Microstructure and debris fracture in amorphous Ni–P-CNT composite coatings after wear

Abstract

Amorphous nickel–phosphorus (Ni–P)-based Carbon Nanotubes (CNTs) composite coatings were prepared by brush electroplating technology. Wear tests for the coatings were conducted. The deformation of the microstructures in the coatings after wear was analyzed by transmission electron microscopy. The results showed that amorphous Ni–P-based composite coatings produced partial crystallization and precipitation of the Ni₃P phase after wear. The degree of crystallization increased with the increase in load. Abrasive debris were collected for scanning electron microscope observation, which would help understand the microscopic mechanism of wear crack nucleation and propagation. The wear fracture of the debris in the amorphous Ni–P-based composite coating was intergranular and quasi-cleavage. The microscopic characteristics of the abrasive debris showed cutting stripes, secondary cracks, intensive areas of CNTs, and grain groups. The nucleation position of the wear crack was at the microstructure defects and grain boundaries; the wear crack propagation path was intergranular.

Keywords: CNTs, coating, nickel, wear, microstructures