Mitigating iron-induced catalytic wear in monocrystalline diamond tools using two-dimensional (2D) materials

Diamond tools are known to wear rapidly during the machining of ferrous materials because of the catalytic effect of iron on diamond graphitization. This work aims to perform a relative comparison of the wear mitigation efficacy of candidate two-dimensional (2D) materials, viz., graphene oxide (GO), hexagonal boron nitride (hBN), molybdenum disulfide (MoS2) and tungsten disulfide (WS2), when used as cutting fluid additives during diamond turning of steel. The 2D material suspensions (0.15 wt.%) are first characterized for their hydrodynamic diameter distributions. Multi-pass turning studies are then conducted using monocrystalline diamond tools. Tool wear, cutting forces and surface roughness are used as the comparison metrics. Overall, graphene oxide has the highest reduction in tool wear (60 %) over the baseline case. It is followed by hexagonal boron nitride, tungsten disulfide and molybdenum disulfide that offered 52 %, 45 % and 38 % wear reduction, respectively, over the baseline case. Overall, hBN provides the best combination of low tool wear, low cutting forces and low surface roughness. The tool wear mitigation efficacy of the materials can be explained in terms of their specific chemical/physical interactions at the iron-diamond interface. X-ray Photo Spectroscopy (XPS) measurements reveal a clear correlation between the tool wear trends and strength of the graphitic carbon/carbide signals obtained on the machined surfaces. XPS measurements in the B1 s and S2p regions shed light on the chemical reactions responsible for the performance of hBN, WS2 and MoS2. The unique surface chemistries of the resulting surfaces offer the potential of a rich exploration landscape for downstream applications.