Sa. Nikulin et al., INVESTIGATION OF QUALITY OF HIGH-RESISTIVE COATINGS OF SUPERCONDUCTING WIRES WITH ACOUSTIC-EMISSION METHOD, IEEE transactions on applied superconductivity, 5(2), 1995, pp. 325-328
Mechanism and kinetics of fracture of electrolytic chrome coatings on
multifilamentary Nb3Sn-based superconductoring wire have been investig
ated with the methods of acoustic emission (AE) and electron microscop
y when developing superconductors for the ITER magnetic system. Coatin
gs 1, 3, and 8 mu m thick of the following three types were obtained b
y varying the electrolyte composition and the mode of precipitation pr
ocess: milk chrome (Cr), hard CT and black Cr. The detected acoustic s
ignal and analysis of AE spectra processed in digital form with a spec
ially designed analyzer of AE signals. Milk Cr coatings are shown tb h
ave the greatest crack resistance at any coating thickness, the same i
s for black Cr but at thickness of 1 to 3 mu m. In these coating the m
icrocracks formation is going by the ductile mechanism. Hard Cr coatin
g have the least resistance to brittle cracks at any thickness.