The use of nanotechnology to improve the bulk and surface properties of steel for structural applications - Nanotechnology in Eco-efficient Construction - page 91

Table 5.2 Recent research on the utilization of nanotechnology to improve the mechanical properties of steel surface

Production
process

Microstructure of surface
layer

Novel properties or
phenomenon Reference Steel type Mechanism(s)

Suh et al.
(2007)

Tool steel
(SKD-61/
equivalent
H13)

UCFT Gradient microstructure

with nano-grains
(average 50 nm) from
the surface to 100 μ m
depth

Improved hardness (37%),
compressive residual
stress (83%), wear
resistance (97%), and
fatigue strength (25%).
Reduced friction
coeffi cient (50%)

Mixed nano-crystals
and amorphous
phase

Xu et al.
(2008)

Carbon steel
(0.7-0.75%
C)

Severe cold
drawing

Nano-grains of α and
cementite

UTS increased from 1352
to 2586 MPa at a true
strain of 3.58;
outstanding wear
resistance

Strain-induced α
transformation
(from cementite
fl akes) and
nano-crystallization

Liu et al.
(2009)

Low carbon
steel (#45)

Added
pressure
shot
peening

Uniformly distributed
equiaxed grains
( ∼ 65 nm) in the top
surface

Doubled the hardness of
the 30- μ m thick surface
layer; enhanced wear
resistance

Nanocrystallization

Extra-AHSS TM

Kwon et al.
(2010)

Adding Mn
and C to
retain
suffi cient
austenite

Nano-scale retained γ
grains (200-500 nm)
embedded in the fi ne
bainite and α ′

Extremely high strength-
ductility balance, e.g.,
TS > 1033 MPa, El >
27.5%, and TS × El >
28,408 MPa.%

Partial reverse
transformation
during continuous
annealing and
transformation
induced plasticity

Ba et al.
(2007)

Cr-Si alloy
steel

Quenching +
tempering +
SFPB

Uniformly distributed
equiaxed α grains
(5-65 nm) in the top
surface

Greatly enhanced
hardness and wear
resistance and reduced
friction coeffi cient

Nanocrystallization
and change in the
dominant wear
mechanics