Effects of lubricants and flow rates on the surface roughness and chip thickness when MQL turning of aero-engine aluminum alloys 6061-T6 and 7076-T6

Abstract

It is agreed upon that labor’s health conditions, as well as environmental pollutions, are broadly influenced by cutting fluids used in machining operations. In order to secure cleaner work parts and environment as well as reduced machining expenses, less fuel consumption is highly recommended. However, the quality of machined parts in the absence of fluid is considered a delicate subject. Under such conditions, the quality of machining process, as well as productivity, could be evaluated by different parameters and criteria including edge and surface quality, chip thickness, cutting force, and tool wear and life, which all seem to be highly influenced by many factors, including lubrication mode (dry and wet) and chip evacuation process. In order to take the benefits while avoiding the disadvantages of lubricated machining, novel lubrication method the so-called minimum quantity lubrication (MQL), which is micro lubrication near dry machining, is proposed. Review of literature denotes that under MQL condition, a low volume of information is available on the effects of mineral and bio-lubricants and various levels of flow rate on machining attributes, in principle average surface roughness (Ra) and chip thickness (hc) when machining aluminum alloys (AAs). To remedy the lack of knowledge determined, the effects of cutting conditions, in principle cutting speed, feed rate, lubricant, and various levels of flow rate on Ra and hc in MQL turning of AA 6061-T6 and AA 7076-T6, are presented. Therefore, three different experimental models, including multiplicative, 2-factor interactions (2FI), and linear models, were used in this study to assess the effects of cutting parameters on the machining outputs. According to experimental observations and despite the design models used, both Ra and hc are statistically significant responses and could be controlled by variation of the cutting parameters used. A strong relationship can be formulated between both responses and experimental parameters used. Although negligible, however, biodegradable cutting fluid with higher viscosity denoted better capability to improve the surface finish. The use of a higher flow rate also led to improved surface finish (up to 50%). It was observed that despite the material used, both flow rate and cutting fluid have insignificant effects on hc.