Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


36487.pdf (4.53 MB)

ETD Abstract Container

Abstract Header

Deposition Kinetics of Titanium and Zirconium Diffusion Coatings on Nickel Microwires via Pack Cementation

Achuthankutty, Ajith
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592133155467387

Abstract Details

2020, MS, University of Cincinnati, Engineering and Applied Science: Materials Science.
Pack cementation is a promising technique to synthesize hollow NiTi microtubes, which impart enhanced heating/cooling efficiency and, thus, faster shape memory response. Prior research investigating the effect of wire size on phase evolution and Kirkendall pore formation during pack titanization showed a significant difference between large (100 µm) and small (25 µm) diameter wires. The first objective of this research is to quantify the titanium deposition kinetics on intermediate-sized Ni wire (75 µm diameter) and determine the required coating time to achieve the desired near-equiatomic NiTi composition. It also explores an ex-situ study of the formation of a dual-pore structure that forms in some of the wires and provides insight for future in-situ investigations of the wire size effect on pack titanizing. Even though binary NiTi shape memory alloys offer excellent biocompatibility, strength, and corrosion resistance, their application is limited to less than 100 ºC. Hence, there is a need to increase the transformation temperatures for high-temperature applications, especially for aerospace applications. Certain ternary alloying additions to NiTi form high temperature shape memory alloys (HTSMAs) as there is an associated increase in the austenite-martensite transformation temperature and, therefore, have attracted considerable attention from researchers. Ni-Ti-Zr is one such HTSMA that provides the additional advantages of weight and cost reduction as compared to its platinum (Pt), gold (Au) and hafnium (Hf) counterparts. In the current research, attempts were made to produce Ni-Ti-Zr wires by co-depositing Ti and Zr on Ni wires using a halide activated pack in a single step process. The samples gained Zr content, but not enough was deposited to increase the transformation temperature. Moreover, a significant variation in the coating thickness was observed, resulting in a significant fluctuation in the composition. Therefore, as a first step, deposition of Zr on Ni wires was conducted to assess the feasibility of a two-step coating process to achieve the desired ternary Ni-Ti-Zr composition. The deposition kinetics, intermetallic phases formed, coating thicknesses, and composition were determined at 925 °C for various coating durations. The samples reached approximately 12-13 at. % Zr after 3 hours of coating. The as-coated wires, upon characterization via optical and laser microscopy, SEM, and EDX, displayed a core-shell structure with intermetallic phases which appeared to be Ni7Zr2 and Ni3Zr around the Ni core demonstrating the feasibility of the deposition process. The outcome of the present study will provide insight to further research regarding fabrication of these HTSMA microtubes, which can be utilized in the automotive, aerospace, and oil industries.
Ashley Paz y Puente, Ph.D. (Committee Chair)
Matthew Steiner, Ph.D. (Committee Member)
Sarah Watzman, Ph.D. (Committee Member)
98 p.
Materials Science
Shape Memory Alloys; Kirkendall Effect; Ni-Ti-Zr; Pack Cementation; High Temperature Shape Memory Alloys; Microwires

Recommended Citations

Citations

  • Achuthankutty, A. (2020). Deposition Kinetics of Titanium and Zirconium Diffusion Coatings on Nickel Microwires via Pack Cementation [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592133155467387

    APA Style (7th edition)

  • Achuthankutty, Ajith. Deposition Kinetics of Titanium and Zirconium Diffusion Coatings on Nickel Microwires via Pack Cementation. 2020. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592133155467387.

    MLA Style (8th edition)

  • Achuthankutty, Ajith. "Deposition Kinetics of Titanium and Zirconium Diffusion Coatings on Nickel Microwires via Pack Cementation." Master's thesis, University of Cincinnati, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1592133155467387

    Chicago Manual of Style (17th edition)

ucin1592133155467387
261
© 2020, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.