Effects of pre-placed coating thickness on thermal fatigue resistance of cast iron with biomimetic non-smooth surface treated by laser alloying

In order to enhance the thermal fatigue resistance of gray cast iron with biomimetic non-smooth surface further, studies on laser alloying of Cr powder with different pre-placed coating thickness were performed to change both the composition and the microstructure of non-smooth unit. Additionally, the optimization of coating thickness was done based on the content of Cr in alloyed zone and the thermal fatigue behaviors of non-smooth samples. The results indicated that there was a critical coating thickness which corresponded to the increase of Cr content in alloyed zone under a definitive laser processing conditions, and the critical thickness was 0.3 mm in this paper. Any coating thicker than 0.3 mm would lead to the waste of alloying powder. The thermal fatigue resistance of non-smooth samples was better than that of smooth sample. In addition among all the non-smooth samples, the sample which was treated by the laser alloying of Cr had superior resistance to thermal fatigue compared with laser melting treated samples. And the thermal fatigue resistance increased with increasing of Cr content in alloyed zone which was caused by pre-placed coating thickening.