Effect of diamond grain shape on gallium nitride nano-grinding process

Abstract

In the grinding process, the quality of the product in the process is affected by many factors. In order to improve the processing quality and take into account the processing efficiency, the selection of a reasonable abrasive grain shape can be considered. This is a low-cost and highly feasible approach. In this article, the molecular dynamics method was employed to simulate the process of grinding GaN with four common synthetic diamond of abrasive grains (spherical, octahedron, cubic and cub-octahedron), and the surface morphology, material removal rate, temperature, potential energy, grinding force, substrate structure deformation, subsurface damage and dislocation were investigated. The results show that the cubic abrasive grain has the highest material removal rate with the number of chip atoms per unit area about 1.68 times that of the cub-octahedron abrasive grain. The lowest subsurface temperature of the octahedron abrasive grain during processing is 498 K. In contrast, the other three grits have similar subsurface temperatures of 540 K, 535 K and 545 K, respectively. The tangential force per unit area of octahedron abrasive grain is about 0.68761 (spherical: 0.23987, cubic: 0.4476, cubo-octahedral: 0.4314), but its potential energy is the most stable during processing. The shape of the abrasive grain has no significant effect on the coefficient of friction, while it has a significant effect on the subsurface damage. The depth of subsurface damage is the smallest for both cubic and cub-octahedron abrasive grain (2.4 nm), while cub-octahedron abrasive grain is more capable of promoting the generation of dislocations within the substrate. In addition, the performance of cubic and cub-octahedron abrasive grain at different grinding depths was further explored. Number of chip atoms, temperature, grinding force and subsurface damage all increase with the grinding depth. Nevertheless, the machining performance of cubic abrasive grain is still superior to that of cub-octahedron abrasive grain when the grinding depth is more than 1 nm. The outcome of this study may provide a micro-scale insight into the selection of abrasive grain shapes for processing GaN substrates.