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Novel coating technologies for electrical steels

Goel, Vishu 2016. Novel coating technologies for electrical steels. PhD Thesis, Cardiff University.
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Abstract

Power loss in transformer cores accounts for approximately 5% of the energy lost as heat. The loss could be reduced by improving the secondary recrystallization methods, grain orientation control, increasing the electrical resistivity of the steel, reducing the thickness of laminations, manipulating the domain structure and applying coatings. Coating grain oriented electrical steel (GOES) helps in reducing the loss by providing electrical resistance, improving the surface roughness and applying beneficial tensile stress. In this work a range of coatings were explored that can be economically applied on GOES to reduce power loss and magnetostriction in working transformers. Coatings were investigated using a range of coating processes including electroless plating, thermal evaporation physical vapour deposition and electron beam physical vapour deposition. The coatings were characterised using a range of processes including Single Strip Testing (SST), Magnetostriction measurement, Vibrating Sample Magnetometer (VSM), magnetic domain imaging, Optical microscopy, Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), X-ray Diffraction (XRD), Surface profilometry, Atomic force microscopy and Raman spectroscopy. Co-Ni-P applied on GOES improved the magnetic properties by applying beneficial tensile stress which aligns the domains in the direction of magnetization and by improving the surface roughness which reduces the number of pinning sites on the surface of steel. The magnetostriction was improved due to the effect of beneficial tensile stress. Similarly Co-PCNT applied on GOES reduced the power loss by improving the surface roughness. CrN, CrAlN, TiAlN improved the power loss and magnetostriction as tensile stress was applied by the coatings which reduced the domain width and hence loss was reduced. The reduction in magnetostriction was due to the high value of Young’s modulus of the coatings as compared to GOES which did not allow the steel to expand under the influence of applied magnetic field. The ceramic coatings could be directly employed in the production line replacing the phosphate coating unit with the Chemical/Physical vapour deposition.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering
Uncontrolled Keywords: Power Loss; Magnetostriction; Stress; Grain Oriented; Coating; Domain.
Date of First Compliant Deposit: 12 August 2016
Last Modified: 17 Mar 2017 05:54
URI: http://orca.cf.ac.uk/id/eprint/93813

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