CN107761035B

CN107761035B - Corrosion-resistant fully-compact thermal spraying metal alloy coating and preparation method thereof

Info

Publication number: CN107761035B
Application number: CN201711087003.3A
Authority: CN
Inventors: 李长久; 田佳佳; 雒晓涛; 李成新; 杨冠军
Original assignee: Xian Jiaotong University
Current assignee: Xian Jiaotong University
Priority date: 2017-11-07
Filing date: 2017-11-07
Publication date: 2020-03-31
Anticipated expiration: 2037-11-07
Also published as: CN107761035A

Abstract

The invention discloses a corrosion-resistant fully-compact thermal spraying metal alloy coating and a preparation method thereof, belonging to the technical field of preparation of spraying materials. The technical scheme comprises the following steps: firstly, spraying composite metal powder with a higher-melting-point metal cladding structure and a self-bonding effect by using a thermal spraying method to prepare a metal alloy coating which is highly compact, well bonded with a substrate and well bonded between interfaces of deposited particles; secondly, the compact metal alloy coating is sprayed to the surface of the coating at a certain relative moving speed by adopting a cold spraying method or a traditional shot blasting method to generate directional high-speed steel shot particle beam, and the metal coating is densified based on the plastic deformation effect generated by high-speed particle collision, so that the completely compact metal alloy coating of the cast block with excellent corrosion resistance is prepared. The method is simple to operate, wide in raw material source and high in preparation efficiency, and the metal alloy coating with excellent corrosion resistance and density close to that of the block can be prepared by the method.

Description

Corrosion-resistant fully-compact thermal spraying metal alloy coating and preparation method thereof

Technical Field

The invention belongs to the technical field of preparation of spray coating materials, relates to the fields of material surface engineering technology, mechanical manufacturing, material protection, petrochemical industry, energy and the like, and particularly relates to a corrosion-resistant fully-compact thermal spray coating of a metal alloy and a preparation method thereof.

Background

Corrosion of metal alloy parts is an important factor limiting their service life. Therefore, many studies have been made to improve the corrosion resistance of metal parts. It is generally believed that the deposition of a protective coating on the surface of a base metal that meets the load bearing properties of the structure is an effective way to improve the corrosion resistance of the base metal. For cathodic protective coatings, the coating may hinder or slow the corrosion of the base metal as an effective barrier to isolate the base metal from the corrosive environment. Therefore, having a fully dense texture is an essential requirement for cathodic protective coatings, as any defects in the coating, such as porosity, particularly through-porosity communicating from the coating surface to the coating-substrate interface, will provide a pathway for corrosive media to pass through the coating to the substrate metal surface, causing or accelerating corrosion of the substrate metal at the interface, rendering the protective effect of the protective coating ineffective.

Thermal spraying, one of the common surface techniques for producing protective coatings on substrates, has a large market share in surface engineering due to a series of advantages. For example, thermal spraying can replace electroplating to deposit hard chromium coatings due to the characteristics of environmental friendliness and no pollution; because the coating preparation can be carried out on site, the preparation of the spray coating is not limited by the size of a base material and the site, and the coating is prepared on the surface of the existing large-scale structural member on the site such as a thermal power plant and the like; moreover, the thermal spraying can use powder to prepare a coating, so that the range of materials is wide, and the thermal spraying metal alloy coating has a great proportion in the application field of thermal spraying because of wide range of selectable metal materials. For example, plasma sprayed Ni-based, Fe-based, and Co-based alloy coatings are widely used to protect components such as boiler tubes, turbine blades, and the like due to their excellent high temperature oxidation and corrosion resistance. However, research has shown that thermal spray coatings have typical porous layered structure characteristics, and because the bonding between the interfaces of the deposited particles in the coating is incomplete, there are usually a large number of interfaces without real bonding between the particles, and these unbound particle interfaces constitute a special kind of slit-type pores in the coating, which are interconnected to form through pores that are continuous from the coating surface to the substrate surface. Such pores provide transmission channels for the penetration or penetration of corrosive media, either liquid or gaseous, to make it fully accessible at the interface between the substrate and the coating, causing corrosion of the substrate, and, depending on the chemical state of the interface, generally accelerating corrosion of the substrate along the interface. The interface combination is gradually weakened by continuous corrosion, and finally the coating is partially or completely peeled off from the surface of the matrix, the protection of the coating is failed, and the matrix is not protected. Therefore, how to ensure that the substrate is protected by the thermal sprayed metal alloy coating by improving the interfacial bonding of the thermal sprayed metal alloy coating or eliminating the through voids becomes a key issue.

In order to solve the above problems, many studies have been made first to reduce the porosity of the coating and to improve the density of the thermal spray coating. The following methods are mainly used: such as increasing the temperature of the impinging particles, increasing the flying particle velocity, etc., by optimizing the spray parameters. However, research shows that although the apparent porosity of the coating can be reduced by process optimization, the methods of the optimized process can not greatly improve the interfacial bonding of the thermal spraying metal alloy coating, so that the through pores in the coating cannot be eliminated only by the thermal spraying method.

Based on the above current situation, in order to meet the requirement of preventing the penetration of corrosive medium to avoid the corrosion of the substrate and ensure the corrosion protection of the coating to the substrate, the coating is usually sealed by using a sealant or remelted to eliminate pores. The hole sealing treatment needs the hole sealing agent to permeate into the pores in the coating under the action of capillary tubes to realize the hole sealing effect, but when the hole sealing treatment is carried out on a structural member on site, or all the pores in the coating cannot be filled with the hole sealing agent due to the fact that gas in the coating cannot be discharged or the viscosity of the hole sealing agent affects, therefore, the pores near the surface are only sealed under most conditions, and the sealing effect gradually disappears along with the progress of abrasion on the industrial and mining with corrosion and abrasion. Typical examples of applications for the remelting treatment of the coating are the series of self-fluxing alloy coating materials, which are completely melted by flame after the sprayed coating is formed or during the spraying process to eliminate pores and to give a metallurgical bonding effect between the coating and the substrate. However, on the one hand, the method is only suitable for coating self-fluxing alloy materials, such as nickel-based self-fluxing alloys, iron-based self-fluxing alloys, cobalt-based self-fluxing alloys, and the like, and on the other hand, the method is generally suitable for coating with a thickness of more than 500 micrometers and less than 1 millimeter, and is not suitable for field implementation of structural components with complicated shapes or larger sizes.

Therefore, how to obtain the metal alloy coating which is only in block density and has no through hole through a simple post-treatment process and a process with wide applicability still is a key problem to be solved for preparing the coating with excellent corrosion resistance through a thermal spraying process to be applied and realizing effective and reliable protection of a base metal material.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention aims to provide a corrosion-resistant fully-compact thermal spraying metal alloy coating and a preparation method thereof.

The invention is realized by the following technical scheme:

the invention discloses a preparation method of a corrosion-resistant fully-compact thermal spraying metal alloy coating, which comprises the following steps:

1) coating composite powder with a shell-core structure with a self-bonding effect as thermal spraying raw material powder, and thermally spraying to obtain a compact metal alloy coating; the compact metal alloy coating is well combined with a matrix and the interface of deposited particles is well combined;

2) the method comprises the steps of generating high-speed steel shot jet particle beam flow with directivity by adopting a cold spray gun or a traditional shot blasting method, spraying the high-speed steel shot jet particle beam flow to the surface of a compact metal alloy coating at a certain relative moving speed, carrying out densification on the metal coating based on a plastic deformation effect generated by high-speed particle collision, completely eliminating a small amount of tiny pores in the coating, forming firm connection on incompletely combined interfaces existing among deposited particles based on a cold welding effect generated by particle collision deformation, and sequentially preparing the completely compact metal alloy coating of the type casting block body without through pores and with excellent corrosion resistance.

Preferably, the shell-core structure coated composite powder with self-bonding effect refers to the shell-core structure composite powder particles which have the advantages that the coating layer is not separated from the coated core particles before the particles are completely melted in the spraying process, and the overall integrity can be maintained; the melting point of the coating material is higher than that of the core material to be coated, the bonding strength between the coating prepared by thermal spraying and the substrate and the bonding strength between particles are high enough, and when the high-speed steel shot is adopted for spraying treatment, the coating does not generate phenomena of erosion, local shedding or overall shedding. Wherein, the coating layer or the shell layer accounts for 3 to 35 percent of the total mass of the composite powder coated by the shell-core structure.

Further preferably, the shell-core structure clad composite powder with self-bonding effect comprises: the shell-core structure coated composite powder with the self-bonding effect comprises:

cladding Ni, Ni-based alloy, Fe or Fe-based alloy powder by refractory metal Mo; alternatively, the first and second electrodes may be,

coating Ni-based alloy powder, Fe-based alloy powder and Cu or Cu alloy powder by using two or three of refractory metals Ta, Mo and W; alternatively, the first and second electrodes may be,

coating Al or Al alloy powder with Fe; alternatively, the first and second electrodes may be,

and coating Zn or Zn alloy powder with Al, Cu, Al alloy or Cu alloy powder.

Preferably, the thermal spraying adopts a plasma spraying method or a flame spraying method; the plasma spraying method includes an atmospheric plasma spraying method, a gas shield plasma spraying method, a low-pressure plasma spraying method or a vacuum plasma spraying method.

Preferably, in the step 2), the high-speed shot blasting particles are spherical stainless steel particles with the particle size range of 100-300 μm. Further preferably, the spherical stainless steel particles are austenitic stainless steel particles, martensitic stainless steel particles, ferritic stainless steel particles or duplex stainless steel particles.

Preferably, in the step 2), a cold spraying device or a steel shot accelerating device is adopted to generate a steel shot jet particle beam flow with the speed of 30-300 m/s, and the steel shots sequentially collide with the surface of the substrate in the process of moving the steel shot jet particle beam flow along the surface, so that the deformation densification cold welding treatment effect can be generated on the coating.

The device for accelerating the steel shots is an accelerating device with controllable and adjustable steel shot feeding quantity, or a cold spraying device, or a particle accelerating device used for sand blasting surface treatment, or other devices used for shot blasting treatment and capable of accelerating the steel shots.

Preferably, in the step 2), high-pressure air or nitrogen is used as accelerating gas, the gas pressure is 0.3-4 MPa, and the gas temperature is 15-200 ℃;

in the spraying process, the moving speed of a spraying gun is 10-500 mm/s, the spraying times are 1-10 times, and the tiny pores in the whole coating are completely eliminated through shot blasting parameter combination.

The invention also discloses a fully-compact thermal spraying metal alloy coating prepared based on the preparation method, and the metal alloy coating has the advantages of high density, low oxide content, no through pores, and excellent bonding performance between the coating and a substrate and between coating particles.

Preferably, the metal alloy coating is well combined with a substrate, is completely compact, has no through pores, has the thickness of 50-400 μm, can completely prevent liquid and gaseous corrosive media from infiltrating or penetrating the coating from the surface of the coating, and can play a role in completely isolating the corrosive media and forming complete corrosion-resistant protection for the substrate by taking the coating as a cathode protective coating.

Compared with the prior art, the invention has the following beneficial technical effects:

the invention discloses a preparation method of a corrosion-resistant fully-compact thermal spraying metal alloy coating, which is prepared by adopting a two-step method. Secondly, carrying out shot blasting densification treatment on the thermal spraying coating prepared in the first step by utilizing a high-speed steel shot particle beam to completely eliminate a small amount of micro pores in the coating, thereby preparing the metal alloy coating which is nearly blocky, completely dense and capable of providing complete corrosion resistance protection for a matrix. The method provides a new solution for the problem of preparing the corrosion-resistant high-performance metal alloy coating with good interface combination and complete compactness which is difficult to solve so far.

Compared with the typical layered structure and the very limited interfacial bonding rate of the conventional thermal spraying metal alloy coating, the metal alloy coating prepared by the method has a completely compact block-like organizational structure, the apparent porosity of the coating is only 0.04%, most of the interfaces between the coatings are chemically bonded, and the bonding strength of the metal alloy coating is higher than 70MPa of that of an adhesive. The coating exhibits complete corrosion protection of the substrate due to the absence of through voids in the coating. Since interfacial bonding of the coating has a significant influence on various properties thereof, the coating exhibits various properties, such as wear resistance, etc., comparable to those of the bulk.

Drawings

FIG. 1 shows the cross-sectional structure and surface morphology of a Mo-coated NiCr shell-core structure NiCr-20Mo composite powder; wherein (a) is a NiCr-20Mo powder section structure (low power); (b) the structure is a NiCr-20Mo powder section structure (high power); (c) the surface appearance of NiCr-20Mo powder;

FIG. 2 is a sectional structure of Ni16Cr20Mo coating prepared by plasma spraying NiCr-20Mo powder; wherein, (a) is the cross-sectional structure (low power) of the plasma spraying Ni16Cr20Mo coating; (b) the cross section structure (high power) of the Ni16Cr20Mo coating is sprayed by plasma;

FIG. 3 is an interface structure of Ni16Cr20Mo single particles and a stainless steel matrix prepared by plasma spraying NiCr-20Mo powder;

FIG. 4 is a cross-sectional structure of the Ni16Cr20Mo coating after spray collision densification treatment by using a cold spraying device as an acceleration steel shot device; wherein (a) is the section structure (low power) of Ni16Cr20Mo coating which is subjected to shot blasting and shot blasting densification treatment; (b) the section structure (high power) of the Ni16Cr20Mo coating which is subjected to shot blasting and shot blasting densification treatment for the steel shot;

FIG. 5 is a comparison of the corrosion resistance of a Ni16Cr20Mo coating after spray collision densification treatment using a cold spray apparatus as an accelerated shot apparatus with a conventional Ni-based alloy coating; wherein, (a) is open circuit potential contrast; (b) polarization curve comparison.

Detailed Description

The present invention will now be described in further detail with reference to specific examples, which are intended to be illustrative, but not limiting, of the invention.

Example 1

The preparation method of the corrosion-resistant fully-compact thermal spraying metal alloy coating comprises the following steps:

step 1: mo and Ni20Cr are respectively used as typical cladding shell materials and core materials as initial materials, and the Mo-clad NiCr shell-core structure NiCr-20Mo composite powder prepared by ball-milling mechanical alloying and subsequent heat treatment is used for preparing coatings. Structure referring to fig. 1, (a) in fig. 1 is a cross-sectional structure (lower magnification) of NiCr-20Mo powder; (b) the structure is a NiCr-20Mo powder section structure (high power); (c) the surface appearance of NiCr-20Mo powder; as can be seen from FIG. 1, the compact Mo shell is completely and uniformly coated on the surface of the NiCr core powder particles, and Mo and the NiCr core particles are metallurgically bonded together through a thin intermediate diffusion layer, so that the shell and the core are firmly connected together to form a complete single molten drop before Mo is completely melted and alloyed with the NiCr in the heating process of the particles in the plasma jet.

The cross-sectional structure of the Ni-based alloy coating prepared by spraying the powder particles coated with the composite structure by the plasma spraying method is shown in fig. 2, and it can be seen from fig. 2(a) that the coating is quite dense and has a uniform structure, but a few tiny pores are observed in the high magnification photograph shown in fig. 2 (b).

Mo is adopted to coat NiCr composite powder, and the cross section structure of a single particle deposited on the surface of stainless steel with the melting point equivalent to that of the particle is sprayed by plasma, so that the bonding state of the particle and a matrix interface is represented. In order to clarify the state of the deposited NiCr-20Mo particles forming bonds with the matrix interface, cross-sectional samples of the above-described Ni16Cr20Mo single particles deposited on the surface of a polished stainless steel matrix were prepared using FIB and the interface was characterized using SEM and TEM. As a result, as shown in FIG. 3, the Ni16Cr20Mo single particles were well bonded to most of the interface between the stainless steel substrates, and only in the most peripheral regions of the particles, they were not bonded to the substrates due to the lowering of the temperature of the spreading front of the particles. When TEM is used for analyzing typical interface characteristics, a plurality of molten pool pits generated by melting micro areas on the surface of the matrix appear at the interface of the particles and the matrix, the oxide film on the surface of the matrix is in a spheroidized state due to melting, so that the particle interfaces are metallurgically bonded together, and the bonding between the particles and the matrix is chemical bonding through the oxide film in a non-melting area.

Through the characterization and the statistics of the results, more than 90% of the interface between the single Ni16Cr20Mo particle and the matrix is connected together through chemical metallurgical bonding, and the area ratio of the bonding interface is only about 40% higher than that of the conventional Ni-based alloy particle. Due to the existence of the unbonded interface area of less than 10 percent at the edge of the single particle, a small amount of micro pores exist in the plasma spraying Ni16Cr20Mo coating, and the micro pores are communicated with each other to form through pores, so that the corrosion medium can reach the interface of the coating and the substrate from the surface of the coating through the pores.

Step 2: and (3) adopting a cold spraying device as a steel shot accelerating device, and after forming a high-speed steel shot beam, carrying out high-speed collision shot blasting densification treatment on the plasma spraying state Ni16Cr20Mo coating, and carrying out pore removal treatment. Even under the high-strength shot blasting treatment condition, the coating structure is complete due to high bonding strength, and the phenomenon of coating falling is not found. The bond strength measurements show that after shot peening, the bond strength of the coating is the same as the as-sprayed measurements, i.e., greater than the strength of the binder used for the measurements, greater than 70 MPa. Under the same steel shot blasting treatment condition, the coating prepared by NiCr alloy powder has the integral falling phenomenon and cannot be densified through steel shot blasting treatment. FIG. 4 shows the structure of the coating after shot peening, wherein (a) shows the cross-sectional structure (lower magnification) of the Ni16Cr20Mo coating after shot peening; (b) the cross-section structure of the Ni16Cr20Mo coating which is subjected to shot blasting and shot blasting densification treatment is high. As can be seen from fig. 4, the coating exhibited a fully dense structure similar to a dense block, with an apparent porosity of only 0.04%.

The results of electrochemical tests on the Ni16Cr20Mo coating sprayed on the surface of Q235 mild steel after shot blasting are shown in fig. 5. From this figure, it can be seen that plasma spray coating of conventional Ni-based alloy coatings exhibits an open circuit potential, corrosion potential and corrosion current comparable to those of sandblasted Q235 mild steel substrates due to the presence of a large number of pores and through pores formed by unbonded interfaces in the coating, indicating that the conventional Ni-based alloy coating has no corrosion protection effect on the substrate. The compact Ni-based alloy coating prepared by the method of the invention shows electrochemical characteristics equivalent to that of a Ni16Cr20Mo coating without matrix adhesion, and shows that the coating prepared by the method of the invention can completely and effectively protect matrix metal from corrosion.

From the results, it can be concluded that the compact metal alloy coating with good interfacial bonding is prepared by coating the composite powder with the shell-core structure having the self-bonding effect by plasma spraying. Then the sprayed coating is densified by adopting a steel shot spraying shot deformation cold welding post-treatment method to obtain the Ni-based alloy coating with excellent corrosion resistance and quite dense with the block.

Example 2

The Mo-coated stainless steel powder is used as a spraying material, a high-molybdenum stainless steel coating with the thickness of 300 microns is prepared on the surface of a common carbon steel substrate by plasma spraying, and shot blasting is carried out on the coating by using a handheld shot blasting gun, wherein the shot blasting adopts 100-mesh steel balls, and the compressed air pressure of the accelerating steel balls is 0.3 MPa. The corrosion resistance of the ordinary low-carbon steel sprayed with the coating is tested by an electrochemical method, and the electrochemical potential and the corrosion current of the ordinary low-carbon steel are not influenced by a substrate and are completely equivalent to the coating, namely the coating realizes complete corrosion protection on the low-carbon steel substrate.

Example 3

The method comprises the steps of adopting Mo-coated FeAl powder as spraying powder, preparing a 150-micron-thick coating on the surface of heat-resistant steel by adopting plasma spraying, and carrying out shot blasting on the coating by adopting a handheld sand blasting gun, wherein the shot blasting adopts 60-mesh steel balls, and the pressure of compressed air is 0.4 MPa. A corrosion resistance test for 50 hours under the condition of simulating the corrosive atmosphere of the garbage incinerator at 400-650 ℃ shows that the coating prepared by the method disclosed by the invention basically does not generate sulfidation corrosion, chlorination corrosion, hydrochloric acid corrosion and the like, and has excellent high-temperature corrosion resistance.

Example 4

Nb is adopted to cover aluminum bronze powder, a coating with the thickness of 200 microns is prepared on the surface of ship steel by adopting plasma spraying, a cold spraying gun is adopted to accelerate 100-mesh steel shots to carry out shot blasting treatment on the coating, the moving speed is 40mm/s, and the shot blasting treatment is uniformly carried out on the surface of the coating for 4 times, so that a compact coating is obtained. After proper heat treatment, an ultrasonic cavitation test is adopted, and test results under standard test conditions show that the cavitation erosion resistance of the coating prepared based on the preparation method is basically equivalent to that of aluminum bronze, and the compact coating prepared based on the preparation method disclosed by the invention has excellent cavitation erosion resistance. The method can be used for cavitation erosion resistance strengthening and repairing remanufacturing of the surface of the ship.

Example 5

Adopting Mo-coated NiTi alloy powder as spraying powder, preparing a coating with the thickness of 200 microns on the surface of a steel matrix by adopting plasma spraying, and carrying out shot blasting treatment; then spraying a 250-micron coating on the surface of the coating, and performing shot blasting again to finally obtain the NiTi-based coating with the thickness of more than 400 microns. Under the condition of clear water, an ultrasonic cavitation test is adopted, and a test result under a standard test condition shows that the cavitation erosion resistance of the coating prepared based on the method is obviously greater than that of the titanium alloy, so that the compact coating prepared by the method has excellent cavitation erosion resistance. The method can be used for cavitation erosion resistance strengthening and repairing remanufacturing of the water turbine blade.

Example 6

The Al powder is coated by Fe, a composite coating in which Al-based FeAl intermetallic compounds are distributed is prepared on a steel substrate, shot blasting densification is carried out by a shot blasting gun, the treated coating is good, and the interface bonding strength is not reduced or any coating is not stripped. After the corrosion resistance of the coating is tested in a seawater corrosion environment for 30 days, the seawater corrosion medium is found to form a passive film only on the surface of the coating, and no seawater penetrates through the coating, so that the coating disclosed by the invention can play a complete corrosion protection role on a steel substrate.

Example 7

The coating with the thickness of about 300 microns is prepared on a low-carbon steel matrix by adopting 12 wt.% Al to coat Zn powder and adopting a flame spraying method, and after the coating is subjected to shot blasting densification treatment by adopting a cold spraying gun and using 80-mesh steel shots, the coating is complete and has good combination. Seawater corrosion tests show that the corrosion medium does not infiltrate into the coating, and the coating has excellent corrosion protection performance on the low-carbon steel matrix.

Claims

1. A preparation method of a corrosion-resistant fully-compact thermal spraying metal alloy coating is characterized by comprising the following steps:

1) coating composite powder with a shell-core structure with a self-bonding effect as thermal spraying raw material powder, and thermally spraying to obtain a compact metal alloy coating; the coating layer or the shell layer accounts for 3 to 35 percent of the total mass of the composite powder coated by the shell-core structure;

2) generating a directional high-speed steel shot jet particle beam flow by adopting a cold spraying or shot blasting method, and jetting the high-speed steel shot jet particle beam flow to the surface of the compact metal alloy coating until a completely compact thermal spraying metal alloy coating without through holes or corrosion resistance is prepared, wherein the thickness of the prepared metal alloy coating is 50-400 mu m, and liquid and gaseous corrosive media can be completely prevented from infiltrating or penetrating the coating from the surface of the coating;

in the step 2), high-pressure air or nitrogen is used as accelerating gas, the gas pressure is 0.3-4 MPa, and the gas temperature is 15-200 ℃;

the moving speed of the steel shot accelerating gun is 10-500 mm/s in the process that the steel shots are sprayed to the surface of the coating, the spraying frequency is 1-10 times, and the micro pores in the whole coating are completely eliminated through shot blasting parameter combination.

2. The method of preparing a corrosion resistant fully dense thermal sprayed metal alloy coating according to claim 1, wherein the core-shell coated composite powder with self-bonding effect is core-shell coated composite powder particles that do not separate from the coated core particles before the particles are completely melted and that can maintain the integrity of the whole during the spraying process; wherein the melting point of the material used as the cladding layer is greater than the melting point of the material used as the core to be clad.

3. The method of preparing a corrosion resistant fully dense thermal sprayed metal alloy coating according to claim 1 or 2, characterized in that the core-shell structure clad composite powder with self-binding effect comprises:

and coating Zn or Zn alloy powder with Al, Cu, Al alloy or Cu alloy powder.

4. The method of preparing a corrosion resistant fully dense thermal sprayed metal alloy coating of claim 1 where the thermal spray is plasma spray or flame spray; the plasma spraying method includes an atmospheric plasma spraying method, a gas shield plasma spraying method, a low-pressure plasma spraying method or a vacuum plasma spraying method.

5. The method for preparing the corrosion-resistant fully dense thermal sprayed metal alloy coating according to claim 1, wherein in the step 2), the high-speed steel shot blasting particles are spherical stainless steel particles with the particle size range of 100-300 μm.

6. The method of making a corrosion resistant fully dense thermal sprayed metal alloy coating of claim 5 where the spherical stainless steel particles are austenitic stainless steel particles, martensitic stainless steel particles, ferritic stainless steel particles, or duplex stainless steel particles.

7. The preparation method of the corrosion-resistant fully dense thermal spray metal alloy coating according to claim 1, wherein in the step 2), a cold spray device or a steel shot accelerating device is adopted to generate a steel shot jet particle beam flow with the speed of 30 m/s-300 m/s, and the steel shots sequentially collide with the surface of the substrate in the process of moving the steel shot jet particle beam flow along the surface, so that the deformation densification cold welding treatment effect can be generated on the coating.

8. The corrosion-resistant fully-dense thermal spraying metal alloy coating prepared by the preparation method of any one of claims 1-7 is characterized by high compactness, low oxide content, no through pores, and excellent bonding performance between the coating and a substrate and between coating particles.