Research on Non-destructive Testing Method of Coating Thickness of Turbine Blade

Abstract

Abstract Turbine blades are an important component of the turbine section of a gas turbine engine. High-temperature blade coating is a key technology for the manufacture of turbine engines, and its complex surface structure is currently lacking an effective non-destructive evaluation method for coating thickness. In this paper, the eddy current field is directly exciting in the substrate metal of the turbine blade coating system to achieve non-destructive detection of the coating thickness and substrate material. The results show that a new method of coating non-destructive testing based on the principle of array induction logging three-coil system is proposed. The shielding coil effectively cancels the direct coupling signal and enhances the signal from the coating and the substrate; when the distance between the transmitting coil and the main receiving coil is 8cm and the scale factor α is about 0.7047, the signal-to-noise ratio is increased by 102 times, and when the scale factor α is about 0.9032, the signal-to-noise ratio is increased by 215 times, the focusing effect is obvious while the scale factor α raises, and the sensitivity is also greatly improved; the receiving array is more than 4cm away from the transmitting coil, reflecting the more obvious change of coating thickness. When the distance between the transmitting coil and the main receiving coil is 4∼9cm, and the scale factor α is about 0.9032, the imaginary part of the measurement signal reflects the coating thickness changes more sensitively, and the real part of the measurement signal reflects substrate material changes more sensitively.