Study on vacuum brazing of high purity alumina for application in proton synchrotron

Abstract

The paper describes an experimental study to evaluate two different vacuum brazing processes to obtain high purity alumina (99.7%) joints suitable for application in rapid cycle proton synchrotron. Two different brazing routes, adopted for making alumina–alumina brazed joints, included (i) multi-step Mo–Mn metallization, followed by brazing with BVAg-8 alloy and (ii) advanced single-step active brazing with CuSil-ABA® alloy. Both the brazing routes yielded helium leak tight and ultra-high vacuum (pressure<10−9mbar) compatible joints. Active-brazed specimens exhibited tensile and mean flexural strengths of 62 and 110MPa, respectively. Metallized-brazed specimens, although associated with relatively lower tensile strength (35MPa) than the targeted value (>50MPa), displayed higher mean flexural strength of 149MPa. The results of the study demonstrated that active brazing is a simple and cost effective alternative to conventional multi-step metallization route for producing quality joints of high purity alumina for application in rapid cycle proton synchrotron machine.