On the Lubricity and Comparative Life Cycle of Biobased Synthetic and Mineral Oil Emulsions in Machining Titanium Ti-6Al-4V at Low Cutting Speed

Abstract

The paper discusses an instrumented tapping test method using a CNC machine tool to compare the lubricity of MWFs by cutting threads in a Ti-6Al-4V alloy at low speed. The method uses a spiral flute tap size typical of industrial practice. A soft synchronous tap holder and spindle mounted dynamometer were incorporated on the machine to measure torque and thrust force. The tapping test method was demonstrated on three groups of MWFs that were commercially available and classified by ASTM E2523-13:2018. The method developed stable results free of chip clogging in tool flutes which could otherwise mask their comparative lubricity. The fully synthetic (FS) group displayed the best lubricity and within this group the FS from renewables (FS-bio) was the best overall. The method was shown to be effective in mitigating biasing effects on lubricity performance due to the generous tool chamfer angle tolerance and was practical and economical to implement. The significance of the results is discussed enabling an understanding of friction effects in tapping using a soft synchronous tap holder. A life cycle assessment of each MWF group found total Greenhouse Gas emitted from the FS group was 17% of the hydrocarbon group whilst FS-bio emitted just 7%.

Comparing Bio-Ester and Mineral-Oil Emulsions on Tool Wear and Surface Integrity in Finish Turning a Ni-Based Superalloy

“…Approximately 16% of the total machining cost of a product is attributed to the CF life cycle [14][15][16]. Still today, coolants used in industry for machining use formulations that are derived from fossil fuels and disposal generate a high waste stream that is incinerated [17]. According to Debnath et al [18], the cost of disposal can be up to four times the purchase cost because CFs are not biodegradable.…”

“…A modern MWF formulated with a vegetable-ester-oil was shown to display enhanced lubricity in machining a hard Titanium alloy at low cutting speed, together with a significant reduction in its life-cycle carbon footprint, compared to fossil-derived CFs [17]. Saleem and Mehmood [6] demonstrated improved surface integrity in turning Inconel 718 using coolants formulated from sunflower and castor oil which were applied using minimum quantity lubrication (MQL).…”

Comparative Cutting Fluid Study on Optimum Grinding Parameters of Ti-6Al-4V Alloy Using Flood, Minimum Quantity Lubrication (MQL), and Nanofluid MQL (NMQL)

“…Titanium is complex to process, machining, due to its high chemical affinity, which makes the chips and debris easily adhere onto the tooling due to very high localized temperature and extreme pressure. This behavior affects the service life of tooling and produces low surface roughness [7][8][9]. An alternative to improve the fluid's cooling performance is to enhance the heat transfer surface area, as well as increasing the velocity of the fluid (high pressure).…”

Long Sump Life Effects of a Naturally Aged Bio-Ester Oil Emulsion on Tool Wear in Finish Turning a Ni-Based Superalloy

“…A modern fully synthetic MWF formulated with a vegetable-ester-oil base has been shown to display enhanced lubricity in machining together with a significant reduction in its life-cycle carbon footprint compared to fossil derived MWFs [28]. Other works studied turning of Inconel 718, using graphene nanofluids applied as MQL [29] and vegetable oil [30].…”