CN106757010B

CN106757010B - Preparation method of fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating

Info

Publication number: CN106757010B
Application number: CN201710034260.4A
Authority: CN
Inventors: 陈菊芳; 董冬梅; 雷卫宁
Original assignee: Jiangsu University of Technology
Current assignee: Jiangsu University of Technology
Priority date: 2017-01-17
Filing date: 2017-01-17
Publication date: 2020-01-03
Anticipated expiration: 2037-01-17
Also published as: CN106757010A

Abstract

The invention discloses a preparation method of a fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating, which comprises the following steps: 1) selecting 45 steel as a laser cladding matrix, removing rust or oil stains on the surface of the matrix by using an acetone solution, and then wiping the matrix clean by using alcohol; 2) uniformly mixing 20% of nickel-coated tungsten carbide and the balance of nickel 45 powder; 3) pre-bonding the mixed powder on the surface of a 45 steel substrate by adopting a pre-setting method, wherein the thickness of the powder is 1mm, and drying in an oven; 4) and carrying out laser cladding by using a fiber laser, wherein the diameter of a light spot is 4mm, and the scanning speed is 12-16 mm/s. According to the invention, by adopting the fiber laser, drying the preset layer at low temperature and adding a certain amount of nickel-coated tungsten carbide powder into the nickel-based powder, the bonding strength of the cladding layer and the matrix is improved, the hardness of the cladding layer is improved, and the cladding layer with uniform and compact structure and few cracks and pore defects is obtained.

Description

Preparation method of fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating

Technical Field

The invention belongs to the technical field of laser cladding metal ceramic composite materials, and particularly relates to a preparation method of a fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating.

Background

The laser cladding technology is formed in 80 years of the 20 th century, is an advanced surface improvement technology, and is widely applied to preparation of intermetallic compound-based composite coatings. The principle is that the local high temperature generated by the high-energy density laser beam is utilized to instantly melt two or more metal interfaces, the cladding material and the matrix realize metallurgical bonding, and a cladding layer with different components from the matrix is formed, so that the material performance is improved. Compared with the technologies of surfacing, thermal spraying and the like, the method has the advantages that: such as high hardness of the cladding layer, good wear resistance, small deformation of the workpiece, stable quality of the cladding layer, high cooling speed, small pollution, high stability and the like. Laser cladding has been widely used in various fields such as the automotive industry, aerospace, oceans and petrochemical industry at present. Therefore, it has wide market prospect.

Cladding materials: the existing cladding materials widely applied mainly comprise: the nickel-based alloy has good compatibility, and the nickel-based alloy also has good wear resistance, corrosion resistance and high-temperature mechanical property. It is also the most used self-fluxing alloy powder.

Nickel-coated tungsten carbide: nickel-coated WC consists of tungsten carbide particles in a nickel-coated layer and a core, which is a carbide ceramic phase with very high hardness, which not only has good metallic properties, low thermal expansion coefficient and good wear resistance, but also has toughness that is better in ceramic materials, and thus is often used as a strengthening phase for metal-based composite coatings. The nickel coating layer on the surface layer is beneficial to improving the wettability of tungsten carbide and alloy solution, and simultaneously, the oxidation and the decomposition of the tungsten carbide in the laser cladding process can be reduced as much as possible.

A laser: the lasers currently used in industry for manufacturing are first generation lasers (CO)₂And YAG laser). In recent years, third generation lasers: fiber lasers are rapidly evolving. Fiber lasers have many advantages over the first two generations of lasers: the fiber laser has compact structure and low manufacturing cost; the fiber laser has high electro-optic conversion efficiency, greatly reduces the power consumption during working and has low operation cost; the resonant cavity of the fiber laser is free of optical lens, adjustment and maintenance, and high in stability; the absorption rate of the metal material to laser light is increased along with the reduction of the wavelength, and the wavelength of the optical fiber laser is about CO₂One tenth of laser, the absorption rate of the material to laser is high due to the short wavelength; the optical fiber laser adopts the optical fiber to transmit laser energy, thereby being convenient for realizing flexible manufacturing and the like.

With the continuous development of science and technology, laser cladding nickel-based ceramic composite coatings are widely concerned and researched by scholars at home and abroad (CN104046982B, CN103447485A), but the problems of uneven cladding layer structure, reduced bonding strength, reduced hardness and the like caused by the defects of cracks, air holes and the like of cladding layers after cladding exist all the time, so that the further popularization and application of the laser cladding nickel-based ceramic composite coatings in industry are limited. At present, the researched cladding coating is generally prepared by using a carbon dioxide laser, and the research on the cladding coating prepared by a fiber laser is relatively less; during the powder presetting period, the generally adopted drying temperature is relatively high, the low-temperature drying is less researched, the possibility of powder oxidation exists when the temperature is too high, and further, certain influence is caused on the performance of a cladding layer; in addition, most of research on tungsten carbide added in the cladding powder is non-cladding type, the research on cladding type is relatively less, and the cladding type tungsten carbide has better wettability and can effectively reduce the oxidative decomposition of the tungsten carbide. Therefore, it is very important to find a perfect method for cladding the nickel-based nickel-coated tungsten carbide cladding coating by laser cladding.

Disclosure of Invention

The invention aims to overcome the problems of uneven cladding layer structure, reduced bonding strength, reduced hardness and the like caused by the defects of cracks, air holes and the like of a cladding layer in the prior art, and provides a preparation method of an optical fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating; by adopting the fiber laser, drying the preset layer at low temperature and adding a certain amount of nickel-coated tungsten carbide powder into the nickel-based powder, the bonding strength of the cladding layer and the matrix is improved, the hardness of the cladding layer is improved, and the cladding layer with uniform and compact tissue, less cracks and less pore defects is obtained.

The invention provides a preparation method of a fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating, which comprises the following steps:

the method comprises the following steps: selecting 45 steel as a laser cladding matrix, removing rust or oil stains on the surface of the matrix by using an acetone solution, and then wiping the matrix clean by using alcohol;

step two: uniformly mixing nickel-coated tungsten carbide and Ni45 nickel-based self-fluxing alloy powder to obtain mixed powder;

step three: pre-bonding the mixed powder on the surface of a 45 steel substrate by adopting a pre-setting method, wherein the thickness of the powder is 1mm, and drying in an oven;

step four: performing laser cladding by using a fiber laser, wherein the diameter of a light spot is 4mm, and the scanning speed is 12-16 mm/s; the laser power is 1600-2000 w, preferably 2000 w; argon is used for protection.

Preferably, in the second step, the content of the nickel-containing tungsten carbide is 20 percent and the content of the Ni45 nickel-based self-fluxing alloy powder is 80 percent by weight.

Preferably, the nickel-coated tungsten carbide in the second step consists of 88 percent of WC and 12 percent of Ni in percentage by mass, and the Ni45 nickel-based self-fluxing alloy powder consists of 13 percent of Cr, 2.5 percent of B, 3 percent of Si, 10 percent of Fe and the balance of Ni in percentage by mass;

preferably, the particle sizes of the nickel-coated tungsten carbide and the Ni45 nickel-based self-fluxing alloy powder in the second step are both-140 meshes to +325 meshes;

preferably, the powder is dried for 1-2 h at 60 ℃ in the third step.

The invention has the following advantages:

1. the optical fiber laser cladding layer has high energy and good stability, and can be used for preparing a laser cladding layer with uniform and compact tissue and few cracks and air hole defects;

2. the nickel-based self-fluxing alloy is matched with steel in all physical indexes, has good compatibility, and also has good wear resistance, corrosion resistance and high-temperature mechanical property;

3. nickel-coated tungsten carbide differs from tungsten carbide in that the former is a coated powder and the latter is a non-coated powder. The core powder of the coated powder is protected by the coating layer, so that the phenomena of oxidation burning loss, thermal decomposition and the like of elements can be avoided or reduced in the coating preparation process, the geometric shape and the crystal structure of the core particle are kept, and the high-quality coating is obtained. The invention adopts the cladding type nickel-clad tungsten carbide, and the embodiment shows that the laser cladding of the nickel-clad tungsten carbide is more beneficial to reducing the oxidative decomposition of the tungsten carbide in the cladding layer than the laser cladding of the tungsten carbide, thereby improving the performance of the cladding layer;

4. according to the invention, a method for drying the powder at low temperature by using the drying oven is adopted, most of the current researches adopt the drying oven with the temperature higher than 100 ℃, compared with the method for drying the powder at high temperature, the low-temperature dried powder can effectively prevent the oxidative decomposition of the powder, and the embodiment also shows that the method for drying the powder at low temperature obtains relatively fewer cladding layer pores and cracks, so that the performance is better;

5. the hardness of the composite coating formed by fiber laser cladding is obviously improved. When the nickel-coated tungsten carbide accounts for 20 percent and the laser power is 1600w, 1800w and 2000w respectively, the hardness of the cladding layer is about 2-3 times of that of 45 steel of the matrix, and the performance of the base material is obviously improved.

Description of the drawings:

FIG. 1 is a schematic view showing the structure of a laser cladding layer of example 1 (60 ℃ C. dry condition);

FIG. 2 is a graph showing the structure of a laser cladding layer of example 1 (drying condition at 120 ℃);

FIG. 3 is a graph of the laser cladding layer structure of example 2 (being nickel-clad tungsten carbide);

FIG. 4 is a microstructure of the laser cladding layer of example 2 (tungsten carbide);

FIG. 5 is a hardness profile of a laser cladding layer of example 3 (laser power 1600 w);

FIG. 6 is a hardness profile of a laser cladding layer of example 3 (laser power 1800 w);

FIG. 7 is a hardness profile of a laser cladding layer of example 3 (laser power 2000 w).

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the description is intended to be exemplary only, and is not intended to limit the scope of the present invention.

The nickel-coated tungsten carbide used in the invention is the nickel-coated tungsten carbide composite powder which is manufactured by the North mine New Material science and technology Limited company and has the model of KF-56.

Example 1

(1) Selecting 45 steel as a laser cladding matrix, removing rust or oil stains on the surface of the matrix by using an acetone solution, and then wiping the matrix clean by using alcohol;

(2) uniformly mixing 20% of nickel-coated tungsten carbide and 80% of nickel 45 powder in percentage by mass;

(3) pre-bonding the mixed powder on the surface of a 45 steel substrate by adopting a pre-setting method, wherein the thickness of the powder is 1mm, and placing the powder in an oven for drying (a. the powder is dried by the oven at 60 ℃ for 1.5h, and b. the powder is dried by the oven at 120 ℃ for 1.5 h);

(4) laser cladding was performed using a fiber laser with a spot diameter of 4mm and a scanning speed of 14 mm/s. The laser power is 1600w, and argon is used for protection.

FIGS. 1 and 2 are the texture maps of the laser cladding layer of example 1, wherein the texture map of the cladding layer is shown in FIG. 1 when the powder is dried by the oven at 60 ℃ for 1.5h, and the texture map of the cladding layer is shown in FIG. 2 when the powder is dried by the oven at 120 ℃ for 1.5 h. As can be seen from the embodiment 1, the low-temperature drying of the powder can effectively reduce the generation of pores in the cladding layer, and has a good promotion effect on the improvement of the quality of the cladding layer.

Example 2

(2) uniformly mixing 20% by mass of nickel-coated tungsten carbide and the balance of nickel 45 powder, and uniformly mixing 20% by mass of tungsten carbide and the balance of nickel 45 powder;

(3) the mixed powder is bonded on the surface of a 45 steel matrix in a preset way by adopting a preset method, the thickness of the powder is 1mm, and the powder is dried for 1.5h at the temperature of 60 ℃ in an oven;

(4) laser cladding was performed using a fiber laser with a spot diameter of 4mm and a scanning speed of 12 mm/s. The laser power is 1800w, and argon gas is used for protection.

Fig. 3 and 4 are texture maps of the laser cladding layer of example 2, the texture map of the nickel-coated tungsten carbide cladding layer with a mass fraction of 20% is shown in fig. 3, and the texture map of the tungsten carbide cladding layer with a mass fraction of 20% is shown in fig. 4. It can be seen from example 2 that the nickel coating is effective in reducing the oxidative decomposition of tungsten carbide and maintains a good geometry.

Example 3

(2) uniformly mixing 20% of nickel-coated tungsten carbide and the balance of nickel 45 powder;

(3) adopting a preset method, presetting and bonding the mixed powder on the surface of a 45 matrix, wherein the thickness of the powder is 1mm, and drying the powder for 1.5h at 60 ℃ by using an oven;

(4) laser cladding was performed using a fiber laser with a spot diameter of 4mm and a scanning speed of 16 mm/s. The laser power is a.1600w, b.1800w and c.2000w, and argon gas is adopted for protection.

FIGS. 5-7 are hardness profiles of laser cladding layers, and a microhardness profile of the cladding layer with a laser power of 1600w is shown in FIG. 5; the microhardness distribution curve of the cladding layer with the laser power of 1800w is shown in FIG. 6; the microhardness profile of the cladding layer at a laser power of 2000w is shown in FIG. 7. From the example 3, it can be seen that the microhardness of the three cladding layers is about 2-3 times of that of 45 steel of the substrate, the performance of the substrate is remarkably improved, but the cladding layer with the power of 2000w is relatively higher in microhardness and smaller in variation range, and the performance is more stable.

Although the embodiments of the present invention have been described in detail, it should be understood that various changes, substitutions, and alterations can be made hereto without departing from the spirit and scope of the invention.

Claims

1. A preparation method of a fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating comprises the following steps:

1) selecting 45 steel as a laser cladding matrix, removing rust or oil stains on the surface of the matrix by using an acetone solution, and then wiping the matrix clean by using alcohol;

2) uniformly mixing nickel-coated tungsten carbide and Ni45 nickel-based self-fluxing alloy powder to obtain mixed powder;

3) pre-bonding the mixed powder on the surface of a 45 steel substrate by adopting a pre-setting method, wherein the thickness of the powder is 1mm, and drying in an oven;

4) performing laser cladding by using a fiber laser, wherein the diameter of a light spot is 4mm, and the scanning speed is 12-16 mm/s; the laser power is 1600-2000 w, and argon is adopted for protection;

according to weight percentage, the content of the nickel-coated tungsten carbide in the step 2) is 20 percent, and the content of the Ni45 nickel-based self-fluxing alloy powder is 80 percent;

the granularity of the nickel-coated tungsten carbide and Ni45 nickel-based self-fluxing alloy powder in the step 2) is between-140 and +325 meshes;

and 3) drying the powder at 60 ℃ for 1-2 h.

2. The preparation method of the fiber laser cladding nickel-based nickel-coated tungsten carbide cladding coating according to claim 1, characterized by comprising the following steps: the laser power in the step 4) is 2000 w.