1. Microstructural modification and mechanical characterization for a laser-induced composite coating during thermal exposure.
- Author
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He, Yanming, Lu, Chuanyang, Zheng, Wenjian, Yang, Jianguo, Chen, Shuangjian, Li, Zhijun, Sun, Yuan, and Gao, Zengliang
- Subjects
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COMPOSITE coating , *MICROSTRUCTURE , *ELECTRON microscopy , *MECHANICAL behavior of materials , *SURFACE coatings - Abstract
Abstract In this work, a composite coating prepared by laser cladding on a Ni-17Mo-7Cr based superalloy was thermally exposed at 1073 K for 240 h. A detailed electron microscopy examination was performed to characterize the microstructure of the aged coating. Results indicate that: the original Mo 6 Ni 6 C dendrites in the aged coating were coarsened while the coarsening layers were essentially the Mo-deficient and Cr-rich Mo 6 Ni 6 C, due to low diffusivity of Mo. Long-term thermal exposure promoted a great amount of nano-sized Mo 6 Ni 6 C and micro-sized Cr 3 C 2 particles being precipitated in the interdendritic zones. In the aged coating, three types of Cr 3 C 2 were presented: discrete Cr 3 C 2 , Cr 3 C 2 close to the graphite and Cr 3 C 2 approaching to the Mo 6 Ni 6 C. The transformation of Mo 6 Ni 6 C to Cr 3 C 2 merely occurred in the newly formed Mo 6 Ni 6 C rather than in the original Mo 6 Ni 6 C dendrites, because deficiency of Mo and enrichment of Cr in the new Mo 6 Ni 6 C depressed their stability. Lastly, the mechanical behavior of the aged coating was characterized by Vickers hardness, nano-indentation and nano-scratch tests with the aim to unveil the effect of microstructural evolution on mechanical properties. Our findings provide basic information to understand the aged-induced microstructural modification and its effect on mechanical properties for a laser-induced coating prepared on the Ni-17Mo-7Cr based superalloy. The results obtained cannot only apply to the investigated Ni-based superalloys, but also to other Hastelloy series superalloys. Highlights • The coarsening layers around original Mo 6 Ni 6 C dendrites were Mo-deficient and Cr-rich Mo 6 Ni 6 C. • Some newly precipitated Mo 6 Ni 6 C were transformed to the Cr 3 C 2 in aging. • The aged interdendritic zones had a higher elastic modulus and hardness than the non-treated ones. • An excellent local wear resistance has been achieved in the aged coating. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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