Effect of initial pH and temperature of iron salt solutions on formation of magnetite nanoparticles

The assessment of creep damage in steels employed in the power generation industry is usually carried out by means of replica metallography, but the several shortcomings of this method have prompted a search for alternative or complementary non-destructive techniques, ranging from ultrasonic to electromagnetic methods, hardness measurements and nuclear techniques. A critical review of the main results obtained to date in the secondary and tertiary stages of creep is presented in this paper, and the advantages and disadvantages of each method are discussed. Ultrasonic and potential drop techniques appear to be the most promising, but further research is needed before they are fully mature for deployment in the field.

A review of non-destructive techniques for the detection of creep damage in power plant steels

A review of three magnetic NDT technologies

Magnetic Barkhausen Noise and hysteresis loop in commercial carbon steel : influence of applied tensile stress and grain size

The dependence of Barkhausen noise on elastic and plastic deformations, achieved in tension and in compression, has been investigated both in Armco iron and a low carbon steel These materials exhibit quite different behaviours, especially with regard to the effect of plastic deformation: a tensile plastic deformation (>1%) induces a marked increase in Barkhausen noise for Armco iron while it induces a steep decrease in the low carbon steel The comparison between the tensile and compressive behaviours, as well as between the elastic and plastic regimes of deformation enables us to attribute these effects to two underlying mechanisms, ie effect of residual internal stresses through magneto-elastic coupling and dislocation–domain wall interaction In Armco iron, the latter mechanism seems to have the strongest influence on the Barkhausen noise, while in the low carbon steel the influence of residual internal stresses prevails

On the role of residual internal stresses and dislocations on Barkhausen noise in plastically deformed steel

Microstructural characterization of quenched and tempered 0.2% carbon steel using magnetic Barkhausen noise analysis

Magnetic Barkhausen emission (MBE) has been used to characterize various microstructures in tempered 0.2 wt% C steel, 2.25Cr—1Mo steel and 9Cr—1Mo steel samples (where the composition is in approximate weight per cent). A two-stage process of irreversible magnetic domain wall movement during magnetization is proposed considering the lath or grain boundaries and second-phase precipitates as the two major obstacles to domain-wall movement. The domain walls overcome these two major obstacles over a range of critical field strengths with some mean values, characteristic of the obstacles. If these two mean values are close to each other, then a single peak, sometimes associated with slope changes, appears in the MBE behaviour. On the other hand, if the mean values are widely separated, then two-peak MBE behaviour appears to indicate the influence of these two major obstacles separately. Based on this, the influence of the dissolution of martensite and/or bainite and the precipitation and growth of the...

On the influence of tempered microstructures on magnetic Barkhausen emission in ferritic steels

Giant magneto-resistive (GMR) sensors are attractive for magnetic flux leakage measurements, especially for the detection of shallow near-side cracks and deeply located defects. An optimized measurement system with magnetic yoke, GMR sensor and selective amplifier has been devised to detect the tangential component of leakage flux from various near-side notches and far-side notches (widths 0.5 mm and 1.0 mm, respectively) in 12 mm thick carbon steel plates. Far-side notches located at nearly 11 mm below the measurement surface have been detected with a good signal-to-noise ratio. The performance of the GMR sensor with lift off has also been studied for possible non-contact examination of hot surfaces and a lift off of 2 mm is expected to ensure the saturation-free detection of near-side as well as far-side notches.

https://iopscience.iop.org/article/10.1088/0957-0233/19/1/015702/pdf

Detection of leakage magnetic flux from near-side and far-side defects in carbon steel plates using a giant magneto-resistive sensor

An assessment of low cycle fatigue damage using magnetic Barkhausen emission in 9Cr–1Mo ferritic steel

The influence on the hysteresis loop and the magnetic Barkhausen emission (MBE) of microstructure within the case of different induction hardened carbon steel shafts has been studied The hysteresis loop shows a distortion with a sudden reduction in the rate of magnetisation (dB/dH ) before approaching the maximum magnetic flux density indicating surface hardening The systematic changes in the MBE profile for different voltages applied during induction heating indicate the microstructural variations within the case A single peak MBE profile for a fully martensitic structure gradually changes into two peaks on reducing the induction hardening voltage indicating the formation of an additional soft ferrite phase within the case The systematic changes in the two MBE peak heights indicate the synergistic decrease in the volume fraction of martensite and the increase in the volume fraction of ferrite phase within the case due to reduction in the induction hardening voltage The changes in the MBE pro

S. Vaidyanathan

Papers

Microstructural characterization of quenched and tempered 0.2% carbon steel using magnetic Barkhausen noise analysis

On the influence of tempered microstructures on magnetic Barkhausen emission in ferritic steels

Detection of leakage magnetic flux from near-side and far-side defects in carbon steel plates using a giant magneto-resistive sensor

An assessment of low cycle fatigue damage using magnetic Barkhausen emission in 9Cr–1Mo ferritic steel

Evaluation of induction hardened case depth through microstructural characterisation using magnetic Barkhausen emission technique