Research On NiCoCrAlYTa Hexabasic Coating Defects By Infrared Thermal Wave Detection

NiCoCrAlYTa hexabasic coating has excellent oxidation resistance, heat corrosion resistance, as well as good plasticity and ductility, and it has been widely used in aeroengine hot-end components. Coating thickness, thickness non-uniform and debonding are directly related to the areoengine hot-end components whether to work effective. Currently, the methods of coating detection methods are eddy current non-destructive testing and electromagnetic nondestructive testing, but both of the methods are not suitable for Ni Co Cr AlYTa hexabasic coating. So now using metallographic test method detects the NiCoCrAlYTa hexabasic coating, however the metallographic test results can’t reflect all the coating blocks’ conditiong completely.In this paper, NiCoCrAlYTa hexabasic coating specimens were studied through simulation and experiment by pulsed infrared thermal wave nondestructive testing. In simulation part, they were simulated that Ni CoCr AlYTa hexabasic coating thickness uneven and debonding defects by ANSYS finite element analysis software, and the defects’ effects on coating surface temperature signals were analyzed. This paper also investigated the effects of pulse energy and thermal excitation time on surface temprerature field, as well as sampling frequence and sampling time. In experiment part, the pulse of infrared thermal wave nondestructive testing system was set up. EvaluatIons were carried out using standard deviation to characterize the heat source temperature field uniformity. The best thermal excitation and relationship between coating thickness and standard deviation were also explored. Last, thickness uniformity of coating different regions were evaluated, and the effects of thermal excitation time on surface temperature field is validated.The results indicated that the type of defects can be judged by tempreture time history curves. When the coating thickness is certain, the more serious the defects are, in other words the greeter of degree of thickeness non-uniform and debonding is, the greater of the maximum temperature difference and the maximum contrast are between defects regions and normal regions. When the defects is certain, the lager the coating thickness is, the maximum temperature difference and the maximum contrast are smaller. At the same time, it was also found that when thermal excitation energy increase, the maximum temperature difference and maximum contrast would become lager. When prolonging thermal excitation time, the maximum temperature difference will be increased, but the maximum contrast will be reduced. The standard deviation of temperature field is proposed as a quantitative indicator, which judge the degeer of coating thickness non-uniform and debongding. The function between thickness of coating and the corresponding standard deviation of temperature field was obtained by polynomial fitting.These findings have a certain significance in further improving the detection of coating thickness, thickness non-uniformity and debonding defects.