22 The Nanocomposite Diffusion Coating of Details Prepared of Boriding
347
and economically if compared to traditional processes with less emission. From
economic and environmental points of view, it is highly desirable to develop and
implement novel surface treatment technologies that are quick, cheap, clean, and
energy efficient.
In this [4] study, new results about the practical adhesion resistance of boride
coating/substrate system formed at the surface of AISI 316 L steel and improved
by means of a diffusion annealing process are received. First, the boriding of AISI
316 L steel was performed by the powder-pack method at 1173 K with different
exposure times (4–8 h). The diffusion annealing process was conducted on the
borided steels at 1273 K with 2 h of exposure using a diluent atmosphere of
boron powder mixture. The mechanical behavior of the boride coating/substrate
system developed by both treatments was established using Vickers and Berkovich
tests along the depth of the boride coatings, respectively. Finally, for the entire
set of experimental conditions, the scratch tests were performed with a continuously increasing normal force, in which the practical adhesion resistance of the
boride coating/substrate system was represented by the critical load. The failure
mechanisms developed over the surface of the scratch tracks were analyzed; the
FeB-Fe 2 B/substrate system exhibited an adhesive mode, while the Fe 2 B/substrate
system obtained by the diffusion annealing process showed predominantly a
cohesive failure mode.
In work [5], a kinetic model was suggested to evaluate the boron diffusion
coefficient in the Fe 2 B layers grown on the Armco iron substrate by the powderpack boriding. This thermochemical treatment was carried out in the temperature
range of 1123–1273 K for treatment times ranging from 2 to 8 h. The boron
diffusion coefficient in the Fe 2 B layers was estimated by solving the mass balance
equation at the (Fe 2 B/substrate) interface with an inclusion of boride incubation
time. To validate the present model, the simulated value of Fe 2 B layer thickness was
compared with the experimental value obtained at 1253 K for a treatment time of
5 h. The morphology of Fe 2 B layers was observed by SEM and optical microscopy.
Metallographic studies showed that the boride layer has a sawtooth morphology in
all the samples.
In work [6], the EN-GJS-400-15 cast iron was pack-borided in a powder mixture
composed of 5% B 4 C, 5% NaBF 4 , and 90% SiC at the three temperatures: 900,
950, and 1000 ◦ C for 2, 4, and 6 h, respectively. The pack-borided EN-GJS-40015 cast iron was characterized by the following experimental techniques: optical
microscopy, XRD analysis, and microhardness Vickers tester. The growth kinetics
of boride layers was also investigated. As a consequence, the boron activation
energy was found to be 212.28 kJ mol −1 for the EN-GJS-400-15 cast iron.
In study [7] the behavior of the borided 316 L stainless steel and 1018 steel is
evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over
6 h of exposure time, resulting in a biphase layer composed of FeB/Fe 2 B phases.
In order to evaluate Fe 2 B phase with no influence from FeB phase, AISI 1018 steel
samples were borided at 1273 K for over 20 min and then diffusion annealed at
1273 K over 2 h to obtain a Fe 2 B monophase layer. The obtained wear rates for FeB
and Fe 2 B phases and for the 316 L stainless steel were compared. Wear resistance
of 316 L stainless steel increases after boriding.
347
and economically if compared to traditional processes with less emission. From
economic and environmental points of view, it is highly desirable to develop and
implement novel surface treatment technologies that are quick, cheap, clean, and
energy efficient.
In this [4] study, new results about the practical adhesion resistance of boride
coating/substrate system formed at the surface of AISI 316 L steel and improved
by means of a diffusion annealing process are received. First, the boriding of AISI
316 L steel was performed by the powder-pack method at 1173 K with different
exposure times (4–8 h). The diffusion annealing process was conducted on the
borided steels at 1273 K with 2 h of exposure using a diluent atmosphere of
boron powder mixture. The mechanical behavior of the boride coating/substrate
system developed by both treatments was established using Vickers and Berkovich
tests along the depth of the boride coatings, respectively. Finally, for the entire
set of experimental conditions, the scratch tests were performed with a continuously increasing normal force, in which the practical adhesion resistance of the
boride coating/substrate system was represented by the critical load. The failure
mechanisms developed over the surface of the scratch tracks were analyzed; the
FeB-Fe 2 B/substrate system exhibited an adhesive mode, while the Fe 2 B/substrate
system obtained by the diffusion annealing process showed predominantly a
cohesive failure mode.
In work [5], a kinetic model was suggested to evaluate the boron diffusion
coefficient in the Fe 2 B layers grown on the Armco iron substrate by the powderpack boriding. This thermochemical treatment was carried out in the temperature
range of 1123–1273 K for treatment times ranging from 2 to 8 h. The boron
diffusion coefficient in the Fe 2 B layers was estimated by solving the mass balance
equation at the (Fe 2 B/substrate) interface with an inclusion of boride incubation
time. To validate the present model, the simulated value of Fe 2 B layer thickness was
compared with the experimental value obtained at 1253 K for a treatment time of
5 h. The morphology of Fe 2 B layers was observed by SEM and optical microscopy.
Metallographic studies showed that the boride layer has a sawtooth morphology in
all the samples.
In work [6], the EN-GJS-400-15 cast iron was pack-borided in a powder mixture
composed of 5% B 4 C, 5% NaBF 4 , and 90% SiC at the three temperatures: 900,
950, and 1000 ◦ C for 2, 4, and 6 h, respectively. The pack-borided EN-GJS-40015 cast iron was characterized by the following experimental techniques: optical
microscopy, XRD analysis, and microhardness Vickers tester. The growth kinetics
of boride layers was also investigated. As a consequence, the boron activation
energy was found to be 212.28 kJ mol −1 for the EN-GJS-400-15 cast iron.
In study [7] the behavior of the borided 316 L stainless steel and 1018 steel is
evaluated under micro-abrasion wear. The boriding was carried out at 1223 K over
6 h of exposure time, resulting in a biphase layer composed of FeB/Fe 2 B phases.
In order to evaluate Fe 2 B phase with no influence from FeB phase, AISI 1018 steel
samples were borided at 1273 K for over 20 min and then diffusion annealed at
1273 K over 2 h to obtain a Fe 2 B monophase layer. The obtained wear rates for FeB
and Fe 2 B phases and for the 316 L stainless steel were compared. Wear resistance
of 316 L stainless steel increases after boriding.