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    Kinetic Investigations of Boronized Cold Work Tool Steels
    (Carl Hanser Verlag, 2014) Topuz, Polat; Yilmaz, Eren; Gundogdu, Emine
    In this study, kinetic examinations on boronized X45NiCrMo4 (DIN 1.2767) and 90MnCrV8 (DIN 1.2842) steel samples are described. Samples were boronized in indirect heated fluidized bed furnace at 1123 K, 1223 K, and 1323 K for 1 h, 2 h, and 4 h. Morphologically and typically examinations of borides formed on the surface of the steel samples were studied by optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD). Boride layer thickness formed on the steel X45NiCrMo4 ranges from 45 mu m to 382 mu m and for the material 90MnCrV8 ranges from 33 mu m to 471 mu m. The hardness of the boride layer formed on the steel X45NiCrMo4 varied between 1713 HV0.1 and 2111 HV0.1 and for the steel 90MnCrV8 between 1716 HV0.1 and 2761 HV0.1. Layer growth kinetics were analyzed by measuring the extent of penetration of FeB and Fe2B sublayers as a function of boronizing time and temperature. The kinetics of the reaction has been determined with K = K-o exp (-Ct/RT) equation. Activation energy (G) of the bonded steel X45NiCrMo4 was determined as 156 kJ/mol and that of the steel 90MnCrV8 was determined as 179 kJ/mol.
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    The Fracture Toughness of Fe2B Formed on Boronized AISI 304
    (Carl Hanser Verlag, 2014) Topuz, Polat; Gundogdu, Emine; Yilmaz, Eren; Gumus, Emre
    In this study, the fracture toughness of Fe2B boride layer on boronized AISI 304 stainless steel was investigated. Samples were boronized in an indirect heated fluidized bed furnace with Ekabor 1 (TM) boronizing agent at 1123 K, 1223 K, and 1323 K for 1 h, 2 h, and 4 h, respectively. The boride phases were investigated by X-ray diffraction (XRD) analysis. Hardness and fracture toughness of borides were measured via Vickers indentation. With increasing boriding temperature and time the fracture toughness values were reduced. The boride layer thickness formed on the boronized samples ranged between 12 mu m and 176 mu m. The hardness of the borides ranged between 1709 HV0.1 and 2119 HV0.1 and fracture toughness was in the range of 2.19-4.47 MPa x m(1/2) depending on the layer thickness and hardness.