The present study uses the smoothed particle hydrodynamics (SPH) and discrete element method (DEM) coupling to investigate influence of the hexagonal boron nitride (hBN) particles on friction of the elastic coarse-grained micronscale iron. The hBN lubricant particles significantly improve the friction performance of iron in various simulation behaviors. The particle size, the air/water background containing the particles, and its temperature result in reduction of the friction coefficient. The surface mending, the protective film, and the energy dissipation are the main mechanisms related to the friction reduction. Additionally, it is worthy to note that the static friction and the kinetic friction can be clearly observed by this elastic coarse-graining.