Picosecond pulsed laser machining of hardened martensitic stainless steel drive shaft

A fundamental method for estimating the laser parameters and for predicting the achievable ablation rate is demonstrated for hardened martensitic stainless steel X46Cr13. The laser ablation rate is evaluated for a range of pulse energies. The effective threshold fluence for ablation and the effective penetration depth are determined for a low and a high energy regime applying the Neuenschwander model. These parameters are used for numerical prediction of the ablated geometry. A very time efficient processing strategy and parameter set is selected and applied for laser machining of micro channels into a high precision drive shaft to increase friction for torque transmission leading to a processing time of 30 s per part, which corresponds to a structuring rate of 0.88 mms-1 . The deviation between the simulation and the ablated depth in the experiment are measured to be below 7 % at a total ablation depth of 25 µm. This demonstrates that the Neuenschwander model is suitable to determine the parameters needed for the prediction of the geometry resulting from an ablation process on martensitic stainless steel.