Microstructure and mechanical properties of interface between laser cladded Hastelloy coating and steel substrate
(1. School of Materials Science and Engineering, Southwest Petroleum University, Chengdu 610500, China;
2. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China;
3. Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, Ministry of Education, North China Electric Power University, Beijing 102206, China)
2. Department of Materials Science and Engineering, College of Engineering, Peking University, Beijing 100871, China;
3. Key Laboratory of Condition Monitoring and Control for Power Plant Equipment, Ministry of Education, North China Electric Power University, Beijing 102206, China)
Abstract: In order to improve the corrosion resistance of carbon steel, Hastelloy coatings were prepared on E235 steel substrate by a high power diode laser with laser scanning speeds of 6 and 12 mm/s, respectively. The interface between the coating and substrate was firstly exposed by dissolving off the substrate. Its microstructure, composition and mechanical properties were systemically studied. Special “edges” along the grain boundary were found at coating/substrate interface. These “edges” consisted of intergranular corrosion area and real grain boundary. The interface of coating mainly displayed austenite structure ascribed to the rapid solidification as well as the dilution of Ni during preparation. Additionally, Hastelloy coating and its interface prepared at the speed of 12 mm/s showed higher hardness than that prepared at the speed of 6 mm/s. Grain boundaries had higher friction coefficient than grains at both coating/substrate interfaces. Moreover, the interface at higher laser scanning speed exhibited smaller grains, lower dilution rates of Ni and Fe as well as a better tribological property.
Key words: Hastelloy coating; laser cladding; interface; microstructure; nano-scratch