Thermal Stability of Microstructure and Hardness of Cold-Sprayed cBN/NiCrAl Nanocomposite Coating
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JTTEE5 21:578–585 DOI: 10.1007/s11666-011-9719-9 1059-9630/$19.00 ASM International
Thermal Stability of Microstructure and Hardness of Cold-Sprayed cBN/NiCrAl Nanocomposite Coating Xiao-Tao Luo and Chang-Jiu Li (Submitted September 14, 2011; in revised form November 25, 2011) cBN/NiCrAl nanocomposite coatings were deposited by cold spraying using mechanically alloyed composite powders. To examine their thermal stability, the nanocomposite coatings were annealed at different temperatures up to 1000 °C. The microstructure of composite coatings was characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results showed that the nanostructure can be retained when the annealing temperature is not higher than 825 °C, which is 0.7 times of the melting point of the NiCrAl matrix. The dislocation density was significantly reduced when the annealing temperature was higher than 750 °C. The reaction between cBN particles and the NiCrAl matrix became noticeable when the annealing temperature was higher than 825 °C. The effects of grain refinement and work-hardening strengthening mechanisms were quantitatively estimated as a function of annealing temperature. The influence of annealing temperature on the contribution of different strengthening mechanisms to coating hardness was discussed.
Keywords
cold spray, dislocation density, grain size, hardness, nanocomposite
1. Introduction Nanocrystalline (nc) materials (grain size
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