阅读说明：本技术 一种基于冷喷涂高速沉积增材制造技术制备金属铱涂层的方法及装置 (Method and device for preparing iridium metal coating based on cold spraying high-speed deposition additive manufacturing technology ) 是由 沈艳芳 梁静静 王吉强 崔新宇 杨金侠 周亦胄 熊天英 于 2020-04-16 设计创作，主要内容包括：本发明公开了一种基于冷喷涂高速沉积增材制造技术制备金属铱涂层的方法及装置,属于抗高温氧化涂层制备技术领域。该方法具体采用冷喷涂高速沉积增材制造技术将烘干后的金属铱粉末沉积到经过表面处理的高温合金基体上,从而获得相成分单一、与基体结合良好的纯金属铱防护涂层。结果表明,冷喷涂高速沉积技术是一种制备纯金属铱涂层的有效方法,较现有金属铱涂层制备工艺相比不仅具有涂层厚度大、致密性高、与基体结合力强、防护效果好等特点,同时还具有涂层基本不存在氧化和涂层的内应力为压应力的主要特点,以及可以实现快速增材制造铱涂层、且涂层局部脱落后可进行现场修复等优点。(The invention discloses a method and a device for preparing a metal iridium coating based on a cold spraying high-speed deposition additive manufacturing technology, and belongs to the technical field of preparation of high-temperature oxidation resistant coatings. The method specifically adopts a cold spraying high-speed deposition additive manufacturing technology to deposit dried metal iridium powder on a high-temperature alloy substrate subjected to surface treatment, so that a pure metal iridium protective coating with single phase component and good combination with the substrate is obtained. The result shows that the cold spraying high-speed deposition technology is an effective method for preparing the pure metal iridium coating, and compared with the existing preparation technology of the metal iridium coating, the method not only has the characteristics of large coating thickness, high compactness, strong bonding force with a substrate, good protection effect and the like, but also has the main characteristics that the coating does not have oxidation basically and the internal stress of the coating is compressive stress, and has the advantages that the iridium coating can be manufactured by rapid material increase, and the field repair can be carried out after the local coating is detached.)

1. A method for preparing a metallic iridium coating based on a cold spraying high-speed deposition additive manufacturing technology is characterized by comprising the following steps: the method takes pure metal iridium powder as spraying powder, and adopts a cold spraying high-speed deposition additive manufacturing technology to prepare the metal iridium protective coating on a high-temperature alloy substrate.

2. The method of making a metallic iridium coating based on a cold spray high speed deposition additive manufacturing technique as claimed in claim 1, wherein: in the cold spray high-speed deposition additive manufacturing technology: the cold spraying equipment with a gas heater is adopted for coating preparation, the gas heating temperature is 500-750 ℃ during spraying, compressed air, nitrogen or argon is used as spraying gas, the gas pressure is 1.5-3.0 MPa during spraying, and the spraying distance is 10-40 mm.

3. The method of making a metallic iridium coating based on a cold spray high speed deposition additive manufacturing technique according to claim 2, wherein: the purity of the pure metal iridium powder is more than 99 percent, and the distribution range of the powder particle size is 1-60 mu m.

4. The method of making a metallic iridium coating based on a cold spray high speed deposition additive manufacturing technique according to claim 3, wherein: in the pure metal iridium powder, the mass percentage of the powder with the granularity of less than 15 mu m is less than 10 percent, the mass percentage of the powder with the granularity of 15 mu m to 45 mu m is more than 90 percent, and the rest is the powder with the granularity of more than 45 mu m.

5. The method of making a metallic iridium coating based on a cold spray high speed deposition additive manufacturing technique as claimed in claim 1, wherein: the thickness of the cold spraying metal iridium coating is 20-300 mu m, and the bonding strength of the coating and the substrate is more than 20 MPa.

6. An apparatus for preparing iridium metal coating used in the method of claim 1, wherein: the device for preparing the iridium metal protective coating on the high-temperature alloy substrate is cold spraying equipment with a gas heater, and the cold spraying equipment comprises a compressed gas supply device, a control system, the gas heater, a powder feeder and a spray gun; feeding powder by using compressed gas and accelerating the powder, wherein the powder feeding gas and main gas are provided by an air compressor with the maximum pressure of 3.5MPa or a nitrogen gas cylinder and an argon gas cylinder, and the flow rate and the powder feeding amount of the powder feeding gas are controlled by a control system; the gas heater heats the main gas, the heated main gas is mixed with the powder in the powder feeder mixing chamber in the spray gun, the heat conduction can be carried out in the spray gun to heat the powder, the scaling process is carried out to accelerate the expansion of the gas and the powder, and the spray gun is fixed on the workbench; the base body is fixed on the sample table, and the spray gun fixed on the working table performs relative motion relative to the sample table, mainly linear motion in a two-dimensional plane and rotary motion in a three-dimensional space.

Technical Field

The invention relates to the technical field of high-temperature oxidation protective coatings, in particular to a method and a device for preparing a metal iridium coating based on a cold spraying high-speed deposition additive manufacturing technology.

Background

Iridium (Ir) as a noble metal of the platinum group has a melting point as high as 2440 ℃, and has high strength, and is applied to a high-temperature oxidation-resistant coating due to its extremely low oxygen permeability and high oxidation resistance. The iridium still has a low oxygen diffusion coefficient at 2100 ℃, and is an ideal oxygen diffusion shielding material. The results of the study show that (Yang Wenbin, Zhang Litong, Hua Yunfeng, et al, Thermal stability of the iridium coating preparation by MOCVD [ J ]. International Journal of reflective Metals and Hard Materials,2009,27(1):33-36, Chen Zhaofeng, Wu Wangping, Cong Xiangna. oxygen resistance coatings of Ir-Zr and Ir by double glaze [ J ]. Journal of Materials Science & Technology,2014,30(3):268 + 274) have a higher service temperature and a longer service life than other iridium coatings of the oxidation resistant coating. The working temperature of a combustion chamber adopting a rhenium/iridium material system can reach 2200 ℃, the engine performance can be obviously improved, when metal iridium is used as a coating, the tough iridium coating not only can reduce surface cracks, but also can relieve thermal stress to a certain extent, so that the coating does not crack (Strife J R, Sheehan J E. Ceramic coatings for carbon-carbon composites [ J ]. Ceramic Bulletin,1988,67 (2): 369-. Since the 80S of the 20 th century, the united states developed a space engine combustion chamber structure with rhenium as the substrate and iridium as the antioxidant coating, and solved the fundamental problems of iridium coating preparation and various key technologies for engineering applications (Henderson S, Stechman C, Wierenga K, et al. performance results for the advanced materials project market (AM-BB) engine [ J ], A1AA,2010,6883: 25-28). The research aiming at the high-temperature oxidation resistant coating in China is started late, and the key problem of iridium coating preparation can not be overcome through more than ten years of research. However, pure iridium has some problems in application: high-temperature oxidation volatilization, micropore expansion, grain boundary segregation, low thermal emissivity and the like, and the service life of the iridium coating is reduced.

Cold spray coating (also called cold gas dynamic spray coating) is a novel spray coating technique in which metal particles are driven by compressed gas to collide with a substrate at a very high speed in a completely solid state, so that the particles are subjected to severe plastic deformation and deposited to form a coating. The cold spraying has the characteristic of solid deposition at low temperature, and can obviously reduce or even completely eliminate adverse effects of oxidation, phase change, segregation, residual tensile stress, grain growth and the like in the traditional hot spraying.

The biggest difference between cold spraying and thermal spraying is that particles are heated to different degrees and impact a substrate; the pre-surface state is different. The three temperatures of the heat source of the traditional thermal spraying technology are respectively as follows: the combustion flame (the temperature is higher than 2000 ℃), the electric arc (the temperature reaches more than 5000 ℃), the plasma (the temperature is higher than 16000 ℃), and the particles are fused, ablated, oxidized and the like in the deposition process; the particles of the cold spray technique do not melt during deposition and the particles form a deposit in the solid state. Compared with additive manufacturing technologies which are characterized by chemical reaction, such as thermal spraying and laser cladding technologies, the cold spraying has the main advantages that:

(1) the spraying efficiency is high, and the deposition thickness is controllable;

(2) the spraying process has less oxidation, no ablation and no grain growth phenomenon, and is suitable for spraying heat-sensitive and phase-change sensitive materials;

(3) the chemical composition of the coating is consistent with that of the raw material;

(4) the heat influence on the matrix is extremely small;

(5) the coating has a compressive stress.

In recent years, a report that a metal iridium coating is prepared by a thermal spraying technology including supersonic flame spraying and atmospheric plasma spraying has been provided, the coating has high quality, and a relatively obvious interface exists between the coating and a substrate, but because the heating temperature is high and the metal iridium needs to be melted and then deposited, the coating is easy to oxidize and change phase, and the bonding strength between the iridium coating and the high-temperature alloy substrate and the subsequent service performance of the coating are influenced. Therefore, the method for preparing the metallic iridium coating by adopting the cold spraying solid deposition additive manufacturing technology is an effective and feasible way for solving the problems that the existing iridium coating is easy to oxidize, the coating has high tensile stress and the bonding strength with the substrate is low.

Disclosure of Invention

The invention aims to provide a method and a device for preparing a metal iridium coating based on a cold spraying high-speed deposition additive manufacturing technology, which solve the problems of coating phase change and oxidation and large tensile stress between a coating and a substrate when the metal iridium coating is prepared by the existing coating preparation technology.

The technical scheme of the invention is as follows:

a method for preparing a metal iridium coating based on a cold spraying high-speed deposition additive manufacturing technology is characterized in that pure metal iridium powder is used as spraying powder, and a cold spraying high-speed deposition technology is adopted to prepare a metal iridium protective coating on a high-temperature alloy substrate.

The cold spraying high-speed deposition technology comprises the following steps: the cold spraying equipment with a gas heater is adopted for coating preparation, the gas heating temperature is 500-750 ℃ during spraying, air, nitrogen or helium is used as spraying gas, the gas pressure is 1.5-3.0 MPa during spraying, and the spraying distance is 10-40 mm.

The purity of the pure metal iridium powder is more than 99 percent, and the distribution range of the powder particle size is 1-60 mu m.

In the pure metal iridium powder, the mass percentage of the powder with the granularity of less than 15 mu m is less than 10 percent, the mass percentage of the powder with the granularity of 15 mu m to 45 mu m is more than 90 percent, and the rest is the powder with the granularity of more than 45 mu m.

The thickness of the cold spraying metal iridium coating is 20-300 mu m, and the bonding strength of the coating and the substrate is more than 20 MPa.

The design principle of the invention is as follows:

a set of reasonable process parameters is required to obtain the iridium coating with less defects and high quality. Although the heating energy of the main gas increases the velocity of the particles, thereby increasing the kinetic energy of the particles so as to be more easily combined with the matrix, the excessive temperature of the main gas can cause the growth of crystal grains inside the powder particles and deteriorate the performance of the sprayed particles; at the same time, the spray particles will melt in the spray gun and clog the spray gun. Of course, the gas temperature cannot be too low, otherwise the acceleration of the sprayed particles is not favoured. In the case of a reduced gas temperature, the gas pressure needs to be increased to deposit the sprayed particles, which is limited by the capacity of the apparatus.

The deposition of the coating of the invention is carried out on a cold spray device with a gas heater. The equipment still works based on the aerodynamic principle, and utilizes high-pressure gas (He, N)₂Mixed gas or air) to carry powder particles through a convergent-divergent tube to generate supersonic two-phase flow, and the supersonic two-phase flow impacts a substrate in a complete solid state and is deposited on the surface of the substrate through large plastic flow deformation to form a coating. The spray gun is designed by using the de Lavel nozzle principle. In the spraying process, when the speed of the particles exceeds the corresponding critical speed, the particles are collided and then deposited on the surface of the substrate to form a coating; otherwise, erosion phenomena will occur.

The invention has the following advantages and beneficial effects:

1. in order to improve the quality of the coating and obtain the coating which has high bonding strength with a matrix and high density, the invention adopts cold spraying equipment with a gas heater to heat compressed air or nitrogen or helium delivered from an air compressor or an air cylinder so as to generate the effects of expansion acceleration and temperature rise, and the compressed air or nitrogen or helium is delivered to a mixing chamber of a de Lavel spray gun at a speed of more than supersonic speed to be mixed with iridium powder therein so as to heat the powder, increase the plastic deformation capability of the powder and promote the deposition of the high-quality cold spraying metal iridium coating. The high-quality metal iridium coating can be obtained by adopting a cold spraying high-speed deposition additive manufacturing technology, the coating does not have oxidation phase change in the deposition process, the characteristic of excellent high-temperature oxidation resistance of the metal iridium is fully kept, the binding force of the coating and a matrix is in a compressive stress state, and the subsequent hole sealing treatment and surface treatment are matched, so that the working procedures are saved, the cost is reduced, and the wide application prospect is realized.

2. The method can effectively avoid the oxidation of the iridium powder in the spraying process, has little influence on the organization structure of the material, reserves the components and the structure of the original spraying powder, and does not generate impurity phases. The metal iridium powder used for cold spraying can be recycled, the coating deposition efficiency is high, the deposition speed is high, and the powder for spraying can be saved. The result shows that cold spraying is an effective method for preparing the iridium protective coating.

3. Compared with the existing preparation process of the metal iridium coating, the cold spraying high-speed deposition technology has the characteristics of large coating thickness, high compactness, strong bonding force with a substrate, good protection effect and the like, also has the main characteristic that the coating does not basically have oxidation, and has the advantages of capability of rapidly increasing the manufacturing of new materials after the coating is locally stripped, field repair and the like.

4. The cold spraying metallic iridium coating prepared by the invention can play a role of a high-temperature protective coating, the temperature range of a design point is between room temperature and 1700 ℃, the coating is corroded by a high-temperature environment, and a working medium can be air, nitrogen, argon or a vacuum environment. The invention fills the technical blank of preparing the iridium coating by the cold spraying high-speed deposition additive manufacturing technology and has obvious better technical effect.

Drawings

FIG. 1 is a schematic view showing the structure of a cold spray apparatus with a gas heater used in the present invention.

In the figure: 1-compressed gas supply device, 2-gas valve, 3-control system, 4-powder feeder, 5-de Lavel spray gun, 6-nozzle, 7-base body, 8-sample stage and 9-gas heater.

Detailed Description

The invention is described in detail below with reference to the accompanying drawings and examples.

The invention adopts cold spraying equipment with a gas heater to prepare the iridium metal protective coating on the high-temperature alloy substrate; as shown in fig. 1, the cold spray apparatus includes a compressed gas supply device 1, a control system 3, a gas heater 9, a powder feeder 4, and a spray gun 6; wherein: compressed gas output by the compressed gas supply device is divided into two paths of gas to be output respectively (first pipeline powder feeding gas and second pipeline main gas) through a main pipeline of a control system, and gas valves 2 are arranged on the main pipeline, the first pipeline and the second pipeline; the first pipeline is connected with a powder feeder 4, the powder feeder is connected with a mixing chamber 5 at the front end of the spray gun, and the control system is used for controlling the flow rate and the powder feeding amount of powder feeding gas in the first pipeline (the first pipeline and the powder feeder are both connected to the control system); the second pipeline is connected with the upper part of the spray gun, and a gas heater is arranged on the second pipeline to heat the main gas conveyed in the second pipeline.

The powder feeding gas and the main gas are both provided by a compressed gas supply device 1, and the compressed gas supply device 1 is an air compressor with the maximum pressure of 3.5MPa or a nitrogen gas cylinder or a helium gas cylinder. The gas heater 9 heats the main gas, the heated main gas is mixed with the powder conveyed by the powder feeder 4 in the spray gun mixing chamber 5, the heat conduction can be carried out in the spray gun 6 to heat the powder, the scaling process is carried out to ensure that the gas and the powder expand and accelerate, and the spray gun is fixed on the workbench; the base body 7 is fixed on a sample table 8, and the spray gun 6 performs relative motion relative to the sample table 8, mainly linear motion in a two-dimensional plane and rotary motion in a three-dimensional space.

In the invention, the spraying raw material is metal iridium powder, and the spraying base material is high-temperature alloy. The spraying equipment is the cold spraying system with the gas heater. The specific process parameters are as follows: the primary air preheating temperature is 500-750 ℃, the spraying distance is 10-30 mm, and the spraying pressure is 1.5-3.0 MPa. Before spraying, the substrate should be degreased by acetone and ethanol, and then sand blasting and coarsening treatment is carried out by 400-mesh 800-mesh white corundum.

The purity of the high-purity metal iridium powder selected as the spraying raw material is more than 99%, and the metal iridium powder is prepared by a gas atomization powder preparation method.

The particle size of the iridium metal powder is as follows: the mass percentage of the metal powder with the granularity of less than 15 mu m is less than 10 percent, the mass percentage of the metal powder with the granularity of 15 mu m to 45 mu m is more than 90 percent, and the rest is the metal powder with the granularity of more than 45 mu m.

Example 1

The spraying raw material is high-purity metal iridium powder with the purity of more than 99%, compressed gas is selected as a spraying medium, the spraying pressure is 2.2MPa, the spraying temperature is 650 ℃, the spraying distance is 25mm, a cold spraying high-speed deposition additive manufacturing technology is adopted to prepare the metal iridium protective coating on the high-temperature alloy substrate, and the spraying time is 300 s. The thickness of the prepared metal iridium coating is 120 mu m, the porosity is less than 1.8%, and the bonding strength between the coating and the substrate is 25 MPa.

Example 2

The spraying raw material is high-purity metal iridium powder with the purity of more than 99%, compressed air is selected as a spraying medium, the spraying pressure is 2.0MPa, the spraying temperature is 600 ℃, the spraying distance is 20mm, a cold spraying high-speed deposition additive manufacturing technology is adopted to prepare the metal iridium protective coating on the high-temperature alloy substrate, and the spraying time is 360 s. The thickness of the prepared metal iridium coating is 110 mu m, the porosity is 2 percent, and the bonding strength between the coating and the substrate is 20 MPa.