| Current demand directs the research towards the innovation of new materials for high performance end products and applications in severe service conditions.Within the development of new raw materials,the shaping of raw materials into useful and effective product has been a hard contest for researchers and engineers.Dry machining is an emerging trend for sustaining the thorough surface integrity of materials.Flood cooling is a conventional method of cooling during the machining process.Beside from the flood coolant machining,several alternative cooling techniques have been developed including cryogenic,minimal quantity lubrication(MQL),high pressure coolant(HPC)machining and hybrid cooling machining.Irrespective of the sustainable and advanced technologies such as MQL,and cryogenic are hard to control in industries.Thus,making them a second choice and which also directs us to find some easy and adoptable methods of cooling.Apart from adoptable,productive and efficient,the surface integrity plays an important role in the service life of the machined components and the method of cooling plays an important role as well.Therefore,the surface integrity and cooling are of significant importance towards the safety,reliability and durability of the machined component in service.There is a need to evaluate the machining of aerospace components with respect to the surface integrity.Machining of aerospace turbine engine materials such as Ni alloys requires proper validation with respect to the surface integrity.Among the Ni based superalloys,Inconel-718 is a candidate material for aerospace applications because of its high resistance to wear,good creep strength at elevated temperature and high corrosion resistance.Surface integrity may be accessed through three components,surface texture or surface roughness,metallurgical layer formation and residual stresses.This thesis consist of a through description and visualization of the surface roughness,residual stresses,subsurface damage and microhardness while turning of Inconel-718 under dry,flood and high pressure coolant(HPC)machining.Based on the current available literature review,a detailed check list has been developed by taking care of coolant effects on surface integrity for superalloys.Also,the machining experiments are performed,under dry and high pressure coolant machining for the visualization of effect of process parameters on surface integrity.Orthogonal turning of difficult-to-machine Inconel 718 alloy is conducted under dry and high pressure coolant machining.The machining parameters and coolant conditions are investigated to optimize the surface integrity.Machining forces,microhardness,machined surface profile,and areal,profile surface topography are analyzed.Results depict that there is an optimum value of cutting speed and coolant pressure to produce satisfactory surface integrity.Under higher cutting speed of 140m/min with coolant pressure150-200bar results in excellent outcomes.High pressure coolant in cutting process can lower the formation of surface deformities,improve the machined surface integrity,and increase productivity.At a higher cutting speed and optimum coolant pressure,cutting forces are decreased,and the surface microhardness as well as the depth of the machining-affected zone is depleted.Further experiments are also conducted for optimization of coolant direction of injection(rake face only,flank face only and both),coolant pressure and cutting parameters for surface roughness Ra.It is concluded that the best combination for optimum results is(A2,B3,and C3);cutting speed 140m/min with coolant pressure 200 bar at both injections(flank and rake)can result in the minimum surface roughness R_a. |
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