Imposed Thermal Fatigue and Post-Thermal-Cycle Wear Resistance of Biomimetic Gray Cast Iron by Laser Treatment
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CAST iron is used in a wide range of applications. Many engine parts (e.g., engine boxes, cylinder heads, cylinder liners, pistons, and cram shafts) are made from cast iron.[1] These components are usually subjected to wear and thermal fatigue or even post-thermal-cycle wear (PTW), which affects only the surfaces of the components.[2–6] Therefore, surface modification directed toward protection against wear and thermal fatigue is absolutely necessary. Norman et al. verified that the mechanism that governed the fatigue damage was multiple microcracking.[7] Gray cast iron specimens with biomimetic coupling stripes were fabricated by laser. Moreover, Zhang et al.[8] found that adjustments in laser processing parameters could effectively improve the fabrication quality of biomimetic coupling units. Sui et al.[9] successfully used biomimetic laser surface treatment (LST) to enhance the pre- and post-thermal fatigue wear QI SUI, HONG ZHOU, and PENG ZHANG are with The Key Lab of Automobile Materials, The Ministry of Education, Jilin University, No. 5988, Renmin Street, Changchun 130025, People’s Republic of China. Contact e-mail: [email protected] DEPING ZHANG is with The Key Lab of Automobile Materials, The Ministry of Education, Jilin University, and also with the State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China. ZHIKAI CHEN is with The Academy of Xuzhou Construction Machinery, Xuzhou Construction Machinery Group, Xuzhou, Jiangsu 221004, People’s Republic of China. Manuscript submitted December 9, 2016. Article published online May 18, 2017 3758—VOLUME 48A, AUGUST 2017
resistance of cast iron. The laser biomimetic process that brings together the biomimetic theory[10] and the laser process has been regarded as an effective surface treatment technology in recent years. This is because the laser biomimetic surface remelting process has several advantages over other conventional surface processes, which include minimum distortion, high hardness, narrow heat-affected zone, easier control, and energy distribution in fiber optics. More specifically, a structure produced using the virtues of laser biomimetic surface remelting technology and consisting of alternating soft and hard phases, without changing the bulk properties of material,[11,12] can remarkably improve the wear and thermal fatigue resistance of materials.[13–15] In particular, Zhou et al.[16] managed to improve the wear resistance of GCr15 bearing steel processed by laser surface melting coupling. They used the biomimetic principle with different processing media, without changing the special properties of substrate materials. Furthermore, Guo et al.[17] stimulated the cuticles of soil animals to improve the wear resistance of compact graphite cast iron with biomimetic units on the surface. This was generated through a biomimetic coupled laser remelting process in air and water films with different thicknesses, respectively (Figure 1). The results
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