Transient liquid phase diffusion bonding for micro PCD tool fabrication

Abstract

In this study, K30 (W 90 wt%, Co 10 wt%) and DX5 (W 84 wt%, Co 16 wt%) tungsten carbide were used as base metals for transient liquid-phase diffusion bonding (TLPDB). The filler metal was MBF20, a type of nickel alloy used to minimize the residual stresses that occur due to the differences in the expansion coefficients of the metals. MBF20 contained B, Si, and Cr, which reduced the melting point of the nickel alloy and enhanced its mechanical properties. The base metal and filler metal surfaces were cleaned by mechanical polishing and cleaning. Diffusion bonding was performed under vacuum at 1,000–1,500 K under low pressure than buckling load conditions. The microstructure on the localized bonded surface was analyzed using scanning electron microscope (SEM) and optical microscopy. Result of no significant change was observed in the diffusion bonding in the low-to-mid temperature range due to insufficient filler metal or base metal dissolution at the bonding site. However, at high temperatures, the filler completely melted and bonded to the base metal on both sides. Our results showed that temperatures approaching the recrystallization temperature were required to provide high-quality welds for ultra-precision joints and micro polycrystalline diamond (PCD) tool fabrication.