Advanced laser surface hardening of microalloyed steels for fatigue enhancement of automotive engine components

ended

Fatigue strength of crankshafts needs to be improved to meet today’s demands of higher performance automotive engines. In some cases, fatigue improvement can be difficult to reach due to poor residual stress distributions in relation to non-uniform/heterogeneous surface strengthened layers produced by standard techniques (induction surface hardening -IH- and deep rolling –DR-). In addition, the limited flexibility and complexity of equipment used for IH and DR may also hamper building next generation of high-performance engine crankshafts. STIFFCRANK will propose a novel laser-based processing strategy for surface hardening of microalloyed steel components, aimed at imparting an optimum distribution of residual stresses under the surface by generating uniform and homogenous hardened layers for improving fatigue resistance of the final steel component. The new strategy will involve using Advanced Laser Surface Hardening (ALSH) techniques for tailoring the energy distributed over the surface area and overcoming the limitations of conventional laser-surface hardening methods due to tempering of overlapped tracks during multi-pass laser beam hardening. Different options of laser processing technology will be employed, such as Laser Linear Oscillation Scanning (LLOS) and Beam shaping, for distribute the laser energy and induced optimum residual stress profiles. In STIFFCRANK, experimental and simulation tests will be combined with extensive measurements of the residual stress profile, detailed microstructural analysis and bending fatigue tests of advanced laser surface hardened steels and crankshafts. At the end of the project, the most promising conditions will be demonstrated by bench testing of full-size crankshafts.