12/4-5/2007 Braze Wetting tests on Molybdenum
Left sample
Pure copper wire 0.5mm diameter was formed into a ring about 12mm diameter
Braze temperature abut 1080-1090 deg C
Right sample
25/75 Gold Copper Alloy wire 0.5mm diameter was formed into a ring about 12mm
diameter.
Braze temperature was 1041-1042 deg C (thermocouples nearby)
25/75 Gold alloy wetting is acceptable …so will continue with next test of simulated joint
The first Joint test was done with 25/75 Gold alloy.
Pic 1 through 4 show good fillets at Shaft outside diameter…but there is some filling of
alloy in the 0.25mm gap between the diaphragm and shaft which would bond the
diaphragm in its working area. A second test will be done with a larger gap and a stop
feature to prevent the flow of alloy.
The production joint actually needs to be brazed at a lower temperature than the 25/75 so
35/65 Gold alloy will be used for the second test.
35/75 will also be tested for wetting the moly prior to the second joint test.