CN107937904B - Method and device for preparing aluminum coating by laser cold spraying - Google Patents

Abstract

The patent of the present invention relates to the technical field of coating preparation by cold spraying. In particular, it refers to a method and device for preparing an aluminum coating by laser cold spraying. The high-speed gas accelerates the metal powder into the powder conveying pipeline. The laser beam is sent out by the laser system and enters the powder conveying pipeline through the optical fiber tube. The size of the laser spot is adjusted to be consistent with the diameter of the output powder beam, that is, the diameter of the spray gun mouth. The laser beam heats the aluminum powder particles to achieve spraying quickly. critical temperature. The monitoring of the powder temperature is monitored by the temperature detection control system and fed back to the laser system. The laser system automatically adjusts the power according to the temperature fed back by the temperature monitoring system combined with the critical temperature value of the powder particles and the absorption efficiency of the laser, so that the temperature of the sprayed aluminum particles is maintained. Spraying was carried out at a critical temperature of 400°C. The aluminum powder particles that have reached the critical temperature are accelerated again by the gas accelerator and are impacted to the surface of the base metal S355 steel through the spray gun and supersonic nozzle to form a coating.

Description

Method and device for preparing aluminum coating by laser cold spraying

technical field

The patent of the present invention relates to the technical field of coating preparation by cold spraying. This technology is to heat the particles to a critical temperature, accelerate the metal particles to supersonic speed by high-speed gas, and produce plastic deformation during the collision with the substrate to form a mechanical mosaic combination with the substrate. A novel method for preparing an aluminum coating.

Background technique

Most of the heating systems used in cold spraying equipment are air heaters. Traditional air heaters heat the air flow from the initial temperature to the required air temperature through heating resistance wires, but the heating efficiency is low, the heating time is long and the heating is uneven. is its main disadvantage. The patent of the invention uses laser to preheat the powder, which can effectively improve the efficiency of heating the powder and reduce energy loss, so that the high-speed cold spray powder can quickly reach the critical temperature and impact the substrate to form a coating.

Contents of the invention

The cold spraying system device involved in the present invention is shown in Figure 1, including: a laser output system, a temperature detection and control system, a powder feeder, a gas accelerator, a spray gun, a supersonic nozzle and a splash particle recovery device. The powder feeder is connected to the spray gun through the powder conveying pipeline, the laser output system is connected to the powder conveying pipeline through the optical fiber tube, the gas accelerator is connected to the powder conveying pipeline through the pipeline, and the supersonic nozzle is located in front of the spray gun and in the closed spraying of the splash particle recovery device Indoors, an exhaust fan is provided at the tail of the splash particle recovery device. The temperature detection and control system is used to monitor the temperature of the aluminum powder particles heated by the laser beam emitted by the laser output system and feed back to the laser output system.

The high-speed gas accelerates the aluminum powder particles into the powder conveying pipeline. The laser beam is emitted by the laser system and enters the powder conveying pipeline through the optical fiber tube. The powder conveying pipeline is made of high-temperature resistant stainless steel pipe to meet the conveying conditions of high-temperature aluminum powder particles, and the size of the laser spot and the output powder can be adjusted. The diameter of the beam is consistent with the diameter of the nozzle of the spray gun, and the laser beam heats the aluminum powder particles to quickly reach the critical temperature of spraying. The monitoring of the powder temperature is monitored by the temperature detection control system and fed back to the laser system. The laser system automatically adjusts the power according to the temperature fed back by the temperature monitoring system combined with the critical temperature value of the powder particles and the absorption efficiency of the laser, so that the temperature of the sprayed aluminum particles is maintained. Spraying was carried out at a critical temperature of 400°C. The laser power range is set at 400-800W, and the heating temperature can be adjusted during the spraying process. The aluminum powder particles that have reached the critical temperature are accelerated again by the gas accelerator and are impacted to the surface of the base metal S355 steel through the spray gun and supersonic nozzle to form a coating. Spraying is carried out in a closed spraying room, and the particles that fall off without impacting the surface of the substrate during the spraying process are recovered by the splash particle recovery device. After the spraying is finished, the dust particles in the airtight spraying room are exhausted by the exhaust fan.

Main features of the invention patent:

(1) In cold spraying equipment, using laser as a heating source can expand the application range of cold spraying technology, for example, it can be applied to the spraying of ceramic coatings.

(2) The laser and temperature monitoring system can accurately control and adjust the heating temperature of powder particles.

(3) The use of laser as a heating source can increase the heating speed, and can effectively make the powder particles heated more uniformly.

Description of drawings

Figure 1 Laser cold spray system.

1. Laser output system; 2. Powder feeder; 3. Gas accelerator; 4. Temperature detection and control system; 5. Spray gun; 6. Supersonic nozzle; 7. Coating; 8. Substrate; 9. Splash particle recovery device ; 10. Airtight spray booth; 11. Exhaust fan.

Fig. 2 Surface and interface morphology of laser cold sprayed aluminum coating.

Detailed ways

(1) Use 180#-1000# sandpaper to polish the surface of the substrate S355 steel, clean it with absolute ethanol, and degrease with acetone to remove the grease and sundries on the surface of the sample to ensure that the surface cleanliness of the substrate reaches Sa3 level;

(2) Use cast iron sand with a particle size of 1mm as abrasive grains, compressed air pressure > 0.8MPa, sandblasting distance of 200mm, and sandblasting angle of 20°, so that the roughness can reach Rz 60μm;

(3) As shown in Figure 1, the high-speed gas transports the pure aluminum powder particles in the powder feeder to the spraying pipeline. The aluminum powder is WFT1532 pure aluminum powder with a diameter of 20-45 μm. Internal parameters of the powder feeder: pressure 3.5MPa, delivery volume 1L/min. Set the speed of the spray gun to 200mm/s, and the distance between the spray gun and the sample to 40mm.

(4) According to the thickness requirements of the sprayed aluminum coating, set the laser parameters, and the diameter of the spot is 3.5mm, which is consistent with the diameter of the nozzle of the spray gun. Referring to the absorptivity of the aluminum powder to the laser and the critical temperature of the aluminum powder, set the laser power to 500W and control the temperature of the aluminum powder to 400°C. During the spraying process, the laser power can be adjusted according to the feedback from the temperature detector.

(5) After the laser heating, the aluminum particles are impacted by the spray gun to the surface of the substrate S355 steel to form a dense aluminum coating. The aluminum powder particles do not melt, and the formed aluminum coating has a low porosity, as shown in Figure 2(a) . The thickness of the aluminum coating is 250 μm, which has good bonding performance with the substrate and no porosity, as shown in Figure 2(b).

Claims (5)

1. A method for preparing an aluminum coating by cold spraying with a device for preparing an aluminum coating by laser cold spraying, the device comprising: the device comprises a laser output system, a temperature detection control system, a powder feeder, a gas accelerator, a spray gun, a supersonic speed spray pipe and a splash particle recovery device; the powder feeder is connected with the spray gun through a powder conveying pipeline, the laser output system is connected into the powder conveying pipeline through an optical fiber pipe, the gas accelerator is connected into the powder conveying pipeline through a pipeline, the supersonic speed spray pipe is positioned in front of the spray gun and in a closed spray coating chamber of the splashing particle recovery device, and an exhaust fan is arranged at the tail part of the splashing particle recovery device; the temperature detection control system is used for monitoring the temperature of the aluminum powder particles heated by the laser beam emitted by the laser output system and feeding the temperature back to the laser output system, and is characterized in that high-speed gas accelerates the aluminum powder particles to enter a powder conveying pipeline, the laser beam is emitted by the laser output system and enters the powder conveying pipeline through an optical fiber pipe, and the aluminum powder particles are heated by the laser beam to quickly reach the critical temperature of spraying; the aluminum powder particles having reached the critical temperature are accelerated again by the gas accelerator and are collided with the surface of the base metal S355 steel through the spray gun and the supersonic nozzle to form a coating layer.

2. The method of claim 1, wherein the powder delivery duct is a high temperature stainless steel pipe to satisfy delivery conditions of the high temperature aluminum powder particles.

3. The method of claim 1 wherein the laser spot size is adjusted to correspond to the diameter of the output powder beam, i.e., the diameter of the spray gun nozzle.

4. The method of claim 1, wherein the monitoring of the powder temperature is monitored by a temperature detection control system and fed back to a laser output system, the laser output system automatically adjusts the power according to the temperature fed back by the temperature detection control system and by combining the critical temperature value of the powder particles and the absorption efficiency of the laser, so that the temperature of the sprayed aluminum particles is maintained at the critical temperature of 400 ℃ for spraying, and the laser power range is set at 400 ~ 800W, so that the heating temperature can be adjusted during the spraying process.

5. The method according to claim 1, wherein the spraying is performed in a closed spraying chamber, particles falling off without hitting the surface of the substrate during the spraying are recovered by a spatter particle recovery means, and dust particles in the closed spraying chamber are discharged by a discharge fan after the spraying is completed.