Gradient material with high wear resistance and impact resistance and follow-up ultrasonic-assisted additive manufacturing method thereof

Abstract

The invention discloses a high-wear-resistance impact-resistance gradient material and a follow-up ultrasonic-assisted additive manufacturing method thereof, and belongs to the technical field of additive manufacturing. According to the method, the gradient material is prepared through a laser three-dimensional forming technology, and raw materials comprise a soft material, hard material metal and hard ceramic powder. Along with the increase of the printing height, the specific gravity of the soft material is continuously reduced, the specific gravity of the hard material is continuously increased until the specific gravity of the hard material is 100%, and the surface layer of the gradient material is a hard ceramic particle reinforced high-hardness layer. In the gradient material laser three-dimensional forming process, follow-up ultrasonic vibration assistance is adopted, convection of liquid soft and hard materials is promoted, a metal molten pool is fully mixed, element segregation and brittle phase precipitation are reduced, hard ceramic particles are promoted to be evenly distributed in the molten pool, and the dispersion strengthening effect is enhanced.

Description

Technical Field

[0001] The present invention belongs to the technical field of additive manufacturing, and in particular relates to a highly wear-resistant and impact-resistant gradient material and a follow-up ultrasonic-assisted additive manufacturing method thereof. Background Art

[0002] High-end fields such as aviation and aerospace have put forward high requirements for metal parts in terms of both wear resistance and impact resistance. However, wear-resistant alloys often have high hardness and poor deformation ability, and there may be network carbides in the alloy structure, resulting in poor impact resistance. As a new type of composite material, the composition / microstructure / performance of functional gradient materials changes with different spatial positions, and the performance of parts can be controlled through material design. Therefore, functional gradient materials are designed so that the surface of the material has high wear resistance and the bottom of the material has high impact resistance, which provides an effective method to achieve the "double high" of metal parts. Laser stereo forming technology is formed layer by layer, and its advantage of high degree of freedom is suitable for gradient material design and preparation.

[0003] At present, the mainstream laser stereo forming gradient material methods are divided into two types: continuous gradient and sudden gradient. If the sudden gradient forming method is adopted, when the thermal expansion coefficient, thermal conductivity and other thermal physical parameters of different pass materials are greatly different, defects such as poor fusion and cracking often occur; Patent CN115433933A discloses a continuous gradient forming method, which adopts the method of connecting multiple powder barrels to the nozzle to realize the continuous supply of powder raw materials with different proportions. However, if the density and melting point of different raw materials in the prepared gradient material are greatly different, it will lead to poor fluidity of the melted liquid metal, and ultimately cause the local composition of the prepared gradient material to be uneven, which is easy to cause element segregation and form brittle intermetallic compounds, deteriorating the impact resistance of the material.

[0004] In addition, the current mainstream methods to improve the wear resistance of the surface of metal materials are surface treatment and particle reinforcement, such as carburizing, nitriding and other surface treatments. However, the high-hardness surface after treatment is brittle and easy to peel off, which reduces the service life. The use of particle reinforcement methods in laser stereo forming will involve the problem of uniform distribution of hard particles in the metal matrix. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a highly wear-resistant and impact-resistant gradient material and a follow-up ultrasonic-assisted additive manufacturing method thereof, so as to solve the problems in the prior art of uneven local composition of continuous gradient materials formed by laser stereo forming and difficulty in uniform distribution of hard particles in the micro-molten pool.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A method for manufacturing a highly wear-resistant and impact-resistant gradient material by means of ultrasonic-assisted additive manufacturing comprises the following steps: Step 1, placing soft material powder, hard material powder and hard ceramic particles in different containers respectively; Step 2, turning on the laser for deposition; During the deposition of each layer, soft material powder and hard material powder are fed simultaneously, the ultrasonic tool head is behind the laser nozzle, the ultrasonic tool head contacts the top of the deposited layer, and ultrasonically vibrates the deposited layer, and the laser nozzle and the ultrasonic tool head run at the same speed along the printing direction; deposition ends when the Nth layer is deposited, where N is a natural number ≥3; From the first deposition layer to the Nth deposition layer, the feeding amount of the soft material powder gradually decreases, and the feeding amount of the hard material powder gradually increases; the hardness of the soft material powder is less than the hardness of the hard material powder; Step 3, depositing a ceramic particle reinforcement layer on the Nth deposition layer. During the deposition process, hard material powder and hard ceramic particles are fed simultaneously. The ultrasonic tool head is behind the laser nozzle. The ultrasonic tool head contacts the top of the deposition layer and ultrasonically vibrates the deposition layer.

[0007] A further improvement of the present invention is: Preferably, in step 2, the soft material content and the hard material content in each deposition layer are controlled by adjusting the powder feeding rate of the soft material powder and the powder feeding rate of the hard material powder; In step 3, the content of hard material and ceramic particles in the ceramic particle reinforcement layer is adjusted by adjusting the powder feeding rate of the hard material powder and the powder feeding rate of the hard ceramic particles.

[0008] Preferably, in step 2, the first deposition layer is a soft material; and the Nth deposition layer is a hard material.

[0009] Preferably, in step 2 and step 3, after a portion of each deposited layer is solidified, the ultrasonic tool head is pressed against the upper end surface of the solidified deposited layer.

[0010] Preferably, in step 2 and step 3, the printing directions between adjacent deposition layers are at a set angle.

[0011] Preferably, in step 2, from the first deposition layer to the Nth deposition layer, as the number of printed layers increases, the reduction in the amount of soft material in each layer and the increase in the amount of hard material are calculated from the total number of deposition layers N.

[0012] Preferably, the material of the printed substrate is the same as the soft material.

[0013] Preferably, in step 3, the number of layers of the ceramic particle reinforcement layer is 1 to 3 layers.

[0014] Preferably, in step 3, the mass proportion of the hard ceramic particles in the ceramic particle reinforcement layer is 5-15%, and the rest is hard material.

[0015] A highly wear-resistant and impact-resistant gradient material obtained by any of the above-mentioned follow-up ultrasonic-assisted additive manufacturing methods, comprising N deposition layers, wherein the first deposition layer is a soft material, the Nth deposition layer is a hard material, and M layers of ceramic particle reinforcement layers are arranged outside the Nth deposition layer; N is a natural number ≥3, and M is a natural number ≥1; from the first deposition layer to the Nth deposition layer, the soft material content gradually decreases, and the hard material content gradually increases; the ceramic particle reinforcement layer is composed of hard material and hard ceramic particles.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention discloses a follow-up ultrasonic assisted additive manufacturing method for a highly wear-resistant and impact-resistant gradient material. The gradient material of the method is prepared by laser stereo forming technology, and the raw materials include soft materials, hard materials, metals and hard ceramic powders. As the printing height increases, the specific gravity of the soft material decreases continuously, and the specific gravity of the hard material increases continuously until the specific gravity of the hard material is 100%, and the surface layer of the gradient material is a high-hardness layer reinforced by hard ceramic particles. In the process of laser stereo forming gradient materials, "follow-up" ultrasonic vibration is used to assist in promoting the convection of liquid soft and hard materials so that the metal molten pool is fully mixed, reducing element segregation and brittle phase precipitation, promoting the uniform distribution of hard ceramic particles in the molten pool, and enhancing the dispersion strengthening effect. In addition, the present invention can use the ultrasonic cavitation effect to produce a degassing effect on the metal molten pool, and break the columnar dendrites caused by the high cooling rate and large temperature gradient inherent in laser stereo forming, homogenize the alloy structure, and optimize the comprehensive mechanical properties of the alloy. Compared with some existing technical solutions that set ultrasonic processing equipment at the bottom of the substrate and perform ultrasonic processing from the bottom, the ultrasonic vibration auxiliary equipment of the present invention is set behind the molten pool, and the ultrasonic tool head moves with the movement of the laser nozzle, which can fully vibrate and degas the molten pool of each deposition layer. The material can be fully vibrated in each layer, and the thermal physical property material is evenly distributed, avoiding the problem of insufficient vibration effect.

[0017] Furthermore, the bottom layer of the gradient material and the substrate material are consistent with 100% soft material, ensuring good compatibility between the bottom layer of the gradient material and the substrate material, and avoiding bottom layer defects.

[0018] The present invention also discloses a highly wear-resistant and impact-resistant gradient material, which is composed of soft and hard raw materials. The first deposition layer is a soft material, the Nth deposition layer is a hard material, and M layers of ceramic particle reinforcement layers are arranged outside the Nth deposition layer; N is a natural number ≥3, and M is a natural number ≥1; from the first deposition layer to the Nth deposition layer, the content of soft materials gradually decreases, and the content of hard materials gradually increases.

[0019] The highly wear-resistant and impact-resistant gradient material is prepared by laser stereo forming technology. When the gradient material is impacted by a large external load, the soft material is responsible for deformation at the bottom. When the surface of the gradient material is subjected to sliding friction, the high-hardness layer reinforced by the surface ceramic particles ensures that the gradient specimen does not suffer significant wear. In the present invention, the composition of the gradient material changes continuously in the height direction, avoiding poor fusion and cracking defects of soft and hard materials due to poor compatibility. The ultrasonic-assisted acoustic flow effect in the molten pool is used to promote heat and mass transfer, so that the liquid soft and hard materials are fully convectively mixed, which can avoid element segregation and the formation of brittle phases, thereby improving the strength of the material. The present invention uses a powder delivery tube outside the nozzle to transport hard ceramic particles, and promotes the uniform distribution of ceramic particles in the molten pool through ultrasonic assistance, avoiding the problem of uneven particles in the mixing process of conventional laser stereo forming particle-reinforced composite materials, and the present invention is convenient for controlling the composition change rate of soft and hard materials in the height direction, and the preparation process is simple. Based on this, the present invention provides a new idea for the partition performance design of new functional gradient materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of composition evolution of the highly wear-resistant and impact-resistant gradient material with continuously changing composition in the present invention; Figure 2 Schematic diagram of the method for preparing a highly wear-resistant and impact-resistant gradient material with continuously changing composition by ultrasonic-assisted laser stereo forming in the present invention; Figure 3 Schematic diagram of the composition evolution of the highly wear-resistant and impact-resistant gradient material with continuously changing composition in Example 1 of the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below in conjunction with the accompanying drawings: In the description of the present invention, it should be noted that the orientations or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention; the terms "first", "second", and "third" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance; in addition, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] See also Figure 1The present invention discloses a method for manufacturing a high wear-resistant and impact-resistant gradient material by means of a follow-up ultrasonic-assisted additive manufacturing method, comprising the following steps: Step 1, cleaning the substrate, selecting soft material powder A, hard material powder B and hard ceramic particles, placing them into different powder cylinders after drying, establishing a three-dimensional model of gradient materials, and importing them into a laser stereo forming device; The soft material powder and the hard material powder are both metal powders, and the hardness of the soft material formed by the soft material powder is less than that of the hard material. For example, common soft materials include nickel-based alloys, magnesium alloys, and aluminum alloys, and hard materials include iron-based alloys.

[0023] As a preferred solution, the soft material and the substrate have the same composition.

[0024] Step 2, introduce protective gas into the laser stereo forming equipment, adjust the nozzle to an appropriate height from the substrate, and then adjust the relative position of the ultrasonic tool head and the nozzle.

[0025] Step 3: When forming the first deposition layer, set the powder feeding rate of the soft material powder A to S max , set the powder feeding rate of hard material B to 0, set the laser power, turn on the laser synchronously, and after the laser melts the alloy powder to form a deposition layer of a certain length on the substrate, adjust the ultrasonic tool head to press tightly on the top of the deposition layer behind the nozzle, turn on the ultrasonic device, and transmit the ultrasound into the molten pool through the deposition layer.

[0026] It should be understood that in this process, after a certain length of the deposited portion in the deposited layer solidifies and the area of ​​the solidified portion is able to support the ultrasonic tool head, the ultrasonic tool head can be placed on the formed part to vibrate the molten pool formed by the laser in front of the ultrasonic tool head as soon as possible.

[0027] Step 4, keep the ultrasonic tool head and the nozzle moving in the same direction at all times. When the first deposition layer is formed, turn off the laser and ultrasonic device, stop feeding powder, and pause the nozzle for a while. During this period, rotate the ultrasonic tool head to set the angle, lower the powder feeding rate of soft material A, and increase the powder feeding rate of hard material B accordingly, so that the total powder feeding rate of soft and hard material alloy powder is constant, start powder feeding, turn on the laser synchronously, and move the nozzle back. After the second deposition layer has a certain length, adjust the position of the ultrasonic tool head according to step 3 and turn on the ultrasonic device.

[0028] In this step, in order to ensure the uniformity of the ultrasonic assisting effect during the printing process, the ultrasonic tool head is always maintained at the same distance behind the laser in the forming direction and pressed tightly against the surface of the deposited layer. After each deposited layer is printed, the ultrasonic tool head is rotated around the laser to a set angle so that the ultrasonic tool head can track behind the nozzle.

[0029] Exemplarily, the vibration frequency of the ultrasonic tool head is 20.0 KHz, and the amplitude is fixed at 5 μm.

[0030] Step 5: After each deposition layer is formed, turn off the laser and ultrasonic device, stop feeding powder, lower the powder feeding rate of soft material A, increase the powder feeding rate of hard material B, keep the total powder feeding rate of soft and hard materials constant, rotate the ultrasonic tool head to a set angle, and always keep the ultrasonic tool head behind the direction of nozzle movement; Step 6: After N deposition layers are formed, the powder feeding rate of soft material A is reduced to 0, and the powder feeding rate of hard material B is increased to S. max , thus completing the deposition of the first deposition layer to the Nth deposition layer.

[0031] The first deposition layer deposited through the above steps is 100% soft material A. As the printing height increases, the material gradually transitions to hard material B until reaching 100% hard material B, which is the Nth deposition layer.

[0032] Step 7, connect the powder cylinder containing hard ceramic particles, feed the hard ceramic particles and hard powder at the same time, set the powder feeding rate, and continue to deposit and form M layers of ceramic particle reinforcement layers, where M is a natural number ≥ 1. During the deposition process, the ultrasonic tool head vibrates behind the nozzle moving direction so that the ceramic particles are evenly distributed in the molten pool during the deposition process.

[0033] In this step, the ceramic particle reinforcement layer includes hard material and hard ceramic particles. The hard material is obtained by laser forming hard material powder, and is the same material as the Nth deposition layer, so that the printed ceramic particle reinforcement layer and the Nth deposition layer have good metallurgical bonding ability. The hard ceramic particles can be hard ceramic powders such as TiB2 or WC. It should be noted that for different hard material powders, when selecting hard ceramic powders, brittle intermetallic compounds should be avoided.

[0034] In this step, by adjusting the powder feeding rate of hard ceramic particles and the powder feeding rate of hard powder, the proportion of hard ceramic particles and the proportion of hard powder in the final ceramic particle reinforcement layer can be adjusted. The specific powder feeding rate is controlled by the speed of the powder feeder.

[0035] In some embodiments of the present invention, the mass proportion of hard ceramic particles in this step is 5-15%.

[0036] It should be understood that the ratio of hard ceramic particles to hard powder in different ceramic particle reinforcement layers can be adjusted. For example, when M is 3, the content of hard ceramic particles can gradually increase from the inside to the outside of the ceramic particle reinforcement layer.

[0037] In some embodiments of the present invention, in the above steps 3 to 6, the specific gravity of the soft material that decreases or the hard material that increases after each layer is printed is calculated based on the number of printing layers N, and the gradient material composition changes continuously in the height direction and is consistent in the horizontal direction, that is, the specific gravity of the soft material and the hard material on each layer is the same.

[0038] On this basis, preferably, the variable of lowering the powder feeding rate of soft material A and hard material B after each layer of printing is completed can be flexibly set according to the number of layers required to prepare gradient material specimens to ensure the continuity of the gradient material composition in height.

[0039] In some embodiments of the present invention, in the above steps 3 to 6, the conveying paths of soft material A powder, hard material B powder, and ceramic powder are isolated during the printing process, and the powder conveying paths do not interfere with each other. Before each replacement of the powder feeding alloy, the powder feeding pipeline should be ensured to be clean.

[0040] It should be understood that in steps 3 to 6, when printing each layer, the proportion of soft material A and hard material B of different heights is controlled by the speed of the powder feeder.

[0041] It should be understood that the powder feeding rate and laser power can be matched with soft and hard materials, that is, in the preparation process of the above-mentioned gradient material, the process parameters of the bottom material can be different from those of the top material, and the printing parameters of each cladding layer can be adjusted.

[0042] In some embodiments of the present invention, the distance between the ultrasonic tool head and the nozzle in the horizontal direction can be adjusted according to the actual forming effect.

[0043] In some embodiments of the present invention, the soft material may be a nickel-based alloy with low hardness, and the hard material may be an iron-based alloy with high hardness. See also Figure 2 The second aspect of the present invention discloses a highly wear-resistant and impact-resistant gradient material obtained by the above-mentioned follow-up ultrasonic-assisted additive manufacturing method. The material includes N deposition layers, the first deposition layer is a soft material, the Nth deposition layer is a hard material, and the Nth deposition layer is provided with M layers of ceramic particle reinforcement layers; N is a natural number ≥3, and M is a natural number ≥1; from the first deposition layer to the Nth deposition layer, the soft material content gradually decreases, and the hard material content gradually increases. After the proportion of hard material reaches 100%, the surface layer of the gradient material is prepared by using a hard material alloy powder reinforced by hard ceramic particles such as TiB2 and WC.

[0044] In some embodiments of the present invention, a highly wear-resistant and impact-resistant gradient material with continuously changing components is provided, which is prepared by laser stereo forming. The raw materials include soft material A, hard material B metal powder and hard ceramic powder. The hardness of hard material B is greater than that of soft material A, wherein soft material A and hard material B are both metal materials, and the metal material can be a metal element or alloy. The bottom of the gradient material is soft material A, and the top is hard material B. In order to further enhance the hardness of the material and thus improve the wear resistance, the surface layer of the material is a hard composite material reinforced with ceramic particles, that is, a ceramic particle reinforced layer. When subjected to a large instantaneous impact load, the bottom soft material deforms and releases the impact force slowly. When subjected to long-term friction, the high hardness layer on the surface resists wear and protects the inside of the material from damage, thereby achieving high impact resistance and wear resistance of the prepared material.

[0045] It should be understood that due to the differences in thermal physical parameters such as thermal expansion coefficient and thermal conductivity, dissimilar materials often produce defects such as cracks and poor fusion during welding. Therefore, in order to avoid the above defects, the present invention adopts a continuous composition transition from (100% soft material A + 0% hard material B) to (0% soft material A + 100% hard material B) to avoid composition mutation and eliminate malicious interfaces. At the same time, since the metal powders of the raw materials of the gradient material are not mixed in the present invention, if the melting points or liquid fluidity of the soft and hard raw materials are greatly different, the inherent characteristics of small molten pool and high cooling rate of laser stereo forming may cause uneven mixing of liquid soft and hard materials, resulting in element segregation and hard-brittle intermetallic compounds. The present invention adopts "follow-up" ultrasonic assistance to promote the generation of acoustic cavitation effect in the liquid molten pool, accelerate the heat and mass transfer process, and avoid the above problems.

[0046] It should be understood that the highly wear-resistant and impact-resistant gradient material with continuously changing composition has consistent composition in the horizontal direction and continuously changes composition in the height direction, wherein the bottom material is 100% soft material consistent with the composition of the substrate, and as the number of printing layers increases, the specific gravity of the soft material A decreases uniformly, and the specific gravity of the hard material B increases uniformly until the specific gravity of the hard material reaches 100%, and then, in order to further improve the hardness of the surface layer of the gradient material and thus enhance the wear resistance of the material, a hard material powder B reinforced with hard ceramic particles such as TiB2 and WC with a certain specific gravity (c%) is used to prepare the surface layer of the gradient material. Specifically, as the number of printing layers increases, the specific gravity of the soft and hard materials of each layer of the gradient material in the present invention changes, and the reduction in the soft material A and the increase in the hard material B should be calculated from the expected total number of deposition layers N to ensure the continuity of the composition of the prepared gradient material in the height direction.

[0047] One of the embodiments disclosed in the present invention provides an example of the composition evolution of the highly wear-resistant and impact-resistant gradient material with continuously changing composition: Figure 3The raw materials of the highly wear-resistant and impact-resistant gradient material with continuously changing composition include 300M steel, high-hardness iron-based alloy and Ti2B powder. It is expected that the total number of layers of gradient material printing is 12 layers, of which the two surface deposition layers are prepared by high-hardness iron-based alloy powder reinforced with Ti2B particles. The gradient material will complete the transformation from 300M steel to high-hardness iron-based alloy during the printing process of 10 layers. Specifically, the bottom layer of the gradient material is 100%---300M steel, the second layer is 90%---300M steel + 10% high-hardness iron-based alloy... The 9th layer is 10%---300M steel + 90% high-hardness iron-based alloy, and the 10th layer is 100% high-hardness iron-based alloy. After the uniform transformation of the soft material to the hard material composition is completed, a certain amount of high-hardness iron-based alloy powder reinforced with Ti2B particles is used to prepare the surface layer of the gradient material.

[0048] The following is further described in conjunction with specific embodiments.

[0049] Example 1 The highly wear-resistant and impact-resistant gradient material with continuously changing composition uses 300M steel as a soft material and a high-hardness iron-based alloy as a hard material, achieving a smooth change of major elements such as Fe, Ni, Cr, and Mo in the height direction, and can ensure that the hardness value of the material increases steadily in the height direction. The final gradient material has the performance characteristics of high hardness on the surface and high toughness on the bottom, has a strong deformation ability, and can withstand large impact loads.

[0050] Furthermore, the chemical composition of the 300M steel powder is C 0.41-0.46%, Si 1.45-1.80%, Mn 0.65-0.90%, Cr 0.65-0.95%, Ni 1.60-2.00%, Mo 0.30-0.40%, V 0.05-1.10%, and the balance is Fe.

[0051] Furthermore, the chemical composition of the high-hardness iron-based alloy powder is C 0.958%, Si 0.265%, Mn 0.244%, Cr 4.3%, Ni 0.07%, Mo 5.21%, Cu 0.08%, Al ≤0.01%, V 1.86%, Co 0.056%, W 6.27%, and the balance is Fe.

[0052] The steps of the method for preparing the highly wear-resistant and impact-resistant gradient material with continuously changing components are as follows: Step 1: Grind the surface of the 300M steel substrate, screen the soft material 300M steel powder and the hard material high-hardness iron-based alloy powder with a 200-mesh sieve, keep them in an oven at 80°C for 6 hours, and then place them in different powder cylinders respectively, establish a three-dimensional model of the gradient material, and import it into the laser stereo forming equipment; Step 2, introducing protective gas into the laser stereo forming equipment, adjusting the nozzle to a proper height from the substrate, and then adjusting the relative position between the ultrasonic tool head and the nozzle; Step 3: Set the powder feeding rate of 300M steel powder to 10 g / min, set the powder feeding rate of high hardness iron-based alloy to 0 g / min, set the laser power to 2000 W, turn on the laser synchronously, and after the laser melts the alloy powder to form a 25 mm long deposition layer on the substrate, adjust the ultrasonic tool head to press tightly on the top of the deposition layer behind the nozzle, with a horizontal distance of 20 mm between the two, turn on the ultrasonic device, and transmit the ultrasound into the molten pool through the deposition layer; Step 4: Keep the ultrasonic tool head and the nozzle moving in the same direction. When the first deposition layer is formed, turn off the laser and ultrasonic device, stop feeding powder, and pause the nozzle for a while. During this period, rotate the ultrasonic tool head 180°, lower the 300M steel powder feeding rate to 9 g / min, and correspondingly increase the hard material high-hardness iron-based alloy powder feeding rate to 1 g / min, so that the total powder feeding rate of soft and hard material alloy powders is consistent, start powder feeding, turn on the laser synchronously, and move the nozzle back. After the second deposition layer has a certain length, adjust the position of the ultrasonic tool head and turn on the ultrasonic device according to step 3; Step 5: After each deposition layer is formed, turn off the laser and ultrasonic device, stop feeding powder, lower the powder feeding rate of 300M steel, increase the powder feeding rate of high-hardness iron-based alloy, keep the total powder feeding rate of 300M steel and high-hardness iron-based alloy constant at 10g / min, rotate the ultrasonic tool head 180°, and always keep the ultrasonic tool head behind the nozzle moving direction; Step 6. After completing the formation of 10 deposition layers, the 300M steel powder feeding rate is reduced to 0, and the high hardness iron-based alloy powder feeding rate is increased to 10 g / min. The powder cylinder containing TiB2 is connected, and the ceramic particle powder feeding rate is set to 0.5 g / min, and the high hardness iron-based alloy powder feeding rate is set to 9.5 g / min. Continue to form 2 layers of ceramic particle reinforced high hardness iron-based alloy deposition layers.

[0053] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for the follow-up ultrasonic-assisted additive manufacturing of highly wear-resistant and impact-resistant gradient materials, characterized in that: The following steps are involved: Step 1, placing soft material powder, hard material powder and hard ceramic particles in different containers respectively; Step 2, turning on the laser for deposition; During the deposition of each layer, soft material powder and hard material powder are fed simultaneously, the ultrasonic tool head is behind the laser nozzle, the ultrasonic tool head contacts the top of the deposited layer, and ultrasonically vibrates the deposited layer, and the laser nozzle and the ultrasonic tool head run at the same speed along the printing direction; deposition ends when the Nth layer is deposited, where N is a natural number ≥3; From the first deposition layer to the Nth deposition layer, the feeding amount of the soft material powder gradually decreases, and the feeding amount of the hard material powder gradually increases; the hardness of the soft material powder is less than the hardness of the hard material powder; Step 3, depositing a ceramic particle reinforcement layer on the Nth deposition layer. During the deposition process, hard material powder and hard ceramic particles are fed simultaneously. The ultrasonic tool head is behind the laser nozzle. The ultrasonic tool head contacts the top of the deposition layer and ultrasonically vibrates the deposition layer.

2. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by ultrasonic-assisted additive manufacturing according to claim 1, characterized in that: In step 2, the soft material content and the hard material content in each deposition layer are controlled by adjusting the powder feeding rate of the soft material powder and the powder feeding rate of the hard material powder; In step 3, the content of hard material and ceramic particles in the ceramic particle reinforcement layer is adjusted by adjusting the powder feeding rate of the hard material powder and the powder feeding rate of the hard ceramic particles.

3. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by ultrasonic-assisted additive manufacturing according to claim 1, characterized in that: In step 2, the first deposition layer is a soft material; the Nth deposition layer is a hard material.

4. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by means of a follow-up ultrasonic-assisted additive manufacturing method according to claim 1, characterized in that: In step 2 and step 3, after a portion of each deposited layer is solidified, the ultrasonic tool head is pressed against the upper end surface of the solidified deposited layer.

5. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by means of a follow-up ultrasonic-assisted additive manufacturing method according to claim 1, characterized in that: In step 2 and step 3, the printing directions between adjacent deposition layers are at a set angle.

6. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by ultrasonic-assisted additive manufacturing according to claim 1, characterized in that: In step 2, from the first deposition layer to the Nth deposition layer, as the number of printing layers increases, the reduction in the amount of soft material in each layer and the increase in the amount of hard material are calculated from the total number of deposition layers N.

7. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by ultrasonic-assisted additive manufacturing according to claim 1, characterized in that: The material of the printed substrate is the same as the soft material.

8. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by means of a follow-up ultrasonic-assisted additive manufacturing method according to claim 1, characterized in that: In step 3, the number of layers of the ceramic particle reinforcement layer is 1 to 3.

9. The method for manufacturing a highly wear-resistant and impact-resistant gradient material by ultrasonic-assisted additive manufacturing according to claim 1, characterized in that: In step 3, the mass proportion of the hard ceramic particles in the ceramic particle reinforcement layer is 5-15%, and the rest is hard material.

10. A highly wear-resistant and impact-resistant gradient material produced by the follow-up ultrasonic-assisted additive manufacturing method according to any one of claims 1 to 9, characterized in that: It includes N deposition layers, the first deposition layer is a soft material, the Nth deposition layer is a hard material, and M layers of ceramic particle reinforcement layers are arranged outside the Nth deposition layer; N is a natural number ≥3, and M is a natural number ≥1; from the first deposition layer to the Nth deposition layer, the content of soft material gradually decreases, and the content of hard material gradually increases; the ceramic particle reinforcement layer is composed of hard material and hard ceramic particles.

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