Deposition of trace coolant elements on flank face in turning of Inconel 718 under high pressure conditions

In this study, the coolant element deposition on the flank face of a coated tool in the turning of Inconel 718 when the coolant jet was supplied from the tool flank side at coolant pressures from 1 to 20 MPa was investigated. The flank wear-land was inspected after the cutting experiments using energy dispersive X-ray spectroscopy analysis to obtain the mappings of chemical elements contained in the workpiece, coating material, and coolant. It was found that coolant jet with pressures higher than 5 MPa extended the tool life dramatically compared to flood cooling. In contrast, increasing the coolant pressure beyond 5 MPa yielded only marginal improvements of the tool life, as has been reported previously for very high coolant pressures. Trace chemical elements contained in the coolant were mainly detected along the border of the tool-work contact area. The amounts of materials deposited had a complicated relationship with the pressure, and a large amount of sodium, silicon, calcium, and phosphorus deposited at very high coolant pressures of 10 and 20 MPa. It was concluded that the saturation of tool life extension at higher coolant pressures was ascribed to the thick deposited layer of a mixture of compounds, such as calcium phosphate and sodium silicide, along the border, which prevented the high-pressure coolant from penetrating into the tool/work contact area.