Active brazing of cBN micro-particles with AISI 1045 steel using ceramic reinforced Ag-based fillers

Abstract

cBN micro-particles have been brazed to medium carbon steel substrate using a new formulation of low-temperature, ceramic reinforced Ag-Cu-Ti alloy and evaluated for their wear resistance in developing cBN brazed tools. TiN and TiB2 microparticles were added as reinforcements independently in different proportions to Ag-Cu-2Ti (Ag-Cu-2wt%Ti) filler alloy and cBN tools were brazed. Wear characteristics of the ceramic reinforced alloys showed that the TiB2 added Ag-Cu-2Ti alloy exhibited excellent abrasion resistance with an improvement of 91–95 % over the commercial Ag-Cu-2Ti alloy. Conversely, the wear performance of the TiN added Ag-Cu-Ti alloys was poor owing to the weak bonding of TiN microparticles by the alloy matrix. The results were compared with 5 wt% TiB2 and TiN added Ag-Cu-5Ti alloys. However a significant improvement in the mechanical properties was not observed and the wetting on cBN was lower for reinforced Ag-Cu-5Ti alloy. Tensile tests showed that the Ag-Cu-2Ti-5TiB2 alloy demonstrated higher tensile strength (305.89 MPa) when compared to the Ag-Cu-2Ti and Ag-Cu-2Ti-5TiN filler materials. Low and high impact dynamic joint strength tests were further carried out on the 2 and 5 wt% reinforced Ag-Cu-2Ti and Ag-Cu-5Ti alloys. TiB2 added Ag-Cu-2Ti alloy displayed sufficient joint strength with TiN added Ag-Cu-2Ti alloys performing marginally better. Bearing in mind the excellent mechanical properties of the Ag-Cu-2Ti-5TiB2 filler and its appreciable joint strength, Ag-Cu-2Ti-5TiB2 filler can be used as an efficient filler material in developing cBN brazed tools for grinding applications.