3RD INTERNATIONAL BLACK SEA MODERN SCIENTIFIC RESEARCH CONGRESS, Samsun, Turkey, 23 - 24 March 2023, no.3, pp.283-291
PH13-8Mo grade stainless steel is frequently used in aircraft landing gear parts, valve and shaft parts, axels that are in contact with petrochemical liquids and under load, and nuclear power plant shafts thanks to its high mechanical strength and excellent corrosion resistance. However, it is a difficult material to process due to its high mechanical properties and low thermal conductivity, and it is necessary to optimize the cutting conditions in order to achieve the desired surface quality properties on the machined parts. In this context, Taguchi method based optimization methodology was applied for minimum surface roughness in the machining of PH13-8Mo grade steel in sustainable cutting environments (dry and minimum quantity lubrication_MQL). The mean roughness heights (Ra) were measured from the surfaces formed in the milling experiments performed with coated carbide inserts at three different cutting speeds and feed rates. The effects of processing parameters on Ra were evaluated by applying analysis of variance. It was observed that while the surface roughness values increased at a certain rate with increasing feed rate, they decreased relatively with the increase in cutting speed. In the MQL method, the surface roughness values were measured 20% lower on average compared to milling in dry conditions. The lowest Ra value was measured as 0.360 μm at a cutting speed of 60 m/min and a feed rate of 0.04 mm/rev in the minimum amount of lubrication cutting medium. As a result of the analysis of variance, the most effective factor on Ra was the feed rate with 45.52%, while the MQL cutting environment was determined as the secondary important factor with 31.28%. The low effect of the increase in cutting speed on Ra (5.42%) was attributed to the cooling effect of the MQL environment as well as the interrupted cutting process of the milling method. These results show that MQL cutting environment should be used to achieve optimum surface roughness when machining materials such as PH13-8Mo stainless steel.