Dc Diode Papvd to Durability
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Transcript of Dc Diode Papvd to Durability
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CVD. See
chemical vapour deposition.
CVI.
See
chemical vapour infiltration.
cyaniding
Carbonitriding using a cyanide-based salt bath
-
IFHT DEFINITION.
See
carbonitriding.
D
DC diode PAPVD.
A
plasma assisted
PVD
process
in
which
the
object
to be
coated
is
made
one of the
cathodes
of a DC
glow discharge,
the
chamber walls acting
as the
earthed
anode.
DC triode PAPVD.
See
triode on plating
and
triode sputter deposition.
deboriding treatment.
A
thermochemical method
for the
removal
of
boron from
a
prior
borided steel surface. The process is conducted in an atmosphere con taining H
2
and CH
4
at
temperatures of 900-1020
0
C. Boron is usually rem oved in the form OfB
2
O
3
.
decarburisation.
Loss of carbon from a steel surface to a level well below that of the core,
often as the result of prolonged high temperature exposure in an oxidising atmosphere.
decarburisation depth.
Distance from the surface of a decarburised object to a specified
limit which depends on the character of the decarburisation. The
limit can be set in terms of a specified structure, hardness, or carbon
content - IFHT DEFINITION.
decorative chrom ium plating. See
chromium plating
decorative coating.
Any
coating primarily produced
to
enhance
the
appearance
of an ob-
ject. For example see
gilding.
degreasing.
Any
methods that achieve
the
removal
of
organic compounds, such
as
grease
or oil, from the surface of an object, e.g., see vapour degreasing.
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denitriding.
Th erm oc he m ica l t rea tment for the remov a l of excess n i t rogen f rom
the surface of a ni t r ided objec t ' - IFH T D EF IN IT IO N .
deposit.
A synonym for coating (noun), but also referring to any adherent surface solid
formed, for exam ple, as a result of wear or corrosion.
deposition.
The act of laying dow n a metallic or non-metallic layer onto a substrate. There
are numerous deposition techniques; these include electroplating, plasma spraying, PVD
and CV D.
deposition rate.
Used in connection with coating technologies, like plasma spraying, p lasma
assisted PVD or CVD. Expressed in mm/min, jiim/min or |nm/hr.
derusting.
See
descaling.
descaling. Any process used for the purpose of removing the scale from heavily oxidised
metal. This can be achieved by mechanical (abrasive blasting, tumbling, brushing) or chem ical
me ans (alkaline descaling, acid descaling (pickling) or salt bath descaling).
designer surface. An engineered surface with optimal constitution, treatment depth and
properties, designed with intent for specific application(s).
detonation gun D-gun) spraying. A combustion spraying techn ique whereby particles of
coating material, typically WC-Co, are passed through a combustion tube, fuelled by a
mixture of oxygen and acetylene gases. Ignition is provided by a spark plug 4.3 or 8.6 times
per second. The com position of the combusting gas can be adjusted to be oxidising, neutral
or reducing. The flame temperature is -3000 K and coating powder particles can attain
velocities ~ 800 m/s. It is an extremely noisy torch (150 dB) requiring intensive screening
and operator protection. Union Carbide C orporation is the principal owner and operator of
this technology. Also see high velocity air fuel (HVA F) spraying and high velocity oxygen
fuel (HVOF) spraying.
D-gun spraying.
See
detonation gun (D-gun) spraying.
diamond coatings. Diamond coatings can be deposited by many methods. Presently, the
most favoured technique is microw ave plasma CV D. Diamond co atings are crystalline and
are usually characterised by a combination of methods which include, Ram an spectroscopy,
X-ray diffraction and surface morphology . Also see
hot ilament CVD
and
microwave plasma
CVD.
diamond-like coatings DL C). Very hard (-3000-4000 kg/mm
2
) carbon coatings with
little or no crystallinity (amorphous). Initially such coatings proved unsatisfactory for tribological
protection because of poor substrate adhesion and unfavourable residual stress. Some recent progress
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has been m ad e wh ereby appropriate sub-layers of transition metal carbides and nitrides are deposited
prior to deposition of a DLC. This is particularly important when depositing DLC onto metallic
substrates. D L C s can be deposited by sputter deposition or plasma assisted C V D .
diffuse cycle. The second part of the boost-diffuse method. See vacuum carburising and plasma
carburising.
diffusion coating.
Any process that produces a surface enriched in another element through solid
state diffusion and (usually) resulting in the formation of intermetallic or interstitial compounds.
Processes include
aluminising, bonding, chromising, sherardising, siliconising
and
vanadising.
By
conven tion, it specifically
excludes
carburising, carbonitriding, nitriding, and nitrocarburising.
diffusion metallising.
'Therm oche mical treatment involving the enrichmen t of the surface layer of
an object with one or mo re metallic element' - IFH T D EFIN ITION .
Diffusion coating with metals alone. Processes include aluminising, chromising, sherardising and
vanadising but should exclud e the technology of siliconising, since silicon is a non-m etal. Ho wever,
som e authors still regard siliconising as a diffusion metallising proc ess.
diffusion period .
That time of a thermoch emical treatment w hen the active specie(s) diffuse into the
substrate. To provide distinction from, for exam ple, the heating and cooling cycles.
diffusion profile.
T he concentration of elements in the diffusion zone following a therm ochem ical
diffusion treatmen t. A lso see
concentration profile.
diffusion w ea r. A term first invok ed by Trent and Lo ladze in the 1950s, to account for the rake face
cratering of cem ented ca rbide cutting tools, observed after cutting plain carbon and lo w alloy steels at
relatively high speed (>1 00m /min). Other workers have termed this effect 'dissolution/diffusion w ear '
or 'solution w ear'. For cemented carbide tools, comprising W C -C o or W C-(W
5
TIJaJ^Jb)C-Co (termed
'straight gra de ' and 'steel cutting gra de' carbides respectively), the W C g rains bec om e sm oothly
wo rn. In the case of 'steel cutting grade ' cemen ted carbides, microsections, m ade no rmal to the rake
face surface, reveal that the W C pha se is preferentially wo rn; the (W,Ti,Ta,Nb)C phase being less
severely wo rn, stands prou d of the adjacent W C grains. Th e preferential w ear of the W C p hase is
attributed to its higher solid solubility limit in y-Fe (present in the hot steel chip shear zone during
cutting) co m pa red to that of the (W,Ti,TaJSfb)C ph ase.
Othe r tool materials, like high speed steel and ceramics can be w orn by this type of mec hanism , e.g.,
whe n sialon tools are used to cut low alloy and plain carbon steels at cutting speed s abov e 20 0 m /min ;
similarly Al
2
O
3
-ZrO
2
ceramics exhibit a similar effect when used to cut titanium alloys at cutting
speeds above 50 m /min. TiN and TiC coatings, deposited by PV D o r CV D, are also worn in this w ay
wh en used to cut steels above 100 m/m in although other mec hanism s like
discrete plastic deforma-
tion
make a s ignif icant contr ibut ion. For fur ther de ta i ls see
Metal Cutting
by E.M . Trent ,
But te rwor ths , 3 rd Edi t ion , 1991.
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diffusion zone.
'That part of the case where elements introduced by
thermochem ical treatment are held in solid solution or partially
precipitated in the matrix. The concentration of these elements
decreases continuously towards the core ' - IFHT DE FINITION
A term used especially in connection with nitrided steels. In this example it refers to the
zone of coherent nitride precipitation, residing beneath the compound layer, which
constitutes 95 to 99 of the depth of the nitrided 'c as e', see
nitriding.
The nitrogen content
of the diffusion zone range s from nearly 20at- adjacent the com pound layer to below
lat- adjacent the core structure.
dimensionless wear coefficient. See Archard s w ear equation.
diode sputter dep osition. A sputter deposition process in which the substrate serves as a
positive or positive-ground electrode, relative to the cathodic sputter sources; a less com-
monly used configuration. Also
see bias sputter deposition.
dip coating. Any technique whereby a coating is formed by immersing a solid in a liquid
which subsequently bonds to the solid surface. The most common types include
hot dip
aluminising or hot dip galvanising. The term also refers to coating by immersion in ce-
ramic slip or even polymeric solutions (organic paints).
dip coating with ceramics.See ceramic dip coating.
dip coating w ith plastics.
See
plastic dip coating.
dip painting. See plastic dip coating.
direct current plasma CVD.
Plasma assisted CVD in which the plasma is generated by a
direct current (DC ) power supply.Often more problematic than
r dio
frequency (RF) plasma
CVD.
discrete plastic deformation. A common wear mechanism of PVD and CVD ceramic
coatings (TiC, TiN and Al
2
O
3
) when used to cut steel at speeds above 100 m/min. The
mechanism increases with increasing cutting speed (temperature) and is the principal rake
face w ear mechanism OfAl
2
O
3
coated cem ented carbide tools. The mechanism culminates
in the rem oval of wear fragments through ductle fracture (see diagram , seque nce 1 to 4 and
micrograp h). It should be appreciated that coating temperatures often exceed 1100
0
C when
cutting steel; at these temperatures TiC, TiN and Al
2
O
3
behave p lastically. Also see P. A.
Dearnley, R. F. Fow le, N. M. Co rbett and D. Doy le,
Surface Engineering,
1993, 9, 312-
318.
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discrete plastic deforma tion A CV D TiC coating undergoing
r ke
face wear throu gh discrete p lastic
deformation caused by the high temperatures and shear stresses developed while cutting an AISI
1046 normalised steel at 300 m/min 0.25 mm/rev. CFD = chip flow direction. Field em ission SEM.
CFD
i
4
DISCRETE
PLASTIC
DEFORMATION
CER MIC
CO TING
SPERITIES
CHIP FLOW
DIRECTION
P. A. Deamley 1994
WE R P RTICLE
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displacement CVD reaction. Also known as an exchange reaction. A CVD reaction be-
tween a volatile compound (MX
2
) and a substrate (Z):
This reaction is usually self-limiting i.e., it stops after a solid layer, M
(s)
, has been deposited
which serves as a diffusion barrier to further reaction. For exam ple see
gaseous chromising.
DLC. See diamond-like coatings
double-stage nitriding.
See comm ents on Floe Process under
gaseous nitriding.
drip-feed carburising. See
gaseous carburising.
dry blast cleaning. A general term encom passing shot blasting, grit blasting and sand blast-
ing.
dry galvanising.
H ot dip galvanising in w hich the object, after degreasing and pickling, is
immersed in an aqueous flux solution, then dried and immersed in a molten zinc bath. A
rather inappropriate term.
drying. The process of removing residues from washing operations by means of hot or cold
air, freon, infra-red radiation or centrifugal action.
dull finish. A surface of poor specular reflectivity. M att surface is also an acceptable term .
duplex nickel plating. A nickel electroplating process involving the deposition of two lay-
ers of nickel: (i) semibright and; (ii) bright. These serve as an undercoat for subsequent
chrome plating.
duplex surface engineering. A com bination of two sequential (and mu tually com pat-
ible, from the treatment temperature perspective) surface engineering methods to
achieve a synergistic surface property design. At the time of writing, much interest is
being shown in extending the application range of thin (~5jLim) ceramic coatings (like
TiN and TiC) to low yield strength (~500-100 0M .Pa) substrates by prior strengthen ing
via a thermo chem ical diffusion treatment. Feasible duplex treatments include: (i) CV D
after carburising, followed by quenching (to permit the y-Fe — > a' -F e transfom ation);
(ii) PVD after nitriding. Note: carburising temperatures ~ CVD temperatures; PVD
temperatures ~ nitriding temperatures. Initial trials have been carried out in two dis-
tinct operations. M ore recent efforts have focused on enabling each process to be car-
ried out sequentially in the same vessel.
durability. The ability of a surface engineered material to endure in-service wear, corro-
sion or fatigue.