Turbine blade thermal barrier coating defect ultrasonic detection ultrasonic transducer and detection method

Abstract

The invention discloses a turbine blade thermal barrier coating defect ultrasonic detection ultrasonic transducer and a detection method, and belongs to the field of array ultrasonic nondestructive detection. The probe mounting surface of the transducer shell is consistent with the surface of the thermal barrier coating of the turbine blade in shape; six pairs of probe cabins are arranged on the transducer shell, each pair of probe cabins comprises a transmitting probe cabin and a receiving probe cabin, the transmitting probe cabins and the receiving probe cabins are distributed in the length direction of the blade, and the six pairs of probe cabins are distributed in the width direction of the blade; the probe cabin penetrates through the transducer shell in the thickness direction of the transducer shell, and an included angle is formed between the probe cabin and a probe mounting surface of the transducer shell; a water immersion ultrasonic probe is arranged in each probe cabin; the six pairs of water immersion ultrasonic probes excite and receive ultrasonic Rayleigh waves propagating along six paths in the coating. According to the array type ultrasonic transmitting-receiving mode, a stable and large-range Rayleigh wave sound field can be formed in the curved surface thermal barrier coating, and the detection capacity and the detection efficiency can be effectively improved.

Description

Technical Field

[0001] The present invention mainly relates to the field of array ultrasonic nondestructive testing, and in particular to an ultrasonic transducer and a detection method for ultrasonic detection of defects in thermal barrier coatings of turbine blades. Background Art

[0002] Thermal barrier coatings have the advantages of high melting point, low thermal conductivity, good corrosion resistance, etc., and play an excellent role in thermal insulation and protection for the substrate. At present, they are widely used in the field of aerospace thermal protection. Aircraft engine turbine blades are key components of modern engines. Because turbine blades are in a high temperature and high pressure working environment for a long time, thermal barrier coatings are very likely to fail and be damaged under the action of alternating loads and thermal stress. The failure forms of thermal barrier coatings mainly include surface cracks of the ceramic layer, debonding between the ceramic layer and the bonding layer, etc. Therefore, efficient non-destructive testing technology is particularly important for turbine blades containing thermal barrier coatings during product delivery and service maintenance. However, traditional ultrasonic testing methods are limited by the detection blind area, and it is difficult to detect tiny crack defects in thermal barrier coatings of turbine blades; the complex curved surface structure of turbine blades also causes problems such as difficult acoustic coupling, poor stability, and low efficiency of ultrasonic testing. Summary of the invention

[0003] In view of the problems that existing ultrasonic detection technology is difficult to detect surface tiny crack defects and is affected by complex curved surface structures, resulting in difficult acoustic coupling, poor stability and low efficiency, the present invention discloses an ultrasonic transducer and detection method for ultrasonic detection of defects in thermal barrier coatings of turbine blades. By exciting ultrasonic Rayleigh waves in the blade coating, high-precision, high-efficiency and high-reliability detection of the blade coating can be achieved, which has important engineering significance for improving the quality control capability of the blade thermal barrier coating.

[0004] The present invention provides an ultrasonic transducer and a detection method for ultrasonic detection of defects in thermal barrier coatings of turbine blades, which can detect micro cracks with a length of 500 μm, a depth of 80 μm, and a groove width of 20 μm in the coating.

[0005] The technical solution is as follows:

[0006] In a first aspect, an ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades is provided, comprising a transducer housing, wherein a probe mounting surface of the transducer housing is consistent with a surface shape of the thermal barrier coating of the turbine blade;

[0007] The transducer housing is provided with six pairs of probe cabins, each pair of probe cabins includes a transmitting probe cabin and a receiving probe cabin, the transmitting probe cabin and the receiving probe cabin are distributed along the length direction of the blade, i.e. longitudinally, and the six pairs of probe cabins are distributed along the width direction of the blade, i.e. transversely; the probe cabins penetrate the transducer housing in the thickness direction of the transducer housing, and an angle is provided between the probe cabins and the probe mounting surface of the transducer housing; and a gap is left between adjacent probe cabins;

[0008] Each probe cabin is equipped with a water immersion ultrasonic probe;

[0009] Six pairs of immersion ultrasonic probes excite and receive ultrasonic Rayleigh waves propagating along six paths in the coating;

[0010] The front end of the immersion ultrasonic probe is 10 mm away from the detection surface.

[0011] Six pairs of immersion ultrasonic probes are installed in the probe cabin in the transducer housing at a certain angle and interval, and the front end of the probe is 10 mm away from the detection surface.

[0012] Six pairs of immersion ultrasonic probes excite and receive ultrasonic Rayleigh waves propagating along six paths in the coating. The probe center frequency is 4 MHz and the probe housing diameter is 4 mm.

[0013] The diameter of the probe cabin is 4.2mm, the angle between the probe cabin and the probe mounting surface of the transducer housing is 35°, the longitudinal spacing between the transmitting probe cabin and the receiving probe cabin in each pair of probe cabins is 28mm, and the lateral spacing between two adjacent sets of probe cabins is 5mm.

[0014] In a second aspect, a method for ultrasonic detection of defects in thermal barrier coatings of turbine blades is provided. The method is implemented by exciting and receiving ultrasonic Rayleigh waves in the blades according to an ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades. The method comprises:

[0015] (1) The probe mounting surface of the ultrasonic transducer for ultrasonic detection of thermal barrier coating defects on turbine blades is fitted to the surface of the blade, and both are immersed in water;

[0016] (2) six pairs of water-immersed ultrasonic probes are excited by ultrasonic pulse transmitting and receiving transducers to excite ultrasonic Rayleigh waves that propagate along six paths along the length of the blade;

[0017] (3) extracting the amplitudes of the Rayleigh waves propagating along the six paths and forming the distribution of the Rayleigh wave amplitudes in the blade width direction;

[0018] (4) By comparing the Rayleigh wave distribution of the inspected blade with that of the intact blade, it is determined whether the inspected object has coating defects. If the Rayleigh wave amplitude on a certain Rayleigh wave propagation path of the inspected blade is larger than that of the intact blade, it indicates that there is a defect on the path.

[0019] Compared with the prior art, the advantages of the present invention are:

[0020] The ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings on turbine blades has a probe mounting surface that is consistent with the curved surface of the blade coating, which can form a stable acoustic coupling;

[0021] The array-type ultrasonic transmitting-receiving method can form a stable, large-scale Rayleigh wave acoustic field in the curved thermal barrier coating, which can effectively improve the detection accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the present invention;

[0023] Figure 2 It is a schematic diagram of the testing principle of the present invention;

[0024] Figure 3 It is the installation schematic diagram of the present invention;

[0025] Figure 4 It is a schematic diagram of the test state of the present invention;

[0026] Figure 5 This is a schematic diagram of the preparation of a micro-crack specimen of a turbine blade test block in the embodiment;

[0027] Figure 6 The second schematic diagram of the preparation of the micro-crack specimen of the turbine blade test block of the embodiment;

[0028] Figure 7 This is a detection signal diagram of path 1 of the embodiment;

[0029] Figure 8 This is a detection signal diagram of path 2 of the embodiment;

[0030] Fig. 9 It is a detection signal diagram of path 3 of the embodiment;

[0031] Fig.10 This is a detection signal diagram of path 4 of the embodiment;

[0032] Fig.11 This is a detection signal diagram of path 5 of the embodiment;

[0033] Fig.12 It is a detection signal diagram of path 6 of the embodiment;

[0034] Fig.13 4 is a distribution diagram of the amplitude of the Rayleigh wave detection signal of the embodiment. DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0036] Ultrasonic detection of defects in thermal barrier coatings on turbine blades Ultrasonic transducers, such as Figure 1 As shown, it includes a transducer housing 1 and six pairs of immersion ultrasonic probes 2 .

[0037] Six pairs of immersion ultrasonic probes 2 are installed in the probe compartment 11 in the transducer housing 1 at a certain angle and a certain interval, and the front end of the probe is 10 mm away from the detection surface.

[0038] Six pairs of immersion ultrasonic probes 2 excite and receive ultrasonic Rayleigh waves propagating along six paths in the coating, such as Figure 2 The ultrasonic wave is incident on the detection surface through the water coupling medium in the transmitting probe cabin 11 to generate Rayleigh waves. After the Rayleigh waves propagate a certain distance, they are received by the probe through the water coupling medium in the receiving probe cabin 11. The probe center frequency is 4MHz and the probe shell diameter is 4mm.

[0039] The probe mounting surface 12 of the transducer housing 1 is consistent with the curved surface of the thermal barrier coating of the turbine blade. Figure 3 As shown in the figure, it can fit completely with the blade during testing to ensure stable acoustic coupling.

[0040] The probe cabin 11 has a diameter of 4.2 mm and penetrates the transducer housing 1 in the thickness direction. The angle between the probe cabin 11 and the probe mounting surface 12 of the transducer housing 1 is 35°. There are six pairs of probe cabins 11. Each pair of probe cabins 11 includes a transmitting probe cabin and a receiving probe cabin. The transmitting probe cabin and the receiving probe cabin are distributed along the length direction of the blade, i.e., longitudinally. The six pairs of probe cabins 11 are distributed along the width direction of the blade, i.e., transversely. The longitudinal spacing between the transmitting probe cabin and the receiving probe cabin in each pair of probe cabins is 28 mm, and the transverse spacing between two adjacent sets of probe cabins is 5 mm.

[0041] This embodiment also provides an ultrasonic method for detecting defects in thermal barrier coatings on turbine blades. The detection process is as follows: Figure 4 As shown, the following steps are included:

[0042] (1) A probe mounting surface (12) of an ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades is fitted to the surface of the blade, and both are immersed in water;

[0043] (2) six pairs of water-immersed ultrasonic probes are excited by ultrasonic pulse transmitting and receiving transducers to excite ultrasonic Rayleigh waves that propagate along six paths along the length of the blade;

[0044] (3) extracting the amplitudes of the Rayleigh waves propagating along the six paths and forming the distribution of the Rayleigh wave amplitudes in the blade width direction;

[0045] (4) By comparing the Rayleigh wave distribution of the inspected blade with that of the intact blade, it is determined whether the inspected object has coating defects. If the Rayleigh wave amplitude on a certain Rayleigh wave propagation path of the inspected blade is larger than that of the intact blade, it indicates that there is a defect on the path.

[0046] The test specimens of this embodiment are a turbine blade specimen 1 with intact coating and two turbine blade specimens 2 and 3 with microcrack defects. Two narrow grooves were prepared perpendicular to the surface of the thermal barrier coating of the blade by electrospark machining, with the dimensions of 500 μm in length, 80 μm in depth and 20 μm in width. A narrow groove 10 mm away from the blade edge was prepared on specimen 2, and two narrow grooves 10 mm and 15 mm away from the blade edge were prepared on specimen 3. The length direction of the narrow groove was perpendicular to the length direction of the blade, as shown in FIG. Figure 5 and Figure 6 shown.

[0047] Ultrasonic Rayleigh wave detection signals of six scanning paths on intact blade coating and samples with microcrack defects, such as Figures 7 to 12 As shown. The time it takes for the ultrasonic wave emitted by the water-immersion ultrasonic probe to reach the receiving probe through the water coupling medium, coating, and water coupling medium in the transmitting probe cabin is t:

[0048]

[0049] Where: L is the Rayleigh wave propagation distance; H is the water distance in the probe cabin; C1 is the Rayleigh wave speed of the thermal barrier coating; C2 is the longitudinal wave speed in water. The Rayleigh wave propagation distance is 28 mm, the water distance in the probe cabin is 10 mm, the Rayleigh wave speed of the thermal barrier coating is 2400 m / s, and the longitudinal wave speed in water is 1480 m / s. Substituting into formula (1), the theoretical Rayleigh wave signal reception time is 25.18 μs. The average peak reception time of the detection signal of the measured paths 1-6 is 25.62 μs, which is basically consistent with the theoretical result. Therefore, the received signal is the Rayleigh wave signal transmitted by the transmitting probe through the blade.

[0050] Comparison of the amplitude distribution of ultrasonic Rayleigh wave detection signals of intact blade coating and samples with microcrack defects Fig.13 As shown in the figure, narrow grooves are processed on path 2 of sample 2 and paths 2 and 3 of sample 3, and the amplitude of the Rayleigh wave detection signal on the path is significantly increased; the signal amplitudes at paths 2 and 3 of intact sample 1 are 255mV and 605mV respectively, and the amplitude of the Rayleigh wave signal on path 2 of sample 2 is 295mV, with an increase of 40mV; the amplitude of the Rayleigh wave signal on paths 2 and 3 of sample 3 is 303mV and 680mV, with an increase of 48mV and 75mV respectively, and the signal amplitude of the path without microcrack defects does not change much. Coating defects can be detected based on the change of Rayleigh wave amplitude, and the detection sensitivity reaches 500μm (length), 80μm (depth), and 20μm (width) surface narrow groove sizes.

Claims

1. Ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades, characterized in that: It includes a transducer housing, wherein a probe mounting surface of the transducer housing is consistent with a surface shape of a thermal barrier coating of a turbine blade; The transducer housing is provided with six pairs of probe cabins, each pair of probe cabins includes a transmitting probe cabin and a receiving probe cabin, the transmitting probe cabin and the receiving probe cabin are distributed along the length direction of the blade, i.e. longitudinally, and the six pairs of probe cabins are distributed along the width direction of the blade, i.e. transversely; the probe cabins penetrate the transducer housing in the thickness direction of the transducer housing, and an angle is provided between the probe cabins and the probe mounting surface of the transducer housing; and a gap is left between adjacent probe cabins; Each probe cabin is equipped with a water immersion ultrasonic probe; Six pairs of immersion ultrasonic probes excite and receive ultrasonic Rayleigh waves propagating along six paths in the coating; The front end of the immersion ultrasonic probe is 10 mm away from the detection surface.

2. The ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades according to claim 1, characterized in that: The center frequency of the six pairs of immersion ultrasonic probes is 4 MHz and the probe shell diameter is 4 mm.

3. The ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades according to claim 1, characterized in that: The diameter of the probe cabin is 4.2mm, the angle between the probe cabin and the probe mounting surface of the transducer housing is 35°, and each pair of probe cabins is relatively inclined outward; the longitudinal spacing between the transmitting probe cabin and the receiving probe cabin in each pair of probe cabins is 28mm, and the lateral spacing between two adjacent sets of probe cabins is 5mm.

4. Ultrasonic detection method for defects in thermal barrier coatings of turbine blades, characterized in that: The method is implemented by using the ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades according to any one of claims 1 to 3 to excite and receive ultrasonic Rayleigh waves in the blade, the method comprising: (1) The installation surface of the ultrasonic transducer for ultrasonic detection of defects in thermal barrier coatings of turbine blades is fitted to the surface of the blade, and both are immersed in water; (2) six pairs of water-immersed ultrasonic probes are excited by ultrasonic pulse transmitting and receiving transducers to excite ultrasonic Rayleigh waves that propagate along six paths along the length of the blade; (3) extracting the amplitudes of the Rayleigh waves propagating along the six paths and forming the distribution of the Rayleigh wave amplitudes in the blade width direction; (4) By comparing the Rayleigh wave distribution of the inspected blade with that of an intact blade, it is determined whether the inspected object has coating defects; If the Rayleigh wave amplitude on the Rayleigh wave propagation path of the inspected blade is larger than the Rayleigh wave amplitude on the same path of the intact blade, it indicates that there is a defect on the path.

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