Thermal Fatigue Crack Resistance of Ductile Iron Biomimetic Crack Blocked Units Fabricated by Laser Remelting
S-Y. Ma, T. Zhou, H. Zhou, X-Y. Pang, B-F Zhi, G. Chang and S-Y. Wang
Nodular iron brake discs often fail due to serious thermal fatigue cracking. The existence of graphite complicates the repair of the crack defects of ductile iron. This study presented a new idea of ductile iron brake disc remanufacturing based on coupled bionics and repaired ductile iron with thermal fatigue cracks discontinuously by bio-inspired crack blocked units fabricated by laser remelting with different laser parameters. Then tensile strength and thermal fatigue crack resistance of the units with various laser energy inputs were tested. The hardness, microstructure and phases in the units were characterized, as well as the anti-crack mechanism of the units being analysed. It was found the units positively impacted both the thermal fatigue resistance and tensile strength. The unit fabricated with a laser energy of 463.68+19-15 J/mm2 exhibited the highest tensile strength and the most significant improvement on thermal fatigue properties, which increased by 20.65 and 250% respectively compared with the untreated sample.
Keywords: Nd:YAG laser, ductile iron, brake disc, laser remanufacture, laser remelting, laser energy, thermal fatigue crack resistance, bionic crack blocked unit