sections was measured. Selecting the material with good molding quality and high hardness for cladding. Wherein, the less defects such as air holes and the like, the higher internal microcosmic hardness of the material, the better the cavitation erosion resistance, the erosion resistance and the corrosion resistance of the sealing surface of the product, and the longer the total service life of the product.

A method for remanufacturing a minimum flow valve sealing surface by utilizing a laser technology finally determines the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent.

And 2, controlling the laser cladding power between 2600W and 2800W, and avoiding the defect of molten liquid drop splashing caused by over severe reaction in the cladding process. And the defects of air holes, impurities and the like caused by incomplete penetration of the bottom can be prevented from forming. The linear speed of cladding is controlled to be 800mm/min to 1000 mm/min.

And 3, effectively protecting the molten pool by using inert gas in the cladding process to prevent the formation of oxides and other impurities.

Example 1.

A functional layer alloy material for laser remanufacturing of a minimum flow valve sealing surface comprises the following components in percentage by mass: 26% of Cr, 1.42% of C, 0.7% of Mn, 2.3% of Ni, 0.9% of Mo, 2.0% of Si, 8.3% of W, 3.0% of Fe and the balance of Co.

A method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology specifically comprises the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent.

And 2, directly feeding the powder into the molten pool by adopting an air-borne powder feeding mode.

And 3, controlling the laser cladding power at 2735W and controlling the cladding linear speed at 900 mm/min.

And 4, performing powder feeding by adopting prefabricated powder feeding, wherein the powder feeding amount is 11g/min, and the thickness of a molten layer is controlled to be 1.1 mm.

And 5, grinding the cladding surface to a designed size, wherein the surface roughness is Ra0.8.

Example 2.

A functional layer alloy material for laser remanufacturing of a minimum flow valve sealing surface comprises the following components in percentage by mass: 26% of Cr, 1.43% of C, 1.3% of Mn, 2.2% of Ni, 1.1% of Mo, 2.0% of Si, 8.2% of W, 3.0% of Fe and the balance of Co.

A method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology specifically comprises the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent.

And 2, adopting prefabricated powder feeding, feeding the powder to the front of the molten layer through a powder pipe, and feeding the powder into the molten pool through rotation of a valve.

And 3, controlling the laser cladding power to 2815W, and controlling the cladding linear speed to 940 mm/min.

And 4, performing powder feeding by adopting prefabricated powder feeding, wherein the powder feeding amount is 10g/min, and the thickness of a molten layer is controlled to be 1.0 mm.

And 5, grinding the cladding surface to a designed size, wherein the surface roughness is Ra0.8.

Example 3.

A functional layer alloy material for laser remanufacturing of a minimum flow valve sealing surface comprises the following components in percentage by mass: 29% of Cr, 1.42% of C, 0.6% of Mn, 1.3% of Ni, 0.7% of Mo, 2.0% of Si, 8.1% of W, 3.0% of Fe and the balance of Co.

A method for remanufacturing a sealing surface of a minimum flow valve by utilizing a laser technology specifically comprises the following steps:

step 1, polishing and cleaning oxide skin of a surface to be clad, and removing oil stains on the surface of the surface to be clad by using a cleaning agent.

And 2, adopting prefabricated powder feeding, feeding the powder to the front of the molten layer through a powder pipe, and feeding the powder into the molten pool through rotation of a valve.

And 3, controlling the laser cladding power to 2690W, and controlling the cladding linear speed to 980 mm/min.

And 4, performing powder feeding by adopting prefabricated powder feeding, wherein the powder feeding amount is 13g/min, and the thickness of a molten layer is controlled to be 1.2 mm.

And 5, grinding the cladding surface to a designed size, wherein the surface roughness is Ra0.8.

The invention provides the effect evaluation of the laser cladding sealing surface and the CV valve sealing surface.

The minimum flow valve manufactured by Copes-Vulcan (CV) of foreign companies has gained widespread acceptance in the industry for its high performance quality. The service life of CV manufactured valves is usually 2-3 times that of domestic repaired valves. Through analysis, the valve sealing surface is subjected to MIG welding, and a compact functional layer is formed by strictly controlling process parameters. However, even such a structure is still sparse in its degree of densification compared to a laser-formed structure, as shown in fig. 1 (a). The sealing surface prepared by the method for remanufacturing the sealing surface of the minimum flow valve by utilizing the laser technology has a fine organization structure, as shown in fig. 1 (b), is beneficial to more uniform distribution of a strengthening phase in a metal structure, and can more effectively prevent the expansion of fatigue cracks. These characteristics will be beneficial to improve the fatigue resistance, creep resistance, erosion resistance and the like of the material on the whole, thereby prolonging the service life of the product.