Brazing of CBN grains with Ag-Cu-Ti/TiX composite filler - The effect of TiX particles on microstructure and strength of bonding layer

• TiB2, TiN and TiC particles suppress the spreading behavior of Ag-Cu-Ti filler.
• Addition of TiB2, TiN or TiC improves the shear strength of brazed joints.
• Reinforcing particles refine the metallurgical microstructure of bonding layer.
• Optimum composite filler is determined as Ag-Cu-Ti/TiB2 (8 wt.%).

In order to improve the comprehensive mechanical performance of brazed joints of cubic boron nitride (CBN) grains/bonding layer/steel matrix, Ag-Cu-Ti/TiX (TiX = TiB2, TiN or TiC) composite filler materials, instead of the pure Ag-Cu-Ti alloy, were developed. As Part I of this work, a detailed investigation on the effects of TiX addition on the microstructure and strength of Ag-Cu-Ti/TiX bonding layer was made based on the evaluation of some fundamental performance (i.e. spreading area, shear strength, metallurgical microstructure and microhardness). Results obtained indicate that, the addition of TiX particles to Ag-Cu-Ti alloy is generally favorable for controlling the spreading behavior and improving the shear strength and microhardness of bonding layer. The metallurgical microstructure of the Ag-Cu-Ti/TiX bonding layer is refined to a certain extent, which is contributed to that the added particles become the potential nucleation agent of the molten Ag-Cu-Ti alloy during brazing. Combined with the effects of the reinforcing particles on the comprehensive performance of the bonding layer, and meanwhile considering the effects of the reinforcing particles on the brazing resultants of CBN grains reported in Part II of this work, the optimum addition to the Ag-Cu-Ti/TiX composite filler materials is determined as the TiB2 particles with 8 wt.% content.

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