Measurement and prediction of surface temperature in relation to laser surface hardening of metals

When the surface of the material is heated above the critical temperature with a laser beam, metallurgical changes occur in the surface region of the material. As the laser beam passes, quenching of the heated surface by the underlying mass of cold metal can produce a transformation hardening depending on the cooling rate. Therefore, the prediction and the measurement of cooling rate in surface hardening is essential. To determine the cooling rate experimentally, the surface temperatures of laser heated workpieces were measured using fast response thermocouples while the surface temperature distribution was predicted theoretically for four different workpiece materials.