Journal of Advanced Materials and Technologies

Journal of Advanced Materials and Technologies

The Effect of Withdrawal Rate on the Microstructural Defects of a New Cobalt-nickel Based Directionally Solidified Superalloy

Document Type : Original Reaearch Article

Authors
Fatemeh Abdolmaleki 1
Masumeh Seifollahi 2
Sayed Mahdi Qazi mirsaeid 3
1 MSc Student, Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran.
2 Assistant Professor, Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran‎.
3 MSc, Researcher, Faculty of Material and Manufacturing Technologies, Malek Ashtar University of Technology, Tehran, Iran, Iran.
10.30501/jamt.2023.396693.1278
Abstract
The microstructure of new cobalt-nickel-based superalloys contains γ´ precipitates. Withdrawal rate and temperature gradient are two important parameters affecting the formation of defects such as segregation, microporosity, and eutectic zones. This research discusses the impacts of the withdrawal rate on these defects. To this end, Bridgman furnace was used for directional growth of the samples under a vacuum at the withdrawal rates of 1.5, 3, and 6 mm/min. Upon increasing the speed of the withdrawal rate mold, segregation of the elements is reduced due to the shorter diffusion time. Co and W elements tend to segregate in the dendritic core while Al, Ti, and Ta tend to segregate in the inter-dendritic regions. Throughout the study, the size of microporosity decreased from 14.3 to 9.5 μm while increasing the withdrawal rate from 1.5 up to 6 mm/min. This decrease in the size of micropores resulted from the lack of melt feeding in the inter-dendritic areas. Moreover, the size of the eutectic zones decreased from 14.6 to 8.9 μm upon increasing the withdrawal rate from 1.5 up to 6 mm/min, mainly due to the smaller melt pools in the final stage of solidification.
Keywords
New Cobalt-Nickel Base
Superalloy
Withdrawal Rate Mold
Eutectic
Microporosity
Segregation Elements
Subjects
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  • Receive Date 21 June 2023
  • Revise Date 21 August 2023
  • Accept Date 05 September 2023