The use of nanotechnology to improve the bulk and surface properties of steel for structural applications - Nanotechnology in Eco-efficient Construction - page 93

Table 5.2 Continued

Production
process

Microstructure of surface
layer

Novel properties or
phenomenon Reference Steel type Mechanism(s)

Li et al.
(2009)

Low-carbon
steel
(0.17% C)

SMAT Uniformly distributed

equiaxed α grains
( ∼ 13 nm) and
cementite
nanoparticles in the
top surface

More than doubled the
surface microhardness;
13% improvement in
fatigue strength
(302 Mpa based on
fatigue life 5 × 10 6 cycles)

Surface
nanocrystallization

Chen et al.
(2011)

304 SS SMAT Hard nanocrystalline α ′

layer, α ′ - γ ultrafi ne
layer, twinning layer,
and compliant coarse-
grained layer from
outer to inner

Outstanding strength-
stiffness-ductility
synergy

Synergy of multiple
deformation
mechanisms and
nano/micro-scale
toughening

Frontán
et al.
(2012)

304 SS SMAT +

plasma
nitriding or
SMAT

Nanocrystalline or
nanotwinned ultrafi ne
crystals

Lower energy absorption
and 40% less impact
deformation than
coarse-grained steel
under ballistic loading

-

Wang et al.
(2012)

Fe-9Cr steel SMAT +

annealing

Gradient microstructure
with α grains ( ∼ 14 nm)
and smaller carbide
particles dispersed
along GBs

Annealing-induced grain
refi nement

α → γ → α phase
transformations