Vacuum brazing of super-Ni/NiCr laminated composite to Cr18–Ni8 steel with NiCrP filler metal

Microstructure of Ni–NiCr laminated composite and Cr18–Ni8 steel joint by vacuum brazing

A study on the microstructure and properties of brazing joint for Cr18-Ni8 steel using a BNi7+9%Cu mixed filler metal

The joining of powder metallurgy products is of importance because of high demand in many industrial applications. In this study, the effect of welding voltage on the joint quality has been investigated using discharge arc stud welding, a low heat input welding method, without gas protection to join steel stubs to microwave sintered compacts containing a powder mixture of 26 atomic % Al and Fe (balance). It has been shown that welds with steel stubs are prone to side cracking in the weld zone and they also suffer from the oxidation of metal powders adjacent to weld zone. The forms of oxides are continuous and laminar type in welds with steel stubs and the composition of weld zone changes with increasing arc voltage.

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The effect of voltage on the arc stud welding of microwave sintered Fe+Al powder mixture

Cylindrical parts made from pre-strengthened Fe–Cu–C and Fe–Zn–C powders, fabricated under 1000 MPa-cold press, were welded in a vacuum furnace at different temperatures by diffusion welding. A novel approach was used where powder metallurgy parts were sintered together with diffusion welding with no extra pressure applied during the welding process. Chemical composition, cold press pressure, and sintering time (consequently welding time) were constant during the experimental works. Samples were examined by means of optical microscopy for metallographic inspection and by energy dispersive spectroscopy for compositional analysis. The shear strength and hardness profiles of joints were determined. It was observed that shear strength and hardness values of welding increased with increasing welding temperature.

Jack Hamill

Papers

Weld techniques give powder metal a different dimension