The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement Materials Analyses for CRAB Cavities Konrad Eiler

Niobium H8 from Heraeus Ductility between 1 and 6% Typical values for tensile strength and hardness Very large grain sizes (on the cm scale) 2 Konrad Eiler

3 Titanium grade 2 – ø25 mm Grain size 3.0 ASTM (125 µm) Rolling direction not apparent evenly distributed Konrad Eiler

4 Titanium grade 2 - crossweld No indication of cracks in the xy plane Typical image of weld pool Konrad Eiler

5 Titanium grade 2 - crossweld Irregularly shaped grain boundaries in yz plane High dislocation density, internal stress Konrad Eiler

6 Titanium grade 2 – grease welds Similar weld pools No indication of cracks MolykoteApiezon Konrad Eiler

7 Titanium grade 2 – grease welds SEM analysis Molykote: purely Titanium in the inner weld pool No indication of MoS 2 Apiezon: Brittle, Si-rich phase on the entire surface Konrad Eiler

8 Nb/Nb55Ti weld Penetration depth of > 2 mm achieved Konrad Eiler 2.1 mm 270 µm 2.1 mm 270 µm

9 Nb/Nb55Ti weld No evident diffusion of Ti into RF surface BSE contrastTi distribution (K α1 ) Konrad Eiler

10 Outlook Niobium Problems with UT  need of calibration blocks Discuss with supplier Titanium grade 2 Validation of grain size requirements Mechanical testing Need of internal specification Presence of Silicon critical Konrad Eiler

11 Outlook Nb/Ti weld Diffusion strongly dependent on Temperature Welding process applicable Konrad Eiler

The HiLumi LHC Design Study is included in the High Luminosity LHC project and is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement

Intercept method (ASTM E 112)

14 Nb&Nb55Ti - EDX analysis Konrad Eiler