Surface Coatings & Tests forLARP Coil Endparts Task Force

D.W.ChengLBNL

February 24, 2012

Overview

• Coating candidates

• How do we qualify these candidates?– Environmental conditions– Battery of Tests– Sample coupon design

• Initial Plasma Spray Results

• Summary and Status

2/24/12D.W.Cheng 2

Coating Candidates

• Plasma Spray (Aluminum Oxide)

• Not specifically covered in here:– Spray-on coatings (Cerakote®)– Surface conversion (micro-arc oxidation)– Vapor deposition

2/24/12D.W.Cheng 3

Plasma Spray Details

• Sulzer Metco powders (Aluminum Oxide)

• Bond layer options– Without bond layer

• LBNL experience in D20, etc.

– With NiCr (80%/20%) bond layer• CERN experience in SMC coils

– With Al-clad NiCr (6%/94%) bond layer• Vendor indicates that the Aluminum component

undergoes an “exothermic reaction at application” that helps the Al2O3 adhere better

2/24/12D.W.Cheng 4

Overview

• Coating candidates

• How do we qualify these candidates?– Environmental conditions– Battery of Tests– Sample coupon design

• Initial Plasma Spray Results

• Summary and Status

2/24/12D.W.Cheng 5

Environmental Conditions

• Known conditions:– Heat Treatment to ~650+ C– Epoxy impregnation– Cryogenic temperatures (77 K and below)– Insulation compatibility– Conductor compatibility

• Possible conditions:– Parts may come into direct contact with cable

(broken insulation, etc.); must provide electrical isolation

2/24/12D.W.Cheng 6

Battery of Tests

• Electrical hipot to >1000V– Uses the same equipment that we hipot coils with

• Material Compatibility (HT at ~665 C in Argon)– In contact with Conductor and Insulation materials

• Thermal Stability – High-temperature & Cryogenic (77K) excursions

– Post-cycle adhesion testing

• Thickness (QA)

• Metallography

2/24/12D.W.Cheng 7

Sample Coupon Design

• Basic Coupon: 2” squares, 1/8” thick– Ti 6Al4V– Stainless 304, Stainless 316– (Other materials can also be used)

• These samples can be used for all tests – Electrical hipot tests– Thermal and material compatibility tests– Adhesion tests– Metallography

• And we can also use actual part geometries

2/24/12D.W.Cheng 8

Sample Coupon Design

2/24/12D.W.Cheng 9

Other Samples

• We can also use actual part geometries

2/24/12D.W.Cheng 10

Electrical Hipot System

• Has adjustable spring-loaded pressure

• Has ¼” ball bearing contact

• Uses existing hipot electronics

2/24/12D.W.Cheng 11

Material Compatibility Testing

• Tube furnace (Argon atmosphere)– Heat treatment schedule (abridged HQ HT

cycle): • 210 C for 24 hours• 400 C for 24 hours• 665 C for 48 hours• 50 C/hour ramps between temperatures.

• Samples placed in contact with• Insulation (S2-glass in this case)• CTD Matrix-cured S2-glass and Nextel AF-10• Cable

2/24/12D.W.Cheng 12

Thermal Stability Tests

• Post-HT tests– Cryogenic (77K) cooldown– Post HT Hipot– Post HT Adhesion tests

• DeFelsko PosiTest AT tester (conforms to ASTM D4541/D7234)

• Can be compared with pre-HT test results

2/24/12D.W.Cheng 13

Cryogenic Dunking

• Standard 77K Cooldown test

2/24/12D.W.Cheng 14

Thickness Testing

• DeFelsko Positector 6000– Uses magnetic/eddy-current principles to

measure coating thicknesses on ferrous and non-ferrous base materials

• Can be used for regular QA

2/24/12D.W.Cheng 15

Overview

• Coating candidates

• How do we qualify these candidates?– Environmental conditions– Battery of Tests– Sample coupon design

• Initial Plasma Spray Results

• Summary and Status

2/24/12D.W.Cheng 16

First Plasma-Sprayed Sample Process

• Sample: – HQ endshoe (old design), SS 304

• Surface treatment: – Plasma Spray Al2O3, no bond layer

• Hipot Test (pre-HT)• Metallography• Heat Treat

– In contact with Matrix-cured Nextel Fabric

• 77K Cooldown Test• Hipot Test (Post-HT)

2/24/12D.W.Cheng 17

Initial Results of Plasma-Spray Test

• Hipot Test (pre-HT)– >1800V first attempt– >1100V subsequent attempts (same point)

• Metallography (see next slide)• Heat Treated In contact with Matrix-cured

Nextel Fabric– No visible surface reaction (although glass

appeared black—but not conductive)• 77K Cooldown Test

– No additional flaking/chipping observed after two cycles

• Post-HT Hipot Test (see following slide)

2/24/12D.W.Cheng 18

Metallography

2/24/12D.W.Cheng 19

195 m

195 m

183 m

134 m

134 m

122 m

73 m 0 m

85 m

15 mm

D.R. DietderichFeb. 23, 2012

Inner surface

OD

OuterSurface

134 m

ID

Post-HT Hipot Test Points

2/24/12D.W.Cheng 20

2000 V -> 3750 V

3150 V -> 2720 V

3550 V -> 2780 V

2850 V -> 3040 V

1300 V 1440 V 1210 V

2080 V -> 2200 V

1st attempt -> 2nd attempt

M. MartchevskiiFeb. 23, 2012

First Plasma-Spray Sample Summary

• Coating thickness (metallography) shows approximately .005” -.007”– A bond layer will add another ~.005” of thickness

• Surface is porous– Visible “wicking” with moisture and curing Matrix

– Wicked curing matrix apparently improves hipot after reaction (pores filled)

• We still need to perform adhesion test (using standard CTD epoxy) using standard sample coupon

2/24/12D.W.Cheng 21

Summary and Current Status

• We have samples designed & fabricated– Stainless 304/316, Ti 6Al4V, others

• A battery of tests have been defined• Sample parts have been sent out to vendors

– A few already received– Others ~1-2 week turnaround time

• The first plasma-sprayed sample has been tested– Initial results appear promising enough for near-term

coil fabrication (HQ Coil 17, etc.)

• Other surface treatments continue to be explored

2/24/12D.W.Cheng 22