Qualification of a Frequency Scanning Eddy Current Equipment for Nondestructive Characterization of New and Serviced High-Temperature Coatings

2001 ◽  
Author(s):  
Giampiero Antonelli ◽  
Paola Crisafulli ◽  
Giacomo Tirone
Keyword(s):  
High Temperature ◽  
Eddy Current ◽  
Gas Turbines ◽  
Structural Damage ◽  
Economic Losses ◽  
Thermal Barriers ◽  
Frequency Scanning ◽  
Non Destructive ◽  
Equipment Qualification

As modern gas turbines are continuously being upgraded, mainly through the increase of their firing temperature and cooling optimization, the prime protection of the high technology and high-cost hot gas path parts is increasingly being transferred to the coatings. In order to avoid the risk of structural damage of these components, with its potential for greater economic losses — mostly traceable to unexpected prime time outages — refurbishment cycle should be dictated by the amount of the life actually expended by the coating. To address the issues of quality and condition assessment of new and serviced high-temperature coatings applied on buckets and vanes, an innovative non-destructive system was developed based on a frequency scanning eddy current technique. It combines outstanding high frequency hardware with model based analysis of raw data. In the paper, quantitative data on equipment qualification are presented, relating to its capability in measuring both the thickness and β-aluminide depletion of MCrAlY coatings applied on Ni-base superalloys. The results of an inspection campaign on serviced blades, performed during major overhauls of ENEL gas turbines, will also be reported, together with recent system upgrades, aiming at extending its applicability to newer coatings such as thermal barriers and over-aluminized MCrAlY’s.

Thickness Measurement of MCrAlY High-Temperature Coatings by Frequency Scanning Eddy Current Technique

1997 ◽  
Author(s):  
Giampiero Antonelli ◽  
Marco Ruzzier ◽  
Fiorenzo Necci
Keyword(s):  
Quality Control ◽  
High Temperature ◽  
Eddy Current ◽  
Coating Thickness ◽  
Gas Turbines ◽  
Plane Electromagnetic Wave ◽  
Vacuum Plasma Spray ◽  
Frequency Scanning ◽  
Current Technique ◽  
Electrical Conductivities

Nondestructive characterization of non-serviced high-temperature coatings can be considered one of the important factors to achieve a higher level of structural integrity of advanced gas turbines. The present paper describes an innovative eddy current technique especially developed for measuring the thickness of metallic (MCrAlY) coatings applied by vacuum plasma spray on Ni-base superalloys. Conventional eddy current techniques, well established for quality control of coating thickness, are not applicable in this case because of the low difference of electrical conductivities of conting and base materials, which is a consequence of their quite similar physical and chemical properties. The new technique employs fast frequency scanning of the electromagnetic field in the range 100 kHz – 10 MHz, corresponding to probing depths from 1 mm to 0.1 mm. Dedicated hardware has been developed, featuring high sensitivity, stability and harmonic rejection. Analysis of the measured data (i.e. probe impedance vs frequency), in order to estimate the relevant diagnostic parameters (coating thickness, coating and base metal electrical conductivities), is carried out on the basis of a theoretical model of interaction between a plane electromagnetic wave and test piece. The results of tests performed on a non-serviced first stage blade are reported and compared with reference destructive data. Reliability, accuracy and practical applicability of the method meets the requirements for in-shop quality control.

Thickness Measurement of MCrAlY High-Temperature Coatings by Frequency Scanning Eddy Current Technique

1998 ◽  
Vol 120 (3) ◽  
pp. 537-542 ◽  
Author(s):  
G. Antonelli ◽  
M. Ruzzier ◽  
F. Necci
Keyword(s):  
Quality Control ◽  
High Temperature ◽  
Eddy Current ◽  
Coating Thickness ◽  
Gas Turbines ◽  
Plane Electromagnetic Wave ◽  
Vacuum Plasma Spray ◽  
Frequency Scanning ◽  
Current Technique ◽  
Electrical Conductivities

Nondestructive characterization of nonserviced, high-temperature coatings can be considered one of the important factors to achieve a higher level of structural integrity of advanced gas turbines. The present paper describes an innovative eddy current technique especially developed for measuring the thickness of metallic (MCrAlY) coatings applied by vacuum plasma spray on Ni-base superalloys. Conventional eddy current techniques, well established for quality control of coating thickness, are not applicable in this case because of the low differences of electrical conductivities of coating and base materials, which is a consequence of their quite similar physical and chemical properties. The new technique employs fast frequency scanning of the electromagnetic field in the range 100 kHz–10 MHz, corresponding to probing depths from 1 mm to 0.1 mm. Dedicated hardware has been developed featuring high sensitivity, stability, and harmonic rejection. Analysis of the measured data (i.e., probe impedance versus frequency), in order to estimate the relevant diagnostic parameters (coating thickness, coating, and base metal electrical conductivities), is carried out on the basis of a theoretical model of interaction between a plane electromagnetic wave and test piece. The results of tests performed on a nonserviced first stage blade are reported and compared with reference destructive data. Reliability, accuracy and practical applicability of the method meets the requirements for in-shop quality control.

Study of Damage Processes in Plasma Sprayed Bond Coat Under Thermal Cycling

1998 ◽  
Author(s):  
P. Bonnet ◽  
S. Abboudl ◽  
B. Normand
Keyword(s):  
High Temperature ◽  
Thermal Cycling ◽  
Bond Coat ◽  
Gas Turbines ◽  
Temperature Oxidation ◽  
Bond Coating ◽  
Engine Efficiency ◽  
Thermal Barriers ◽  
Plasma Sprayed ◽  
Damage Processes

Abstract Plasma sprayed thermal barriers are used as insulating materials in the hot sections of gas turbines to decrease the metal temperatures during service and men allow a higher combustion temperature for better engine efficiency. They usually contain a bond coating to protect the substrate from high temperature oxidation and a top coat with a low thermal conductivity. This study evaluate and identify the mechanisms of degradation of a vacuum plasma sprayed NiCoCrAlYTa bond coat subjected to thermal cycling at high temperature. The microstructure and micro-composition of the coating layer were analyzed by scanning electron microscopy and energy dispersive X-ray analysis to elucidate the improvement and degradation mechanisms of the material. The thermal cycling provokes some morphological and chemical modifications changes within this material. These modifications provoke a perturbation of the heat transfer within the material.

Eddy current technique with high temperature SQUID for non-destructive evaluation of non-magnetic metallic structures

Cryogenics ◽  
1996 ◽  
Vol 36 (2) ◽  
pp. 83-86 ◽  
Author(s):  
Y. Tavrin ◽  
H.-J. Krause ◽  
W. Wolf ◽  
V. Glyantsev ◽  
J. Schubert ◽  
...  
Keyword(s):  
High Temperature ◽  
Eddy Current ◽  
Metallic Structures ◽  
Non Destructive Evaluation ◽  
Current Technique ◽  
Non Destructive

Characterization of the Wear in the Turbojet Fins

2015 ◽  
Vol 640 ◽  
pp. 29-34
Author(s):  
Zohra Labed ◽  
Djamel Guechi ◽  
Necib Brahim
Keyword(s):  
Fatigue Damage ◽  
Eddy Current ◽  
Non Destructive ◽  
Non Destructive Techniques

The wear is very difficult to characterize because of its complexity and its measurement phenomenon. Our work is to prepare samples Fan blades, worn, to determine the nature of the wear and damage them. For these reasons, the characterization of these samples was conducted in different microscopic and macroscopic scales. We used non-destructive techniques such as eddy current and penetrant methods. The results obtained allowed us to see the deterioration of fins from one floor to another. These results are directly related to the effects of mechanical, thermal and pressure. It has been, in addition to detecting a different type of damage these fan blades that is the fatigue damage.

scholarly journals CHARACTERIZATION OF CEMENT-BASED COMPOSITE EXPOSED TO HIGH TEMPERATURES VIA ULTRASONIC PULSE METHOD

2018 ◽  
Vol 15 ◽  
pp. 99-103 ◽  
Author(s):  
Iva Rozsypalová ◽  
Michal Vyhlídal ◽  
Richard Dvořák ◽  
Tomáš Majda ◽  
Libor Topolář ◽  
...  
Keyword(s):  
Compressive Strength ◽  
High Temperature ◽  
Ambient Temperature ◽  
High Temperatures ◽  
Pulse Method ◽  
Ultrasonic Pulse ◽  
Measured Data ◽  
Experimental Programme ◽  
Non Destructive

In this paper, the attention is paid to the investigation of the influence of high temperature acting on specimens made from specially designed cement-based composite. The experimental programme was carried out on six sets of beam specimens with the dimensions of 20 × 40 × 200 mm. The specimens were loaded to a pre-set temperature of 100, 200, 400, 600, 800 and 1000 °C and then the temperature was kept for 60 minutes. When the temperature loading had been done, the specimens were left to cool down to the ambient temperature. After that, the ultrasonic pulse method was used to determine the degree of damage of temperature loaded specimens. The measured data obtained by this non-destructive method are in high correlation with values of informative compressive strength of the composite obtained after the temperature loading of specimens.

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