Effect of iron particle size on the diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels

In the present work, diffusion bonding of Fe–5%Cu powder compact to wrought carbon steels was studied. Effects of iron particle size and carbon content of the solid component on the bond strength, which is the maximum shear stress required to obtain separation at the interface, were investigated. Atomized iron powders with the mean particle size of 36, 56, 90, 106, and 148 μm and wrought steels with 0.22, 0.33, and 0.47 wt% carbon content were used. To evaluate the bonding zone, “ring shear” test, standard metallography technique, and micro-hardness test were employed. The results showed a profound effect of carbon content of the solid steel on the diffusion bonding process. It is suggested that the diffusion of carbon through the interface during sintering influences the swelling of the powder compact, thereby affect strength of the bonding zone. A direct relationship between the depth of carbon diffusion and the maximum stress required to separate the bond interface was noticed. It was also found that there is an optimum iron particle size, in which, maximum swelling with narrow carbon diffusion layer occur. The highest strength was obtained for iron powder with mean particle size of 80 μm bonded to the 0.33 wt% wrought carbon steel.