A process for achieving diffusion bonding of dissimilar materials by powder metallurgy process

Abstract

The present application relates to the technical field of metal heat treatment, in particular to a process for realizing diffusion connection of dissimilar materials through powder metallurgy process, which controls the mechanical properties, dimensional accuracy, surface morphology and structural integrity of the formed blank by selection of alloy elements, regulation of component ratio, optimization of additive component and content, presses the wear-resistant material powder into a blank, and realizes blank forming and increases the bonding strength of the blank and the parts by controlling parameters such as sintering temperature, sintering time and sintering pressure, so as to manufacture a steel-based typical structural part with local high wear resistance, which greatly improves the strength, wear resistance and service life of mechanical parts. The dissimilar material connection process is suitable for engineering forming design and preparation production of local reinforced wear-resistant structural parts such as mine machinery, oil and gas pipeline, offshore platform and bridge structure.

Description

Technical Field

[0001] This invention relates to the processing technology of wear-resistant parts made of high-wear-resistant, high-strength, and high-toughness low-alloy steel, belonging to the field of dissimilar material joining technology, specifically a process for achieving diffusion joining of dissimilar materials through powder metallurgy. Background Technology

[0002] In fields such as construction machinery and mining machinery, the hardness and load-bearing capacity of parts used to withstand impact loads directly affect their service life. Taking rotary drilling rigs used for hole drilling in foundation engineering as an example, the arc plate and reinforcing ring of the rotary drilling rig rod are located on each section of the machine lock rod and bear the pressure and torque of the drilling rig. Therefore, as key load-bearing components, the arc plate and the drill rod reinforcing ring need to have high tensile strength, wear resistance, and impact resistance. Currently, high-quality arc plates and reinforcing rings typically employ diffusion bonding technology. Under specific temperature, time, and pressure conditions, the welding surfaces of two or more parts to be joined are brought into close contact, allowing atomic diffusion to occur on the surfaces of the two parts, forming a transition layer. This results in a strong bond at the contact interface, increasing the local wear resistance of the parts. This approach meets service requirements while saving costs. However, traditional diffusion bonding often only connects one surface, i.e., the connection between plates, resulting in a small contact area and weak shear and impact resistance. In extremely harsh rock formations, drill rods are subjected to both pressure and impact during operation. Parts chipping, cracking, curling, and poor wear resistance become major failure points for drill rod accidents. Therefore, improving the local wear resistance and impact resistance of parts and achieving a tight bond between components has become a pressing technical challenge for domestic rotary drilling rig suppliers. Summary of the Invention

[0003] To address the above problems, this invention provides a process for diffusion bonding of dissimilar materials using powder metallurgy, which is simple and efficient for manufacturing locally reinforced, wear-resistant, high-strength, and high-impact mechanical structural components.

[0004] The objective of this invention is achieved through the following technical solution: A process for diffusion bonding of dissimilar materials using powder metallurgy involves preparing high-performance wear-resistant material molded blanks with specific shapes using a ball milling-cold pressing method, and then fabricating locally reinforced steel structural components using powder metallurgy forming technology. The process includes the following steps: I. Preparation of the molding blank: ①. The composition of high-performance wear-resistant materials, the alloy powder, by mass percentage includes: C: 0.15-0.45%, Cr: 0.5-2.5%, Si: 0.3-1.0%, Mn: 0.5-1.5%, Mo: 0-1.0%, Ni: 0.5-2.5%, balance Fe, with a small amount of unavoidable trace impurities; ②. Powder preparation: Weigh the alloy powder according to the specified ratio under vacuum conditions, and add 0.6 to 1.5% of the total weight of dispersant and lubricant; ③. Ball milling: The prepared powder is ball-milled and mixed to mechanically alloy it; ④. Pressing: The ball-milled powder is pressed into a specific shape of wear-resistant material blank in a cold press mold under a pressure of 600-900MPa for 60-300s. II. Machining of steel components: The mounting groove that matches the molded blank is machined into the wear-resistant part of the steel base, and the connecting surface of the steel base and the molded blank is mechanically ground. III. Assembly: The molded blank and the steel base are assembled through the mounting groove to form a steel base structure. The steel base structure is fixed on the diffusion bonding furnace using a graphite mold. The furnace door is closed and a vacuum is drawn. A pressure of 1 to 5 MPa is applied to the graphite punch to press the molded blank and the steel base together. IV. Sintering and Shaping: When the vacuum level reaches -0.1 MPa, first heat to 250-300℃ at a rate of 6℃ / min and hold at this temperature for 60 min; continue heating to 750-900℃ at a rate of 6℃ / min and hold at this temperature for 60 min; then heat to 1100-1300℃ at a rate of 4℃ / min; after reaching the temperature, operate the diffusion bonding furnace to apply a pressure of 30-60 MPa to the graphite punch, hold at the temperature and pressure for 60-90 min, and after sintering, unload the pressure to allow the steel-based structural component to cool to room temperature in the diffusion bonding furnace.

[0005] Furthermore, the particle size of the alloy powder in step 1① is ≤74μm.

[0006] Furthermore, the dispersant and lubricant in step one ② are zinc stearate and / or vinyl bis-stearamide.

[0007] Furthermore, in step 1③, anhydrous ethanol of one-third of the total weight of the alloy powder is added to fully disperse and mix the alloy powder evenly. After ball milling, the powder is dried in a vacuum drying oven and then ground into powder using a mortar and pestle under vacuum.

[0008] Furthermore, in step 1③, a planetary ball mill is used for mechanical mixing, with zirconia grinding beads of sizes of 10mm, 6mm and 2mm, a rotation speed of 100-150r / min, a grinding time of 6-48h, and a 5min pause after every 30min of grinding.

[0009] Furthermore, the alloy powder in step 1① also includes ceramic powder additives, which account for 0.25 to 6% of the total weight.

[0010] Furthermore, in step two, the surface roughness at the connection between the steel base and the molded blank is less than Ra6.3.

[0011] The beneficial effects of this invention are: This invention utilizes powder metallurgy technology to achieve integrated forming of high-performance powder sintering and diffusion bonding of typical components, producing typical structural parts with locally enhanced wear resistance. It is applicable to the engineering forming design and manufacturing of locally enhanced wear-resistant structural parts for mining machinery, oil and gas pipelines, offshore platforms, bridge structures, and other applications. This invention controls the mechanical properties, dimensional accuracy, surface morphology, and structural integrity of the formed blank through the selection of alloying elements, adjustment of component ratios, and optimization of additive composition and content. Furthermore, by controlling parameters such as sintering temperature, sintering time, and sintering pressure, it achieves blank forming and increases the bonding strength between the blank and the component, producing typical steel-based structural parts with locally high wear resistance, significantly improving the strength, wear resistance, and performance of mechanical components. Compared with existing technologies, this invention, on the one hand, ensures the basic shape of the wear-resistant area through high-performance wear-resistant powder pressing, thereby improving the local wear resistance of components; on the other hand, the integrated forming process of wear-resistant blank sintering and high-temperature diffusion bonding of parts achieves both precise forming of the wear-resistant material and ensures a tight bond between the wear-resistant material and the component, increasing the bonding area and enhancing the performance of typical components.

[0012] Furthermore, the integrated molding process of sintering the molded blank and bonding the parts at high temperature reduces the number of preparation steps, shortens the production time, and improves the utilization rate of materials and the performance and service life of structural components.

[0013] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0014] Figure 1 A flowchart illustrating the process of diffusion bonding of dissimilar materials in powder metallurgy.

[0015] Figure 2 Schematic diagram of a mold for diffusion bonding of dissimilar materials in powder metallurgy process; Detailed Implementation

[0016] In the diagram: 1-Graphite punch, 2-Graphite jacket, 3-Molded blank, 4-Steel base component. Example 1

[0017] This invention discloses a process for diffusion bonding of dissimilar materials using powder metallurgy. By selecting alloying elements, adjusting the composition ratio, and optimizing the composition and content of additives, the mechanical properties, dimensional accuracy, surface morphology, and structural integrity of the formed blank are controlled. Wear-resistant material powder is pressed into a blank, and then the blank is formed and the bonding strength between the blank and the component is increased by controlling parameters such as sintering temperature, sintering time, and sintering pressure. This process produces typical steel-based structural components with locally high wear resistance.

[0018] This embodiment uses the preparation of the reinforcing ring of a rotary drilling rig as an example to illustrate the technical solution of the present invention in detail: Rotary drilling rigs are construction machines used for drilling holes in foundation engineering, especially in rock formations where the working conditions are extremely harsh. Components such as the drill rod reinforcing ring and arc plate, located on each section of the drill rod, bear the pressure and torque exerted by the drilling rig during drilling operations. These are critical load-bearing parts of the rotary drilling rig, and their hardness and load-bearing capacity directly affect their service life. Therefore, the drill rod reinforcing ring, arc plate, and other related components must possess high tensile strength, wear resistance, and impact resistance.

[0019] A rotary drilling rig's drill rod reinforcing ring was fabricated using an integrated forming process combining high-performance wear-resistant billet sintering and high-temperature diffusion bonding of parts; for example... Figure 1 The process flow diagram shown first uses a cold pressing method to press high-performance wear-resistant powder into a blank to ensure the specific shape of the local area that needs to be enhanced to enhance wear resistance. Then, through powder metallurgy and diffusion bonding integrated forming process, the blank is sintered into a wear-resistant material and connected with the steel part to obtain a typical steel-based structural component with localized reinforced wear-resistant material with high dimensional accuracy and good wear resistance.

[0020] The specific implementation is as follows: I. Production of high-performance wear-resistant molded blanks: ①. High-performance wear-resistant materials, the alloy powder includes the following components by mass percentage: C: 0.20%, Cr: 0.6%, Si: 0.6%, Mn: 1.3%, Mo: 0.2%, Ni: 1.0%, with the balance being Fe and containing a small amount of unavoidable trace impurities; the original powder particle size is ≤74μm (within 200 mesh); ②. Powder preparation: Weigh each powder according to the proportion under vacuum conditions, and add 0.6 wt.% of zinc stearate as a dispersant and lubricant. ③. Ball milling: Add one-third of the total weight of anhydrous ethanol to the powder prepared in step ② to fully disperse and mix the powder evenly. Then, perform mechanical mixing on a planetary ball mill using zirconia grinding beads with sizes of 10 mm, 6 mm, and 2 mm. The speed is 150 r / min, and the ball milling time is 48 h, with a 5 min break after every 30 min of ball milling. After ball milling, separate the mixed powder from the grinding beads, dry it in a vacuum drying oven with anhydrous ethanol, and grind the lumps produced during the drying process in a mortar and pestle under vacuum to obtain alloyed powder. ④. Pressing: The alloyed powder mixed in step ③ is pressed into shape on a press. Before pressing, the inner wall of the cold pressing mold is lubricated with polytetrafluoroethylene. The pressing pressure is 600MPa, and the pressure is held for 300s to press into a wear-resistant material molded blank of a specific shape.

[0021] II. Machining of steel components: The steel base is processed, and according to the usage requirements of the part and the shape of the molding blank, the mounting groove that matches the molding blank is machined at the connection between the steel base and the molding blank (i.e. the wear-resistant part of the part), such as cylindrical, cuboid, T-shaped and dovetail-shaped, etc.; then the surface of the connection between the steel base and the molding blank is precision polished to make the surface roughness less than Ra 6.3.

[0022] III. Assembly: Based on the dimensions and usage requirements of the drill pipe reinforcing ring, an integrated graphite mold for powder sintering and diffusion bonding was designed and manufactured. The molded blank was embedded in the mounting groove of a steel substrate to form a steel-based structural component, which was then placed into the graphite mold. Figure 2 As shown, boron nitride is sprayed onto the mold surface as a release agent; the steel-based structural component is fixed on the diffusion bonding furnace using a graphite mold, the furnace door is closed and a vacuum is drawn to a vacuum degree of -0.1 MPa, and a pressure of 3 MPa is applied to the graphite punch to make the molded blank and the steel base tightly bonded.

[0023] IV. Sintering and Shaping: When the vacuum level inside the furnace reaches -0.1 MPa, the temperature is raised. First, it is heated to 300°C at a rate of 6°C / min and held at this temperature for 60 min for pre-additive removal. Then, it is heated to 800°C at a rate of 6°C / min and held at this temperature for 60 min for final additive removal. Then, it is heated to 1100-1300°C at a rate of 4°C / min. After reaching the temperature, the diffusion bonding furnace is operated to slowly apply a pressure of 45 MPa to the graphite punch and hold it at this temperature for 60-90 min. After sintering, the pressure is released, and the parts are allowed to cool slowly to room temperature in the diffusion bonding furnace.

[0024] This invention utilizes an integrated forming process of high-performance wear-resistant billet sintering and high-temperature diffusion bonding of parts. This process induces atomic diffusion on the surfaces of two or more connecting components, forming a transition layer and creating a strong bond at the contact interface. This achieves the connection between dissimilar materials with significantly different properties. The principle involves preparing locally reinforced structural billets with enhanced wear resistance through mechanical alloying, and then using powder metallurgy to achieve integrated forming of high-performance powder sintering and diffusion bonding of typical components, thus producing steel-based structural components with locally enhanced wear resistance. During the high-performance wear-resistant material powder pressing process, the mechanical properties, dimensional accuracy, surface morphology, and structural integrity of the formed billet are controlled primarily through the selection of alloying elements, the adjustment of component ratios, and the optimization of additive composition and content. In the high-performance wear-resistant billet forming and part diffusion bonding process, parameters such as sintering temperature, sintering time, and sintering pressure are used to achieve billet forming and increase the bonding strength between the billet and components, thereby improving the strength, wear resistance, and performance of components in mining machinery, bridge structures, and other applications.

[0025] This invention's integrated forming process, on the one hand, ensures the basic shape of the wear-resistant area through powder pressing, thereby improving the local wear resistance of parts; on the other hand, the integrated forming process of sintering the wear-resistant blank and high-temperature diffusion bonding of the parts achieves a tight bond between the wear-resistant material and the steel-based component, increasing the bonding area between the two, optimizing the performance of typical parts, and solving the current problem of enhancing the local wear resistance of typical parts in fields such as bridges, high-rise buildings, oil and gas pipelines, mining machinery, ships, and offshore platforms. At the same time, it significantly saves materials, reduces manufacturing processes, shortens manufacturing time, and improves production efficiency. Example 2

[0026] This embodiment takes the fabrication of the arc plate of a rotary drilling rod as an example. The part is required to be weldable, and the non-welded parts have excellent wear resistance. According to the performance requirements of the part, ceramic particles such as TiB2, SiC, Al2O3, and ZrO2 can be added to the alloy powder as additives to further improve the local wear resistance of the structural parts.

[0027] I. Preparation of the molding blank: ①. The composition of high-performance wear-resistant materials, the alloy powder, by mass percentage includes: C: 0.35%, Cr: 1.0%, Si: 0.7%, Mn: 1.0%, Mo: 0.5%, Ni: 1.3%, TiB2: 0.3%, balance Fe, with a small amount of unavoidable trace impurities; alloy powder particle size ≤74μm; ②. Powder preparation: Weigh the powders according to the proportions under vacuum conditions, and add 0.6 to 1.5 wt.% of zinc stearate or vinyl bis-stearamide as a dispersant and lubricant. ③. Ball milling: The powder prepared in step ② is mechanically mixed in a planetary ball mill using zirconia grinding beads with sizes of 10 mm, 6 mm and 2 mm, at a speed of 100 r / min for 20 h, with a 5 min break every 30 min of ball milling; during the ball milling process, anhydrous ethanol of one-third of the total weight of the alloy powder is added to ensure that the powder is fully dispersed and mixed evenly. After the ball milling is completed, the mixed powder is separated from the grinding beads, dried in a vacuum drying oven with anhydrous ethanol, and the lumps produced during the drying process are ground into powder in a mortar and pestle under vacuum to obtain alloyed powder; ④. Pressing: The powder mixed by ball milling is pressed into a specific shape of wear-resistant material blank in a cold pressing mold at a pressure of 700MPa for 270s.

[0028] II. Machining of steel base components: Low carbon steel is used to machine the steel base components. Installation grooves that match the molded blank are machined in the wear-resistant parts of the steel base components. The connecting surfaces of the steel base components and the molded blank are mechanically ground to make the surface roughness of the connecting surfaces less than Ra 6.3.

[0029] 3. Assembly: The molded blank and the steel base are assembled to form a steel base structure. The steel base structure is fixed on the diffusion bonding furnace using a graphite mold. The furnace door is closed and a vacuum is drawn. A pressure of 2.2 MPa is applied to the graphite punch to press the molded blank and the steel base together.

[0030] IV. Sintering and Forming: When the vacuum level reaches -0.1 MPa, first heat to 280℃ at a rate of 6℃ / min and hold at this temperature for 60 min; continue heating to 850℃ at a rate of 6℃ / min and hold at this temperature for 60 min; then heat to 1100℃ at a rate of 4℃ / min; after reaching the temperature, operate the diffusion bonding furnace to apply a pressure of 35 MPa to the graphite punch, hold at this temperature and pressure for 70 min, and after sintering, unload the pressure, allowing the steel-based structural component to slowly cool to room temperature in the diffusion bonding furnace. The resulting arc plate steel-based low-carbon steel matrix has excellent weldability. After heat treatment, the molded blank can reach a hardness of HV730, a tensile strength of 1750 MPa, and an elongation of 16.5%, which enhances its wear resistance while maintaining weldability. Example 3

[0031] This embodiment takes the preparation of the key sleeve body and key strip of rotary drilling as an example. The key sleeve body and key strip are torsion transmission parts, which are required to have excellent comprehensive performance and high wear resistance and high impact resistance.

[0032] I. Preparation of the molding blank: ①. The composition of high-performance wear-resistant materials, the alloy powder, by mass percentage includes: C: 0.4%, Cr: 1.8%, Si: 0.8%, Mn: 1.5%, Mo: 0.8%, Ni: 2.0%, TiB2: 0.45%, balance Fe, with a small amount of unavoidable trace impurities; original powder particle size ≤74μm; ②. Powder preparation: Weigh the powders according to the proportions under vacuum conditions, and add 0.6 to 1.5 wt.% of zinc stearate or vinyl bis-stearamide as a dispersant and lubricant. ③. Ball milling: The powder prepared in step ② is mechanically mixed in a planetary ball mill using zirconia grinding beads with sizes of 10 mm, 6 mm and 2 mm, at a speed of 130 r / min for 30 h, with a 5 min break after every 30 min of ball milling; during the ball milling process, anhydrous ethanol of one-third of the total weight of the alloy powder is added to ensure that the powder is fully dispersed and mixed evenly. After the ball milling is completed, the mixed powder is separated from the grinding beads, dried in a vacuum drying oven with anhydrous ethanol, and the lumps produced during the drying process are ground into powder in a mortar and pestle under vacuum to obtain alloyed powder; ④. Pressing: The powder mixed by ball milling is pressed into a specific shape of wear-resistant material blank in a cold pressing mold at a pressure of 850MPa for 180s.

[0033] II. Machining of steel base components: 35CrMo or 42CrMo alloy steel is used as the steel base component material. The mounting groove that matches the molded blank is machined on the steel base component. The connecting surfaces of the steel base component and the molded blank are mechanically ground to make the surface roughness of the connecting surfaces less than Ra 6.3.

[0034] 3. Assembly: The molded blank and the steel base are assembled through the mounting slot to form a steel base structure. The steel base structure is fixed on the diffusion bonding furnace using a graphite mold. The furnace door is closed and a vacuum is drawn. A pressure of 5MPa is applied to the graphite punch to press the molded blank and the steel base together.

[0035] IV. Sintering and Forming: When the vacuum degree inside the furnace reaches -0.1 MPa, first heat to 250℃ at a rate of 6℃ / min and hold at this temperature for 60 min; continue heating to 900℃ at a rate of 6℃ / min and hold at this temperature for 60 min; then heat to 1200℃ at a rate of 4℃ / min; after reaching the temperature, operate the diffusion bonding furnace to apply a pressure of 55 MPa to the graphite punch and hold at this temperature and pressure for 85 min; after sintering, unload the pressure and allow the steel-based structural parts to slowly cool to room temperature in the diffusion bonding furnace. The resulting steel-based structural parts have excellent comprehensive mechanical properties in their base part, which is characteristic of 35CrMo or 42CrMo alloy steel, and can withstand the extrusion load when transmitting torque; after heat treatment, the hardness of the pressed blank can reach HV700, the tensile strength is 1600 MPa, and the elongation is 16.5%, maintaining high wear resistance and impact resistance during key operation.

[0036] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit them. Modifications to the implementation methods or equivalent substitutions of some technical features by those skilled in the art, without departing from the essence of the technical solutions of the present invention, should all be covered within the scope of protection claimed by the present invention.

Claims

1. A process for diffusion bonding of dissimilar materials using powder metallurgy, characterized in that: High-performance wear-resistant material blanks with specific shapes are prepared by ball milling-cold pressing. Through powder metallurgy forming technology, the sintering of high-performance wear-resistant materials and diffusion bonding with the matrix alloy are realized to prepare typical structural parts with enhanced local wear resistance. Includes the following steps: I. Preparation of the molding blank: ①. The composition of high-performance wear-resistant materials, the alloy powder, by mass percentage includes: C: 0.15-0.45%, Cr: 0.5-2.5%, Si: 0.3-1.0%, Mn: 0.5-1.5%, Mo: 0-1.0%, Ni: 0.5-2.5%, balance Fe, with a small amount of unavoidable trace impurities; ②. Powder preparation: Weigh the alloy powder according to the specified ratio under vacuum conditions, and add 0.6-1.5% of the total weight of dispersant and lubricant; ③. Ball milling: The prepared powder is ball-milled and mixed to mechanically alloy it; ④. Pressing: The ball-milled powder is pressed in a cold press mold at a pressure of 600-900MPa for 60-300s to form a wear-resistant material blank of a specific shape; II. Machining of steel components: A mounting groove that matches the molded blank is machined into the wear-resistant part of the steel base. The mounting groove is cylindrical, cuboid, T-shaped or dovetail-shaped. The connecting surfaces of the steel base and the molded blank are mechanically ground. III. Assembly: The molded blank and the steel base are assembled through the mounting groove to form a steel base structure. The steel base structure is fixed on the diffusion bonding furnace using a graphite mold. The furnace door is closed and a vacuum is drawn. A pressure of 1 to 5 MPa is applied to the graphite punch to press the molded blank and the steel base together. IV. Sintering and Shaping: When the vacuum level reaches -0.1 MPa, first heat to 250-300℃ at a rate of 6℃ / min and hold at this temperature for 60 min for pre-additive removal; continue heating to 750-900℃ at a rate of 6℃ / min and hold at this temperature for 60 min for final additive removal; then heat to 1100-1300℃ at a rate of 4℃ / min; after reaching the temperature, operate the diffusion bonding furnace to apply a pressure of 30-60 MPa to the graphite punch, hold at the temperature and pressure for 60-90 min, and after sintering, unload the pressure to allow the steel-based structural component to cool to room temperature in the diffusion bonding furnace.

2. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: The alloy powder particle size in step 1① is ≤74μm.

3. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: The dispersant and lubricant in step 1② are zinc stearate and / or vinyl bis-stearamide.

4. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: In step 1③, anhydrous ethanol of one-third of the total weight of the alloy powder is added to fully disperse and mix the alloy powder evenly. After ball milling, the powder is dried in a vacuum drying oven and then ground into powder using a mortar and pestle under vacuum.

5. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: Step 1③ involves mechanical mixing using a planetary ball mill with zirconia grinding beads of 10mm, 6mm, and 2mm in size. The milling speed is 100–150 r / min, and the milling time is 6–48 h, with a 5-min pause after every 30 min of milling.

6. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: The alloy powder in step 1① also includes ceramic powder additives, which account for 0.25 to 6% of the total weight.

7. The process for achieving diffusion bonding of dissimilar materials through powder metallurgy according to claim 1, characterized in that: In step two, the surface roughness at the connection between the steel base and the molded blank is less than Ra6.3.

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