Fabrication and grinding performance of CVD diamond coated Ni-based brazed diamond grinding tools

Monolayer brazed diamond grinding tools are widely used in precision grinding of hard and brittle materials. However, few cutting edges and macro-fracture of abrasive particles lead to the decreased sharpness. In this paper, diamond coated nickel-based (Ni-based) brazed diamond grinding tools were fabricated successfully by hot filament chemical vapor deposition (HFCVD) method. Molecular dynamics (MD) simulation was used to explore the deposition mechanism of carbon atoms on brazing material substrate. The simulation results indicate that carbon atoms undergo multiple processes including combining with Ni atoms, catalyzing graphitization, and ultimately forming diamond structures and diamond films. Afterwards, grown diamond coatings were deposited on the brazed diamond grinding tools in the HFCVD apparatus. The surface morphology and various spectral analysis results show that both abrasive grains and brazing materials with diamond coatings in the late growth stage appear numerous polycrystalline micro-edge structures. The Ni element content of the brazing materials gradually decreased to 1 %, while the C element content gradually increased to 99 %. The carbides and other components formed are dropped in the brazing material as the increased deposition time. Grinding experiments on alumina ceramics were conducted using brazed grinding tools with grown diamond coatings. Micro-edge average height continues to rise and ground surface roughness decreases with the deposition time. The slight wear and micro-fracture are the dominant wear characteristics of grinding tools with late-growth diamond coatings. The results of the grinding force and grinding temperature measurements illustrate that the growth and increased thickness of the diamond coatings improve the hardness, wear resistance and thermal conductivity of uncoated abrasive grains, and micro cutting edges further improves the sharpness of the grains and reduces grain-workpiece friction. The novel brazed diamond grinding tools have improved the comprehensive grinding performance. • Diamond films can be deposited on the Ni-based brazing materials through MD simulation. • Diamond fim deposition mechanism on the brazing material are investigated by various characterization methods. • Diamond coatings are deposited on the Ni-brazed diamond grinding tools by HFCVD method. • Alumina ceramics are ground using various diamond coated brazed grinding tools, and grinding quality and worn features are analyzed. • Grinding forces and temperatures are measured during grinding experiments to compare the grinding force and energy changes.