Papers by Keyword: Mass Balance Equation

Abstract: The present work estimated the growth kinetics of Fe2B layers formed at the surface of AISI 4140 steels. The thermochemical treatment was applied in order to produce the Fe2B phase, considering temperatures of 1123, 1173, 1223 and 1273 K with five exposure times (2, 4, 5, 6, and 8 h), using a 4 mm thick layer of boron carbide paste over the material surface. The growth of boride layers was described by the mass balance equation between phases in thermodynamic equilibrium, assuming that the growth of boride layers obeys the parabolic growth equation and the boron concentration at the interfaces remains constant. Also, the boron diffusion coefficient at the Fe2B ( ) was established as a function of boriding temperature. Likewise, the parabolic growth constant (k), the instantaneous velocity (v) of the Fe2B/substrate interface and the weight-gain of borided steels were established as a function of the parameters and , which are related to the boride incubation time ( ) and boron surface concentration ( ), respectively.

Abstract: The boron diffusion in the Fe2B and FeB borided phases formed at the surface of AISI H13 tool steels during the paste boriding process was estimated. The treatment was carried out at temperatures of 1173, 1223 and 1273 K with 2, 4, 6 and 8 h exposure times for each temperature using a 4 mm layer thickness of boron carbide paste over the material surface. The boride layers were characterized by the GDOES technique to determine in quantitative form the presence of the alloying elements on the borided phases. The boron diffusion coefficients and were determined by the mass balance equation and the boride incubation time assuming that the boride layers obey the parabolic growth law. Also, the mass gain produced by both boride layers at the surface of the tool steels was determined. Finally, the boron diffusion coefficients were interpreted as a function of the treatment temperature, obtaining the activation energy values for the diffusion controlled growth of Fe2B and FeB hard coatings.

Abstract: This study evaluates the boron diffusion in the Fe2B phase formed at the surface of AISI 1018 steels during the paste boriding process. The treatment was carried out at temperatures of 1123, 1173, 1223 and 1273 K with 2, 4, 5, 6 and 8 h exposure times for each temperature using a 4 mm layer thickness of boron carbide paste over the material surface. The boron diffusion coefficient Fe2B D was determined by the mass balance equation and the boride incubation time assuming that the boride layers obey the parabolic growth law, while the boron concentration profile along the interphase Fe2B/substrate was unknown. The boron diffusion coefficient was interpreted as a function of the treatment temperature, obtaining the activation energy value for diffusion controlled growth of Fe2B boride phase.