J. Mater. Sci. Technol. ›› 2019, Vol. 35 ›› Issue (2): 344-350.DOI: 10.1016/j.jmst.2018.10.011

• Orginal Article • Previous Articles     Next Articles

Epitaxial growth and oxidation behavior of an overlay coating on a Ni-base single-crystal superalloy by laser cladding

Jingjing Liangac, Yongsheng Liub, Jinguo Lia*(), Yizhou Zhoua*(), Xiaofeng Suna   

  1. aInstitute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
    bState Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
    cSpace Manufacturing Technology (CAS Key Lab), Beijing, 100094, China
  • Received:2018-07-30 Revised:2018-08-28 Accepted:2018-08-29 Online:2019-02-05 Published:2018-12-21
  • Contact: Li Jinguo,Zhou Yizhou
  • About author:

    These authors contributed equally to this work.

Abstract:

An overlay coating material was deposited on a single crystal superalloy SRR99 by laser cladding. The microstructure and oxidation behavior of this coating was investigated through scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicated that although the composition of the coating was chosen based on the γ' composition in René N5 superalloy, the primary solidification phase of this coating during laser cladding was γ-Ni. Furthermore, under the laser cladding condition, fine parallel dendrites grew epitaxially in the coating from the substrate, indicating the single crystal structure of the substrate was reproduced. When the single crystal MCrAlY coating was oxidized at 1000℃, both θ-Al2O3 and α-Al2O3 formed during initial oxidation process. As the oxidation time proceeded, the presence of θ-Al2O3 facilitated the formation of NiAl2O4 spinel oxide. Once the spinel was observed, it flourished and induced some porosity in the scale. When the scale thickness increased to 6-7 μm, large area spallation of the scale began.

Key words: Laser cladding, Single crystal growth, Epitaxy, Overlay coating