CN115537704B - Preparation method of explosion-sprayed nickel-based lubricating coating - Google Patents

Abstract

The present invention relates to a method for preparing an explosion-sprayed nickel-based lubricating coating, the method comprising the following steps: (1) pretreatment of a substrate: after deoxidation and roughening treatment of a metal substrate or a sample surface by a high-pressure sandblasting process, ultrasonic cleaning and drying in an alcohol solution are performed to obtain a pretreated substrate; (2) preparation of a spraying composite powder: 80-95 wt.% spherical NiCrAlY powder and 5-20 wt.% lubricant spherical silver powder are mixed evenly in a low-energy ball mill to obtain a spraying composite powder; (3) preparation of a coating: first spraying spherical NiCrAlY powder on the surface of the pretreated substrate by an explosion spraying technique to obtain a NiCrAlY transition layer; then spraying the spraying composite powder on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating. The equipment required by the present invention is simple, the process is controllable, and the cost is low. The bonding strength between the prepared nickel-based lubricating coating and the metal substrate is greater than 40 MPa, and the lubrication performance is excellent from room temperature to 300°C, and it has important application prospects in the lubrication and wear resistance of the surface of shaft parts.

Description

A method for preparing a nickel-based lubricating coating by explosion spraying

Technical Field

The invention relates to the technical field of metal surface treatment, and in particular to a method for preparing an explosion-sprayed nickel-based lubricating coating.

Background technique

Solid lubricating coating materials are an important way to solve the high-temperature friction and wear of high-end equipment mechanical parts in the fields of aerospace, nuclear energy, etc. Developed countries such as Europe, the United States, and Japan are at the international leading level in the research and development of solid lubricating coating material technology. In the last century, NASA's Green Research Center used nickel alloy as the matrix phase, Ag+ _CaF2 / _BaF2 as the composite lubricating phase, _{and Cr3C2} / _Cr2O3 as the enhanced anti-wear _phase to pioneer the development of the PS series of nickel-based lubricating coatings, which were successfully applied to components such as spacecraft swing bearings and air bearings, achieving the technical difficulties of lubrication and wear resistance in a wide temperature range from room temperature to 650℃ (NASA/TM-2010-216774). In China, in the past two decades, many scientific research institutions and scholars have systematically carried out research on nickel-based solid lubricating coatings, and have carried out a lot of fruitful work in the diversification of preparation processes (spraying, laser cladding) and the diversification of collaborative lubrication design. However, there are still some problems with the performance of nickel-based solid lubricating coatings, mainly manifested in low coating layer-base bonding and poor lubrication and wear resistance.

Excellent spraying preparation technology and process are key factors to ensure that solid lubricating and wear-resistant coatings have good organizational structure and excellent performance. Thermal spraying technologies such as supersonic flame spraying and plasma spraying are currently the most common means of coating preparation, but the coatings they prepare have disadvantages such as low bonding strength, easy peeling, high porosity, insufficient wear resistance, and high thermal damage to the substrate during the spraying process. Compared with them, explosion spraying technology uses the shock wave energy generated by the explosion of combustible gas to accelerate the heating of the powder to be sprayed, bombarding the surface of the sprayed substrate to form a coating. The prepared coating has more advantages in terms of layer-base bonding, density, and wear resistance; at the same time, the workpiece has little thermal damage during the preparation process, the size and shape of the workpiece are not restricted, and the types of materials that can be sprayed cover metals, ceramics and other multi-material systems. However, there is currently no relevant literature reporting the use of explosion spraying technology for the preparation of nickel-based lubricating coatings.

Summary of the invention

The technical problem to be solved by the present invention is to provide a method for preparing an explosion sprayed nickel-based lubricating coating with low cost and good coating performance.

In order to solve the above problems, a method for preparing a nickel-based lubricating coating by explosion spraying according to the present invention comprises the following steps:

⑴Pretreatment of substrate:

After the metal substrate or sample surface is deoxidized and roughened by high-pressure sandblasting, it is ultrasonically cleaned and dried in an alcohol solution to obtain a pretreated substrate;

(2) Preparation of spray composite powder:

80-95 wt. % spherical NiCrAlY powder and 5-20 wt. % lubricant spherical silver powder are uniformly mixed in a low-energy ball mill to obtain a spray composite powder;

⑶Preparation of coating:

The spherical NiCrAlY powder is first sprayed on the surface of the pretreated substrate by using the explosion spraying technology to obtain a NiCrAlY transition layer; then the spray composite powder is sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating.

In the step (1), the material of the metal substrate or sample is one of 304 stainless steel, GH4169 nickel-based high-temperature alloy, TC4 titanium alloy, and Inconel 718 alloy.

In the step (1), the pressure of the compressed air in the high-pressure sandblasting process is 0.6-0.8 MPa, and the particle size of the aluminum oxide sand used is 40-100 μm.

The particle size of the spherical NiCrAlY powder in step (2) is 20-60 μm, and its components are 20-22 wt. % Cr, 10-12 wt. % Al, 1-1.5 wt. % Y and 64.5-79 wt. % Ni.

The purity of the spherical silver powder in step (2) is 99.99% and the particle size is below 48 μm.

In the step (2), the rotation speed of the low-energy ball mill is controlled at 150-200 r/min, the ball-to-material ratio is 1:2-1:5, and the time is 2-5 h.

The explosion spraying process in step (3) refers to that the fuel is acetylene and propane, the combustion-supporting gas is oxygen, and the carrier gas is nitrogen; the acetylene inlet pressure ranges from 1.35 to 1.45 bar, and the air intake time is 4 to 90 ms; the propane inlet pressure ranges from 1.8 bar, and the air intake time is 4 to 55 ms; the oxygen is divided into two paths, and the air intake times are 3 to 70 ms and 3 to 90 ms respectively; the filling ratio of the fuel gas and oxygen is 42% to 61%, and the oxygen-carbon ratio is 1.015:1 to 1.945:1; the nitrogen inlet pressure ranges from 1.80 to 2.20 bar, and the air intake time is 95 ms to 250 ms; the powder feeding time is 50 to 105 ms; the spraying distance (the distance from the muzzle to the sample surface) is 200 to 250 mm; and the explosion frequency is controlled at 4 to 5 times per second.

The front barrel used for the explosion spraying is a trumpet-shaped barrel, with an inner diameter of 18 mm at the rear end and 27 mm at the front end.

In step (3), the thickness of the NiCrAlY transition layer is between 70 and 100 μm; the thickness of the NiCrAlY-Ag lubricating coating is between 200 and 500 μm.

Compared with the prior art, the present invention has the following advantages:

1. The present invention adopts explosion spraying process for spraying. Compared with plasma spraying and supersonic spraying technology, explosion spraying is an intermittent working mode with a frequency controlled at 4 to 5 times per second, which causes very little thermal damage to the substrate or parts.

2. The present invention uses acetylene and propane as fuels, and by adjusting the filling-to-gun ratio of acetylene and propane, a high flying speed is given to the spray powder, while the oxidation of the metal powder and the burning of the low-temperature elements can be reduced, thereby obtaining a high-density coating that cannot be matched by other spraying methods.

3. The present invention has simple equipment, controllable process and low cost, and can be used to prepare surface coatings for large-sized and complex parts.

4. The nickel-based lubricating coating prepared by the method of the present invention has uniform composition, a coating thickness between 200 and 500 μm, a bonding strength with the metal substrate greater than 40 MPa, and a friction coefficient less than or equal to 0.3 from room temperature to 300 °C. It has important application prospects in the surface lubrication and wear resistance of shaft parts.

BRIEF DESCRIPTION OF THE DRAWINGS

The specific implementation modes of the present invention will be further described in detail below in conjunction with the accompanying drawings.

Figure 1 is an electron microscope image of the cross section of the nickel-based lubricating coating prepared in Example 1 of the present invention. Among them: a is an electron image; b is a Fe element distribution map; c is a Ni element distribution map; d is a Cr element distribution map; e is an Al element distribution map; and f is an Ag element distribution map.

FIG. 2 is a bearing sample with a nickel-based coating prepared in Example 2 of the present invention.

Detailed ways

A method for preparing a nickel-based lubricating coating by explosion spraying comprises the following steps:

⑴Pretreatment of substrate:

The metal substrate or sample surface is deoxidized and roughened by high-pressure sandblasting. The pressure of the compressed air is 0.6-0.8 MPa, and the particle size of the aluminum oxide sand used is 40-100 μm. After treatment, ultrasonic cleaning and drying in an alcohol solution are performed to obtain the pretreated substrate.

Wherein: the material of the metal matrix or sample is one of 304 stainless steel, GH4169 nickel-based high-temperature alloy, TC4 titanium alloy, and Inconel 718 alloy.

(2) Preparation of spray composite powder:

80~95 wt. % spherical NiCrAlY powder and 5~20 wt. % lubricant spherical silver powder are mixed in a low-energy ball mill, the speed is controlled at 150~200 r/min, the ball-to-material ratio is 1:2~1:5, and the time is 2~5 hours. After mixing evenly, the spray composite powder is obtained.

Among them: the particle size of the spherical NiCrAlY powder is 20~60μm, and its components are 20~22wt.% Cr, 10~12wt.% Al, 1~1.5 wt.% Y and 64.5~79 wt.% Ni.

The purity of the spherical silver powder is 99.99% and the particle size is below 48 μm.

⑶Preparation of coating:

Spherical NiCrAlY powder is first sprayed on the pretreated substrate surface using explosion spraying technology to obtain a NiCrAlY transition layer with a thickness of 70~100μm; then the spray composite powder is sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating with a thickness of 200~500μm.

Among them: the explosion spraying process refers to the fuel being acetylene and propane, the combustion-supporting gas being oxygen, and the carrier gas being nitrogen; the acetylene inlet pressure range is 1.35~1.45bar, and the air intake time is 4~90ms; the propane inlet pressure range is 1.8 bar, and the air intake time is 4~55ms; the oxygen is divided into two paths, and the air intake times are 3~70ms and 3~90ms respectively; the filling ratio of the fuel gas and oxygen is 42%~61%, and the oxygen-carbon ratio is 1.015:1~1.945:1; the nitrogen inlet pressure range is 1.80~2.20bar, and the air intake time is 95ms~250ms; the powder delivery time is 50~105ms; the spraying distance (the distance from the muzzle to the sample surface) is 200~250mm; and the explosion frequency is controlled at 4~5 times/second.

The front barrel used for explosion spraying is a trumpet-shaped barrel with an inner diameter of 18 mm at the rear end and 27 mm at the front end.

Example 1 A method for preparing a nickel-based lubricating coating by explosion spraying comprises the following steps:

⑴Pretreatment of substrate:

The surface of the 304 stainless steel block substrate was deoxidized and roughened by high-pressure sandblasting. The pressure of the compressed air was 0.6-0.8 MPa, and the particle size of the aluminum oxide sand used was 100 μm. After treatment, it was ultrasonically cleaned and dried in an alcohol solution to obtain a pretreated substrate.

(2) Preparation of spray composite powder:

85g of spherical NiCrAlY powder and 15g of lubricant spherical silver powder were mixed in a low-energy ball mill with a rotation speed of 200 r/min, a ball-to-material ratio of 1:2, and a time of 2 h. After uniform mixing, 100g of spray composite powder was obtained.

⑶Preparation of coating:

Spherical NiCrAlY powder was first sprayed on the pretreated substrate surface using CCDS2000 explosion spraying technology to obtain a NiCrAlY transition layer with a thickness of 70 μm; then the spray composite powder was sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating with a thickness of 230 μm.

Among them: the explosion spraying process refers to the fuel being acetylene and propane, the combustion-supporting gas being oxygen, and the carrier gas being nitrogen; the acetylene inlet pressure range is 1.35~1.45bar, and the air intake time is 4~60ms; the propane inlet pressure range is 1.8 bar, and the air intake time is 4~45ms; the oxygen is divided into two paths, and the air intake times are 3~50ms and 3~64ms respectively; the filling ratio of the fuel gas and oxygen is 43%, and the oxygen-carbon ratio is 1.015:1; the nitrogen inlet pressure range is 1.80~2.20bar, and the air intake time is 95ms~199ms; the powder delivery time is 50~105ms; the spraying distance (the distance from the muzzle to the sample surface) is 250mm; and the explosion frequency is controlled at 5 times/second.

The composition and thickness of the obtained nickel-based lubricating coating were characterized by SEM microscopy, as shown in Figure 1. It can be found from the figure that the total thickness of the coating is about 300 μm, the thickness of the transition layer is about 70 μm, and the thickness of the composite layer is about 230 μm; Ni, Cr, Al, and Ag elements are evenly distributed in the coating.

The bonding strength of the obtained nickel-based lubricating coating was tested by the adhesion method, and its bonding strength was greater than 44 MPa.

The lubrication performance of the obtained nickel-based lubricating coating from room temperature to 300 °C was characterized by using an HT-1000 friction and wear tester. The friction conditions were nickel-based lubricating coating-GH4169 alloy bolt, speed 0.2 m/s, and load 10 N. The test results are shown in Table 1.

Table 1

It can be seen from Table 1 that the friction coefficient of the coating from room temperature to 300°C is less than or equal to 0.3.

Example 2 A method for preparing a nickel-based lubricating coating by explosion spraying comprises the following steps:

⑴Pretreatment of substrate:

The surface of 304 stainless steel block or bearing sample is deoxidized and roughened by high-pressure sandblasting process, the pressure of compressed air is 0.6~0.8 MPa, and the particle size of aluminum oxide sand used is 60 μm. After treatment, ultrasonic cleaning and drying in alcohol solution are carried out to obtain the pretreated substrate.

(2) Preparation of spray composite powder:

90g of spherical NiCrAlY powder and 10g of lubricant spherical silver powder were mixed in a low-energy ball mill with a rotation speed of 180 r/min, a ball-to-material ratio of 1:2, and a time of 3 h. After uniform mixing, 100g of spray composite powder was obtained.

⑶Preparation of coating:

Spherical NiCrAlY powder was first sprayed on the pretreated substrate surface using CCDS2000 explosion spraying technology to obtain a NiCrAlY transition layer with a thickness of 100 μm; then the spray composite powder was sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating with a thickness of 250 μm (as shown in Figure 2).

Among them: the explosion spraying process refers to the fuel being acetylene and propane, the combustion-supporting gas being oxygen, and the carrier gas being nitrogen; the acetylene inlet pressure range is 1.35~1.45bar, and the air intake time is 4~88ms; the propane inlet pressure range is 1.8 bar, and the air intake time is 4~55ms; the oxygen is divided into two paths, and the air intake times are 3~50ms and 3~80ms respectively; the filling ratio of the fuel gas and oxygen is 47%, and the oxygen-carbon ratio is 1.945:1; the nitrogen inlet pressure range is 1.80~2.20bar, and the air intake time is 95ms~199ms; the powder delivery time is 50~100ms; the spraying distance (the distance from the muzzle to the sample surface) is 200mm; and the explosion frequency is controlled at 5 times/second.

The obtained nickel-based lubricating coating has a bonding strength greater than 41 MPa and a friction coefficient less than 0.3 from room temperature to 300 °C.

Example 3 A method for preparing a nickel-based lubricating coating by explosion spraying comprises the following steps:

⑴Pretreatment of substrate:

The surface of Inconel 718 alloy was deoxidized and roughened by high-pressure sandblasting. The pressure of compressed air was 0.6-0.8 MPa, and the particle size of the aluminum oxide sand used was 60 μm. After treatment, the surface was ultrasonically cleaned and dried in an alcohol solution to obtain the pretreated substrate.

(2) Preparation of spray composite powder is the same as in Example 1.

⑶Preparation of coating:

Spherical NiCrAlY powder was first sprayed on the pretreated substrate surface by explosion spraying technology to obtain a NiCrAlY transition layer with a thickness of 75 μm; then the spray composite powder was sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating with a thickness of 225 μm.

Among them: the explosion spraying process refers to the fuel being acetylene and propane, the combustion-supporting gas being oxygen, and the carrier gas being nitrogen; the acetylene inlet pressure range is 1.35~1.45bar, and the air intake time is 4~88ms; the propane inlet pressure range is 1.8 bar, and the air intake time is 4~50ms; the oxygen is divided into two paths, and the air intake times are 3~50ms and 3~80ms respectively; the filling ratio of the fuel gas and oxygen is 52%, and the oxygen-carbon ratio is 1.015:1; the nitrogen inlet pressure range is 1.80~2.20bar, and the air intake time is 95ms~250ms; the powder delivery time is 50~105ms; the spraying distance (the distance from the muzzle to the sample surface) is 250mm; and the explosion frequency is controlled at 4 times/second.

The obtained nickel-based lubricating coating has a bonding strength greater than 40 MPa and a friction coefficient less than 0.3 from room temperature to 300 °C.

Claims (6)

1. A method for preparing a nickel-based lubricating coating by explosion spraying, comprising the following steps: ⑴Pretreatment of substrate: After the metal substrate or sample surface is deoxidized and roughened by high-pressure sandblasting, it is ultrasonically cleaned and dried in an alcohol solution to obtain a pretreated substrate; (2) Preparation of spray composite powder: 80-95 wt. % spherical NiCrAlY powder and 5-20 wt. % lubricant spherical silver powder are uniformly mixed in a low-energy ball mill to obtain a spray composite powder; the particle size of the spherical NiCrAlY powder is 20-60 μm, and the components thereof are 20-22 wt. % Cr, 10-12 wt. % Al, 1-1.5 wt. % Y and 64.5-79 wt. % Ni; the purity of the spherical silver powder is 99.99%, and the particle size is below 48 μm; ⑶Preparation of coating: The spherical NiCrAlY powder is first sprayed on the surface of the pretreated substrate by using the explosion spraying technology to obtain a NiCrAlY transition layer; then the spray composite powder is sprayed on the NiCrAlY transition layer to obtain a NiCrAlY-Ag lubricating coating; the explosion spraying process refers to that the fuel is acetylene and propane, the combustion-supporting gas is oxygen, and the carrier gas is nitrogen; the acetylene inlet pressure range is 1.35-1.45 bar, and the air intake time is 4-90 ms; the propane inlet pressure range is 1.8 bar, and the air intake time is 4-55 ms; the oxygen is divided into two paths, and the air intake times are 3-70 ms and 3-90 ms respectively; the filling ratio of fuel gas and oxygen is 42%-61%, and the oxygen-carbon ratio is 1.015:1-1.945:1; the nitrogen inlet pressure range is 1.80-2.20 bar, and the air intake time is 95 ms-250 ms; the powder feeding time is 50-105 ms; the spraying distance is 200-250 mm; the explosion frequency is controlled at 4~5 times/second. 2. A method for preparing a nickel-based lubricating coating by explosion spraying as claimed in claim 1, characterized in that the material of the metal substrate or sample in step (1) is one of 304 stainless steel, GH4169 nickel-based high-temperature alloy, TC4 titanium alloy, and Inconel 718 alloy. 3. A method for preparing a nickel-based lubricating coating by explosion spraying as claimed in claim 1, characterized in that: the pressure of the compressed air in the high-pressure sandblasting process in step (1) is 0.6~0.8 MPa, and the particle size of the aluminum oxide sand used is 40~100 μm. 4. The method for preparing a nickel-based lubricating coating by explosion spraying as claimed in claim 1, characterized in that: in the step (2), the speed of the low-energy ball mill is controlled at 150-200 r/min, the ball-to-material ratio is 1:2-1:5, and the time is 2-5 h. 5. A method for preparing a nickel-based lubricating coating by explosion spraying as claimed in claim 1, characterized in that the front barrel used for explosion spraying in step (3) is a trumpet-shaped barrel with a rear end inner diameter of 18 mm and a front end inner diameter of 27 mm. 6. The method for preparing a nickel-based lubricating coating by explosion spraying as claimed in claim 1, characterized in that: in the step (3), the thickness of the NiCrAlY transition layer is between 70 and 100 μm; and the thickness of the NiCrAlY-Ag lubricating coating is between 200 and 500 μm.