The effect of the addition of multi-walled carbon nanotubes to the vegetable-based cutting oil used in the mql system on machining outputs in turning of PH 13-8 MO steel

The purpose of this study is to determine the optimum processing conditions in turning of PH13-8 Mo stainless steel. For this purpose, the effects of the cutting parameters on the cutting temperature and surface roughness were investigated under different cooling lubrication conditions of PH13-8 Mo steel. During the turning experiments, coated cemented carbide (PVD TiAlN-(AlCr)2O3) cutting tools were used. The experiments were performed at fixed cutting depth (0.8 mm), three different cutting speeds (120, 180, 240 rpm), and three different feed rates (0.10, 0.15, 0.20 mm/rev). Experimental study was conducted in two stages and experiment designs were made by using L9 and L27 vertical indexes of Taguchi. In both experimental designs, the above mentioned cutting parameters were kept constant. In the L9 experimental design, it is aimed to optimize the nano fluid concentration ratios (0.3, 0.6 and 0.9% by volume). For this purpose, nanofluids were prepared by adding multi-walled carbon nanotube (MWCNT) solid nanoparticles into the vegetable based cutting oil used in the MQL system. In the L27 experimental design, optimization of cooling/lubrication conditions (dry, MQL and Nano MQL) is aimed by keeping the above mentioned cutting parameters constant. The signal noise ratio (S/N) was used to evaluate the data obtained from the experiments. Variance analysis (ANOVA) was performed to determine the effect of control factors on the results. In addition, multiple regression analysis was applied to determine the relationship between dependent variables and independent variables. As a result of the experiments, the optimal concentration rate for MWCNT nanofluids was found to be 0.6% by volume. Based on the L9 experiment design performed in the first stage, the best surface roughness value was obtained at a cutting rate of 180 m/min, 0,10 mm/rev feed rate and 0.6% by volume concentration. When the temperature values in the cutting zone were examined, the lowest cutting temperature was observed at a cutting speed of 120 m/min, a feed rate of 0.10 mm/rev and a concentration of 0.3% by volume. Based on the L27 experiment design performed in the second stage, the best surface roughness value was obtained at a cutting speed of 180 m/min, a feed rate of 0.10 mm/rev and under NanoMQL cooling/lubrication conditions. The parameters providing optimum cutting temperature were determined as 120 m/min cutting speed, 0,10 mm/rev feed rate, and NanoMQL cooling/lubrication condition.