Electron-beam rapid quenching of an ultra high-strength alloy steel
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Rapid quenching using electron beams has been used to treat the surface layers of an ultra high-strength alloy steel. The microstructure of the treated surface layers has been investigated by optical, scanning and electron microscopy and by X-ray diffractometry. The microstructure produced by conventional solid state quenching of the same steel has also been examined for comparison. This microstructural study shows that the rapid quenching process leads to a high degree of grain refinement and an increase in solid solubility which, in turn, increases the amount of retained austenite. The lowering ofM s temperature due to the high cooling rate and the increased solid solubility favour the formation of twinned martensite. These interlinked phenomena have increased the microhardness of the rapidly quenched layer considerably, with respect to that of the solid state quenched steel.
KeywordsMicrostructure Austenite Surface Layer Martensite Solid State
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