Study On The Interface Diffusion Between DZ22B And NiCrAlCoSi_x Alloy

High temperature protective coating is an important way to make up for the deficiency of high temperature oxidation resistance of superalloy.In view of the mutual diffusion between the high temperature thermal protective coating and the base alloy in the service process,which leads to the degradation of the high temperature mechanical properties of the base and the high temperature oxidation resistance of the coating,the idea of using the high entropy alloy with the sluggish diffusion effect as the high temperature protective coating is put forward.High entropy alloy has excellent mechanical properties,diffusion resistance and high temperature oxidation resistance.It is expected to obtain an economic and efficient thermal barrier coating when it is applied to the thermal barrier coating system as a bonding layer material of thermal barrier coating.The mutual diffusion of interface elements with alloy matrix and the structural stability are the key factors determining the coating life.Therefore,by means of scanning electron microscope,energy spectrum analyzer,X-ray diffractometer and other equipment and instruments,the high-temperature diffusion behavior and microstructure evolution law of coating/matrix alloy interface under vacuum state are studied through the experiment of high-temperature diffusion of diffusion couple between coating and matrix alloy.The main results are as follows:The experimental results show that the as-cast NiCrAlCoSi_x?x=0,0.1,0.2,0.4?high entropy alloys are more developed dendrite structure,and the alloy is mainly composed of BCC?Al Ni?solid solution phase.With the increase of Si content,the growth of dendrites is hindered,and the grains grow uniformly in all directions to form cellular dendrites.Al and Ni elements are mainly enriched in dendrites,Cr and Si elements are mainly enriched in dendrites,and Co elements are evenly distributed.The experimental results of high temperature diffusion couple of coating/base alloy show that the distribution and content of elements in the diffusion layer are different with different diffusion rate.Elements Cr,Co,Al and Si diffuse from the high entropy alloy to the DZ22B matrix,and elements Ni and W diffuse from the DZ22B matrix to the high entropy alloy.After annealing for 30 days,the phase of interdiffusion layer is BCC?Ni Al?+Ni₃Al.After annealing for 40 and 50 days,the phase of the interdiffusion layer becomes??Ni?+Ni₃Al.The growth kinetics of diffusion layer of DZ22B Ni Cr Al Co Si_x?x=0,0.1,0.2,0.4?alloy is also studied.The results show that the thickness of the mutual diffusion layer grows approximately in a straight line with the increase of heat treatment time,and its growth is mainly controlled by the interface reaction.In order to build the database of atom mobility of Ni Cr Al Co Si system high entropy alloy,firstly,two binary systems BCC Cr-X?Co,Si?are selected to calculate the mutual diffusion coefficient.The results show that the mutual diffusion coefficient of two binary systems BCC Cr-X?Co,Si?increases with the increase of temperature,and increases slightly with the increase of element mole fraction.The average value of ???_crcr^co at 1423 K is 1.21×10^-16m²/s,and the average value of ???_crcr^co at 1473 K is 1.86×10^-16m²/s.The average value of ???_crcr^si at 1423 K is 2.07×10^-16m²/s,and the average value of ???_crcr^si at 1473 K is 3.67×10^-16m²/s.