Effect of liquid nitrogen cooling on grain growth and properties of laser cladding in-situ (Ti, Nb)C/Ni composite coatings

• Published in: Materials characterization 2019-06, Vol.152, p.115-129
• Main Authors: Shuting, Sun, Hanguang, Fu, Ping, Xuelong, Guo, Xingye, Lin, Jian, Lei, Yongping, Wu, Wenbo, Zhou, Jianxin
• Format: Article
• Language: English
• Subjects: Composite coatings; Laser cladding; Liquid nitrogen cooling; Textural characteristics; Wear resistance
• ISSN: 1044-5803; 1873-4189
• DOI: 10.1016/j.matchar.2019.04.012

In-situ (Ti, Nb)C/Ni composite coatings with liquid nitrogen cooling were fabricated on Cr12MoV die steel by laser cladding. The phase constitution, microstructure characteristics, micro-segregation behavior of elements, micro-hardness and wear resistance of coatings was explored. The results showed that the liquid nitrogen cooled coating was composed of (Ti, Nb)C, Cr7C3, Cr23C6 and γ-Ni(Fe), and the growth of (Ti, Nb)C was restrained. The segregation behavior of Cr, Nb and Ti elements, crack sensitivity and pores were remarkably reduced. The nanometer chromium carbides and higher dislocation density were also observed by TEM. According to EBSD results, the coatings showed stronger textural characteristics, and the imposing liquid nitrogen cooling refined the microstructure and increased slightly the high angle grain boundaries. In addition, γ-Ni matrix in the liquid nitrogen cooled coating increased the amount of Nb, Cr and Ti elements, resulting in higher elastic modulus and average hardness. The tribochemical reaction was also occurred during the wear test from XPS results. The liquid nitrogen cooled coating showed excellent wear resistance, and it was improved 73% than air cooled coating. [Display omitted] •(Ti, Nb)C/Ni composite coatings with liquid nitrogen cooling was fabricated on Cr12MoV die steel by laser cladding.•The imposing liquid nitrogen cooling refined the microstructure and suppressed the growth of (Ti, Nb)C particles.•The nanocrystallines and higher dislocation density were observed in the liquid nitrogen cooled coating.•The coatings showed stronger textural characteristics, and the high angle grain boundaries were also increased slightly.•The micro-hardness and wear resistance of liquid nitrogen cooled coating exhibited clear improvement.