The method of preparing Pt Al high temperature protective coating on the surface of niobium alloy includes the following steps :(1) pretreatment of the surface of niobium alloy substrate, ultrasonic cleaning with acetone, then rinse with deionized water, and blow dry for reserve; (2) Put the niobium alloy matrix treated by step (1) into the ion sputtering apparatus for the preparation of Pt layer; (3) The Niobium alloy matrix containing Pt layer prepared by Step (2) is embedded and permeated with Al to prepare Pt-Al high-temperature protective coating on the surface of niobium alloy. The Pt Al high temperature protective coating contains 60 ~ 70wt % Al element, 2 ~ 8wt % Pt element and 20 ~ 30wt % Nb element. The Pt Al high temperature protective coating prepared by the invention is continuous, compact and smooth, and metallurgically combined with niobium alloy matrix. The bonding strength is high and the preparation process is vacuum ion sputtering, which is different from the traditional electroplating method and has the advantages of simple operation and energy saving.
Compared with the development of aero-engine, the turbine blade is used in a more demanding environment, which puts forward higher requirements on the performance of blade materials. Niobium is considered as one of the important candidate materials for high-temperature structural materials because of its high melting point, moderate density and high specific strength at high temperature. However, niobium has poor oxidation resistance, which forms pest oxidation at 600℃, greatly limiting its application. According to relevant research reports, coating niobium alloy surface with protective coating can effectively improve the high temperature oxidation resistance of niobium alloy, but also take into account its high temperature mechanical properties, and the coating protection is easy to achieve, the effect is remarkable, so it is widely used.
Aluminide coating is the most widely used coating at present. It mainly relies on the combination of aluminum and oxygen at high temperature to form a dense alumina film to prevent the diffusion of oxygen, so as to improve the oxidation resistance of materials. However, aluminide coating has poor mechanical properties at high temperature and weak thermal shock resistance, which will cause coating failure under load. Platinum-modified aluminide coating has been proved to improve the adhesion between Al2O3 film and matrix, enhance the microstructure stability of the coating, and inhibit the outward diffusion of elements. Platinum can improve the selective formation of oxide film, and generate new oxide layer quickly after the oxide film falls off, that is, it has self-healing function. The doping of platinum can reduce the internal stress and improve the adhesion of oxide film to a certain extent. In addition, the presence of platinum also reduces the enrichment of S element, so the interface between metal layer and oxide layer loses the possibility of producing holes. It has also been reported that platinum can reduce the diffusion rate of matrix elements into the coating, thus reducing the formation of harmful oxides. Many research results show that compared with other modified aluminide coatings, the high-temperature oxidation resistance of platinum-modified aluminide coatings is much better than other coatings.
