X-band Accelerating structure Review NOVEMBER 2014 SiC to copper brazing Anastasiya Solodko, on behalf of the CLIC study team, CERN

2 31-January-2013 X-band Accelerating structure Review NOVEMBER Contents 1.Aim of the study 2.Components 3.Introduction 4.Metallization tests 5. Brazing tests and results 6.Future program 7.Conclusion

3 31-January-2013 X-band Accelerating structure Review NOVEMBER Aim  There are several CLIC components which contain SiC parts. A good thermal contact between copper and SiC parts is required.  The aim of the study is to define and to choose a technique which allows accomplish a brazed joint between copper and SiC tubes.

X-band Accelerating structure Review NOVEMBER 2014 RF COMPACT LOAD Components AS with damping material RF GATE VALVE A. Samoshkin

5 31-January-2013 X-band Accelerating structure Review NOVEMBER Introduction  Thermal properties of materials to be joint have to be taken into account.  There are several approaches to braze SiC and Cu:  Braze with active brazing alloy;  Braze with metallization of SiC;  Braze with ductile brazing alloy (based on Au/Cu) with high temperature;  Braze with ductile brazing alloy (based on Sn) with low temperature.  Results depend on:  Choice of metallization layers;  Choice of brazing alloy;  Choice of thermo cycle.

X-band Accelerating structure Review NOVEMBER 2014 SiC load for Compact Load Proposal 1 Metallization tests (March 2013) A. Samoshkin Simplified pieces Objectives of metallization: -to facilitate wetting of the brazing alloy on the assembly (Ti); -to reduce the internal stress of the junction; -to ensure brazing.

X-band Accelerating structure Review NOVEMBER 2014 Metallization tests (March 2013) Test 1: sputtering Test 3: sputtering  Ti-Cu Test 2: chemical deposition of Cu  Ti-Nb  Ti-Mo-Cu A. Samoshkin

8 31-January-2013 X-band Accelerating structure Review NOVEMBER Brazing tests 1 & 2 (May 2013) Test 1  Sn/Ag 80/20 brazing alloy;  No metallization;  T ~ 250 °C Crack Broken peace Results: not good Test 2  CuSil-ABA brazing alloy (Ag/Cu/Ti, 63/35.25/1.75);  Metallization Au-Ni;  T ~ 815 °C Results: not good

9 31-January-2013 X-band Accelerating structure Review NOVEMBER Brazing test 3&4 (May 2013) Test 3  Ag/Cu/Ti 68.8/26.7/4.5 brazing alloy;  Ti-Nb metallization;  T ~ 910 °C Test 4  Ag/Cu/Ti 68.8/26.7/4.5 brazing alloy;  Ti-Mo-Cu metallization;  T ~ 910 °C Results: not good Crack Removed from the oven After 5 min Results: not good Crack on horizontal plane and then a break at the level of the brazed joint. The SiC tube cracked some minutes after the exit from the oven. A vertical side crack of the coating and an inside crack at the level of the brazed joint were observed. Possible explanation: a thermal shock occurred at the exit from the oven and it caused these cracks.

X-band Accelerating structure Review NOVEMBER 2014 Brazing tests 5 (May 2013) & 6 (October 2014) Test 5  Ticusil Ag/Cu/Ti 68.8/26.7/4.5 brazing alloy;  Au-Cu metallization;  T ~ 900 °C  Molybdenum ring b/w SiC and Cu;  Brazing alloy Ag/Cu/Ti 63/35.25/1.75;  T ~ 800 ᴼC. Test 6 Results: not good

11 31-January-2013 X-band Accelerating structure Review NOVEMBER Brazing tests (future program) Test 1  Ti-NEG (Ti, Zr, V)/ Mo-NEG sputtering; Test 2  Ti-Cu (1 µm, 5 µm) sputtering Test 3  Ti-Mo-Ni-Cu: Ti-Mo-Ni + 2 µm of Cu – sputtering + 8 µm of Cu - electroplating; Some successful tests have been already done at KEK But the test samples had a simple bar shape 2 cm in diameter and 5 cm long To make a simple test with broken SiC part (from the brazing test N6). To see how the coated part will react with brazing alloy. For all mentioned future tests Choice of brazing alloys and temperature:  Sn/Ag 90/10  305 °C  Sn/Ag 96.5/3.5  221 °C Test 4  Cr-Cu (10-60 µm sputtering + electroplating) /unrestricted/dissertation.pdf Copper ring SiC ring Test pieces

12 31-January-2013 X-band Accelerating structure Review NOVEMBER Conclusion  Observations:  Tests N3 and N4 were performed with samples which already passed thermo cycle;  Probably, the cooling cycle after the brazing cycle was too quick.  Performed tests allowed:  To test different metallization and brazing techniques;  To eliminate some technical solutions.  The next tests will be performed in the nearest future with:  Low temperature brazing;  Sn/Ag brazing alloy;  Slow cooling.

13 31-January-2013 X-band Accelerating structure Review NOVEMBER EXTRA MaterialThermal expansion coefficient SiC4.6×10 -6 Cooper16.5×10 -6 Molybdenum5.2×10 -6 Niobium7.3×10 -6 Titanium8.6×10 -6