Laser Brazing of a Hexagonal Boron Nitride Block to a Cemented Carbide Plate with Silver-Copper-Titanium Alloy Filler in Argon Atmosphere Including Different Oxygen Contents

Abstract

Relationship between oxidation of Ag-Cu-Ti braze alloy and oxygen contents was investigated in the laser brazing of a hexagonal boron nitride block to cemented carbide plate in Ar atmosphere. The laser brazing was conducted in Ar-flow atmosphere in a vacuum chamber, and changing Ar-flow rate with and without pre-evacuation. No oxidation of the braze alloy was found after 3-min Ar-flow atmosphere over 5 L/min without pre-evacuation and at 5 L/min with pre-evacuation. When the Ar flow rate increased to 10 L/min without pre-evacuation, the oxygen content decreased to 3.8 ppm. In this case, the average shear strength of the brazed joint was about 8 MPa and a fracture occurred at the hexagonal, boron nitride side of the specimen, near the interface.