J. Mater. Sci. Technol. ›› 2022, Vol. 111: 99-110.DOI: 10.1016/j.jmst.2021.09.038

• Research Article • Previous Articles     Next Articles

Joining dissimilar metal of Ti and CoCrMo using directed energy deposition

Vioni Dwi Sartikaa,1, Won Seok Choia,1, Gwanghyo Choia, Jaewook Hana,b, Sung-Jin Changc, Won-Seok Kod, Blazej Grabowskie, Pyuck-Pa Choia,*()   

  1. aDepartment of Materials Science and Engineering, Korea Advanced Institute of Science and Technology, Daejeon 34141, Republic of Korea
    bGangwon Regional Division, Korea Institute of Industrial Technology, Gangwon 25440, Republic of Korea
    cDivision of Measurement and Analysis, National Nanofab Center, Daejeon 34141, Republic of Korea
    dSchool of Materials Science and Engineering, University of Ulsan, Ulsan 44610, Republic of Korea
    eInstitute for Materials Science, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany
  • Received:2021-05-21 Revised:2021-09-15 Accepted:2021-09-15 Published:2022-06-10 Online:2021-11-26
  • Contact: Pyuck-Pa Choi
  • About author:* Korea Advanced Institute of Science and Technology, Republic of Korea. E-mail address: p.choi@kaist.ac.kr (P.-P. Choi).
    First author contact:

    1These authors contributed equally to this work.

Abstract:

We report laser cladding of pure titanium on a CoCrMo alloy using directed energy deposition. Using electron microscopy, the microstructural evolution upon varying the process parameters, especially laser power and powder feed rate, was investigated in relation to crack formation. Cladding layers showing dilution rates of more than 5% contained cracks due to the formation of the brittle Co2Ti intermetallic phase. The observed cracks could be ascribed to a mismatch in thermal expansion and a resulting stress of more than 440 MPa acting on the Co2Ti phase, as determined by density functional theory and nanoindentation. Furthermore, an excess laser energy caused chemical inhomogeneity and unmelted Ti powder particles, while a deficient laser energy resulted in a lack of fusion. Neither cracks nor partially melted powders were observed for a powder feed rate of 3 g/min and a laser power of 225-300 W, for which the dilution rate was minimized to less than 5%. For such samples, the cladding layers comprised pure α-Ti and a uniform CoTi interface with Co2Ti islands.

Key words: Additive manufacturing, Dissimilar metal joining, Titanium, Cobalt-based alloy