ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 12, pp. 1930−1935. © Pleiades Publishing, Ltd., 2014.
Kinetics of Vanadium Carbide Coating Produced
on AISI D2 Steel by Thermoreactive
, Ali Shafyei
, and Mohammad Reza Aboutalebi
Department of Materials, ENSAM University, 151 Boulevard de l'Hôpital, Paris, 75013 France
Isfahan University of Technology, Isfahan, Iran
Iran University of Science and Technology, Tehran, Iran
Received January 5, 2015
Abstract—AISI D2 cold-work tool steel is usually used for the purpose of hardness and wear resistance. Ther-
moreactive diffusion coating (TRD) treatment can be applied to this type of tool steel to improve the surface
hardness. Since the rollers made of D2 tool steels are susceptible to wear fatigue, its surface hardness is of critical
importance. A vanadium carbide coating was applied to the D2 tool steel samples by immersion in a borax liquid
bath containing ferrovanadium, aluminum, and boric acid. Coating process and hardening heat treatment were
carried out simultaneously in two steps. Firstly the samples were preheated up to 500°C and then TRD coating
was performed on the samples at various temperatures for different times. Secondly the samples were undergone
a mar-tempering heat treatment cycle in which the samples were austenitized in a BaCl
molten bath at 1070°C
for 30 minutes, oil quenched and then a two stage tempering treatment was applied to the quenched samples. The
surface hardness of the coated sample was evaluated as 2300–3200 HV at various conditions while the hardness
of the bulk was measured as 670–720 HV. XRD analysis of the coating showed that the main component was
vanadium carbide (V
). Finally the kinetic study of coating was carried out based on determined rate curves,
which showed that the diffusion of carbon atoms in the coating layer controlled the coating process.
* The text was submitted by the authors in English.
AISI D2 cold work tool steel is basically used for the
purpose of hardness and wear resistance. Since the metal-
forming rollers made of D2 tool steel are susceptible to
wear fatigue, their hardening heat treatment and surface
hardness are of crucial importance [1, 2].
Using surface treatment on tool steels can improve
the surface hardness and/or wear resistance and reduce
the friction [3, 4]. The thermoreactive diffusion process
(TRD) is a viable method for coating of tool steels with
a hard resistance of carbide layer [5, 6]. The obtained
layers have excellent adhesion with the substrate .
TRD process uses molten borax containing dissolved
carbide forming elements, in which the chemical
reaction occurs between carbon atoms present in the
substrate and dissolved carbide forming elements atoms,
thereby the hard and wear resistance carbide layer is
formed [3, 8].
The carbon content in the substrate affects positively
the growth rate. For example, in steel the carbon content
of the austenite matrix, not the total carbon content, is
nearly linear relative to a thickness of the carbide coating
[8, 9]. Depending on the process parameters and carbon
content of the substrate the layers of various thicknesses
are formed [10, 11].
The TRD process requires a relatively high tempera-
ture from 800 to 1250°C and immersion time ranges from
0.5 to 10 h [4, 12]. Vanadium and niobium are commonly
used as additives in borax baths to obtain carbide lay-
ers, whose hardness is superior to 2000 HV [13, 14]. To