阅读说明：本技术 一种激光复合超高速激光熔覆制备高性能铁基涂层的方法 (Method for preparing high-performance iron-based coating by laser composite ultra-high-speed laser cladding ) 是由 鲁金忠 徐祥 罗开玉 杜家龙 彭明新 于 2020-02-11 设计创作，主要内容包括：本发明涉及超高速激光熔覆技术,特指一种激光复合超高速激光熔覆制备高性能铁基涂层的方法。该方法首先在工件表面超高速激光熔覆一层铁基涂层,然后关闭送粉器并调整激光功率、扫描速度和激光头焦点位置,往回对涂层进行一次激光扫描实现二次熔化和再结晶,如此往复直至加工到需要的涂层厚度。本发明通过激光二次扫描使涂层熔化和再结晶,解决超高速激光熔覆层表面颗粒附着问题和多层超高速激光熔覆层间缺陷问题,改善铁基涂层的组织和综合性能。(The invention relates to an ultrahigh-speed laser cladding technology, in particular to a method for preparing a high-performance iron-based coating by laser composite ultrahigh-speed laser cladding. The method comprises the steps of firstly carrying out ultrahigh-speed laser cladding on the surface of a workpiece to form an iron-based coating, then closing a powder feeder, adjusting laser power, scanning speed and the focal position of a laser head, carrying out primary laser scanning on the coating back to realize secondary melting and recrystallization, and repeating the steps until the required coating thickness is obtained. The invention melts and recrystallizes the coating through laser secondary scanning, solves the problem of particle adhesion on the surface of the ultra-high-speed laser cladding layer and the problem of defects between multiple layers of ultra-high-speed laser cladding layers, and improves the structure and the comprehensive performance of the iron-based coating.)

1. A method for preparing a high-performance iron-based coating by laser composite ultrahigh-speed laser cladding is characterized by comprising the following specific steps:

(1) grinding and polishing a metal workpiece to be processed, and cleaning the metal workpiece for later use by using alcohol;

(2) sieving and drying the needed iron-based powder, and filling the processed iron-based powder into a powder feeder;

(3) mounting a metal workpiece to be processed on a processing machine tool for ultra-high-speed laser cladding, and clamping by using a chuck and a thimble;

(4) adjusting the processing head of the ultra-high-speed laser cladding to enable the position of a laser focus to be located 1-5mm above the workpiece, and adjusting a nozzle of a powder feeding device to enable the powder focus to coincide with the laser focus;

(5) setting processing parameters, starting a powder feeder, starting an ultra-high-speed laser cladding processing system, and cladding a first iron-based coating along the axial direction of a metal workpiece;

(6) lifting the processing head of the ultra-high speed laser cladding by 2mm upwards, sequentially reducing the laser power of the ultra-high speed laser cladding in the step (5) by 5-15%, reducing the scanning speed by 20-50%, not opening the powder feeder, and adjusting the moving direction of the X axis in the processing program to be the axial reverse direction of the workpiece in the step (5), wherein the moving distances are the same; starting the ultra-high-speed laser cladding processing system, keeping other parameters of the ultra-high-speed laser cladding unchanged, and performing laser secondary scanning melting and recrystallization on the first iron-based coating processed in the step (5);

(7) and (5) measuring the thickness of the iron-based coating processed in the steps (5) and (6), lifting the processing head of the ultra-high-speed laser cladding upwards by the height equivalent to the thickness of the iron-based coating, performing laser cladding processing and laser secondary scanning melting and recrystallization on the second layer, wherein the laser process parameters of the laser cladding processing and the laser secondary scanning melting and recrystallization are respectively the same as those of the steps (5) and (6), and repeating the steps until the iron-based coating with the required thickness is processed.

2. The method for preparing the high-performance iron-based coating by laser composite ultra-high speed laser cladding as claimed in claim 1, wherein in the step (1), the metal workpiece is a rotary part including a shaft and a valve.

3. The method for preparing the high-performance iron-based coating by laser composite ultra-high speed laser cladding according to claim 1, wherein the iron-based powder in the step (2) can be replaced by iron-based ceramic mixed powder, and the particle sizes of the powder are 15-53 μm.

4. The method for preparing the high-performance iron-based coating by laser composite ultra-high speed laser cladding as claimed in claim 1, wherein the processing machine tool for ultra-high speed laser cladding in the step (3) is a three-axis linkage numerical control machine tool, the maximum working stroke of an X axis is 3500mm, and the moving speed is 0-10000 mm/min; the maximum working stroke of the Y axis is 350mm, the moving speed is 0-10000mm/min, the maximum working stroke of the Z axis is 350mm, the moving speed is 0-3000mm/min, the servo rotating speed of the main shaft is 0-300r/min, and the diameter of the manual three-jaw chuck is phi 640 mm.

5. The method for preparing the high-performance iron-based coating by laser composite ultra-high speed laser cladding as claimed in claim 1, wherein the powder feeding device in the step (4) is a special double-cylinder coaxial powder feeder for ultra-high speed laser cladding, the powder feeding speed is 30-150 g/min, and the conveying distance is 1.5-6 m.

6. The method for preparing the high-performance iron-based coating by the laser composite ultra-high speed laser cladding as claimed in claim 1, wherein the ultra-high speed laser cladding process parameters in the step (5) are that the diameter of a light spot is 0.5-3 mm, the laser power is 1500-8000W, the scanning speed is 10-200 m/min, the overlapping rate is 60-80%, and the argon protective gas flow is 10-15L/min.

Technical Field

The invention relates to an ultrahigh-speed laser cladding technology, in particular to a method for preparing a high-performance iron-based coating by laser composite ultrahigh-speed laser cladding.

Background

The ultra-high speed laser cladding technology is a process method which adopts a synchronous powder feeding mode, utilizes high-energy-density beam to simultaneously melt an additive material and the surface of a base material moving at a high speed, forms a cladding layer with extremely low dilution rate and metallurgical bonding with a base after rapid solidification, greatly improves the cladding rate, and obviously improves the process characteristics of wear resistance, corrosion resistance, heat resistance, oxidation resistance and the like of the surface of the base material. The method is particularly suitable for repairing and remanufacturing shaft parts, can also be used for processing planes and complex curved surfaces, has wide application prospect in the fields of engineering machinery, aerospace industry and metallurgy, and becomes a green remanufacturing process capable of replacing the traditional electroplating technology.

Rotary parts such as shaft parts, hydraulic supports, rollers, stand columns, ocean platform pipelines and the like have requirements on the wear resistance or corrosion resistance of the outer surface or the inner surface, and are a main application field in the surface treatment industry. The iron-based alloy powder has the advantages of good hardness, compactness, bonding strength and the like, and is widely applied to laser cladding manufacture. However, in the ultra-high-speed laser cladding process, manufacturing defects such as cracks and air holes of a cladding layer inevitably occur, and problems such as semi-melting and unmelted particles adhesion occur on the surface of the coating, so that the surface roughness is relatively high, the workload of subsequent secondary processing is increased, and the production cost of an enterprise is seriously increased.

Disclosure of Invention

Aiming at the problems, the invention aims to provide a method for preparing a high-performance iron-based coating by laser composite ultrahigh-speed laser cladding.

The purpose of the invention is realized by the following technical means:

a method for preparing a high-performance iron-based coating by laser composite ultrahigh-speed laser cladding is characterized by mainly comprising the following steps of:

(1) grinding and polishing a metal workpiece to be processed, and cleaning the metal workpiece for later use by using alcohol;

(2) sieving and drying the needed iron-based powder, and filling the processed iron-based powder into a powder feeder;

(3) mounting a metal workpiece to be processed on a processing machine tool for ultra-high-speed laser cladding, and clamping by using a chuck and a thimble;

(4) adjusting the processing head of the ultra-high-speed laser cladding to enable the position of a laser focus to be located 1-5mm above the workpiece, and adjusting a nozzle of a powder feeding device to enable the powder focus to coincide with the laser focus;

(5) and setting processing parameters, starting a powder feeder, starting an ultrahigh-speed laser cladding processing system, and cladding the first iron-based coating along the axial direction of the metal workpiece.

(6) Lifting the processing head of the ultra-high speed laser cladding by 2mm upwards, sequentially reducing the laser power of the ultra-high speed laser cladding in the step (5) by 5-15%, reducing the scanning speed by 20-50%, not opening the powder feeder, and adjusting the moving direction of the X axis in the processing program to be the axial reverse direction of the workpiece in the step (5), wherein the moving distances are the same; and (5) starting the ultra-high-speed laser cladding processing system, keeping other parameters of the ultra-high-speed laser cladding unchanged, and carrying out laser secondary scanning melting and recrystallization on the first iron-based coating processed in the step (5).

(7) And (5) measuring the thickness of the iron-based coating processed in the steps (5) and (6), lifting the processing head of the ultra-high-speed laser cladding upwards by the height equivalent to the thickness of the iron-based coating, performing laser cladding processing and laser secondary scanning melting and recrystallization on the second layer, wherein the laser process parameters of the laser cladding processing and the laser secondary scanning melting and recrystallization are respectively the same as those of the steps (5) and (6), and repeating the steps until the iron-based coating with the required thickness is processed.

2. In the step (1), the metal workpiece refers in particular to a rotary part comprising a shaft and a valve.

3. The iron-based powder in the step (2) can be replaced by iron-based ceramic mixed powder, and the particle size of the powder is 15-53 mu m.

4. The processing machine tool for ultra-high speed laser cladding in the step (3) is a three-axis linkage numerical control machine tool, the maximum working stroke of an X axis is 3500mm, and the moving speed is 0-10000 mm/min; the maximum working stroke of the Y axis is 350mm, the moving speed is 0-10000mm/min, the maximum working stroke of the Z axis is 350mm, the moving speed is 0-3000mm/min, the servo rotating speed of the main shaft is 0-300r/min, and the diameter of the manual three-jaw chuck is phi 640 mm.

5. And (4) the powder feeding device is a special double-cylinder coaxial powder feeder for ultrahigh-speed laser cladding, the powder feeding speed is 30-150 g/min, and the conveying distance is 1.5-6 m.

6. The technological parameters of the ultra-high speed laser cladding in the step (5) are that the diameter of a light spot is 0.5-3 mm, the laser power is 1500-8000W, the scanning speed is 10-200 m/min, the lap joint rate is 60-80%, and the argon protective gas flow is 10-15L/min.

The invention discloses a high-performance iron-based coating prepared by laser composite ultrahigh-speed laser cladding, and aims to realize melting and recrystallization of the iron-based coating by performing laser secondary input on the surface of the coating on the basis of preparing the iron-based coating by the existing ultrahigh-speed laser cladding, and improve the structure and comprehensive performance of the iron-based coating.

The invention has the beneficial effects that:

(1) for a single-layer iron-based coating, the invention can effectively improve the problems of unmelted and semi-melted powder adhesion on the surface, reduce the workload of subsequent secondary processing, greatly improve the working efficiency and save the production cost of enterprises.

(2) For the preparation of the iron-based coating with the thickness requirement, the defects of unmelted particles, cracks, air holes and the like between layers in the process of multilayer ultra-high-speed laser cladding are solved, and the structure and the comprehensive performance of the iron-based coating are improved.

Drawings

FIG. 1 is a schematic diagram of an iron-based coating prepared by the method provided by the invention, wherein 1 is a secondary melting and recrystallization layer obtained in step (6), 2 is an ultra-high-speed laser cladding layer obtained in step (5), and 3 is a metal workpiece.

FIG. 2 is a sectional microscopic view of the embodiment of the present invention, (a) is a sectional microscopic view of an ultra-high-speed laser cladding iron-based coating, and (b) is a sectional microscopic view of a laser composite ultra-high-speed laser cladding iron-based coating.

Detailed Description

The present invention will be described in more detail with reference to the following drawings, but the present invention is not limited to the embodiments.

Take an example of preparing an ultra-high-speed laser cladding iron-based alloy cladding layer on the surface of a pipe fitting.

(1) Grinding and polishing a metal pipe fitting to be processed, cleaning and drying the metal pipe fitting by using alcohol for later use, wherein the diameter of the pipe fitting is 200mm, the wall thickness is 8mm, and the length is 500 mm;

(2) screening and drying the needed iron-based alloy powder, and then loading the iron-based alloy powder into a powder feeder, wherein the iron-based alloy powder comprises the following main elements in percentage by mass: 0.1% of C, 16.72% of Cr, 1.0% of Si, 0.41% of Mn, 4.39% of Ni, 1.73% of Mo and the balance of Fe, wherein the powder particle size is 15-53 mu m;

(3) installing a metal pipe fitting to be processed on a processing machine tool for ultra-high-speed laser cladding, clamping and adjusting and correcting the coaxiality error of the metal pipe fitting to be processed and a chuck within 0.1mm by using the chuck and a thimble;

(4) adjusting the processing head of the ultra-high-speed laser cladding to enable the position of a laser focus to be located 2.4mm above the workpiece, and adjusting the powder feeding nozzle to enable the powder focus to coincide with the laser focus;

(5) setting processing parameters, wherein the diameter of a laser spot of ultra-high-speed laser cladding is 1.2mm, the laser power is 3800W, the scanning speed is 40m/min, the overlapping rate is 75%, the argon protective gas flow is 12L/min, opening a powder feeder, setting the powder feeding speed to be 50g/min, starting an ultra-high-speed laser cladding processing system, and finishing cladding of a first iron-based coating with the length of 300mm (200mm is a clamping part) along the axial direction of a metal workpiece.

(6) And (3) lifting the processing head of the ultra-high-speed laser cladding by 2mm upwards, sequentially reducing the laser power of the ultra-high-speed laser cladding to 3400W, reducing the scanning speed to 24m/min, keeping other laser cladding process parameters unchanged without opening a powder feeder and adjusting the moving distance of an X axis in the processing program to-300 mm, starting an ultra-high-speed laser cladding processing system, and performing laser secondary scanning melting and recrystallization on the first iron-based layer processed in the step (5).

FIG. 2 (b) shows a sectional micrograph of an ultra-high-speed laser cladding layer obtained by applying the method of the present invention, and compared with the micrograph (a) of the cross section of the cladding layer obtained without using a secondary laser scanning melting and recrystallization process, interlayer pores and unmelted particles are significantly improved, the adhesion phenomenon of the unmelted particles does not exist on the surface, the flatness of the surface is significantly improved, and the workload of secondary processing is reduced.