Improving Commercial Motor Bike Rim Disc Hardness Using a Continuous-Wave Infrared Fibre Laser

This study is focused on examining the feasibility of applying laser hardening to a commercial metallic bike rim, employing a CW IR fibre laser. The research comprises two main phases. The first phase involves an assessment of the impact of laser parameters on the metallic microstructure, while the second phase involves the actual laser hardening of the bike rim. A comprehensive evaluation encompassing hardness measurements, optical microscopy, and scanning electron microscopy was conducted on the samples. The microstructure type can be manipulated by skilfully adjusting the laser parameters, allowing for the creation of various microstructure variants within the laser-hardened zone for specific laser conditions. In this regard, multiple microstructure types were observed. The hardness of the laser-processed zones exhibited variations corresponding to the specific microstructure. Notably, the molten zone (MZ) and the second heat-affected zone (HAZ II) exhibited the highest levels of hardness. Furthermore, it was observed that a scan overlap of ≥ 75% led to an augmentation in hardness. This study sheds light on the intricate interplay between laser parameters, microstructure, and resultant hardness in the context of laser hardening of metallic materials.