Casting-infiltration preparation method of TiB2 and ultrahigh-toughness steel composite material

Abstract

The invention relates to the technical field of metal matrix composite material preparation, and discloses a TiB2 and ultrahigh strength and toughness steel composite material casting infiltration preparation method which comprises the following steps: S1, TiB2 metal ceramic particles are pretreated, then TiB2 powder and a pore forming agent are mixed according to the volume ratio of 6.5: 3.5-7.5: 2.5, and sintering is performed after cold press molding to obtain a preform with the porosity of 42-48%; s2, the TiB2 metal ceramic particles are subjected to surface sensitization and activation, and then Cr / Mo gradient layers are deposited on the surfaces of the TiB2 metal ceramic particles through a chemical plating method; s3, the ultrahigh strength and toughness steel is put into a medium-frequency induction furnace to be smelted, and after smelting, Ce (0.3 wt%-0.8 wt%) and B (0.1 wt%-0.3 wt%) are added; and after the temperature of the solution is increased to 1500-1700 DEG C, degassing is carried out by rotatably blowing argon to control the oxygen potential content. According to the casting-infiltration preparation method of the TiB2 and ultrahigh strength and toughness steel composite material, a three-dimensional porous structure with macroscopic pores and microcosmic pores is constructed, the casting-infiltration resistance of molten steel is remarkably reduced, meanwhile, the interface wettability is optimized through a Cr / Mo gradient coating, the Fe-B diffusion reaction is inhibited, and uniform fusion of a TiB2 reinforced phase and a steel matrix is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of the preparation of metal matrix composites, and specifically to a method for preparing TiB2 and ultra-high strength and toughness steel composites by casting infiltration. Background Art

[0002] Iron and steel enterprises, as the foundation of national construction, are crucial to the country's economic development; the CO2 emissions from traditional iron and steel enterprises exceed the standard, and the single steel materials prepared often have defects such as resource waste, poor wear resistance, and insufficient toughness. Therefore, the research and development of high-strength, high-toughness, and high-wear-resistant materials is crucial for the development of the steel industry.

[0003] Cermets have excellent properties such as high strength, high toughness, and high temperature resistance, and are ideal reinforcing phases for enhancing ultra-high strength and toughness steel matrix composites. Combining the high strength and high wear resistance of cermets with the high plasticity and high toughness of ultra-high strength and toughness steel is one of the means to prepare ultra-high strength and toughness composites with high wear resistance, high strength, and high toughness; common ceramic particles include carbide ceramics and oxide ceramics. For example, a NiCo modified oxide ceramic particle reinforced iron-based composite material and its casting method and application with the invention patent application number CN202411051284.7 use NiCo modified oxide ceramic particles to reinforce the iron-based composite material. Although NiCo modification can improve the interfacial bonding strength between ZTA ceramic particles and the iron matrix and the wear resistance of the composite material, due to the limited corrosion resistance of the NiCo alloy itself in a strong corrosion environment, its application in special harsh environments is limited; CN202411815038.4 uses WC-Co to reinforce the Fe-based composite material. Although the hardness of WC-Co ceramic particles ≥ 66HRC can significantly improve the wear resistance of the composite material, in some special environments, such as extreme conditions of high temperature and strong corrosion, the performance stability of WC-Co ceramic particles needs further research.

[0004] TiB2 has many excellent properties such as high temperature resistance, ultra-high hardness, excellent thermal conductivity, and oxidation resistance, and is an ideal ceramic phase for enhancing ultra-high strength and toughness steel; compounding ultra-high strength and toughness steel with TiB2 can significantly improve the performance of the steel and also save raw material costs. Therefore, a method for preparing TiB2 and ultra-high strength and toughness steel composites by casting infiltration is proposed. Summary of the Invention

[0005] (I) Technical Problems to be Solved

[0006] In view of the deficiencies of the prior art, the present invention provides a method for preparing TiB2 and ultra-high strength and toughness steel composites by casting infiltration, which has the advantages of optimizing and improving the performance of ultra-high strength and toughness steel matrix titanium diboride composites, and solves the problems of weak interfacial bonding, uneven distribution, and insufficient wear resistance of traditional composites.

[0007] (2) Technical solution

[0008] To achieve the above object of optimizing and improving the performance of the ultra-high strength and toughness steel-based titanium diboride composite material, the present invention provides the following technical solution: A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration, comprising the following steps:

[0009] S1: Pretreat the TiB2 cermet particles, and then mix the TiB2 powder (D50 = 13 - 17 μm) and the pore-forming agent (NH4HCO3) in a volume ratio of 6.5:3.5 - 7.5:2.5, and sinter (1320 - 1380 °C / 2 h) after cold pressing to obtain a preform with a porosity of 42 - 48%;

[0010] S2: Sensitize and activate the surface of the TiB2 cermet particles, and then deposit a Cr / Mo gradient layer on the surface of the TiB2 cermet particles by electroless plating;

[0011] S3: Put the ultra-high strength and toughness steel into an intermediate frequency induction furnace for melting, and add Ce (0.3 - 0.8 wt%) and B (0.1 - 0.3 wt%) after melting; after the melt temperature rises to 1500 - 1700 °C, use rotating spray argon to remove gas and control the oxygen potential content;

[0012] S4: Place the TiB2 preform as the core material in a mold for heating, pour in the high-temperature steel liquid, stir to make it fully fused, apply an axial static magnetic field of 0.3 - 0.8 T, synchronously use a laser for local heating, and then perform pressure holding and solidification;

[0013] S5: Heat-treat the cast-infiltration sample, austenitize at 950 - 1150 °C for 1 h, then oil quench, then temper at 200 - 300 °C for 2 h, then perform forging processing, and finally perform performance testing.

[0014] Preferably, the preform uses a cemented carbide mold, the inner wall is sprayed with a molybdenum disulfide release agent (thickness 0.08 - 0.12 mm), the pressing parameters are a uniaxial pressure of 190 - 210 MPa, the pressure holding time is 4 - 6 min, it has a three-dimensional pore structure, the macroscopic channel diameter is 550 - 650 μm, and the microscopic pores are 20 - 40 μm.

[0015] Preferably, the pretreatment of the TiB2 cermet particles includes:

[0016] Step 1: Immerse the TiB2 cermet particles in acetone and ultrasonically treat for 13 - 17 min to remove surface oil-based particle contaminants;

[0017] Step 2: Then soak in a 10% NaOH solution at 55 - 65°C for 8 - 12 min to neutralize the residual acidic substances, and rinse with deionized water until neutral.

[0018] Step 3: Subsequently, immerse additionally in a 10% HCl solution for 25 - 35 s, wash with water and then dry with nitrogen. After drying, perform sensitization and activation treatments.

[0019] Preferably, the surface sensitization and activation treatment process of the TiB2 cermet particles is as follows:

[0020] Step 1: Sensitize the TiB2 cermet particles in a SnCl2 solution for 5 - 10 min to ensure uniform adsorption of Sn 2+ uniformly adsorbed;

[0021] Step 2: Subsequently, activate in an AgNO3 solution for 3 - 5 min. Transfer the sensitized substrate quickly into the activation solution to avoid oxidation of Sn 2+ oxidation.

[0022] Preferably, in step S2, a Cr / Mo gradient layer is deposited on the surface of the TiB2 preform by a step - gradient electroless plating method. The mass ratio of Cr:Mo in the electroless plating solution is 2.5:1 - 3.5:1. The complexing agent for the Cr plating solution is sodium citrate with a concentration of 60 - 90 g / L, and the pH value is adjusted to 4.5 ± 0.2 with sulfuric acid. The deposition temperature is 85 ± 2°C, and the stirring rate is 200 rpm. The complexing agent for the Mo plating solution is disodium EDTA with a concentration of 40 - 60 g / L, and the pH value is adjusted to 9.0 ± 0.2 with NaOH. The deposition temperature is 75 ± 2°C, and the stirring rate is 150 rpm. The number of superimposed plating layers is four, and the ratio of Cr:Mo from the first layer to the fourth layer gradually changes from 3:1 → 2:1 → 1:2 → 1:3, and the plating solution is changed every 1 - 2 h.

[0023] Preferably, in step S3, a bottom - pouring casting - infiltration process is adopted. Preheat the preform to 1080 - 1120°C and then place it in the mold. The pouring temperature is 1580 ± 10°C, the pouring time is 7 - 9 s, and the filling speed is 0.23 - 0.27 m / s.

[0024] Preferably, in step S4, after pouring the TiB2 preform into the high - temperature molten steel and fully fusing, apply an axial static magnetic field of 0.3 - 0.8 T. The magnetic field direction is parallel to the pouring direction, and at the same time, use a laser local heating power density of 1.8×10 4 -2.2×10 4 W / cm2 to scan back and forth transversely along the surface of the preform at a speed of 8 - 12 mm / s, so that the surface temperature reaches 1580 - 1620°C and the internal gradient drops to 1430 - 1470°C.

[0025] Preferably, the pressure-holding solidification process after the TiB2 preform is poured into the high-temperature molten steel and fully fused in step S4 is specifically as follows:

[0026] Step 1: Set the pressure to 45 - 55 MPa for pressure-holding solidification for 110 - 130 s, and apply pressure immediately after the molten steel filling is completed;

[0027] Step 2: Adopt water cooling by passing water through the outer wall of the mold (flow rate 8 - 12 L / min).

[0028] (III) Beneficial effects

[0029] Compared with the prior art, the present invention provides a method for preparing TiB2 and ultra-high strength and toughness steel composite by casting infiltration, which has the following beneficial effects:

[0030] 1. In the method for preparing TiB2 and ultra-high strength and toughness steel composite by casting infiltration, by constructing a dual-scale three-dimensional porous structure of macro pores and micro pores, the casting infiltration resistance of the molten steel is significantly reduced. At the same time, the interfacial wettability is optimized by the Cr / Mo gradient coating, and the Fe-B diffusion reaction is inhibited, realizing the uniform fusion of the TiB2 reinforcing phase and the steel matrix, and solving the defects of weak interfacial bonding and uneven distribution in traditional composites.

[0031] 2. In the method for preparing TiB2 and ultra-high strength and toughness steel composite by casting infiltration, acetone ultrasonic cleaning, NaOH / HCl chemical treatment and SnCl2 / AgNO3 sensitization activation technology are adopted to significantly improve the surface activity and adsorption capacity of TiB2. Combined with the step-by-step gradient electroless plating method, an interfacial transition layer is formed, effectively improving the wettability and chemical stability between TiB2 and the steel matrix, and breaking through the technical bottleneck of easy failure of the traditional single-layer coating interface.

[0032] 3. In the method for preparing TiB2 and ultra-high strength and toughness steel composite by casting infiltration, Ce (0.3 - 0.8%) and B (0.1 - 0.3%) are added to the molten steel, and an ultra-low oxygen potential is achieved through the CeO2 / B2O3 composite oxide film to inhibit the formation of the Fe2B brittle phase; at the same time, a (Ti, Cr, Mo)B2 nano-transition layer is in-situ formed at the interface, significantly improving the interfacial bonding strength, which is superior to the interfacial stability of the traditional single deoxidation process.

[0033] 4. In the method for preparing TiB2 and ultra-high strength and toughness steel composite by casting infiltration, a 0.5T axial static magnetic field is used to inhibit the turbulence of the molten steel and the segregation of TiB2, and the interfacial tension and solidification path are regulated by laser local heating, realizing the precise matching of the molten steel filling rate and pressure-holding solidification, and breaking through the problems of composition segregation and pore defects caused by traditional single-field regulation.

[0034] 5. The preparation method of the TiB2 and ultra-high strength and toughness steel composite material by casting infiltration can significantly improve the tensile strength of the composite material to the ultra-high strength and toughness level, effectively guarantee the elongation rate, and has excellent impact toughness under low-temperature environments. Its wear resistance is greatly improved compared with traditional steel-based composite materials, and its stability under high-temperature and strong corrosion environments is significantly enhanced, meeting the application requirements of extreme working conditions and filling the technical gap of insufficient corrosion resistance of TiB2 / steel composite materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a schematic structural diagram of the three-dimensional porous pore preform of the present invention;

[0036] Figure 2 It is a schematic process diagram of the electroless plating method of the present invention;

[0037] Figure 3 It is a schematic diagram of the phase composition of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments and drawings of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

[0039] Please refer to Figures 1-3 , the alloy composition combination system of the ultra-high strength and toughness steel material used in the experiment of the present invention is 0.23C, 1.96Si, 1.93Mn, 0.07Ni, 1.94Cr, 0.35Mo, Nb + Ti + V + Al + Cu + B ≤ 0.24.

[0040] Step 1: Pretreatment of raw materials. Immerse the TiB2 metal ceramic particles in acetone and ultrasonically treat them for 13 - 17 minutes to remove surface oil-based particle contaminants. Then soak them in a 10% NaOH solution at 55 - 65°C for 8 - 12 minutes to neutralize the remaining acidic substances. Rinse them with deionized water until neutral, and then additionally immerse them in a 10% HCl solution for 25 - 35 seconds. After washing with water, dry them with nitrogen;

[0041] Step 2: Preparation of the three-dimensional porous preform. Mix according to a volume ratio of TiB2:NH4HCO3 = 6.5:3.5 - 7.5:2.5, add a 2wt% aqueous solution of polyvinyl alcohol (PVA) (5% concentration) as a binder, and mix in a V-type mixer for 2 hours (30 rpm). Then place it in a cemented carbide mold, spray a molybdenum disulfide release agent (thickness 0.08 - 0.12 mm) on the inner wall, and demold it at a uniaxial pressure of 190 - 210 MPa, a holding pressure time of 4 - 6 minutes, and a pressure increase rate of 10 MPa / s to obtain a green body;

[0042] Step 3: Vacuum sintering. Heat at 4 - 6 °C / min to 580 - 620 °C (to remove PVA), and hold for 0.8 - 1.2 hours; then heat at 7 - 9 °C / min to 1330 - 1370 °C, and hold for 1.8 - 2.2 hours (vacuum degree ≤ 10 -2 Pa); cool in the furnace to 200 °C and then take out; subsequently, measure the porosity by mercury intrusion method (45 ± 3%), and confirm that the three-dimensional pore distribution is a macroscopic channel of 600 ± 50 μm and a microscopic pore of 30 ± 10 μm;

[0043] Step 4: Sensitization and activation treatment of TiB2 cermet particles. Sensitize the TiB2 cermet particles in SnCl2 solution for 5 - 10 min to ensure uniform adsorption of Sn 2+ ; then activate in AgNO3 solution for 3 - 5 min, and quickly transfer the sensitized substrate into the activation solution to avoid oxidation of Sn 2+ ;

[0044] Step 5: Deposit a Cr / Mo gradient layer on the surface of the preform by a stepwise gradient electroless plating method. The mass ratio of Cr:Mo in the electroless plating solution is 2.5:1 - 3.5:1. The complexing agent for the Cr plating solution is sodium citrate with a concentration of 60 - 90 g / L, adjust the pH value to 4.5 ± 0.2 with sulfuric acid, the deposition temperature is 85 ± 2 °C, and the stirring rate is 200 rpm; the complexing agent for the Mo plating solution is disodium EDTA with a concentration of 40 - 60 g / L, adjust the pH value to 9.0 ± 0.2 with NaOH, the deposition temperature is 75 ± 2 °C, and the stirring rate is 150 rpm; configure the solution according to different ratios, and stack the plating layers in four layers successively. The ratio of Cr:Mo from the first layer to the fourth layer gradually changes from 3:1 → 2:1 → 1:2 → 1:3, and change the plating solution every 1 - 2 h;

[0045] Step 6: Batching and charging the furnace. Place the ultra-high strength and toughness steel matrix steel into a melting equipment, select a 1-ton medium-frequency induction furnace (950 - 1050 Hz, 580 - 620 kW), and protect it with argon; set the power to 380 - 420 kW, the argon flow rate to 18 - 22 L / min, and heat to 1580 - 1620 °C after melting; then add active elements, spray B4C powder (0.7 - 0.8 kg) into the molten pool with an argon carrier, and press Ce blocks (4.8 - 5.2 kg) into the bottom of the molten pool with a bell; then carry out degassing by rotary injection, set the parameters of the graphite rotor (380 - 420 rpm, argon 13 - 17 L / min, 18 - 22 minutes), and monitor the oxygen content with a Celox oxygen probe (corresponding oxygen content ≤ 15 ppm);

[0046] Step 7: Cast infiltration process; preheat in a box-type resistance furnace at 1100 °C for 30 minutes (protected by N2); then preheat the HT250 mold to 600 °C and spray a zirconia-based coating (thickness 0.5 mm); use bottom gating (gate Φ40 mm), pouring temperature 1580 °C, filling time 8 s; apply an axial static magnetic field of 0.3 - 0.8 T (EM-500 electromagnet, current 150 A), with the direction parallel to the pouring flow; simultaneously use a laser heat source to control, a fiber laser (IPGYLS-4000, wavelength 1070 nm), power density 2×10 4 W / cm 2 , scanning speed 10 mm / s, forming a temperature gradient of 1600 °C → 1450 °C; then carry out pressure holding and solidification, apply a pressure of 50 MPa using a hydraulic press (Y32-315T) and hold the pressure for 120 s; use a cooling control system, water-cool the outer wall of the mold (flow rate 10 L / min), and the solidification rate gradient is 5 mm / s (surface layer) → 1 mm / s (core);

[0047] Step 8: Post-treatment and performance optimization; heat-treat the sample, austenitize at 950 - 1150 °C for 1 hour (protected by 95% N2 + 5% H2), oil quench to room temperature (cooling rate 120 °C / s), then temper at 200 - 300 °C for 2 hours and air cool; then carry out machining; then carry out sandblasting, white corundum sand (75 - 85 mesh), air pressure 0.55 - 0.65 MPa, spray distance 90 - 110 mm, time 2.5 - 3.5 minutes; finally carry out performance testing, the mechanical property testing includes:

[0048] Tensile test (ASTM E8) shows that the tensile strength is 1600 - 1820 MPa and the elongation is 8 - 9%;

[0049] Impact test (ASTM E23) shows that the impact energy is 40 - 45 J at -40 °C;

[0050] Microstructure analysis by TEM / EDS shows that the thickness of the interfacial (Ti,Cr,Mo)B2 transition layer is 100 - 200 nm, and significantly reduces or inhibits the formation of the Fe2B phase, and the interfacial bonding strength ≥ 420 MPa.

[0051] Example 1:

[0052] To verify the effectiveness of the cast infiltration preparation method of TiB2 and ultra-high strength and toughness steel composites, experiments under basic conditions were first carried out, and the following are the specific steps.

[0053] Step 1: Preparation of preform: The TiB2 particles were successively ultrasonically cleaned in acetone for 15 min → treated with 10% NaOH (60 °C × 10 min) → 10% HCl (30 s) → rinsed with deionized water → dried with nitrogen. Then, TiB2 and the pore former NH4HCO3 (particle size 100 - 200 μm) were mixed at a volume ratio of 3:7, and 2 wt% polyvinyl alcohol (PVA) was added as a binder. Subsequently, cold isostatic pressing was carried out (pressure 200 MPa, holding pressure for 5 min) to obtain a preform with dimensions of 200 × 150 × 30 mm. Then, it was heated to 1350 °C (heating rate 5 °C / min) in a vacuum sintering furnace, held for 2 h, and cooled with the furnace to obtain a dual-scale structure preform with a porosity of 45% (macro-channel diameter 600 ± 50 μm, micro-pores 30 ± 10 μm).

[0054] Step 2: A Cr / Mo gradient layer (Cr:Mo = 4:1) was deposited on the surface of the preform by a stepwise gradient electroless plating method. The number of plating layers was successively stacked six layers, and the ratio of Cr:Mo from the first layer to the sixth layer gradually changed from 4:1 → 3:1 → 2:1 → 1:2 → 1:3 → 1:4, and the plating solution was changed every 1 h. The molten steel was melted and processed in an intermediate frequency induction furnace. Intermediate alloys such as pure iron, Fe-Cr, and Fe-Mo were added under argon protection. After complete melting, 0.4 Ce blocks and 0.1 B4C powder were added. After the melt temperature rose to 1600 °C, degassing was carried out by rotary spraying (argon flow rate 15 L / min), and the hydrogen content was reduced to 1.2 ppm.

[0055] Step 3: Cast infiltration composite process. The preform was preheated to 1100 °C (heating rate 10 °C / min) in a resistance furnace, held for 30 min, and then placed in the mold cavity. The mold was preheated to 600 °C, and a zirconia-based coating (thickness 0.5 mm) was sprayed on the surface. Subsequently, bottom gating was used for pouring, the molten steel pouring temperature was 1580 °C, and the filling time was 8 s. A 0.5 T axial static magnetic field (frequency 50 Hz) was applied synchronously, and a fiber laser (wavelength 1070 nm, power 4 kW) was used to scan and heat the surface of the preform (scanning speed 10 mm / s) to form a temperature gradient of 1600 °C on the surface → 1450 °C inside. Then, pressure holding and solidification were carried out at 50 MPa (applied by a hydraulic press) for 120 s.

[0056] Step 4: Post-treatment and performance testing. Heat treatment: The casting was austenitized at 1050 °C (holding for 1 h) + oil quenched to room temperature, and then tempered at 250 °C for 2 h. Finally, the performance was tested.

[0057] Example 2:

[0058] On the basis of the basic conditions, this example further explored the influence of the multi-layer structure preform on the performance of the final composite material, especially its performance in terms of interfacial bonding strength and wear resistance.

[0059] Step 1: Preform design, multi-layer structure, outer layer (contact surface): TiB2 content 80%, porosity 40%, channel diameter 500 μm, Cr / Mo coating thickness 5 μm; middle layer: TiB2 content 60%, porosity 45%, channel diameter 700 μm, Cr / Mo coating thickness 3 μm; inner layer (back plate): TiB2 content 40%, porosity 50%, channel diameter 800 μm, no coating; each layer of preform is bonded by Al2O3 micropowder (particle size 5 μm) and silica sol, and the whole is sintered after lamination (1300 °C / 1 h);

[0060] Step 2: Melt purification: Electromagnetic stirring (frequency 20 Hz, current 200 A) is used to refine the grains, and the melt superheat is controlled at 80 °C;

[0061] Step 3: Cast infiltration process, directional solidification, pouring temperature 1600 °C, combined with selective laser melting (power density 3×10 4 W / cm 2 ) to form a molten pool on the surface of the preform, and the solidification rate gradient is 8 mm / s on the surface layer → 3 mm / s in the middle layer → 1 mm / s in the inner layer; Apply a 0.8 T pulsed magnetic field (pulse frequency 10 Hz) to suppress melt turbulence; Use gas pressure infiltration (pressure 8 MPa, argon medium), and the pressure holding time is 180 s;

[0062] Step 4: Post-treatment and performance testing, heat treatment, the casting is austenitized at 1050 °C (holding for 1 h) + oil quenched to room temperature, and then tempered at 250 °C for 2 h; Finally, the performance is tested.

[0063] Example 3:

[0064] Based on the results of the first two examples, the experiment in this example aims to explore the effects of adjusting the Cr / Mo ratio of the chemical coating and optimizing the addition amounts of Ce and B during melting on the tensile strength and impact toughness of the composite material.

[0065] Step 1: Repeat the operation in Step 1 of Example 1;

[0066] Step 2: Deposit a Cr / Mo gradient layer (Cr:Mo = 3:1) on the surface of the preform by the step-by-step gradient electroless plating method. The number of plating layers stacked in sequence is four layers, and the ratio of Cr:Mo in the first layer to the sixth layer gradually changes from 3:1 → 2:1 → 1:2 → 1:3, and the plating solution is changed every 1 h;

[0067] Step 3: Place the molten steel in an intermediate frequency induction furnace for melting and treatment. Add intermediate alloys such as pure iron, Fe-Cr, and Fe-Mo under argon protection. After complete melting, add 0.6 Ce blocks and 0.2 B4C powder. After the melt temperature rises to 1600 °C, degas by rotary injection (argon flow rate 15 L / min) until the hydrogen content drops to 1.1 ppm;

[0068] Step 4: Cast infiltration composite process. Preheat the preform in a resistance furnace to 1100 °C, keep it warm for 30 min and then place it in the mold cavity; preheat the mold to 600 °C and spray a zirconia-based coating (thickness 0.5 mm) on the surface; then use bottom gating for pouring, with the molten steel pouring temperature of 1580 °C and the filling time of 8 s; simultaneously apply an axial static magnetic field of 0.5 T (frequency 50 Hz), and use a fiber laser (wavelength 1070 nm, power 4 kW) to scan and heat the surface of the preform (scanning speed 10 mm / s) to form a temperature gradient of 16,000 °C on the surface → 1450 °C inside; then carry out pressure holding and solidification at 50 MPa (applied by a hydraulic press) for 120 s;

[0069] Step 5: Post-treatment and performance testing. Heat treatment: Austenitize the casting at 1050 °C (keep warm for 1 h) + oil quenching, immediately immerse it in liquid nitrogen (-196 °C) for 30 minutes after oil quenching to reduce the retained austenite content, and then carry out two-stage tempering: The first stage: 250 °C × 1 h to eliminate quenching stress; the second stage: 400 °C × 1 h to promote carbide precipitation; finally, carry out performance testing.

[0070] As can be seen from the above table, with the optimization of process parameters, especially when the surface treatment of the preform is improved by the step-by-step gradient electroless plating method and the contents of Ce and B are appropriately increased, the composite material not only exhibits higher tensile strength, better impact toughness, and significantly enhanced wear resistance, but also shows excellent mechanical properties under extreme low temperature conditions; these results indicate that the preparation method of the present invention can effectively improve the overall performance of the TiB2 and ultra-high strength and toughness steel composite material, and has broad application prospects.

[0071] In summary, the casting infiltration preparation method of the TiB2 and ultra-high strength and toughness steel composite material significantly reduces the casting infiltration resistance of the molten steel by constructing a dual-scale three-dimensional porous structure of macroscopic pores and microscopic pores. At the same time, the interfacial wettability is optimized by the Cr / Mo gradient coating, and the Fe-B diffusion reaction is inhibited, realizing the uniform fusion of the TiB2 reinforcing phase and the steel matrix, and solving the defects of weak interfacial bonding and uneven distribution of traditional composite materials.

[0072] Moreover, for the method for preparing the TiB2 and ultra-high strength and toughness steel composite material by cast infiltration, acetone ultrasonic cleaning, NaOH / HCl chemical treatment, and SnCl2 / AgNO3 sensitization and activation technologies are adopted to significantly improve the surface activity and adsorption capacity of TiB2. Combining with the step-by-step gradient electroless plating method, an interfacial transition layer is formed to effectively improve the wettability and chemical stability between TiB2 and the steel matrix, breaking through the technical bottleneck of the easy failure of the interface of the traditional single-layer coating.

[0073] Moreover, for the method for preparing the TiB2 and ultra-high strength and toughness steel composite material by cast infiltration, Ce (0.3-0.8%) and B (0.1-0.3%) are added to the molten steel. An ultra-low oxygen potential is achieved through the CeO2 / B2O3 composite oxide film to inhibit the formation of the brittle Fe2B phase. At the same time, an in-situ formed (Ti, Cr, Mo)B2 nano-transition layer is formed at the interface, significantly improving the interfacial bonding strength, which is superior to the interfacial stability of the traditional single deoxidation process.

[0074] Moreover, for the method for preparing the TiB2 and ultra-high strength and toughness steel composite material by cast infiltration, a 0.5T axial static magnetic field is used to inhibit the turbulence of the molten steel and the segregation of TiB2. Combining with laser local heating to regulate the interfacial tension and solidification path, the accurate matching of the molten steel filling rate and pressure holding solidification is realized, breaking through the problems of composition segregation and pore defects caused by traditional single-field regulation.

[0075] Moreover, for the method for preparing the TiB2 and ultra-high strength and toughness steel composite material by cast infiltration, the tensile strength of the composite material is significantly increased to the ultra-high strength and toughness level, the elongation rate is effectively guaranteed, and the impact toughness is excellent under low-temperature environments. The wear resistance is greatly improved compared with traditional steel-based composite materials, and the stability under high-temperature and strong corrosion environments is significantly enhanced, meeting the application requirements of extreme working conditions, filling the technical gap of the insufficient corrosion resistance of TiB2 / steel composite materials, and solving the problems of weak interfacial bonding, uneven distribution, and insufficient wear resistance of traditional composite materials.

[0076] All relevant modules involved in this system are hardware system modules or functional modules that combine computer software programs or protocols in the prior art with hardware. The computer software programs or protocols themselves involved in this functional module are all well-known technologies to those skilled in the art, and they are not the improvements of this system. The improvement of this system is the interaction relationship or connection relationship between each module, that is, the overall structure of the system is improved to solve the corresponding technical problems to be solved by this system.

[0077] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration, characterized in that, Including the following steps: S1: Pretreat the TiB2 cermet particles. Subsequently, mix TiB2 powder (D50 = 13 - 17 μm) and pore-forming agent (NH4HCO3) at a volume ratio of 6.5:3.5 - 7.5:2.5, and sinter (1320 - 1380 °C / 2 h) after cold pressing to obtain a preform with a porosity of 42 - 48%; S2: Sensitize and activate the surface of the TiB2 cermet particles, and then deposit a Cr / Mo gradient layer on the surface of the TiB2 cermet particles by electroless plating; S3: Put the ultra-high strength steel into an intermediate frequency induction furnace for melting. After melting, add Ce (0.3 - 0.8 wt%) and B (0.1 - 0.3 wt%); after the melt temperature rises to 1500 - 1700 °C, use rotating and blowing argon to remove gas and control the oxygen potential content; S4: Place the TiB2 preform as the core material in a mold and heat it. Pour in the high-temperature molten steel, stir to make it fully blend, apply an axial static magnetic field of 0.3 - 0.8 T, synchronously use a laser for local heating, and then carry out pressure holding and solidification; S5: Heat-treat the sample after cast infiltration, austenitize at 950 - 1150 °C for 1 h, then oil quench, then temper at 200 - 300 °C for 2 h, then carry out forging processing, and finally carry out performance testing.

2. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration according to claim 1, characterized in that, The preform uses a cemented carbide mold, the inner wall is sprayed with molybdenum disulfide release agent (thickness 0.08 - 0.12 mm), the pressing parameters are uniaxial pressure of 190 - 210 MPa, the pressure holding time is 4 - 6 min, it has a three-dimensional pore structure, the macroscopic channel diameter is 550 - 650 μm, and the microscopic pores are 20 - 40 μm.

3. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration according to claim 1, characterized in that, The pretreatment of the TiB2 cermet particles includes: Step 1: Immerse the TiB2 cermet particles in acetone and ultrasonically treat for 13 - 17 min to remove surface oil-based particle contaminants; Step 2: Then soak in a 10% NaOH solution at 55 - 65 °C for 8 - 12 min to neutralize the remaining acidic substances, and rinse with deionized water until neutral; Step 3: Subsequently, immerse in a 10% HCl solution for 25 - 35 s, wash with water and dry with nitrogen. After drying, carry out sensitization and activation treatment.

4. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting penetration according to claim 1, characterized in that, The processing flow of the surface sensitization and activation of the TiB2 cermet particles is: Step 1: Sensitize the TiB2 cermet particles in a SnCl2 solution for 5 - 10 min to ensure uniform adsorption of Sn2+; Step 2: Then activate in an AgNO3 solution for 3 - 5 min. Transfer the sensitized substrate quickly into the activation solution to avoid oxidation of Sn2+.

5. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration according to claim 1, characterized in that, In step S2, a Cr / Mo gradient layer is deposited on the surface of the TiB2 preform by a stepwise gradient electroless plating method. The mass ratio of Cr:Mo in the electroless plating solution is 2.5:1 - 3.5:

1. The complexing agent for the Cr plating solution is sodium citrate with a concentration of 60 - 90 g / L. The pH value is adjusted to 4.5 ± 0.2 with sulfuric acid. The deposition temperature is 85 ± 2 °C, and the stirring rate is 200 rpm. The complexing agent for the Mo plating solution is disodium EDTA with a concentration of 40 - 60 g / L. The pH value is adjusted to 9.0 ± 0.2 with NaOH. The deposition temperature is 75 ± 2 °C, and the stirring rate is 150 rpm. The number of superimposed plating layers is four. The ratio of Cr:Mo in the first to the fourth layer gradually changes from 3:1 → 2:1 → 1:2 → 1:3, and the plating solution is changed every 1 - 2 h.

6. The preparation method of a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration according to claim 1, characterized in that, In step S3, a bottom-pouring casting infiltration process is adopted. The preform is preheated to 1080 - 1120 °C and then placed in the mold. The pouring temperature is 1580 ± 10 °C, the pouring time is 7 - 9 s, and the filling speed is 0.23 - 0.27 m / s.

7. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting infiltration according to claim 1, characterized in that, In step S4, after the TiB2 preform is poured into the high-temperature molten steel and fully fused, an axial static magnetic field of 0.3 - 0.8 T is applied. The magnetic field direction is parallel to the pouring direction, and at the same time, the laser local heating power density is 1.8×10 4 -2.2×10 4 W / cm2, and it reciprocates horizontally along the surface of the preform at a speed of 8 - 12 mm / s, so that the surface temperature reaches 1580 - 1620 °C and the internal gradient drops to 1430 - 1470 °C.

8. A method for preparing a TiB2 and ultra-high strength and toughness steel composite material by casting penetration according to claim 1, characterized in that, In step S4, the pressure-holding solidification process after pouring the TiB2 preform into the high-temperature molten steel and fully fusing is specifically as follows: Step 1: The pressure is set to 45 - 55 MPa for pressure-holding solidification for 110 - 130 s, and the pressure is applied immediately after the molten steel filling is completed. Step 2: Water cooling is carried out by passing water through the outer wall of the mold (flow rate 8 - 12 L / min).

Images