Influence of laser hardening on the tribological properties of forged steel for hot rolls

The influence of laser hardening on the tribological behaviour of a forged steel for hot profiled rolls is evaluated using a customary test rig which provides the rolling–sliding contact between the roll and a C40 plain carbon steel counterpart. Samples treated with different lasers and processing parameters were considered. Starting from a base value of 300 HV the surface hardness was increased up to 800 HV and the total case depth ranged from 1.2 to 2 mm. The benefits of the laser treatment could be clearly observed at low test temperature, due to the positive influence of a hard martensite microstructure in preventing severe metallic wear by adhesive fracture. The influence of laser hardening was less evident at high temperature, where the tendency of different microstructures towards the formation of wear protective oxide layers could result in a better or worse resistance compared to the base steel, respectively. The capability of the roll material to produce wear particles and their entrapment within the contact interface resulted of fundamental importance for the formation of oxide glazes.