Sustainable technology for remanufacturing of carburized steels by laser hardening

Abstract

The development of functional recovery technology for surface treatments is crucial for remanufacturing—a key green innovation technology for achieving a carbon-neutral, circular economy. Laser hardening (LH), a type of surface treatment method, is known to be able to reform the partial surface of metals. This study focuses on the use of LH to allow the repair of friction-fatigue damage in used carburized martensite steel gears. As the surface of the fatigued specimen was rapidly heated by the laser and then cooled, the thin hardening layer quenched the surface layer. In addition, prior austenite (γ) grain refinement and restoration of the retained austenite phase in the LH quenched layer were realized for the friction-fatigued specimen. Exploiting these characteristics, the friction-fatigued specimens were reheat-treated with LH; as a result, the number of cycles to failure increased by 3.8 times compared to that before LH treatment. For remanufacturing as a small lot production of many products, the LH technique incurs lower environmental and processing costs than other surface treatments and is particularly beneficial when applied to gears and bearings, which are especially susceptible to wear and tear.