On brazing of cubic boron nitride abrasive crystals to steel substrate with alloys containing Cr or Ti

Abstract

An investigation has been carried out to gain information about the capabilities of some filler alloys for direct brazing of CBN (cubic boron nitride) grits to a steel substrate. It has been found that a Ni-Cr alloy, known for effective diamond brazing, failed to show satisfactory wetting and bonding characteristics towards CBN under the same brazing conditions as that of diamond. The situation could not be improved either by increasing the wt% of Cr or the brazing temperature. Also, prolongation of the brazing time did not show any significant change. It was further revealed that a Ag-Cu-Ti alloy, which is well established for the brazing of diamond and ceramics, exhibited good wetting and bonding towards CBN at moderate temperature. Based on the thermodynamic properties of various materials, characteristic properties of elements of group IV B to VI B and the physical observations made during the investigation, it is suggested that the transition elements of group IV B, such as Ti or Zr, are preferred to transition elements of group VI B, such as Cr, as an activator to promote the wetting characteristics of the braze alloy towards CBN, which is far more chemically stable than diamond.