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CN-118241152-B - Method for preparing Si-Hf-Yb co-permeation coating on TiAl alloy surface

CN118241152BCN 118241152 BCN118241152 BCN 118241152BCN-118241152-B

Abstract

The invention discloses a method for preparing a Si-Hf-Yb co-permeation coating on the surface of a TiAl alloy, which is in a multi-layer structure and sequentially comprises a silicide surface layer rich in Hf and Yb, a TiSi 2 +Ti 5 Si 3 outer layer, a TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 transition layer and a TiAl 2 inner layer from outside to inside. The method adopts a diffusion embedding infiltration process, combines with control of the components of the infiltration agent and the process conditions, realizes simultaneous co-infiltration deposition of Hf, yb and Si, enables Yb and Hf in the infiltration layer to be doped into an SiO 2 oxide film after oxidation, plays a role in optimizing the oxide film tissue structure and inhibiting the growth of the oxide film, effectively improves the high-temperature oxidation resistance of TiAl alloy, and is suitable for the aerospace field.

Inventors

  • XIANG JIAYI
  • ZHANG CHONG

Assignees

  • 西北有色金属研究院

Dates

Publication Date
20260505
Application Date
20240322

Claims (8)

  1. 1. A method for preparing a Si-Hf-Yb co-permeation coating on the surface of a TiAl alloy is characterized in that the Si-Hf-Yb co-permeation coating is of a multi-layer structure and sequentially comprises a silicide surface layer rich in Hf and Yb, a TiSi 2 +Ti 5 Si 3 outer layer, a TiSi 2 +Ti 5 Si 3 +Ti(Al,Si) 2 transition layer and a TiAl 2 inner layer from outside to inside, and the method comprises the following steps: step one, polishing TiAl alloy step by step, then putting the polished TiAl alloy into absolute ethyl alcohol or acetone for ultrasonic cleaning, and drying to obtain pretreated TiAl alloy; Weighing the powder of Si, hf, yb 2 O 3 , naF and Al 2 O 3 , mixing, grinding and drying to prepare a penetrating agent; Filling the penetrating agent prepared in the second step into a crucible, embedding the pretreated TiAl alloy in the first step into the penetrating agent in the crucible, compacting, covering the crucible, sealing by adopting high-temperature sealing mud mixed by silica sol and Al 2 O 3 , and then placing in a high-temperature resistance furnace; and step four, heating and preserving heat of the crucible filled in the high-temperature resistance furnace in the step three, so that the penetrating agent diffuses, embeds and penetrates the TiAl alloy, and a Si-Hf-Yb co-penetrating coating is obtained on the surface of the TiAl alloy.
  2. 2. The method for preparing the Si-Hf-Yb co-permeation coating on the surface of the TiAl alloy, which is characterized in that in the first step, the TiAl alloy is polished step by adopting 80# to 2000# SiC water sand paper, and the ultrasonic cleaning time is 0.25h to 0.5h.
  3. 3. The method for preparing the Si-Hf-Yb co-permeation coating on the surface of the TiAl alloy, which is characterized by comprising the following steps of weighing 10-20% of Si, 5-15% of Hf, 1-5% of Yb 2 O 3 %, 3-10% of NaF and the balance Al 2 O 3 according to the following mass percentages, wherein the particle sizes of the Si, hf, yb 2 O 3 and Al 2 O 3 are all smaller than 200 meshes, and the NaF is analytically pure.
  4. 4. The method for preparing the Si-Hf-Yb co-diffusion coating on the surface of the TiAl alloy according to claim 1, wherein the grinding time in the second step is 2-4 hours, the drying temperature is 100 ℃, and the drying time is 0.5-1 hour.
  5. 5. The method for preparing the Si-Hf-Yb co-diffusion coating on the surface of the TiAl alloy according to claim 1, wherein the thickness of the diffusion agent covered on the surface of the pretreated TiAl alloy in the crucible after compacting and the distance between the pretreated TiAl alloy and the bottom of the crucible in the third step are not less than 10mm.
  6. 6. The method for preparing the Si-Hf-Yb co-penetrating coating on the surface of the TiAl alloy, according to claim 1, wherein the mixing ratio of the silica sol and the Al 2 O 3 in the third step is that lkg-l.5 kg of Al 2 O 3 is added into every 1L of the silica sol with the mass concentration of 30% -40%.
  7. 7. The method for preparing the Si-Hf-Yb co-diffusion coating on the surface of the TiAl alloy, which is characterized by comprising the following steps of heating from room temperature to 900-1100 ℃ at a temperature rising rate of 5-10 ℃ per minute and keeping the temperature for 3-12 hours, taking out a crucible from a high-temperature resistance furnace, and air-cooling to the room temperature.
  8. 8. The method for preparing the Si-Hf-Yb co-permeation coating on the surface of the TiAl alloy, which is characterized by comprising the steps of taking out the TiAl alloy with the Si-Hf-Yb co-permeation coating on the surface in a crucible cooled to room temperature by air, putting the TiAl alloy into distilled water, ultrasonically cleaning the TiAl alloy for 0.5-1 h to remove residual permeation agent powder, and then putting the TiAl alloy into a 100 ℃ oven for heat preservation for 0.5-1 h for drying.

Description

Method for preparing Si-Hf-Yb co-permeation coating on TiAl alloy surface Technical Field The invention belongs to the technical field of material surface coating and modification, and particularly relates to a method for preparing a Si-Hf-Yb co-permeation coating on the surface of a TiAl alloy. Background Compared with the traditional titanium alloy and nickel-based superalloy, the gamma-TiAl-based intermetallic compound alloy has low density (3.9 g/cm 2), large elastic modulus, high specific strength, better heat resistance and creep resistance, and becomes one of the most potential alloys for high-temperature components of aerospace engines. However, the engine has a severe high-temperature, high-airflow and strong-gas corrosion environment, and the TiAl alloy part can be subjected to strong high-temperature oxidation in the service process. The high Ti content in the TiAl alloy makes the surface of the TiAl alloy incapable of generating a continuous and compact Al 2O3 protective film at high temperature, but generates loose TiO 2+Al2O3 oxide, so that effective protection of alloy parts is difficult to generate. With the gradual solving of the problems of poor room temperature plasticity and the like which obstruct the application of the TiAl alloy, the oxidation resistance of the TiAl alloy at more than 800 ℃ becomes one of the key factors for determining the service capacity of the TiAl alloy. The method is the most effective and economic method for improving the high-temperature oxidation resistance of the TiAl alloy, the currently developed high-temperature oxidation resistance coating process of the TiAl alloy surface is mainly concentrated on diffusion aluminizing, plasma spraying, physical vapor deposition and other technologies (Qu Jing, xie Faqin, wu Xiangqing and the like; gamma-TiAl alloy high-temperature oxidation resistance coating research progresses; rare metal materials and engineering, 2022,51 (10): 3929-3936.) and mainly has the following problems that (1) the diffusion aluminizing coating has large thermal expansion coefficient difference with a substrate and is easy to generate longitudinal penetration cracks, (2) the plasma spraying coating has poor bonding force with the substrate and higher porosity, and (3) the physical vapor deposition methods such as ion plating, magnetron sputtering and the like need specific equipment for preparing the coating, the equipment structure is complex, and the equipment has larger limitation on the shape and the size of a substrate workpiece. The silicide coating has low density, high melting point and good thermal stability, and can generate protective oxide SiO 2 at high temperature, thereby effectively improving the compactness and self-healing capacity of the oxide film. The silicide coating is prepared by adopting diffusion embedding infiltration, so that a coating with strong binding force (metallurgical bonding) and uniformity and compactness can be obtained. And the embedding and infiltration process is simple and convenient, the common high-temperature resistance furnace is adopted, the cost is low, the limitation on the shape and the size of the base body workpiece is small, and the method is suitable for actual production and application. However, the TiAl alloy silicide coating still has some limitations in application, such as the free energy of formation of TiO 2 and SiO 2 is close at high temperature, loose and easily-peeled TiO 2 is still formed, the coating and the matrix alloy element are mutually diffused at high temperature, so that the coating is degraded, the protective life of the coating is reduced, and the thermal expansion coefficient between an oxide film and the coating generated at high temperature is not matched, so that cracking and peeling are easy to occur in the oxidation process of a cold-hot cycle. The silicide coating is subjected to element doping modification, so that the coating organization structure can be optimized, and the service performance of the coating is further improved. Research shows that Hf and Yb can effectively modify silicide coating. W.Wang et Al perform embedding infiltration on the Nb-Si-based alloy surface to prepare a Si-Al-Hf co-infiltration coating, hfO 2 particles generated by Hf oxidation are distributed at the interface of an oxide film and the coating to inhibit crack growth caused by vacancy aggregation, so that MoSi 2-Yb2O3 composite coating is prepared on a C/C composite material by plasma spraying by improving the adhesion (W.Wang,B.Zhang,C.Zhou.Formation and oxidation resistance of Hf and Al modified silicide coating on Nb-Si based alloy.Corrosion Science,2014,86:304-309.).C.C.Wang of the oxide film, yb 3+ fills gaps in SiO 2, improves the viscosity of SiO 2, inhibits effective transmission of oxygen in SiO 2, and delays oxidation of the coating (C.-C.Wang,K.Z.Li,D.-Y.He,et al.Oxidation behavior of plasma-sprayed MoSi2-Yb2O3 composite coating at 1700℃.Ceramics International,202