Optimization of Semiconductor Superlattice for Spin-Polarized Electron Source
Erosion-Corrosion of Superlattice PVD CrN/NbN Coatings Yashodhan Purandare Tribology Group...
-
Upload
kerry-rodgers -
Category
Documents
-
view
230 -
download
10
Transcript of Erosion-Corrosion of Superlattice PVD CrN/NbN Coatings Yashodhan Purandare Tribology Group...
Erosion-Corrosion of Superlattice PVD CrN/NbN Coatings
Yashodhan Purandare
Tribology Group
Mechanical Engineering Department.
Tribology Group at Strathclyde:
• Group headed by Prof. Margaret Stack.
PhD students:
• 1. Mathew T. Mathew
• 2. Buddhadev Jana.
• 3. Yashodhan Purandare.
• 4. Owen Fozzard. (undergrad. student)
Visiting Scientists:
• 1. Dr. Hussein Jawan.
• 2. Dr. Weijiu Huang.
Progressing Projects:
• Micro-abrasion-corrosion mapping of pure metals in aqueous slurries
• Micro-abrasion mapping of bio-materials
• Mapping micro-abrasion interactions in bio-oils
• Nanoscale studies of erosion-corrosion of "superlattice" PVD coatings in aqueous conditions
Projects continued
•An impinging jet study of the erosion-corrosion of MMC composite based coatings in aqueous conditions
•Predictive modelling of erosion-corrosion of metallic and composite materials in aqueous slurries
•Sliding wear-corrosion mapping in aqueous conditions
•Effects of applied load on the sliding-wear-corrosion map in aqueous conditions
Facilities:
• Impinging Jet Erosion Apparatus
• Rotating Cylinder Electrode Apparatus
• Micro-Abrasion Apparatus (Plint TE66)
• Pin on ring apparatus for sliding in corrosive conditions
Impinging Jet Erosion Apparatus
Rig Highlights:
• Reuse of the erodent particles.
• Minimum erosive loss of the system.
• Protection of the pump and the pipeline from the erosion.
• Small size samples .
….continued
• Use of Erodent particles from size 100-1000 microns.
• Easy control of Impact velocity of slurry and impact angle .
• Flexibility of Impact velocity from 1 - 12 m/sec.
• Computer controlled Potentiostat for corrosion experiments.
• Impact angle adjustment from 10 degrees to 90 degrees.
Calibration of rig:
EJECTOR
X DISTANCE
EXIT NOZZLEDRIVING NOZZLE
PERSPEX
SUCTION TUBE
SS
TUBE
S.S.TUBE
‘Heart’ of the rig.
Calibration curves:
Reproducibility
10.00
15.00
20.00
0 2 4 6 8 10 12 14 16
Time intervals (each 30 secs)
Co
nce
ntr
atio
n w
t %
Conc
Concentration Vs 'x' Distance
-10
0
10
20
30
40
50
-10 -8 -6 -4 -2 0 2 4
Distance in mm
Co
nce
ntr
atio
n w
t %
concentration Vs Impact velocity
0
10
20
30
40
50
60
70
0 2 4 6 8 10
Impact velocity ( m/s)
Co
ncen
trati
on
wt
%
2 mm 2.5 mm 3.0 mm 3.7 mm
Erosion of Pure Metals
Aluminium
02468
101214
0 20 40 60 80 100
Impact angle (degrees)
Eros
ion
rate
(mg/
kg)
Copper
1111.211.411.611.8
1212.212.4
0 20 40 60 80 100
Impact angle (degrees)
Eros
ion
rate
(mg/
kg)
Erosion of WC-Co-Cr Cermets:
WC-Co Erosion
0
2
4
6
8
10
0 20 40 60 80 100
Angles in degrees
Ero
sio
n r
ate
in m
g/k
gs
Atomic force Microscopy
……………AFM
Superlattice Coatings
Schematic Superlatice Coating microstructure
Superlattice coatings:
• Surperlattice coatings are the extrinsic super hard coatings - hardness of the coatings exceeds 40Gpa.
• These coatings have a high oxidation resistance and can be used upto 700ºC, e.g. TiAlN coating.
• The total thickness of the multilayer coatings is in the range of few microns.
…...continued
• The bilayer of the coating is known as the superlattice period. A typical superlattice period can be around 1.6 – 4 nm.
• Coatings can be divided into five groups depending on the composition of the bilayer.
Metal superlatticesNitride superlatticesCarbide superlatticesOxide superlatticesNitride, Carbide, or Oxide/ Metal superlattices
CrN/NbN superlattice coatings:
• CrN/NbN coatings have been manufactured at the Engineering Group at Sheffield Hallam University, led by Dr Papken Hovsepian.
• CrN has superior mechanical properties where as NbN has excellent corrosion resistance.
• The combination of both produce excellent tribological properties.
• There has been very little work to investigate the performance in combined erosion -corrosion conditions.
Aim of the project
Erosion: CrN/NbN superlattice coating
Study of coating performance at different impact angles of slurry.
Study of coating performance at different slurry impact velocities.
Study the wear mechanism of coating.
Construction of mechanism maps & Construction of wastage map.
Modelling to correlate impact angle, velocity & the erosion rate.
Erosion-Corrosion:CrN/NbN superlattice coating
Study performance of coatings for aqueous corrosion at different potentials.
Study performance of coatings for aqueous corrosion at different pHs.
Construction of erosion-corrosion regime maps
Construction of Wastage maps in synergism.
Results:
-2000
-1500
-1000
-500
0
500
1000
1500
0.0001 0.001 0.01 0.1 1 10
log I
pote
ntia
l (m
v)
20 degrees
30 degrees
45 degrees
60 degrees
90 degrees
Polarisation curves at varied degrees of impact angle of slurry.
Discussions:
• Results shows the effect of impact angle on the erosion behaviour.
• Pure metals and CrN/NbN coatings are to be investigated further for the erosion behaviour with respect to Impact angle of slurry as well as impact velocity.
• Polarisation curves for CrN/NbN superlattice coatings, to some extent, show a change in the synergistic wear data which is to be investigated further to nanoscale with the help of Atomic Force Microscopy (AFM).
Acknowledgement :
Tribology group at Strathclyde.
Surface Engineering Group at Sheffield Hallam University.
Staff of Mechanical Engineering in Strathclyde University.
Technical Staff of Lab M2 and M15 in Mechanical Engineering.
All those who have directly and indirectly helped me!!!
Questions & Suggestions:
• All suggestions welcomed!!!
• Address for correspondence:
Prof. M. M. StackDepartment of Mechanical Engineering,
University of Strathclyde,
James Weir Building, 75 Montrose street,
Glasgow G1 1XJ. Email: [email protected]
Thank you !