Kinetics of the Formation of Boride Layers on EN-GJL-250 Gray Cast Iron

Abstract

In the present work, the EN-GJL-250 gray cast iron was pack-borided in a powder mixture consisting of 5 % B4C, 5 % NaBF4, and 90 % SiC. The boriding treatment was carried out in the temperature range 900°C–1000°C during 2, 4, and 6 h. The morphology of the generated boride layers was observed by an optical microscope and a scanning electron microscope. The phases in the borided layer were identified by X-ray diffraction (XRD) analysis, and Vickers microhardness testing was used to determine the microhardness profiles along the boride layers. The growth kinetics of boride layers was studied and the mass gain was estimated for the given boriding conditions. The regression model was also used to predict the total boride-layer thickness. As a result, the boron activation energy for EN-GJL-250 gray cast iron was estimated as 134.21 kJ mol−1 and compared with the literature data.