Microstructural Evolution and Mechanical Evaluation of a Laser-Induced Composite Coating on a Ni-Based Superalloy during Thermal Exposure

oleh: Yuebing Li, Yanming He, Chuanyang Lu, Wenjian Zheng, Jianguo Yang, Donghong Wang, Limei Wang, Yuan Sun, Zengliang Gao

Format: Article
Diterbitkan: MDPI AG 2019-05-01

Deskripsi

A Ni&#8722;17Mo&#8722;7Cr-based superalloy was laser surface-modified to improve its tribological properties. Si particles were employed as coating materials. Si melted on the surface of the alloy during the process, triggering the formation of Mo<sub>6</sub>Ni<sub>6</sub>C carbides and Ni&#8722;Si intermetallics. A defect-free coating obtained was mostly made up of primary Mo<sub>6</sub>Ni<sub>6</sub>C and &#947;-Ni<sub>31</sub>Si<sub>12</sub>, as well as a eutectic structure of &#946;<sub>1</sub>-Ni<sub>3</sub>Si and &#945;-Ni-based solid solution (&#945;-Ni (s.s)). The volume fraction of hard reinforcements (Mo<sub>6</sub>Ni<sub>6</sub>C, &#947;-Ni<sub>31</sub>Si<sub>12</sub>, and &#946;<sub>1</sub>-Ni<sub>3</sub>Si) reached up to 85% in the coating. High-temperature microstructural stability of the coating was investigated by aging the coating at 1073 K for 240&#8722;480 h, to reveal its microstructural evolution. In addition, the mechanical performance of the coating was investigated. The nanoscale elastic modulus and hardness of Mo<sub>6</sub>Ni<sub>6</sub>C, &#947;-Ni<sub>31</sub>Si<sub>12</sub>, and &#945;-Ni (s.s) were characterized using the nanoindentation tests. The nanoscratch tests were performed to measure the local wear resistance of the coating. Lastly, the Vickers hardness distribution across the cross-section of the coating before and after thermal exposure was compared. The work performed provides basic information understanding the microstructural evolution and mechanical performance of laser-induced coatings on Ni-based superalloys.