Method for improving high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy material

Abstract

This invention relates to a method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials, and relates to the field of high-strength, tough, and heat-resistant structural metal materials. The alloy material is composed of a Ti matrix and Cr, Mo, and Si alloying elements, which are distributed in the titanium alloy matrix in the form of solute atoms. The mass percentage of the alloying elements is: Cr: 2-8%, Mo: 2-8%, Si: 0.5-1.5%, with the remainder being Ti. The preparation method is as follows: Ti powder, Cr powder, Mo powder, and Si powder are ball-milled and mixed, followed by spark plasma sintering and high-temperature oxygen-environment heat treatment to obtain a high-strength and high-toughness Ti-Cr-Mo-Si alloy material with high temperature resistance and oxidation resistance. This invention achieves the construction of a dense bimodal TiO2-SiO2 oxide film, a Ti-Cr-Mo-Si alloy matrix, and a nano-deformed TiN twin layer through the synergistic effect of high-energy ball milling, spark plasma sintering, and high-temperature oxidation treatment. The resulting back stress strengthening, grain refinement strengthening, solid solution strengthening, and twin strengthening effects synergistically enable the prepared alloy material to exhibit excellent high-temperature oxidation resistance and excellent mechanical properties, effectively solving the problem that high-temperature materials cannot synergistically improve high-temperature oxidation resistance and mechanical properties during service.

Description

Technical Field

[0001] This invention relates to a method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials, belonging to the field of high-strength, tough, and heat-resistant structural metal materials. Background Technology

[0002] Titanium-based composites, with their low density, high specific strength, and excellent high-temperature service performance, have gained wider application in aerospace and weaponry compared to high-temperature titanium alloys. However, with the development of aerospace technology, higher service temperatures are required for the titanium-based composites used. Si, due to its strong oxygen affinity, can form a protective SiO2 barrier, making it a key element for improving the high-temperature oxidation resistance and high-temperature stability of titanium-based materials. Research results show that when the Si content exceeds 0.4 wt.%, coarse and brittle Ti5Si3 phases easily precipitate at the α / β phase interface, severely impairing the material's room-temperature mechanical properties. Simultaneously, in a high-temperature aerobic environment, Ti5Si3 / Ti composites undergo selective oxidation: because the chemical reactivity of the Ti matrix is ​​higher than that of the Ti5Si3 reinforcing phase, the Ti matrix oxidizes preferentially, forming a loose oxide film composed of granular TiO2 on the surface of the composite material. When the oxidation temperature increases above 600℃, the growth rate of TiO2 particles increases dramatically, causing them to grow continuously with increasing oxidation temperature and time. This leads to a thicker oxide layer, which eventually peels off, resulting in a decline in the material's high-temperature oxidation resistance and making it difficult to meet the requirements of high-temperature structural materials. Therefore, overcoming the trade-off between high-temperature oxidation resistance and room-temperature mechanical properties of titanium-based composites and achieving synergistic optimization of both is of great significance for the research and development of high-temperature structural materials for extreme environments.

[0003] In titanium-based composites, large plastic deformation can effectively refine the Ti5Si3 reinforcing phase. However, during long-term high-temperature service, the precipitated silicides continue to grow, deteriorating the stability of the material's high-temperature microstructure and mechanical properties. Cooled multi-directional forging (DMDF) refines the Ti5Si3 reinforcing phase, constructing submicron and nanoscale dual-scale silicides within the titanium-based composite matrix, achieving a synergistic improvement in room-temperature strength and toughness. However, the continuous growth of the Ti5Si3 reinforcing phase under long-term service conditions at 650℃ worsens its mechanical properties and high-temperature oxidation resistance. Therefore, how to overcome the challenges of decreased high-temperature oxidation resistance and deteriorated room-temperature mechanical properties caused by high Si content through microstructure control, and achieve a synergistic balance between room-temperature and high-temperature performance, is a critical bottleneck issue that urgently needs to be addressed for the widespread application of high-Si structural materials in aerospace technology, high-end equipment, and other fields. Summary of the Invention

[0004] To address the problem that Ti-Si alloys are prone to precipitating brittle Ti-Si intermetallic compounds, resulting in poor room temperature toughness and insufficient high-temperature oxidation resistance, the present invention aims to provide a method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloys. This method improves the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloys through adjustments to alloying elements and synergistic process control, specifically including the following steps: (1) Weigh Ti, Mo, Cr and Si powders according to the component ratio, mix them evenly using a planetary ball mill, and dry them to obtain a uniformly mixed Ti-Cr-Mo-Si composite powder.

[0005] (2) The composite powder is subjected to discharge plasma sintering to obtain Ti-Cr-Mo-Si alloy material.

[0006] (3) The Ti-Cr-Mo-Si alloy material obtained in step (2) is placed in a muffle furnace for high-temperature oxidation treatment to obtain Ti-Cr-Mo-Si high-temperature resistant and oxidation-resistant alloy material.

[0007] Preferably, the alloy composition of the present invention comprises Cr: 2-8%, Mo: 2-8%, Si: 0.5-1.5%, and the remainder being Ti.

[0008] Preferably, the ball milling process parameters in step (1) of the present invention are: ball-to-material ratio of 5:1 to 10:1, rotation speed of 160 to 500 r / min, ball milling time of 2 to 24 hours, and wet milling with anhydrous ethanol as solvent.

[0009] Preferably, in step (2) of the present invention, the sintering temperature is 900-1500℃, the holding time is 5-30 min, and the pressure is 5-50 MPa.

[0010] Preferably, in the high-temperature oxidation process of step (3) of the present invention: the oxidation temperature is 600-1000℃ and the oxidation time is greater than 5 min.

[0011] Preferably, the alloy material of the present invention is composed of Ti and Mo, Cr, and Si alloying elements, wherein Si is distributed in the alloy matrix as a substitution solid solution.

[0012] This invention adds Cr and Mo transition elements to the Ti-Si system. Compared to Ti, Si, existing in solid solution in the matrix, exhibits higher chemical activity under high-temperature aerobic conditions. During high-temperature oxidation, Si preferentially reacts with oxygen to generate fluid SiO2, which fills the interface of TiO2 particles, increasing the density of the oxide film while inhibiting the growth of TiO2 particles. Additionally, Mo... 6+ Cr6+ Replace Ti 4+ Entering the TiO2 lattice reduces the oxygen vacancy concentration in the TiO2 lattice and maintains its lattice electrical neutrality, significantly improving the alloy's high-temperature oxidation resistance.

[0013] The beneficial effects of this invention are: (1) The Ti-Cr-Mo-Si alloy material of the present invention breaks through the technical bottleneck of insufficient high-temperature oxidation resistance of traditional Ti5Si3 / Ti-based composite materials. The Si element in solid solution induces the matrix to form a dense dual-scale TiO2-SiO2 oxide layer during high-temperature oxidation. The amorphous SiO2 oxide penetrates the interior of the oxide layer and is distributed at the interface of TiO2 grains, effectively increasing the high-temperature stability of rutile TiO2 and the density of the oxide film, and significantly improving the high-temperature oxidation resistance. Under the condition of oxidation in an air environment of 800℃ for 120 h, the mass gain is reduced by nearly three times compared with Ti-6Cr-4Mo alloy. The oxidation kinetic curve changes from a linear curve without protection to a parabolic curve with protection, effectively solving the problem of rapid growth and peeling of oxide layer at high temperature.

[0014] (2) The Ti-Cr-Mo-Si alloy material of the present invention solves the technical pain point of brittle failure of titanium alloy caused by the addition of high silicon content. Compared with the catastrophic brittle failure of Ti-0.9Si alloy, the ultimate tensile strength of this alloy is increased to 1279MPa and the elongation can reach up to 6.5%. Its mechanical properties are superior to existing commercial low silicon titanium alloys and high silicon titanium-based composite materials.

[0015] (3) The Ti-Cr-Mo-Si alloy material of the present invention breaks through the technical limitation of unstable bonding between the oxide layer and the substrate of traditional titanium alloys. During the high-temperature oxidation process, a nano-scale TiN interface layer containing deformed twins is formed in situ. This interface layer can effectively alleviate the thermal stress caused by the difference in thermal expansion coefficient between the oxide layer and the substrate, reduce the dissolution of oxygen in the substrate and enhance the bonding force of the oxide layer, and avoid the failure of oxide layer peeling during high-temperature cycle service. At the same time, the powder metallurgy + SPS sintering process is adopted, which has moderate requirements for equipment and energy consumption and is more suitable for large-scale industrial production. Attached Figure Description

[0016] Figure 1 is a schematic diagram illustrating the formation principle of the surface oxide layer during the oxidation process of the Ti-Cr-Mo-Si alloy material described in this invention at 800℃. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention, but the scope of protection of the present invention is not limited thereto.

[0018] In an embodiment of the present invention, as shown in Figure 1, the formation process of the surface oxide layer of the high-strength and high-toughness Ti-Cr-Mo-Si alloy material with high temperature resistance and oxidation resistance of the present invention during oxidation at 800℃ is as follows: Stage I corresponds to the initial oxidation stage, Stage II corresponds to the titanium nitride nanotwin formation stage, and Stage III corresponds to the later silicon dioxide sealing stage. During the cyclic oxidation process, reactions as shown in formulas (1), (2), and (3) occur.

[0019] Ti + O₂ = TiO₂ (1) 2Ti+N2=2TiN (2) Si + O2 = SiO2 (3) The following specific embodiments will be used for further explanation.

[0020] Example 1 A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials specifically includes the following steps: S1: 30g of alloy raw materials Cr, Mo, Si powder and Ti powder were mixed in a composition ratio of Ti-6Cr-4Mo-0.9Si. The mixture was homogenized using a planetary ball mill with a ball-to-material ratio of 5:1, a rotation speed of 160 r / min, and a milling time of 24 h. Anhydrous ethanol was used as a wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo-Si composite powder.

[0021] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1250℃, a holding time of 8 min, and a pressure of 40 MPa to obtain a high-strength and high-toughness Ti-Cr-Mo-Si alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1279 MPa and the elongation at break was 6.5%.

[0022] S3: After oxidation treatment by holding the material in a muffle furnace at 800℃ for 10 h, Ti-Cr-Mo-Si alloy material is obtained.

[0023] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 9μm.

[0024] Example 2 A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials specifically includes the following steps: S1: 30g of alloy raw materials Cr, Mo, Si powder and Ti powder were mixed in a composition ratio of Ti-6Cr-4Mo-1.2Si. The mixture was homogeneous using a planetary ball mill with a ball-to-material ratio of 5:1, a rotation speed of 300 r / min, and a milling time of 4 h. Anhydrous ethanol was used as the wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo-Si composite powder.

[0025] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 900℃, a holding time of 30min, and a pressure of 50 MPa to obtain a high-strength and high-toughness Ti-Mo-Si alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1212 MPa and the elongation at break was 1.2%.

[0026] S3: After oxidation treatment by holding the material in a muffle furnace at 700℃ for 8 hours, Ti-Cr-Mo-Si alloy material is obtained.

[0027] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 10 μm.

[0028] Example 3 A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials specifically includes the following steps: S1: 30g of alloy raw materials Cr, Mo, Si powder and Ti powder were mixed in a composition ratio of Ti-6Cr-4Mo-1.5Si. The mixture was homogeneous using a planetary ball mill with a ball-to-powder ratio of 10:1, a rotation speed of 500 r / min, and a milling time of 2 h. Anhydrous ethanol was used as a wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo-Si composite powder.

[0029] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1300℃, a holding time of 8 min, and a pressure of 50 MPa to obtain a high-strength and high-toughness Ti-Mo-Si alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1284 MPa and the elongation at break was 1.9%.

[0030] S3: After oxidation treatment by holding the material in a muffle furnace at 600℃ for 7 h, Ti-Cr-Mo-Si alloy material is obtained.

[0031] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 12μm.

[0032] Example 4 A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials specifically includes the following steps: S1: 30g of alloy raw materials Cr, Mo, Si and Ti powder were mixed in a ratio of Ti-2Cr-8Mo-0.9Si. The mixture was homogenized using a planetary ball mill with a ball-to-material ratio of 5:1, a rotation speed of 300 r / min and a milling time of 4 h. Anhydrous ethanol was used as a wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo-Si composite powder.

[0033] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1400℃, a holding time of 8 min, and a pressure of 40 MPa to obtain a high-strength and high-toughness Ti-Mo-Si alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1099 MPa and the elongation at break was 0.9%.

[0034] S3: After oxidation treatment by holding the material in a muffle furnace at 900℃ for 6 hours, Ti-Cr-Mo-Si alloy material is obtained.

[0035] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 10 μm.

[0036] Example 5 A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials specifically includes the following steps: S1: 30g of alloy raw materials Cr, Mo, Si powder and Ti powder were mixed in a composition ratio of Ti-8Cr-2Mo-0.9Si. The mixture was homogenized using a planetary ball mill with a ball-to-material ratio of 7:1, a rotation speed of 400 r / min, and a milling time of 4 h. Anhydrous ethanol was used as a wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo-Si composite powder.

[0037] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1500℃, a holding time of 8 min, and a pressure of 40 MPa to obtain a high-strength and high-toughness Ti-Mo-Si alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1217 MPa and the elongation at break was 1.4%.

[0038] S3: After oxidation treatment by holding the material in a muffle furnace at 1000℃ for 9 h, Ti-Cr-Mo-Si alloy material is obtained.

[0039] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 9μm.

[0040] Comparative Example 1 A method for preparing a high-strength and high-toughness Ti-Cr-Mo alloy material with high temperature resistance and oxidation resistance, specifically including the following steps: S1: 30g of alloy raw materials Cr, Mo and Ti powder were mixed in a composition ratio of Ti-6Cr-4Mo. The mixture was homogenized using a planetary ball mill with a ball-to-material ratio of 7:1, a rotation speed of 400 r / min and a milling time of 4 h. Anhydrous ethanol was used as the wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-Cr-Mo composite powder.

[0041] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1300℃, a holding time of 8 min, and a pressure of 40 MPa to obtain a high-strength and high-toughness Ti-6Cr-4Mo alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 1120 MPa and the elongation at break was 5.2%.

[0042] S3: After oxidation treatment by holding the material in a muffle furnace at 800℃ for 10 h, Ti-Cr-Mo-Si alloy material is obtained.

[0043] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 25 μm.

[0044] The oxidation weight gain per unit area of ​​the samples prepared in Example 1 and Comparative Example 1 of this invention was 1.5 mg / cm² and 6.9 mg / cm², respectively, and the oxide layer thickness was 9 μm and 25 μm, respectively. Compared with Ti-Cr-Mo alloy, Ti-Cr-Mo-Si alloy has a smaller oxidation weight gain per unit area and a thinner oxide layer, exhibiting extremely prominent oxidation resistance. The oxide film of Ti-Cr-Mo alloy is mainly composed of loose and porous TiO2, Cr2O3 cannot form a continuous protective layer, MoO3 is prone to volatilization and defects, oxygen and metal ion diffusion are not significantly hindered, the oxidation reaction is violent, and the weight gain and thickness are relatively large. After incorporating Si, Si works synergistically with Cr and Mo to quickly form a continuous and dense Cr2O3 protective film, while blocking the grain boundary channels of the oxide film, significantly blocking oxygen permeation and ion diffusion, effectively inhibiting the oxidation process, thereby significantly reducing the oxidation weight gain and oxide layer thickness.

[0045] Comparative Example 2 A method for preparing a high-strength and high-toughness Ti-Si alloy material with high temperature resistance and oxidation resistance, specifically including the following steps: S1: 30g of alloy raw material Si powder and Ti powder were mixed in a composition ratio of Ti-0.9Si. The mixture was homogenized using a planetary ball mill with a ball-to-material ratio of 7:1, a rotation speed of 400 r / min, and a milling time of 4 h. Anhydrous ethanol was used as the wetting agent. The mixed powder was dried in a vacuum drying oven to obtain Ti-0.9Si composite powder.

[0046] S2: The composite powder was subjected to spark plasma sintering at a sintering temperature of 1300℃, a holding time of 8 min, and a pressure of 40 MPa to obtain a high-strength and high-toughness Ti-0.9Si supersaturated solid solution alloy material with high temperature resistance and oxidation resistance. The mechanical properties of the alloy were measured as follows: the ultimate tensile strength was as high as 990 MPa and the elongation at break was 1.9%.

[0047] S3: After oxidation treatment by holding the material in a muffle furnace at 800℃ for 10 h, Ti-Cr-Mo-Si alloy material is obtained.

[0048] The high-temperature resistant and oxidation-resistant Ti-Cr-Mo-Si alloy material obtained through the above steps was held in a muffle furnace at 800℃ for 120 hours. The oxidation weight gain per unit area was measured by TGA thermogravimetric analysis and scanning electron microscopy, and the oxide layer thickness was 23 μm.

[0049] The oxidation weight gain per unit area of ​​the samples prepared in Example 1 and Comparative Example 2 of this invention was 1.5 mg / cm² and 6.2 mg / cm², respectively, and the oxide layer thickness was 9 μm and 23 μm, respectively. Compared with Ti-Si alloy, Ti-Cr-Mo-Si alloy has better oxidation resistance, with lower oxidation weight gain and oxide layer thickness. During oxidation of Ti-Si binary alloy, SiO2 is scattered and cannot form a complete barrier layer, and it is easy to generate brittle phases that cause film cracking and peeling, resulting in limited oxidation protection. In contrast, in quaternary alloy, Cr and Mo, together with Si, form a continuous amorphous SiO2 barrier layer at the interface, constructing a stable and dense composite oxide film. This not only eliminates diffusion channels but also relieves internal stress and improves the film-substrate adhesion, comprehensively inhibiting the oxidation reaction, resulting in a thinner oxide layer and less weight gain per unit area.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials, characterized in that: The high-temperature oxidation resistance of Ti-Cr-Mo-Si alloys can be improved by adjusting alloying elements and synergistically applying processes. Specifically, the following steps are included: (1) Weigh Ti, Mo, Cr and Si powders according to the component ratio, mix them evenly using a planetary ball mill, and dry them to obtain a uniformly mixed Ti-Cr-Mo-Si composite powder; (2) The composite powder is subjected to spark plasma sintering to obtain Ti-Cr-Mo-Si alloy material; (3) The Ti-Cr-Mo-Si alloy material obtained in step (2) is placed in a muffle furnace for high-temperature oxidation treatment to obtain Ti-Cr-Mo-Si high-temperature resistant and oxidation-resistant alloy material.

2. The method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials according to claim 1, characterized in that: The alloy composition has the following mass percentages: Cr: 2-8%, Mo: 2-8%, Si: 0.5-1.5%, with the remainder being Ti.

3. The method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials according to claim 1, characterized in that: The ball milling process parameters in step (1) are: ball-to-material ratio of 5:1 to 10:1, rotation speed of 160 to 500 r / min, ball milling time of 2 to 24 hours, and wet milling with anhydrous ethanol as solvent.

4. The method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials according to claim 1, characterized in that: In step (2), the discharge plasma sintering process is as follows: the sintering temperature is 900-1500℃, the holding time is 5-30 min, and the pressure is 5-50 MPa.

5. The method for improving the high-temperature oxidation resistance of Ti-Cr-Mo-Si alloy materials according to claim 1, characterized in that: In step (3), the high-temperature oxidation process is as follows: the oxidation temperature is 600-1000℃ and the oxidation time is greater than 5 min.

6. The Ti-Cr-Mo-Si alloy material prepared by the method according to any one of claims 1 to 5, characterized in that: The alloy material is composed of Ti and Mo, Cr and Si alloying elements, wherein Si is distributed in the alloy matrix as a substitution solid solution.

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