Compatibility of surface treatments

1
Compatibility of surface treatments and
assembling techniques with Ti-Zr-V performances
Pedro Costa Pinto CERN 1211 Geneva 23 CH on
behalf of the CCS section
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Outline
I COMPATIBILITY WITH SURFACE TREATMENTS
a) Substrate Cleaning b) Substrate
etching c) Stripping d) NEG
cleaning
II COMPATIBILITY WITH ASSEMBLING TECHNIQUES
a) Cutting b) Welding
III CONCLUSIONS
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I COMPATIBILITY WITH SURFACE TREATMENT
CHEMICAL SUBSTRATE CLEANING
DEGREASING

• SOLVENT (Percloroetilene C2Cl4)

• DETERGENT US gt 5W/L T60oC (ALMECO P18 for
  stainless steel and NGL 17.40 for Al and Cu)

• RINSING (water lt 2MW.cm)

• DRYING (primary vacuum oven for stainless steel
  and Al filtered compressed N2 for Cu)

PICKLING

• STRONG CHEMICAL ATTACK (NetInox (HNO3/HF) for
  stainless steel NaOH for Al HCL for Cu)

• RINSING (water lt 2MW.cm)

• for the Cu, PASSIVATION with H2CrO4

• RINSING

• DRYING (vacuum oven for stainless steel and Al
  filtered compressed N2 for Cu)

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I COMPATIBILITY WITH SURFACE TREATMENT
- For hazardous materials (ex. Be)
O2 PLASMA CLEANING
In situ pure O2 plasma removes carbon from the
substrate without hazardous waste.
CO

• Standard NEG coating sputtering assembling

C

• Inject O2 (about 10-2Torr)

• The central wire is polarized positive relative
  to the chamber

O2
O2
O2
CO2
O2

• Start reverse sputtering

CHEMICAL SPUTTERING

• O2 C -gt CO CO2

• Key issues

Chemical sputtering yield gtgt physical sputtering
yield
O2 energy about 100eV
maximize evacuation of CO and CO2
SUCCESSEFULLY APPLIED TO LHCb Be CHAMBER
CO
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I COMPATIBILITY WITH SURFACE TREATMENT
ETCHING improve adhesion, increase roughness,
increase smoothness
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I COMPATIBILITY WITH SURFACE TREATMENT
ETCHING improve adhesion, increase roughness,
increase smoothness
Example standard LSS (Long Straight Sections of
the LHC) chambers.
Length 0.3 7 m Diameter 80 mm
Vacuum brazing
DN100CF flange
OFE Cu sleeve
OFS Cu tube
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I COMPATIBILITY WITH SURFACE TREATMENT
ETCHING improve adhesion, increase roughness,
increase smoothness
Example standard LSS (Long Straight Sections of
the LHC) chambers.

• Cu tube bought ( gt 6 Km)

• Standard Cu cleaning Pickling

• Welding

• Standard cleaning Pickling

• NEG coating

• Thermal cycling 10x(RT-250C) followed by high
• pressure water rinsing to evaluate adhesion

PEEL-OFF
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I COMPATIBILITY WITH SURFACE TREATMENT
ETCHING improve adhesion, increase roughness,
increase smoothness
Example standard LSS (Long Straight Sections of
the LHC) chambers.
Analysis

• Endoscopy peel-off only in a longitudinal
• 1-5 cm wide band.

• Particles composition (EDS) Cu and TiZrV

• Surface morphology (SEM) Cu particles detached.
  

ACTIONS
Conclusion

• Mechanical removal of most of the Cu particles
• (Cloth and Karcher).

• Amiss extrusion tool did not allowed the draining
  of
• the copper shaving.

• Chemical etching of the internal surface with
• NH4S2O3 (about 60mm).

• Copper shaving remained incrusted in the
• tubes surface.

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I COMPATIBILITY WITH SURFACE TREATMENT
ETCHING improve adhesion, increase roughness,
increase smoothness
Several chemical and electrochemical techniques
applied to Cu, Al, Ti, Inconel.
Cu standard
Cu smooth (SUBU)
Cu rough (Cu6)
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I COMPATIBILITY WITH SURFACE TREATMENT
STRIPPING remove a TiZrV NEG coating.

• ETCHING 3-Nitro Benzene Sulfonic Acid Sodium
  Salt (C6H4NNaO5S) - 100 g/l
• HF (40)

• RINSING (water max 2MW.cm)

• DRYING (primary vacuum oven for stainless steel
  and Al compressed N2 for Cu)

• if HAZARDOUS substrate material (Be) the same
  treatment, but outside CERN.
• THALES (UK).

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I COMPATIBILITY WITH SURFACE TREATMENT
CLEANING A TiZrV NEG coating rinsing.

• RINSING WITH DEMINERALISED WATER ( lt 2MW.cm)

TiZrV NEG LSS chamber already cycled 10 time was
water rinsed.
OK
Pumping speed measured after standard activation
cycle
Water rinsing can be applied to remove free
particles from TiZrV NEG coatings.
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I COMPATIBILITY WITH SURFACE TREATMENT
CLEANING A TiZrV NEG coating degreasing.
STANDARD DEGREASING (with NGL)

• The previous chamber was degreased with NGL.

NO PUMPING

• Standard activation cycle

• XPS analysis

NGL can not be used to degrease TiZrV surface.
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II COMPATIBILITY ASSEMBLING TECHNIQUES
Some vacuum components have to be NEG coated
before their final assembling
Examples vacuum chambers for the warm magnets of
the LHC, for the LEIR.
CUTTING
WELDING
LEAK TEST
STORAGE
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II COMPATIBILITY ASSEMBLING TECHNIQUES
Examples vacuum chambers for the warm magnets of
the LHC, for the LEIR.
CUTTING

• The tools must be cleaned (alcohol).

• The interior of the chamber must be protected
  from the metallic shaving.

• The workshop atmosphere must have a low level of
  hydrocarbons contamination.

• The time between cutting and re-pumping must be
  minimized.

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II COMPATIBILITY ASSEMBLING TECHNIQUES
Examples vacuum chambers for the warm magnets of
the LHC, for the LEIR.
WELDING (TIG)

• Remove the NEG coating from the welding surfaces.

• Tools must be degreased.

• the interior of the chamber must be protected
  against the gases and particles
• released during welding.

• Effective cooling close to the welding seam to
  minimize
• the NEGs area affected by the heating.

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III CONCLUSIONS
Degreasing UNAVOIDABLE and pickling necessary for
strongly oxidized surfaces..
SUBSTRATE CLEANING
Reverse O2 plasma WORKS to remove carbon from
hazardous substrates.
Can be used to improve adhesion and change
surface morphology.
SUBSTRATE ETCHING
Well established procedure. Outside CERN if
hazardous substrate.
NEG STRIPPING
Possible to remove free particles from the NEGs
surface (rinsing).
NEG CLEANING
Impossible to degrease.
SO FAR
Ok but it is a delicate task. Minimization of air
exposure time requires the detailed planning for
all operations. The personnel involved must be
well informed about the special procedures to
take with NEG manipulation.
CUTING WELDING
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Acknowledgments
Gonzalo Arnau SEM and EDS analysis
Said Atieh welding analysis
Sergio Calatroni O2 plasma cleaning
Leonel Ferreira chemical surface treatments
Mauro Taborelli XPS analysis
Thank you.