Dry sliding friction wear behaviour of high power diode laser hardened steels and cast iron

Abstract

High power diode laser hardening of steels, namely AISI 1018l AISI 4140 and grey cast iron has been carried out at a power level of 4 kW. A rectangular laser beam of 13 × 4 mm was used for hardening at scan speeds of 1000, 1500 and 2000 mm min⁻¹. The laser heat treated surfaces were characterised for their microstructure using optical and scanning electron microscopy which revealed different levels of martensitic transformation based on the scan speed employed in processing the samples. The microhardness profile of the heat treated region revealed much higher hardness values as compared with that of base metal. The wear resistance of the laser heat treated samples was evaluated in the pin on disc machine as per ASTM standard G-99A at a constant load of 10 kg and a sliding speed of 5 m s⁻¹. The results indicated highest wear resistance for sample processed at 1000 mm min⁻¹ in the case of AISI 1018 steel, while in the case of AISI 4140 steel and cast iron, the sample processed at 2000 and 1500 mm min⁻¹ exhibited the highest wear resistance in the range of test parameters employed. The wear scars after the test have been studied using scanning electron microscopy which revealed oxidative wear and microploughing of the surface under test conditions.