Tailored Forming of Hybrid Bevel Gears with Integrated Heat Treatment

“In recent years, multi-material designs of technical components have been gaining in importance. When combining different materials in a single component, it is possible to achieve high performance and extended functionality while simultaneously saving cost-intensive or rare materials. One promising approach to manufacture hybrid parts such as bi-metal gears is the utilization of the technology of tailored forming. This technology includes three main process steps: producing of bi-metal workpieces, forming and finishing. At the example of bevel gears, bi-metal preforms were produced by laser cladding of the martensitic steel X45CrSi9-3 on a cylindrical substrate made of the carbon steel C22.8 and formed to the final gear geometry by means of hot die forging. Subsequently, the hot bevel gears were directly quenched from hot-forming temperature by an air-water spray and self-tempered using the residual heat. To analyse the effect of each process step on the microstructure, specimens were extracted from cladded, forged and heat treated components and investigated by means of metallographic analysis and hardness measurements. The results demonstrate that cladded workpieces were successfully formed to complex toothed parts without any defects. The hot forming process has a positive impact on the welded layer and the interface zone by grain refinement and the associated improved mechanical properties. The required hardness values at the tooth flanks were achieved by the integrated heat treatment".