Manufacturing of High-Performance Bi-Metal Bevel Gears by Combined Deposition Welding and Forging

The present paper describes a new method concerning the production of hybrid bevel gears
using the Tailored Forming technology. The main idea of the Tailored Forming involves the creation
of bi-metal workpieces using a joining process prior to the forming step and targeted treatment
of the resulting joint by thermo-mechanical processing during the subsequent forming at elevated
temperatures. This improves the mechanical and geometrical properties of the joining zone. The aim
is to produce components with a hybrid material system, where the high-quality and expensive
material is located in highly stressed areas only. When used appropriately, it is possible to reduce
costs by using fewer high-performance materials than in a component made of a single material.
There is also the opportunity to significantly increase performance by combining special load-tailored
high-performance materials. The core of the technology consists in the material-locking coating of
semi-finished parts by means of plasma-transferred-arc welding (PTA) and subsequent forming.
In the presented investigations, steel cylinders made of C22.8 are first coated with the higher-quality
heat-treatable steel 41Cr4 using PTA-welding and then hot-formed in a forging process. It could
be shown that the applied coating can be formed successfully by hot forging processes without
suffering any damage or defects and that the previous weld structure is completely transformed into
a homogeneous forming-typical structure. Thus, negative thermal influences of the welding process
on the microstructure are completely neutralized.

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