Machinability Improvement for Sintered Bearing Cap of Automobile Engines by a Method of Surface Modification

This modification process provides a method to a soft layer on surface of sintered material only where it is necessary for machining without deteriorating the material's strength properties. The soft layer is created on the objected surface through permeating aqueous solution of boric oxide to prevent the diffusion of graphite during sintering. Since the retained graphite is dispersed in the pore of soft ferrite matrix and gives a lubrication action during machining, it was confirmed that the machinability of developed material was greatly improved in compared to the material without the modification.