Investigation of the effect of ultrasonic assisted milling and minimum quantity lubrication methods on the machinability of Hardox 500 steel

Hardox steel is widely used in agriculture, mining and transportation due to its mechanical properties such as high wear resistance, high impact resistance, high hardness, high durability and long life. The machinability of Hardox 500 is difficult as its high hardness and wear resistance lead to tool wear and low machining speed. Recently, various processing and cooling methods have been developed to increase machinability. Ultrasonic assisted milling (UAM), one of these methods, is a method used as an alternative to conventional milling (CM) in the milling of traditionally difficult-to-machine materials. In addition, minimum quantity lubrication (MQL) is a cooling method used to provide lubrication and cooling in the cutting area. In this study, the impacts of machining method, feed rate and spindle speed on cutting force, surface roughness and tool wear in milling of Hardox 500 steel were investigated. In the MQL method, mixtures with nano-sized SiC particles were obtained and applied to the cutting area. In the study, MQL reduced cutting forces by up to 19 %, surface roughness by 18 %, and tool wear by 30 % compared to dry machining, while UAM further decreased cutting forces by 17 %, surface roughness by 15 %, and tool wear by 12 % compared to CM. These results demonstrate that MQL and UAM significantly enhance machining performance over conventional and dry methods.