Molybdenum-based composite material with low residual stress and high toughness and preparation method thereof

Abstract

The invention discloses a molybdenum-based composite material with low residual stress and high strength and toughness and a preparation method thereof, an integrated process system of molybdenum-based composite material component design, powder metallurgy, forging deformation and ultrasonic treatment is formed, and in the molybdenum-based composite component design step, the molybdenum-based composite material comprises, by weight, 1.0%-3.0% of ZrO2, 0.5%-1.5% of C powder and the balance Mo. The residual stress of the molybdenum-based composite material is effectively reduced, the common problem of preparation of the high-strength and high-toughness molybdenum-based composite material for high-end equipment is solved, and the application range of the high-strength and high-toughness molybdenum-based composite material is expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of powder metallurgy, and specifically relates to a low residual stress and high-toughness molybdenum-based composite material and a preparation method thereof. Background Art

[0002] Molybdenum is a type of high-temperature material with important strategic significance. It is widely used in aviation, aerospace, nuclear energy and other fields due to its excellent room temperature and high temperature strength, high elastic modulus and good thermal conductivity. However, its disadvantages such as low-temperature brittleness and high plastic-brittle transition temperature limit its further development and application. In some special fields such as rocket nozzles and nozzle throat liners, people have higher requirements on the performance of molybdenum materials, requiring the materials to have high strength, toughness and ablation resistance. In order to improve and overcome its inherent defects, molybdenum-based composites are usually prepared by doping ceramic phases into pure molybdenum or its alloys. These composite materials not only "inherit" the excellent properties of the matrix itself, but also have some characteristics of the reinforcement.

[0003] At the same time, residual internal stress will be generated during the forging deformation of molybdenum-based composite materials, affecting the strength, processing accuracy, and corrosion resistance of the material. Although traditional heat treatment processes such as annealing can eliminate residual stress and improve mechanical properties and machinability, they require long-term heat preservation at high temperatures, which is costly, inefficient, and energy-intensive. The ultrasonic impact method has the advantages of high efficiency and energy saving. Its principle is to transmit ultrasonic frequency mechanical vibrations to the inside of the molybdenum-based composite rod, prompting particles to move and collide with dislocations, so that dislocations overcome resistance, dislocations open, and achieve stress relaxation, eliminating residual stress at the microscopic level. Summary of the invention

[0004] In view of the shortcomings and defects of the prior art, the present invention provides a method for preparing a low residual stress and high-strength and toughness molybdenum-based composite material. The method has a simple process and good feasibility. The prepared molybdenum-based composite material has excellent properties such as high-temperature strength, high toughness, and ablation resistance.

[0005] The specific technical solutions are as follows:

[0006] A method for preparing a low residual stress and high-toughness molybdenum-based composite material comprises the following steps:

[0007] Step 1: Design steps of the composition of molybdenum-based composite materials: select ZrO2: 1.0%-3.0%, C powder: 0.5%-1.5% according to weight percentage, and the balance is highly dispersed Mo powder, use a ball mill to mix for 27-36 hours, sieve twice with 100 mesh, and vacuum pack the prepared composite powder.

[0008] Step 2: Powder metallurgy step: cold isostatic pressing the molybdenum-based composite material powder at a pressure of 190-220 MPa for 20-40 min, placing the blank in a medium frequency induction sintering furnace for high-temperature sintering at a sintering temperature of 1930-1950° C. for 210 min-270 min;

[0009] Step 3: Forging deformation step: the molybdenum-based composite material sintered rod is subjected to forging deformation processing. In the forging deformation step, a rotary cutter is used for forging. In the first forging, the heating temperature is 1450°C-1500°C, the holding time is 120min-180min, the final forging temperature is controlled at 1300°C-1350°C, and the pass deformation is 30%-45%; in the second forging, the heating temperature is 1400°C-1450°C, the holding time is 70min-100min, the final forging temperature is controlled at 1250°C-1300°C, and the cumulative deformation of the pass is 60%-75%;

[0010] Step 4: Ultrasonic treatment step: The molybdenum-based composite forged rod is subjected to ultrasonic treatment. In the ultrasonic treatment step, an ultrasonic impact device is used with a frequency of 21kHz-25kHz, a current of 1A-3A, and an impact time of 1min-3min.

[0011] Compared with the prior art, the present invention has the following beneficial technical effects:

[0012] 1. The high-strength and tough molybdenum-based composite material designed and prepared by the present invention has a room temperature tensile strength of up to 831 MPa and a fracture toughness of up to 31.7 MPa·m 1 / 2 The flexural strength reaches 1883MPa, and the high temperature strength at 800℃ can reach 510MPa.

[0013] 2. In this application, the high-temperature toughness of molybdenum-based composite materials is improved by the dispersion enhancement of ZrO2 ceramic phase particles. ZrO2 powder and C powder react to form ZrC ceramic phase during high-temperature sintering, which improves the density of the molybdenum matrix, refines the grains, and induces phase transformation toughening during the sintering process. Part of the ZrO2 powder forms dispersed particles in the molybdenum matrix, thereby improving the high-temperature toughness, thermal shock resistance and mechanical strength of the molybdenum-based composite materials.

[0014] 3. When ultrasonically treating molybdenum-based composite materials, the present invention uses ultrasound to annihilate dislocations and eliminate residual stress, thereby improving tensile strength and elongation after fracture. The residual stress is eliminated to improve mechanical properties, reducing the residual stress by about 46%. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a microscopic morphology of the molybdenum-based composite material prepared by the present invention;

[0016] Figure 2 is the residual stress of the Mo-based composite forging blank before and after ultrasonic treatment;

[0017] Figure 3 Tensile strength of Mo-based composite rods before and after ultrasonic treatment. DETAILED DESCRIPTION

[0018] The present invention is described below in conjunction with the accompanying drawings and specific embodiments. The embodiments described are only a part of the embodiments of the present invention, rather than all the embodiments.

[0019] Example 1

[0020] A method for preparing a low residual stress and high-toughness molybdenum-based composite material comprises the following steps:

[0021] Step 1: Design steps of molybdenum-based composite material composition: select ZrO2: 1.0%, C powder: 0.5% according to weight percentage, and the balance is highly dispersed Mo powder, use a ball mill to mix for 30 hours, sieve twice with 100 mesh, and vacuum pack the prepared composite powder.

[0022] Step 2: Powder metallurgy step: cold isostatic pressing the molybdenum-based composite material powder at a pressure of 200 MPa for 30 minutes, and placing the blank in a medium frequency induction sintering furnace for high-temperature sintering at a sintering temperature of 1930° C. for 240 minutes;

[0023] Step 3: Forging deformation step: the molybdenum-based composite material sintered rod is subjected to forging deformation processing. In the forging deformation step, a rotary cutter is used for forging. In the first forging, the heating temperature is 1450°C, the holding time is 120minmin, the final forging temperature is controlled at 1320°C, and the pass deformation is 35%; in the second forging, the heating temperature is 1420°C, the holding time is 80min, the final forging temperature is controlled at 1290°C, and the cumulative deformation of the pass is 65%;

[0024] Step 4: Ultrasonic treatment step: The molybdenum-based composite material forging rod is subjected to ultrasonic treatment. In the ultrasonic treatment step, an ultrasonic impact device is used with a frequency of 21 kHz, a current of 1 A, and an impact time of 1 min.

[0025] The low residual stress and high strength molybdenum-based composite material has a residual stress reduced by 40%, a room temperature tensile strength of 789 MPa, and a fracture toughness of 29.6 MPa·m 1 / 2 , flexural strength is 1791MPa, and high temperature tensile strength at 800℃ is 450MPa.

[0026] Example 2

[0027] A method for preparing a low residual stress and high-toughness molybdenum-based composite material comprises the following steps:

[0028] Step 1: Design steps of the composition of molybdenum-based composite materials: select ZrO2: 3.0%, C powder: 1.5% according to weight percentage, and the balance is highly dispersed Mo powder, use a ball mill to mix for 36 hours, sieve twice with 100 mesh, and vacuum pack the prepared composite powder.

[0029] Step 2: Powder metallurgy step: cold isostatic pressing the molybdenum-based composite material powder at a pressure of 220 MPa for 40 minutes, and placing the blank in a medium frequency induction sintering furnace for high-temperature sintering at a sintering temperature of 1950° C. for 270 minutes;

[0030] Step 3: Forging deformation step: the molybdenum-based composite material sintered rod is subjected to forging deformation processing. In the forging deformation step, a rotary cutter is used for forging. In the first forging, the heating temperature is 1500°C, the holding time is 180minmin, the final forging temperature is controlled at 1350°C, and the deformation amount of each pass is 40%; in the second forging, the heating temperature is 1450°C, the holding time is 100min, the final forging temperature is controlled at 1300°C, and the cumulative deformation amount of each pass is 70%;

[0031] Step 4: Ultrasonic treatment step: The molybdenum-based composite material forging rod is subjected to ultrasonic treatment. In the ultrasonic treatment step, an ultrasonic impact device is used with a frequency of 25 kHz, a current of 2 A, and an impact time of 3 minutes.

[0032] The low residual stress and high strength molybdenum-based composite material has a residual stress reduction of 54%, a room temperature tensile strength of 831 MPa, and a fracture toughness of 31.7 MPa·m 1 / 2 , flexural strength is 1883MPa, and high temperature tensile strength at 800℃ is 510MPa.

Claims

1. A method for preparing a low residual stress and high toughness molybdenum-based composite material, characterized in that: The steps include: Step 1: Selection of Mo-based composite materials: Select ZrO2 and C powder according to weight percentage, and the balance is highly dispersed Mo powder, use a ball mill to mix for 27-36 hours, sieve twice with 100 mesh, and vacuum pack the prepared molybdenum-based composite material powder; Step 2: Powder Metallurgy: The molybdenum-based composite material powder is cold isostatically pressed into a blank at a pressure of 190-220 MPa and maintained at a pressure of 20-40 min. The blank is placed in a medium frequency induction sintering furnace for high-temperature sintering at a sintering temperature of 1930-1950°C and a holding time of 210 min-270 min. Step 3: Forging deformation: The molybdenum-based composite material sintered rod is subjected to forging deformation processing, and a rotary breaking machine is used for forging. In the first forging, the heating temperature is 1450℃-1500℃, the holding time is 120min-180min, the final forging temperature is controlled at 1300℃-1350℃, and the deformation amount of each pass is 30%-45%; in the second forging, the heating temperature is 1400℃-1450℃, the holding time is 70min-100min, the final forging temperature is controlled at 1250℃-1300℃, and the cumulative deformation amount of each pass is 60%-75%; Step 4: Sonication: The molybdenum-based composite forged rods were ultrasonically treated to eliminate residual stress.

2. The method for preparing the low residual stress and high toughness molybdenum-based composite material according to claim 1, characterized in that: The weight percentages are selected as ZrO2: 1.0%-3.0%, C powder: 0.5%-1.5%, and the balance is highly dispersed Mo powder.

3. The method for preparing the low residual stress and high toughness molybdenum-based composite material according to claim 1, characterized in that: An ultrasonic impact device is used with a frequency of 21kHz-25kHz, a current of 1A-3A, and an impact time of 1min-3min.

4. The method for preparing a low residual stress and high toughness molybdenum-based composite material according to any one of claims 1 to 3, characterized in that: The residual stress of the low residual stress and high strength and toughness molybdenum-based composite material can be reduced by 46% on average, the room temperature tensile strength can reach up to 831MPa, and the fracture toughness can reach 31.7MPa·m 1 / 2 The flexural strength reaches 1883MPa, and the high temperature strength at 800℃ can reach 510MPa.

Images