Electron microscopy examines reactor steels
2
-New equipment Electron microscopy examines reactor steels Metallurgists at AEA Thermal Reactor Services' Harwell Laboratories have developed electron microscopy techniques which identify the extent of embrittlement in reactor steels, one of the life-limiting ageing processes of reactor pressure vessels. Owing to the combined effects of heat and neutron irradiation, embrittlement can result from the precipitation of minute amounts of copper already present in reactor pressure vessel steel. Copper precipitates have a crystal lattice structure and can exist in two forms: face-centred cubic (FCC) and body-centred cubic (BCC). The new work reveals the locations and proportions of these forms in the steel and this provides information on mechanisms of embrittlement. Copper has been shown to exist as innocuous FCC precipitates formed during the original manufacturing process, and also as new BCC precipitates produced by neutron irradiation. The BCC precipitates cause embrittlement because they pin dislocations in the steel and reduce its ductility. Irradiated alloys, including steels, have been studied for many years' with electron microscopes and this has gradually increased the understanding of their behaviour. AEA Thermal Reactor Services have been able to identify the small BCC copper precipitates, which range in size up to 2 nm in diameter, by using a state-of-the-art electron microscope - a field emission gun scanning transmission electron microscope ( FEGSTEM ). This machine provides a finely focused electron beam some 1 to 2 nm in diameter which is capable of generating X-rays from extremely small volumes of material. However, the emission of X-rays as a radioactive decay product can in some cases limit the resolution obtainable with standard energy dispersive X-ray detectors used in the microchemical investigations. Novel and proprietary sample preparation techniques have been developed to produce specimens small enough to reduce dramatically the number of unwanted and misleading by-product X-rays emitted but of a size suitable to exploit the FEGSTEM's full potential. This approach has been successfully used to examine for signs of copper precipitation in materials obtained from in-service reactors by remote milling. The ability to perform this type of analysis on such material has made assessment of the degree of pressure vessel embrittlement possible, even in circumstances where little was known of the start-of-life condition. Excellence in NDT through a Tradition of Innovation and Expertise We design and manufacture the world's most advanced AE instrumentation. Maintaining this position requires constant product improvements and new applications of AE technology. We've applied this knowledge to traditional NDT - eddy current, ultrasonics, and resistivity. Acoustic emission: LOCAN 320 is highly sophisticated for aging aircraft, composite, and petrochemicalvessel testing. Ultrasonics: UltraPac II is the low cost, modular, PC-based, digital, C-Scan system. Resistivity: M100 and M200 Eddy Current: SmartEDDY 2.0 measurecracksand case depth, and detect for high and magEDDYfor low frequency spot weld quality. PC-based systems. Contact your area rep or PAC's corporate sales staff today for information on the latest in NDT instrumentation. Euro ~ n t ~ Acom~ t'raa= ~ P~'~ YSICAL Phone: 33-14-356-2210 FAX:33-1-43-56-6565 Ntppm phy~tc~Acome~, J~pea ACOOSrlCS pho.e: 81-3-3498-3570 FAX:81-3-3498-8450 PAC/Rocklmd Sc/mtl/'tc C_~sbH, Germany CORPOFtATION Phone" 49-6182-32-72 FAX-49-6182-32-71 USA Phone: 609896-2255FAX: 609895-9726 Phone: 44-954-31612 FAX: 44-954-31102 NDT International February 1991 57
Transcript of Electron microscopy examines reactor steels
-New equipment Electron microscopy examines reactor steels
Metallurgists at AEA Thermal Reactor Services' Harwell Laboratories have developed electron microscopy techniques which identify the extent of embrittlement in reactor steels, one of the life-limiting ageing processes of reactor pressure vessels. Owing to the combined effects of heat and neutron irradiation, embrittlement can result from the precipitation of minute amounts of copper already present in reactor pressure vessel steel.
Copper precipitates have a crystal lattice structure and can exist in two forms: face-centred cubic (FCC) and body-centred cubic (BCC). The new work reveals the locations and proportions of these forms in the steel and this provides information on mechanisms of embrittlement.
Copper has been shown to exist as innocuous FCC precipitates formed during the original manufacturing process, and also as new BCC precipitates produced by neutron irradiation. The BCC precipitates cause embrittlement because they pin dislocations in the steel and reduce its ductility.
Irradiated alloys, including steels, have been studied for many years' with electron microscopes and this has gradually increased the understanding of their behaviour. AEA Thermal Reactor Services have been able to identify the small BCC copper precipitates, which range in size up to 2 nm in diameter, by using a state-of-the-art electron microscope - a field emission gun scanning transmission electron microscope ( FEGSTEM ). This machine provides a finely focused electron beam some 1 to 2 nm in diameter which is capable of generating X-rays from extremely small volumes of material.
However, the emission of X-rays as a radioactive decay product
can in some cases limit the resolution obtainable with standard energy dispersive X-ray detectors used in the microchemical investigations. Novel and proprietary sample preparation techniques have been developed to produce specimens small enough to reduce dramatically the number of unwanted and misleading by-product X-rays emitted but of
a size suitable to exploit the FEGSTEM's full potential.
This approach has been successfully used to examine for signs of copper precipitation in materials obtained from in-service reactors by remote milling. The ability to perform this type of analysis on such material has made assessment of the degree of pressure vessel embrittlement possible, even in circumstances where little was known of the start-of-life condition.
Excellence in NDT through a Tradition of Innovation and Expertise
We design and manufacture the world's most advanced AE instrumentation. Maintaining this position
requires constant product improvements and new applications of AE technology. We've applied this knowledge to
traditional NDT - eddy current, ultrasonics, and resistivity.
Acoustic emission: LOCAN 320 is highly sophisticated for aging aircraft,
composite, and petrochemical vessel testing.
Ultrasonics: UltraPac II is the low cost, modular, PC-based, digital,
C-Scan system.
Resistivity: M100 and M200 Eddy Current: SmartEDDY 2.0 measure cracks and case depth, and detect for high and magEDDY for low frequency
spot weld quality. PC-based systems.
Contact your area rep or PAC's corporate sales staff today for information on the latest in NDT instrumentation.
Euro ~ n t ~ A c o m ~ t'raa= ~ P~'~ Y S I C A L Phone: 33-14-356-2210 FAX: 33-1-43-56-6565
Ntppm phy~tc~ Acome~, J~pea ACOOSrlCS pho.e: 81-3-3498-3570 FAX: 81-3-3498-8450
PAC/Rocklmd Sc/mtl/'tc C_~sbH, Germany CORPOFtATION Phone" 49-6182-32-72 FAX-49-6182-32-71
USA Phone: 609 896-2255 FAX: 609 895-9726 Phone: 44-954-31612 FAX: 44-954-31102
NDT International February 1991 57
-New equipmen This new knowledge should make it possible to assess the extent to which reactor steels degrade in use, by making comparisons between samples taken at different times and with unirradiated steel, giving station owners a realistic idea of how much longer they can be kept in service. Furthermore, the development of truly micromechanistic models of embrittlement will make it possible to go outside the existing database, enabling plant operators to assess embrittlement and monitor the success of any alleviation strategy employed, such as pressure vessel annealing.
AEA Thermal Reactor Services, Risley, Warrington, Cheshire WA3 6A T, UK
Automat ic hardness testing for disc brake rotors
Disc brake rotors can be checked for proper hardness at 800 parts per hour using a Brinell hardness tester from K. J. Law Engineers.
The Model 26267 uses two Brinell test heads to inspect two rotors at once. This allows the part manufacturer to double production speed while reducing the labour intensity of the test operation.
The heart of the system is the Model 8700 Verimatic microprocessor. It controls the test sequence and converts the test results into Brinell numbers or indentation diameters for digital display. Specific features include automatic calibration and standardized interfacing for statistical process control.
In operation, rotors are fed into the machine hat side up and metered two at a time into the test station for hardness testing. The test heads descend, contact the parts and perform the test. Repeatable accuracy is _+ 0.02 mm or better. As rotors leave the machine they are
Automatic Brinell hardness tester from K. J, Law
stamped and segregated into two categories based on pre-selected accept/reject limits.
K. J. Law Engineers Inc, 42300 W. Nine Mile Road, Novi, Michigan 48050-3627, USA
Eddy current tester for aircraft maintenance
Sophisticated eddy-current test technology and state-of-the-art computer technology are combined in the new Defectoscop AF from Forster. The device meets the stringent requirements imposed by the
aircraft maintenance industry.
The test equipment is easy to use, with a menu-based interactive operation and a 127 mm CRT monitor. A dialogue is built-up between the tester and the machine which constantly indicates all the main settings for the tester's information. More than 100 complete machine settings can be stored internally or on a memory card. The machine automatically retrieves the stored values if a test has to be repeated.
The internal signal memory can be used to save test signals for later use as reference signals, for example, or for documentation of the test results.
A frequency range from 100 Hz to 10 MHz offers a wide range of applications: crack testing on and below the material surface, crack testing in rivet holes, corrosion detection, indication of thermal damage, material identification, layer thickness measurement and thickness measurement.
The instrument can be used for static and dynamic testing. Scanning and rotating probes of all types can be connected. The built-in RS 232 interface also ensures that it can be connected to a higher-level host computer.
Institut Dr. Forster, GmbH & Co. KG, In Laisen 70, Postfach 1564, D-7410 Reutlingen, Germany
Microprocessor-based eddy current tester from Forster for use in aircraft maintenance
58 NDT International February 1991
