**Microstructural Evolution and Mechanical Properties of Hybrid Bevel Gears Manufactured by Tailored Forming**

#### **Bernd-Arno Behrens 1, Anna Chugreeva 1,\*, Julian Diefenbach 1, Christoph Kahra 2, Sebastian Herbst 2, Florian Nürnberger 2 and Hans Jürgen Maier 2**


 **\***Correspondence:chugreeva@ifum.uni-hannover.de;Tel.:+49-51176218280

Received: 17 September 2020; Accepted: 8 October 2020; Published: 13 October 2020

**Abstract:** The production of multi-metal bulk components requires suitable manufacturing technologies. On the example of hybrid bevel gears featuring two different steels at the outer surface and on the inside, the applicability of the novel manufacturing technology of Tailored Forming was investigated. In a first processing step, a semi-finished compound was manufactured by cladding a substrate using a plasma transferred arc welding or a laser hotwire process. The resulting semi-finished workpieces with a metallurgical bond were subsequently near-net shape forged to bevel gears. Using the residual heat after the forging process, a process-integrated heat treatment was carried out directly after forming. For the investigations, the material combinations of 41Cr4 with C22.8 (AISI 5140/AISI 1022M) and X45CrSi9-3 with C22.8 (AISI HNV3/AISI 1022M) were applied. To reveal the influence of the single processing steps on the resulting interface, metallographic examinations, hardness measurements and micro tensile tests were carried out after cladding, forging and process-integrated heat treatment. Due to forging and heat-treatment, recrystallization and grain refinement at the interface and an increase in both, hardness and tensile strength, were observed.

**Keywords:** hybrid components; bevel gears; hot forging; tailored forming; process-integrated heat treatment; air-water spray cooling; self-tempering
