Modeling of the Growth Kinetics of Boride Layers in Powder-Pack Borided ASTM A36 Steel Based on Two Different Approaches

Abstract

An indispensable tool to choose the suitable process parameters for obtaining boride layer of an adequate thickness is the modeling of the boriding kinetics. In this work, two mathematical approaches were used in order to determine the value of activation energy in the Fe2B layers on ASTM A36 steel during the iron powder-pack boriding in the temperature range of 1123–1273 K for treatment times between 2 and 8 h. The first approach was based on the mass balance equation at the interface (Fe2B/substrate) and the solution of Fick’s second law under steady state (without time dependent). The second approach was based on the same mathematical principles as the first approach for one-dimensional analysis under non-steady-state condition. The measurements of the thickness (Fe2B), for different temperatures of boriding, were used for calculations. As a result, the boron activation energy for the ASTM A36 steel was estimated as 161 kJ·mol−1. This value of energy was compared between both models and with other literature data. The Fe2B layers grown on ASTM A36 steel were characterized by use of the following experimental techniques: X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray Spectroscopy (EDS). Finally, the experimental value of Fe2B layer’s thickness obtained at 1123 K with an exposure time of 2.5 h was compared with the predicted thicknesses by using these two approaches. A good concordance was achieved between the experimental data and the simulated results.

Metallurgical Characterization and Kinetics of Borided 34CrNiMo6 Steel

“…In that study, it has been noted that activation energy values change with the chemical composition of the steel because alloying elements can often act as a barrier for boron diffusion. It has also been shown [4,16,42,43], that the activation energy also depends on the methods used for measuring the thickness of the boride layer, surface preparation, the type and size of the boriding powders, and whether a single-phase (FeB) or double-phase boride layer (FeB + Fe2B) is formed (due to boron potential). The collision factor is constant and is a measure of the effective collisions between reacting species.…”

“…Many models have been developed over the years to optimize the thicknesses of boride layers obtained in industrial boriding applications [14][15][16]. Ortiz-Domínguez et al [16] and Zuno-Silva et al [17] indicated that boron diffusion was dependent upon the mass balance at the Fe2B-substrate interface on ASTM A36 and AISI 1045 steels. Another model was developed by Keddam and Kulka [18] to explain the boriding kinetics of AISI D2 steels.…”

Effect of thermochemical treatments on the surface hardening of a circular saw blade: A microstructure comparison of nitride layers, boride layers and TiN coating formed on ASTM A1011 steel

“…Cost of tool is also not negligible. A proposed solution consist of developing a hard, dense, wear-and corrosion-resistant coating formed on a surface with certain affinity in fracture toughness, as well as the creation of a dislocation interface that prevents the propagation of the corrosive medium to the substrate and the propagation of micro-cracks [1][2][3][4][5][6][7][8][9][10][11][12]. In particular, nitriding of tool surfaces is one of the most commonly used types of heat treatment of tool steels.…”

Recycling of the Powder-pack Boriding Mixture: Microstructural Characterization of Fe2B Layers on ASTM A36 Steel

“…These phases consist of orthorhombic and tetragonal lattices (body-centered) respectively. One basic advantage of boride layers is that they can reach high hardness values (between 1800-2000 HV), kept at high temperatures [1][2][3][4][5][6][7][8]. In the present study, the microstructure of the single phase layer (Fe2B) and the recycling of the powder-pack boriding mixture until it is no longer possible to form any layers on the surface of the ASTM A36 borided steel have been investigated at 1173 K with exposure time of 2 h by dehydrated paste-pack method.…”