NCSX Friction Coating Peer Review March 16, 2007 NCSX

March 16,20072 Introduction WBS 14 will use some revision of the 0.5” McGinnis/Williamson shim (see left) between modular coils Friction-encouraging and insulating properties are needed in these shims

NCSX March 16,20073 Testing Setup A traditional tension/compression testing machine has been configure to pull “double shear” combinations. Side rams allow the application of normal (transverse) loads

NCSX March 16,20074 Typical Test Combination A 0.38” thick x 1.00” wide center element receives the application of friction- encouraging medium (if any) Wider (1.50”) side plates are added to each side of the center element with an axial overlap of 1.0” The normal/transverse load (10 kip max) is added at the center of the overlap areas (2 in**2 total area)

NCSX March 16, nd Design Test Combination The original design called for a maximum loading of 10 kip over the available area A choice was made to reduce the test area rather than upgrade the test rig after analysts began predicting 17 ksi loading needs. The lessened area results in 10 kip max applied on two series ½ in**2 areas (1 in**2 total)

NCSX March 16,20076 Early Test Observations File Summary.xls lists the outcomes of 21 trials –G-10 on SS (ambient,1trial) m=0.18 –SS on SS (amb/cold, 4 trials) m= –SS/diamond/SS (amb/cold, 16 trials) mavg=0.53 Many combinations The fundamental failure in the diamond-assisted trials was the tearing of the seated diamonds along/through the surface of the stainless –The tear-outs look like aerial views of perfectly plowed fields –This may be the functional limit of the material

NCSX March 16,20077 Emergent Bad News The nickel-bound CT-provided diamond coating could not survive LN2 dunk testing –The coating bubbled and flaked off The epoxy in the epoxy-bound diamond coating seemed to becomes a lubricant after the joints’ first “give” at ultimate slip load

NCSX March 16,20078 Better Product Ceradyne’s EKAgrip10 was deposited onto 4 mil shim stock and tested. –CoeffFricton Mu’s of and were obtained at loadings of 6 ksi and 9.5 ksi respectively. –Survived the dunk test without incident –Diamond size is small (~0.4 mil); nice for ass’y crews

NCSX March 16,20079 Really Better Solution Plasma-sprayed alumina emerged as the big winner –1) Mu's from 0.50 to 0.71 at pressures from 6 ksi to 17 ksi –2) Infinite electrical isolation to 45 ksi compressive loading (at 9 volts) –3) The ability to "give" as the test set-up (always imperfect) aligns itself while the slip load is applied to failure –4) The ability to maintain its peak mu (and load) during slip to failure. The diamond solutions fall in load capacity after slipping starts.

NCSX March 16, Alumina - Linear Relationship? w/o binder Nice outlier

NCSX March 16, Alumina Images

NCSX March 16, Next Steps Finish scan of alumina with & without binder Perform cycle testing at ZZ% (90?) of 17 ksi slip load –Need chit (# cycles, % of slip) Investigate/Procure on-site plasma spray rig Others?