| Inconel718 superalloy is a Nickel-based superalloy,widely used in high-temperature applications such as aircraft,and land-based and marine turbines.Owing to both Complex composition and chemical properties of active elements,it is easy to oxidize at high temperature.Meantime,it is difficult for them to meet the demand of high temperature oxidation properties in higher temperature,which stimulates the emergence of high temperature protection coating technology.To solve these problems,the NiCoCrAlY alloyed layer were prepared on Inconel718 superalloy surface by doubleglow plasma surface alloying technology.The alloying elements were distributed gradedlyin diffusion layer.So the coating has good performance on binding force.SEM 、EDSand XRD are used to analyze the microstructure,composition and phase structure of the surface,properties like hardness,adherence and high-temperature oxidation resistance also were tested.The optimμm process parameters of NiCoCrAlYalloyed layer were listed as follows: source voltage: 960 V,cathode voltage: 405 V,air pressure: 40 Pa,holding time:3.5h.The NiCoCrAlYwith a 5μm-diffusion layer showed the excellent properties of bonding、Hardness and strength.A simple scale consisting of continuous outer layer Cr2O3 and thinner inner layer Al2O3 is produced at 750℃ in NiCoCrAlY coating,which Stops diffusion of O2 into the substrate,its resistance to high temperature oxidation is Excellent.a part of Cr2O3 translates into NiCr2O4 in the outer oxide layer at 850℃,which reduce the adhesion strength of the the outer oxide layer.the shrinkage occurs in the outer oxide at the same time.most of Cr2O3 translates into NiCr2O4 in the outer oxide layer at 950℃,it peels off the outer layer,but the inner oxide film Al2O3 still keeps good shape,alloy layer sample is still better than matrix with oxidation resistance.overall,NiCoCrAlY alloyed layer significantly increases the high temperature oxidation resistance of the IN718 superalloy. |
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