Formation and kinetics of FeB/Fe2B layers and diffusion zone at the surface of AISI 316 borided steels

• Published in: Surface & coatings technology Vol. 205; no. 2; pp. 403 - 412
• Main Authors: CAMPOS-SILVA, I, ORTIZ-DOMINGUEZ, M, BRAVO-BARCENAS, O, DONU-RUIZ, M. A, BRAVO-BARCENAS, D, TAPIA-QUINTERO, C, JIMENEZ-REYES, M. Y
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier 01.10.2010
• Subjects: Activation energy; Applied sciences; Austenitic stainless steels; Boriding; Cross-disciplinary physics: materials science; rheology; Diffusion; Diffusion layers; Exact sciences and technology; Gain; Heat treatment; Materials science; Mathematical models; Metals. Metallurgy; Physics; Production techniques; Steels; Surface treatments; Thermochemical treatment and diffusion treatment; Thermochemical treatment; Interfaces; Austenitic stainless steel; Boriding; Borides; Stainless steel-316; Scattering; Surface treatments; Modelling; Diffusion zone; Kinetics; Diffusion model
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2010.06.068

The kinetics of the FeB/Fe2B layers and diffusion zone at the surface of AISI 316 steels exposed to the powder-pack boriding process were studied in this work. FeB/Fe2B layers and diffusion zone measurements were taken at different temperatures and exposure times to validate diffusion-controlled growth during the boriding process. In order to obtain the boron diffusion coefficients at the FeB/Fe2B layers and diffusion zone, a mathematical model based on the mass balance at the growing interfaces was proposed. The activation energy values estimated for the FeB and Fe2B layers were 204 and 198kJmola degree 1 respectively. In addition, the activation energy value obtained for the diffusion zone was 116kJmola degree 1. The diffusion model was extended to estimate the FeB/Fe2B layer thicknesses, and the depth of the diffusion zone at the temperature of 1243K with 3 and 5h of exposure, based on the experimental parameters ascribed to the boriding process. Finally, the effects of the FeB/Fe2B growth and diffusion zone, on the weight gain of borided steels and on the instantaneous velocity of the interfaces were incorporated in the model.