Ultra High Temperature Hot Corrosion Behavior Of Al-Re Coating In Different Mediums And Its Modified Exploration

With the development trend of advanced gas turbine engine "high thrust" and "big push weight ratio",The service temperature of the aerial engine hot end components continues to rise,Which is bound to put forward higher requirements for the thermal barrier coating metal bonding layer protecting aircraft engine hot end parts from thermal oxidation corrosion.Al-Re coating,is a thermal barrier coating capable of generating a metal barrier layer that still has good stability at very high temperatures.However,its mechanism is relatively weak.In this paper,the preparation and organizational properties of Al-Re coating is the basis,the ultrahigh temperature thermal corrosion behavior and mechanism of Al-Re coating in three different corrosive medias?75%Na₂SO₄+25% K2SO₄?75%Na₂SO₄+25%Na Cl?40%Na₂SO₄+60%V₂O₅?at 1050? were systematically studied,so as to provide a theoretical basis for the development of new anti-ultra-high temperature oxidation corrosion metal bonding layer.Simultaneously,we attempt to introduce nano-SiC particles into aluminum rare earth coatings by laser fusion technique,and then to develop new anti-ultra-high temperature oxidation of metal bonding layer to provide technical support.The major work and the results obtained are as follows:?1?Studied the preparation and micro-structure of Al-Re coating on the surface of Ni-based super-alloy.In the study,we make nano-CeO2 as a rare earth components,use solid powder embedding method preparing Al-Re coating on the surface of nickel-based super-alloy GH4033,the optimal formulation of penetrant and the aluminizing process parameters were obtained by orthogonal experiment,analyzing the micro-structure of the prepared Al-Re coating.Research shows that:Under the experimental conditions in this paper,optimal formulation of penetrant is 3wt.%NH4Cl?9wt.%CeO2?45wt.% Al and 43 wt.% Al2O3.The heat treatment process was carried out at 850 ? for 10 h and then kept at 1000 ? for 2 h.The Al-Re coating prepared by the above-mentioned infiltration and infiltration process is uniform,compact and has a thickness of about 250?m,and it consists mainly of Ni-Al phase and Ni2Al3 phase.?2?The thermal corrosion behavior of Al-Re coating in 75% Na₂SO₄+25% K2SO₄ at 1050?was studied.Research shows that:Al-Re coating encountered severe thermal corrosion under experimental condition,mainly in the performance of requiring longer time?about 30 hours?for the Al-Re coating to enter the steady state oxidation and the maintenance time is extremely short?30-60h?.Analysis that,in the ultra-high temperature experimental condition,molten salt has a stronger melting effect,can melt the protective alumina film forming on the surface of Al-Re coating quickly,increasing the failure rate of coating.With the continuous consumption of protective Al element in Al-Re coating,when the content of aluminum in the coating is lowerthan that of the protective alumina film to form the desired antioxidant element threshold,coating protective effect weakened,the coating gradually failed.?3?The thermal corrosion behavior of Al-Re coating in 75%Na₂SO₄+25%Na Cl at 1050?was studied.Research shows that:It is difficult for to form Al-Re coating to form protective alumina film at the initial stage of thermal corrosion at 1050? in chlorosulfate,the coating is in a steady-state oxidation stage only for greater than 10 h to 30 h,and the subsequent 50 hours it is always in a rapid weight gain state.When hot corrosion is carried out for 50 hours,the coating has almost no continuous oxide film and more serious internal oxidation corrosion occurred,at this point the coating has tended to fail completely.Na Cl in Chlorine Sulfate,not only caused it difficult to form protective alumina film on the surface of Al-Re coating in the early hot corrosion period,but also induced the overall exfoliation of the protective alumina film after the Al-Re coating was introduced shortly after steady state oxidation,the experimental temperature of ultra-high temperature further exacerbates the effect of chlorine from chlorosulfate in the damage of oxide film on the fur-face of Al-Re coating.?4?The thermal corrosion behavior of Al-Re coating in 40%Na₂SO₄+60%V₂O₅ at 1050 ?was studied.Research shows that:during the hot corrosion process,a thin layer of protective alumina film is contained on the surface of the Al-Re coating only in 10 h,and then the first 20 hour,the protective alumina film was melted away.When hot corrosion is carried out for 50 hours,most of the coating occurred more severe internal oxidation of vulcanization corrosion,the coating tends to fail.V₂O₅ in the sulfate,not only as a reactant involved in the damage of Al-Re coating,but also acts as a catalyst to accelerate corrosion of the Al-Re coating.At the same time,the experimental temperature of ultra-high temperature further exacerbates the effect of V₂O₅ from mixed salt film in the damage of oxide film on the fur-face of Al-Re coating.?5?Explore the process of laser cladding nano SiC particle modified Al-Re coating and its modified micro-structure.Research shows that:Alcohol mixed water as dispersion medium,with0.25% polyethylene glycol plus 0.25% tetramethylammonium hydroxide as the dispersant,With polyvinyl alcohol as the binder can prepare Na-no silicon carbide slurry with good dispersion stability more capable for using.With the laser process parameters of laser power 180 W,scanning speed 35mm/s,out of focus 20 mm,we can prepare a good laser melting nano SiC particles modified Al-Re coating.After laser melting modifying,the coating structure was significantly refined,the upper tissue presents snowflakes and contains irregularly shaped crystals,the middle is a uniform snowflake crystal,the lower part of the organization change gradually from the snow-like to the dendritic to the round-like crystals.