Atmospheric Pressure Plasma Jet Assisted Micro-milling Of Inconel 718

Due to its excellent mechanical properties,nickel-based alloy Inconel718 is extensively used in aerospace and automobile industries to manufacture different structural components,such as gas turbine.However,Inconel718 shows the poor machinability owing to its high hardness and its high-temperature strength makes it hard to machine.In this regard,dry machining is one of the most environment-friendly methods for machining Inconel 718.However,this method offers problems such as the excessive amount of heat,short tool life,high power consumption and poor surface finish,which can be solved by using various cutting fluids.In addition to dry machining,many non-conventional machining techniques have also been developed due to their increased machining performance.Cold plasma assisted machining is a new machining technique where atmospheric pressure cold plasma jet is used as an external source during the machining.The atmospheric pressure cold plasma jet is produced by discharged gas and inserts to the cutting zone to stiff material surface and reduce material properties and to have an effect on cooling and lubrication.The atmospheric pressure cold plasma jet assisted micro-milling is also known as a promising technique due to its favorable applications,such as it can significantly improve the cooling and lubricating effects in cutting zone.The aim of this research work is to investigate the influence law and mechanism of plasma jet on mico-milling of Inconel718;the first part of the research work explains plasma generating mechanism and various methods of the cold plasma jet.The influences of various discharge parameters on features of the plasma jet were investigated in this research work.The experiments found that when the discharge form was bare electrode,the discharge voltage was 1.53 kV,the nitrogen flow rate was 12 L/min,and the nozzle outlet diameter was 2.5 mm,a uniform,stable and relatively long cold plasma jet could be obtained,and the jet temperature is close to room temperature.In order to study the mechanism of cold plasma jet assisted cutting,plasma modification and tensile test of Inconel718 surface were investigated using cold plasma jet.The results showed that the atmospheric pressure cold plasma jet could improve the wettability of the metal surface in a short time,and the surface was modified to be super hydrophilic.On the other hand,the cold plasma jet could effectively reduce fracture strength of metal material,providing theoretical basis for machinability improvement by cold plasma jet assisted micro-milling of Inconel718.On the basis of mechanism research,micro-milling experiments were carried out under different atmospheres,and all machined surfaces processed by various cutting methods were compared.The influences of atmospheric pressure cold plasma jet on cutting force,cutting temperature,surface roughness,surface micro morphology and residual stress were thus investigated.The analysis results indicated that the use of atmospheric cold plasma jet could reduce the cutting force and temperature during the micro-milling process of Inconel718 nickel alloy,and obtain better surface quality.