Two stages for the evolution of crystallite size and texture of electrodeposited Ni–ZrC composite coating

Abstract

In this work, the evolution of crystallite size and crystalline preferred orientation (texture) of the electrodeposited Ni–ZrC composite coating has been investigated by using Rietveld X-ray diffraction (XRD) line profile analysis. The influences of both ZrC micron- and nano-particle concentrations on the microstructure evolution of the composite coating have been studied. Pole figures reconstructed by Rietveld refinements and measured by XRD and relative texture coefficients are all applied to characterize the variation of texture. With increasing ZrC particle concentrations in electrolyte from 1 to 40g/L, the evolution of both crystallite size and texture can be divided to two stages, which can be named as texture-modified and crystallite-refined stage. At the first stage, strong depressing of <220> fiber texture synchronizes with the decreasing of crystallite size along <200> direction, which reduces more quickly than those along <111> and <220> directions. At the second stage, the strong fiber texture has been totally depressed and the crystallite shape changes from anisotropy to isotropy. And the crystallite sizes along <200>, <111> and <220> directions all decrease gradually with the increasing of ZrC concentration. Compared with the ZrC micron-particles, ZrC nano-particles lead the composite coating with smaller crystallite size, weaker texture, higher microstrain and higher dislocation density at the same particle concentration. The evolution of crystallite size and texture is ascribed to the incorporation of the second phase ZrC particles into the coating.