CN105478762A - A Laser Forming Method for Cr3C2-FeCr Composite Components - Google Patents

Abstract

The invention relates to a laser forming method of a Cr3C2-FeCr composite component. Raw material powder selected in the laser forming method comprises, by weight percent, 4.23-6.31% of graphite, 39.82-47.25% of Cr, 3.26-5.16% of Mo, 0.59-0.71% of rare earth oxide and the balance Fe. Raw materials are in the form of powder, and the particle size of metal Fe powder, metal Cr powder, metal Mo powder and graphite powder is 50-200 microns. Quantitative conveying of powder formed through lasers is finished through a multi-hopper conveying system, four-pipe coaxial and discontinuous powder sprayers are adopted for laser forming, an inner and outer gradient layering structure of the Cr3C2-FeCr component can be achieved by controlling the powder conveying system and a laser head, and the fracture toughness of the Cr3C2-FeCr component can reach more than 70% of Fe base alloy.

Description

A Laser Forming Method for Cr3C2-FeCr Composite Components

technical field

The invention belongs to the field of laser forming, and relates to a laser forming method for a Cr ₃ C ₂ -FeCr composite material component.

Background technique

The carbide types of Cr mainly include M ₃ C ₂ , M ₃ C, M ₇ C ₃ and M ₂₃ C ₆ and other types, and the ones with better thermodynamic stability are Cr ₃ C ₂ , Cr ₇ C ₃ and Cr ₂₃ C ₆ , Cr ₃ C ₂ and Cr ₇ C ₃ are commonly used as reinforcing phases of metal matrix composites (MMC). Among them, Cr ₃ C ₂ can still maintain a relatively high hardness under high temperature conditions, and also has strong corrosion resistance and wear resistance. Cr ₃ C ₂ -FeCr has good high-temperature wear resistance, and can replace expensive nickel-based, cobalt-based alloys and their composite materials in medium-temperature environments.

The preparation technology of MMC can be divided into in-situ self-generation and forced addition according to the different ways of adding reinforcing particles. Adding Cr ₃ C ₂ particles to laser processing composite materials will cause Cr ₃ C ₂ in the material to decompose and regenerate carbides such as Cr ₇ C ₃ , which becomes one of the difficulties in laser processing of Cr ₃ C ₂ composite materials. The in-situ self-generation technology uses alloy design to react and nucleate in situ in the matrix metal to generate one or several thermodynamically stable reinforcement phases. This method avoids the decomposition of the external reinforcement, saves energy, resources and can reduce emissions. The reinforcement surface of the material is pollution-free, and the product performance is excellent. However, the process has strict requirements, is difficult to master, and the composition and volume fraction of the reinforcing phase are not easy to control.

The laser forming process uses the method of small-volume cumulative forming, which can control the uniform distribution of the reinforcing phase at a macroscopic level, and provides the possibility for powder-fed laser in-situ forming particle-reinforced MMC. The bulk density difference between metal powder and graphite powder is large. During the laser forming process, it is easy to cause stratification due to the large difference in powder density, which will cause uneven distribution of the reinforcement phase in the formed part, and will change the design of the reinforcement phase. composition, greatly reducing the performance of Cr ₃ C ₂ -FeCr composite parts. Therefore, the present invention adopts the online continuous powder feeding laser in-situ compound forming method to prepare Cr ₃ C ₂ -FeCr composite material parts, so that the reinforced phase of the formed parts is continuous and controllable.

Contents of the invention

The technical problem to be solved by the present invention is to provide a laser forming method of a Cr ₃ C ₂ -FeCr composite material component with controllable reinforcement phase distribution. The method of the present invention starts from the in-situ synthesis route and the laser forming process, and provides a new laser forming method for Cr ₃ C ₂ -FeCr composite material structural parts, which can make the reinforcing phase uniformly distributed in the composite material, and realize Cr with excellent performance. Laser forming of ₃ C ₂ -FeCr composite parts.

The inventive method mainly comprises the following steps:

(1) Raw material formula and pretreatment

The raw material formula is: graphite 4.23~6.31wt.%, Cr39.82~47.25wt.%, Mo3.26~5.16%, rare earth oxide 0.59~0.71wt.%, Fe balance; raw materials are in powder form, metal Fe The particle size of Cr, Mo powder and graphite powder is 50~200 microns; the metal Cr powder and rare earth oxide powder are ball milled for 0.5~5 hours;

(2) Powder feeding and mixing

The multi-hopper spiral powder feeding mixing system is adopted, and the multi-hopper screw powder feeding mixing system is composed of four powder feeders respectively connected to a common laser head through powder feeding pipes, and the mixed powder of Cr and rare earth oxide is put into the first In one hopper, Fe powder is placed in the second hopper, Mo powder is placed in the third hopper, graphite powder is placed in the fourth hopper, four powder feeders feed powder at the same time, and the powder is controlled by adjusting the screw speed proportion;

(3) Laser forming

The laser head uses 4 coaxial discontinuous nozzles to feed powder around the molten pool, so that the components of the molten pool are evenly distributed; the digital graphics of the designed parts are layered and sliced, and the laser scanning path is established. During the forming process, the screw speed is adjusted. , so that the proportion of the locally generated reinforcing phase Cr ₃ C ₂ in the component changes continuously in a gradient, that is, the outer layer of the component is Cr ₃ C ₂ -FeCr composite material, the inner layer is a metal matrix material, and the final raw materials used meet the steps ( 1) Proportional requirements.

A fiber/ _CO2 laser is employed in step (3). Fiber/CO ₂ laser output power 100~3000W, spot diameter 0.2~4mm, overlap rate 10~80%, laser head Ar gas flow 0.2~13L/min, powder feeder Ar gas flow 0.2~12L/min, laser Head scanning speed 3~125mm/s.

The multi-hopper screw powder feeding mixing system used in the present invention is composed of four powder feeders respectively connected to a laser head through powder feeding pipes, as shown in Figure 1 . The powder feeder is composed of a hopper, a screw and a fluidizer, and the screw is driven by a DC stepping motor.

The properties of Cr ₃ C ₂ -FeCr composites depend on the content, size and uniform distribution of Cr ₃ C ₂ . The invention uses a multi-hopper screw powder feeding and mixing system to feed powder immediately, and uses a coaxial discontinuous laser head to form Cr ₃ C ₂ -FeCr composite material parts, realizes the distribution control of the reinforcement phase, and eliminates Cr ₃ C ₂ in the composite material In the case of uneven distribution, laser forming of Cr ₃ C ₂ -FeCr composite structural parts with adjustable Cr ₃ C ₂ content is realized.

The method of the present invention separately forms the surface layer and the inner layer of the component at the same time, controls the powder feeding composition, and realizes the laser manufacturing of the metal matrix composite material parts of the inner and outer layered structures, so that the inside of the part has the toughness of the metal material, and the surface layer has wear resistance and high temperature resistance. Oxidation function, and the overall fracture toughness of the part is more than 70% of that of similar metal parts.

Description of drawings

Figure 1 Schematic diagram of the structure of the multi-hopper screw powder feeding mixing system.

detailed description

The present invention will be further described in conjunction with embodiments.

Embodiment one

A Cr ₃ C ₂ -FeCr composite material metallurgical annealing furnace roll laser forming method, comprising the following process:

(1) The raw material is in the form of powder, the particle size of metal Fe, Cr, Mo powder and graphite powder is 50-200 microns or more; the raw material composition is: graphite 4.23wt.%, Cr43.37wt.%, Mo3.26%, rare earth Oxide 0.59wt.%, Fe48.55wt.%; ball mill and mix Cr powder and rare earth oxide for 2 hours.

(2) Use a multi-hopper screw powder feeding mixing system for powder feeding and instant mixing. Put the mixed powder of Cr and rare earth oxides into the first hopper, Fe powder in the second hopper, and Mo powder in the third In the hopper, graphite powder is placed in the fourth hopper; 4 powder feeders feed powder at the same time, and the content of Cr ₃ C ₂ in the powder reaction product is adjusted by the screw speed.

(3) Laser forming

The laser head for laser forming adopts 4 coaxial discontinuous nozzles to feed powder around the molten pool so that the components of the laser molten pool can be evenly distributed; the digital graphics of the parts to be processed are sliced in layers, and the laser scanning path is established, and then The composition of the powder feeding is controlled, and the laser forming is carried out by the CNC machine tool to realize the laser forming of the internal and external layered structure of the component, forming a special structural part whose outer layer is wear-resistant Cr ₃ C ₂ -FeCr composite material, and the inner matrix is a metal matrix. Laser processing uses a fiber laser with an output power of 550W, a spot diameter of 0.35mm, an overlap rate of 38%, an Ar gas flow of the laser head of 4.6L/min, an Ar gas flow of the powder feeder of 7.3L/min, and a scanning speed of the laser head of 12mm/s. .

The inside of the formed part has the toughness of metal materials, and the surface layer has the functions of wear resistance and high temperature oxidation resistance, and the overall fracture toughness of the part is more than 70% of that of similar metal parts.

Embodiment two

A Cr ₃ C ₂ -FeCr composite material thermoforming mold laser forming method, comprising the following processes:

(1) The raw material is in the form of powder, the particle size of metal Fe, Cr, Mo powder and graphite powder is 50-200 microns or more; the raw material composition is: graphite 5.19wt.%, Cr39.82wt.%, Mo5.16%, rare earth Oxide 0.71wt.%, Fe balance; Cr powder, rare earth oxide ball mill and mix for 2.5 hours.

(2) Use a multi-hopper screw powder feeding mixing system for powder feeding and instant mixing. Put the mixed powder of Cr and rare earth oxides into the first hopper, Fe powder in the second hopper, and Mo powder in the third In the hopper, graphite powder is placed in the fourth hopper; 4 powder feeders feed powder at the same time, and the content of Cr ₃ C ₂ in the powder reaction product is adjusted by the screw speed.

(3) Laser forming

The laser head for laser forming adopts 4 coaxial discontinuous nozzles to feed powder around the molten pool so that the components of the laser molten pool can be evenly distributed; the digital graphics of the parts to be processed are sliced in layers, and the laser scanning path is established, and then Control the powder feeding composition and laser scanning route, use CNC machine tools to realize laser forming of the inner and outer layered structures of composite parts, and form special structural parts with wear-resistant Cr ₃ C ₂ -FeCr composite materials as the outer layer and the inner matrix as the metal matrix. Laser processing uses a CO ₂ laser with an output power of 800W, a spot diameter of 0.25mm, an overlap rate of 55%, an Ar gas flow rate of the laser head of 3.8L/min, an Ar gas flow rate of the powder feeder of 6.2L/min, and a scanning speed of the laser head of 14mm/min. s.

The inside of the formed part has the toughness of metal materials, and the surface layer has the functions of wear resistance and high temperature oxidation resistance, and the overall fracture toughness of the part is more than 70% of that of similar metal parts.

Embodiment Three

A Cr ₃ C ₂ -FeCr composite material hot continuous rolling conveying roll laser forming method, comprising the following process:

(1) The raw material is in the form of powder, the particle size of metal Fe, Cr, Mo powder and graphite powder is 50-200 microns or more; the raw material composition is: graphite 6.31wt.%, Cr47.25wt.%, Mo4.86%, rare earth Oxide 0.64wt.%, Fe40.94wt.%; Cr powder and rare earth oxides were ball milled and mixed for 3 hours.

(2) Use a multi-hopper screw powder feeding mixing system for powder feeding and instant mixing. Put the mixed powder of Cr and rare earth oxides into the first hopper, Fe powder in the second hopper, and Mo powder in the third In the hopper, graphite powder is placed in the fourth hopper; 4 powder feeders feed powder at the same time, and the content of Cr ₃ C ₂ in the powder reaction product is adjusted by the screw speed.

(3) Laser forming process

The laser head for laser forming adopts 4 coaxial discontinuous nozzles to feed powder around the molten pool so that the components of the laser molten pool can be evenly distributed; the digital graphics of the parts to be processed are sliced in layers, and the laser scanning path is established, and then Control the powder feeding composition and laser scanning route, use CNC machine tools to realize laser forming of the inner and outer layered structures of composite parts, and form special structural parts with wear-resistant Cr ₃ C ₂ -FeCr composite materials as the outer layer and the inner matrix as the metal matrix. Laser processing uses a fiber laser with an output power of 900W, a spot diameter of 0.40mm, an overlap rate of 30%, an Ar gas flow of the laser head of 7.8L/min, an Ar gas flow of the powder feeder of 7.5L/min, and a scanning speed of the laser head of 28mm/s. .

Claims (3)

1. a Cr ₃c ₂the laser forming method of-FeCr composite element, is characterized in that comprising the steps:

(1) composition of raw materials and pretreatment

Composition of raw materials is: graphite 4.23 ~ 6.31wt.%, Cr39.82 ~ 47.25wt.%, Mo3.26 ~ 5.16%, rare earth oxide 0.59 ~ 0.71wt.%, Fe surplus; Raw material adopts powder, the particle size of metal Fe, Cr, Mo powder and graphite powder 50 ~ 200 microns; By Metal Cr powder and RE oxide powder ball milling 0.5 ~ 5 hour;

(2) powder feeding and batch mixing

Adopt many hoppers spiral powder feeding hybrid system, described many hoppers spiral powder feeding hybrid system is connected to form respectively by powder feeding pipe and a common laser head by four powder feeders, the mixed-powder of Cr and rare earth oxide is put into the 1st hopper, Fe powder is placed in the 2nd hopper, Mo powder is placed in the 3rd hopper, graphite powder is placed in the 4th hopper, 4 powder feeder powder feedings simultaneously, and is controlled the ratio of powder by adjustment screw speed;

(3) laser forming

Described laser head adopts the coaxial discontinuous nozzle of 4 pipe, encircles powder feeding to molten bath, makes each uniform composition distribution in molten bath; To the digital figure hierarchy slicing of design part, set up laser beam scan path, in forming process, adjusting screw(rod) rotating speed, makes the wild phase Cr that local generates ₃c ₂ratio in component becomes gradient consecutive variations, and namely component skin is Cr ₃c ₂-FeCr composite, internal layer is metal matrix material, and the raw material of final utilization meets the proportion requirement of step (1).

2. the laser forming method according to patent requirements 1, is characterized in that, adopts optical fiber/CO in step (3) ₂laser instrument, power output 100 ~ 3000W, spot diameter 0.2 ~ 4mm, overlapping rate 10 ~ 80%, laser head Ar throughput 0.2 ~ 13L/min, powder feeder Ar throughput 0.2 ~ 12L/min, laser head sweep speed 3 ~ 125mm/s.

3. the laser forming method according to patent requirements 1, is characterized in that, described powder feeder is made up of hopper, screw rod and Fluidizer, and described screw rod is promoted by DC stepper motor.