Machinability of AISI 1050, aisi 4140 and aisi E52100 steels by different cutting tools and development of models

In this study, the effects of cutting parameters and tool geometry as well as theeffects of workpiece hardness and tool hardness on tool life, tool wear, chipdisposability and surface roughness have been investigated in machining bothhot-rolled and heat-treated steels of AISI 1050, AISI 4140 and AISI E 52100steels by coated carbide, cermet, ceramic and cubic boron nitride (CBN) cuttingtools. Optimal cutting conditions for maximum tool life were determined usingthe Taguchi technique. Predictive tool life equations were derived.Furthermore, predictive equations for Ra, Rz and Rmax type surface roughnesscalculations were developed using Central Composite Design and ResponseSurface Techniques together with help of experimental data when machiningsteels. In addition, types of tool wear were shown by examining worn surfacesby a scanning electron microscope (SEM). The effect of control factors on chiptype and chip curvature radius was investigated by examining the chips formedduring the machining tests.The results indicate that the cutting speed, feed rate, tool hardness, workpiecehardness and their interactions were found out to be the most effective factorsamong control factors on tool life. It is observed that the predictive equationsprovided more reliable results.In machining hot-rolled AISI 1050 and AISI 4140 steels, nose wear and craterwear observed on ceramic tools. In machining heat-treated steels, however, anotch wear occurred on uncoated ceramic tools. In machining hardened steels,fracture was effective for coated carbide and ceramic tools while crater wearwas found to be dominant for uncoated ceramics. However, for machining non-heat treated AISI E 52100 steels, flank wear and fracture of coating layer oncoated carbide tool took place while flank wear and crater wear were observedon uncoated and coated ceramic. Moreover, in machining spheroidized AISI E52100 steels, mechanical fatigue cracks were observed on carbide tool at heavycutting conditions. Flank wear and crater wear occurred for ceramic tool whenmachining the same type of steel. Finally, flank wear and crater wear werefound to be effective on ceramic and CBN tool when machining hardened andtempered steel of AISI E 52100 under lower and medium cutting conditions; butceramic tools were fractured in heavier cutting conditions.As for the evaluating the surface roughness, the feed rate was found to be themost effective control factor on surface roughness, which is followed by cuttingspeed and depth of cut. A better surface roughness was obtained in machiningthe hot-rolled steel of AISI 1050 by coated ceramic tools. Surface roughnessvalues decreased in machining the hot rolled steel of AISI 4140 by uncoatedtools. In general, a better surface roughness was obtained in machining theheat-treated steel by CBN, which is followed by uncoated ceramic, coatedceramic and coated carbide tools. Furthermore, chip types and chip curvatureswere found to be depending on the depth of cut and cutting speed, respectively.