High performance sinter-hardening materials for synchronising hubs

Abstract

The development of synchronising hubs is driven by the need for more complex shapes and higher performance; at the same time as there is a strong pressure on costs. Many high performance synchronising hubs are currently produced using diffusion bonded materials with relatively high alloy contents, but there is a desire to move to materials and processes with better cost/performance ratios. This implies a move from nickel and molybdenum, whose costs are high and unstable, to pre-alloyed materials, preferably based on chromium with no or small additions of plain nickel. Pre-alloyed powders with 1·8%Cr provide a suitable basis for sinter-hardening. By carefully selecting the additions of copper or nickel and the carbon content, properties can be tailored for different strength requirements. The usage of CCT diagrams can assist in optimising composition depending on which cooling rate that can be applied.