Minimum Lubrication Conditions Research Articles

Cutting tool wear in turning 316L stainless steel in the conditions of minimized lubrication

316L stainless steel has emerged as one of the most used material in design and manufacturing for automotive, aerospace, marine, civil nuclear to produce critical components (valves, seats, pipes etc.). Despite, their huge application, during the machining of 316L stainless steel numerous challenges arise in terms of tool wear that are very detrimental for the surface of machined part. To obtain an extended life of tool used for machining commonly 316L stainless steel two different methods of cooling based on minimum lubrication condition, namely Minimum Quantity Lubrication (MQL) method and Minimum Quantity Cooling Lubrication (MQCL) with the addition of extreme pressure and anti-wear (EP/AW) method, respectively were settled. The use of the MQL method resulted in a reduction of the cutting tool wear by approximately 9% compared to the MQCL + EP/AW method and by approximately 21% compared to dry machining. Further, the highest values of wear indices were achieved during dry machining and the lowest ones in the method of minimized lubrication which validate the minimum lubrication as beneficial for reducing the wear progress.

Investigation on tribological performance of CuO vegetable-oil based nanofluids for grinding operations

With ball-bearing and tribofilm lubrication effects, CuO vegetable oil-based nanofluids have exhibited excellent anti-wear and friction reduction properties. In this study, CuO nanofluids were synthesized by a one-step electro discharge process in distilled water containing polysorbate-20 and vegetable oil as a nanoparticle stabilizer and source of fatty-acid molecules in the base fluid, respectively. Pin-on-disk tribotests were conducted to evaluate the lubrication performance of synthesized CuO nanofluids between brass/steel contact pairs under various loadings. Surface grinding experiments under minimum lubrication conditions were also performed to evaluate the effectiveness of the synthesized nanofluids in improving the machining characteristics and surface quality of machined parts. The results of pin-on-disk tests revealed that adding nanofluids containing 0.5% and 1% (mass fraction) CuO nanoparticles to the base fluid reduced the wear rate by 66.7% and 71.2%, respectively, compared with pure lubricant. The lubricating action of 1% (mass fraction) CuO nanofluid reduced the ground surface roughness by up to 30% compared with grinding using lubricant without nano-additives. These effects were attributed to the formation of a lubrication film between the contact pairs, providing the rolling and healing functions of CuO nanoparticles to the sliding surfaces. The micrography of ground surfaces using a scanning electron microscope confirmed the tribological observations.

Minimum lubrication technique using silicone oil for friction reduction of stainless steel

Liquid lubricants are widely used to reduce the friction and wear of mechanical components. In this research, silicone oil was used in order to investigate its effectiveness in the lubrication of stainless steel. Specifically, the aim was to assess the friction reduction characteristics of silicone oil under minimum lubrication conditions. Silicone oil lubricants can be easily recycled, and they are comprised of relatively non-hazardous chemicals. Also, silicone oil lubricants are well known for their thermally stable properties. They have a relatively high flash point temperature and a high auto-ignition point temperature. Friction experiments were performed using silicone oil as the lubricant for stainless steel specimens. As a means to apply the minimum amount of lubricant, the thermal evaporation coating method was used. The stainless steel plates were slid against stainless steel balls in the friction tests. The results of the friction experiments showed that the thermally evaporated silicone oil lubricant was effective in reducing the friction of stainless steel. It was also found that the friction signal of the lubricated condition was more stable than that of the unlubricated condition. The results of this work demonstrated the possibility of minimum lubrication for friction reduction of metals.

Topography-related effects on the lubrication of nanostructured hard surfaces

This study reports the effect of nanoscaled surface structure of some hard coatings on the (micro-) frictional behaviour of systems under minimum lubrication conditions with modest contact pressures and low sliding speeds (below 1 mm/s). For this purpose, Cr-N coatings with a randomly crater-like topography and with varying dimensions of surface features as well as a smooth Cr-N surface were tested with a microtribometer. The friction on the samples was measured as a function of the viscosity of the applied mineral base oil and the sliding velocity. For all tests, the structured surfaces exhibited lower friction than the smooth surface. Furthermore, it was possible to detect variations in the lubrication-promoting effect of the structures depending on the oil viscosity and the sliding speed. Indications for the existence of an optimum topographic scale for this type of surface structure were found.