Feb. 9th, 2010, Tuesday
“Low-Temperature
Colossal Supersaturation
(LTCSS) of Stainless
Steels” [PDF]
Sunniva R. Collins,
Ph.D. Senior Research
Fellow, Swagelok Company
Abstract
Low-temperature
colossal
supersaturation
(LTCSS) is a novel
diffusional surface
hardening process
for carburization of
austenitic stainless
steels and other
alloys without the
precipitation of
carbides. The
formation of
carbides is
kinetically
suppressed, enabling
extremely high or
colossal carbon
supersaturation. As
a result, surface
carbon
concentrations in
excess of 12 at.%
are routinely
achieved. This
treatment increases
the surface hardness
by a factor of four
to five, improving
resistance to wear,
corrosion, and
fatigue, with
significant retained
ductility.
Swagelok won the
2006 Engineering
Materials
Achievement Award
for its development
and
commercialization of
this breakthrough
technology. At
present, Swagelok
uses the technology
for treatment of
tube fitting rear
ferrules, mostly
manufactured in type
316 stainless steel.
Swagelok is
commercializing
LTCSS as SAT 12sm,
and formed the
Swagelok Technology
Services Company in
2007 to direct these
efforts.
LTCSS provides a
uniform and
conformal hardened
gradient surface
with no risk of
delamination or
peeling. The
hardness layer is at
least 25μm thick,
with a near surface
hardness of ≈HV1200
(over 70 HRC). The
thickness of the
hardened layer can
be increased further
by additional
carburization
treatments. Hardness
depths of 10μm to
50μm have been
routinely achieved.
The treatment
retains the
austenitic phase and
is completely
non-magnetic. In
addition, because
parts are treated at
low temperature,
they do not distort
or change
dimensions. In
addition to
austenitic stainless
steels, research
efforts are underway
to extend the
technology to other
industrially
important alloys,
such as
precipitation-hardening
stainless steels,
duplex alloys,
nickel-based alloys,
and cobalt-based
alloys.
This
talk will describe
the LTCSS
technology, and will
discuss research
findings from a
recent Department of
Energy project that
quantified the
performance
improvements for
treated materials.
Biography
As senior research
fellow at Swagelok
Company, Sunniva R.
Collins is
responsible for
coordinating the
company’s academic
and governmental
research
partnerships. She
joined Swagelok in
1995 as a research
metallurgist and has
served in
engineering
management positions
including manager,
standards and
product regulatory
compliance. Most
recently, Collins
acted as the
technical director
of Swagelok
Technology Services
Company, a wholly
owned subsidiary of
Swagelok Company.
Collins
received her
doctorate and
master’s degree in
materials science
and engineering from
Case Western Reserve
University and her
bachelor’s degree
from the University
of Michigan. She was
Swagelok’s Principal
Investigator on a
three-year
DoE-funded project
to evaluate low
temperature colossal
supersaturation
(LTCSS, now being
commercialized by
Swagelok as the SAT
12 process) , which
completed at the end
of 2006. On this
project, she was
responsible for
program management
of collaborative
research with Case
Western Reserve
University (CWRU),
Oak Ridge National
Laboratory (ORNL)
and other industry
partners. The
results of this
research have been
recognized with the
2006 ASM Engineered
Materials
Achievement Award,
and a 2008 R&D 100
Award.
Dr.
Collins has worked
to develop key
standards on
welding, surface
finish requirements,
and corrosion test
methods for the
semiconductor
equipment industry.
She has also
instructed courses
for ASME on
Bioprocessing
Equipment (BPE) and
for the
International
Society of
Pharmaceutical
Engineers (ISPE).
Collins is a Fellow
of ASM International
(FASM) and is
currently serving on
the ASM Board of
Trustees. She was
the Cleveland
Chapter Chair from
2000 to 2001. She is
listed in Who’s Who
in America, Who’s
Who in Science and
Engineering, and
Who’s Who in
American Women.
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