INVESTIGATIONS OF TRIBOLOGICAL BEHAVIOUR IN MACHINING OPERATION FOR A SINGLE POINT CUTTING TOOL IN PRESENCE OF COOLANT

Abstract

Dry turning is considered environmentally safe but the manufacturing rate may be slow due to the effect of combined machinability parameters (i) speed, (ii) feed and (iii) depth of cut. The cutting tool has relative velocity insitu contact with the workpiece. The possibility of sticking material and plastic deformation of the cutting tool may be increased. The surface morphology may get affected due to adhesive particles and other cutting parameters and finally dimensional accuracy of workpiece depends on the same. Conventional cutting fluids may be used to smoothen the process but do not show more remarkable improvement due to recent development of new hard engineering materials and strict high standards of manufacturing. Straight oils and mineral oils were used by researchers at the interface of cutting tool and workpiece but lubrication was found more effective than cooling. Servocut cutting oils with water emulsions were used but the majority of conventional cutting fluids provided marginal improvement in machinability characteristics like surface roughness, tool wear, surface morphology etc. The need was found for the preparation of novel cutting fluid and supplied in the control way to the cutting tool surface to prevent wastage. Therefore, cutting fluids with nanoparticles were developed of Al2O3and TiO2 separately in distilled water of 1.0%W/W separately. Biocompatible (Tween 20) surfactant was used for preventing agglomeration of particles. Nano-cutting fluids were used on pin-on-disc tribometer for determining tribological properties during sliding and on lathe machine for observing machinability characteristics. Cryogenic cooling was done with a direct supply of LN2 at the interface of pin-on-disc of tribometer and the rake surface of single point cutting tool on lathe machine. Tribological properties and machinability characteristics of prepared nano-cutting fluids were compared with dry, wet, and cryogenic cooling condition. It has been found that the lowest value coefficient of friction and specific wear rate was found at direct supply LN2 and increasing order with nano-cutting fluid with nanoparticles TiO2 tribometer. The coefficient of fiction was 0.93 and specific wear rate was 4.365X10−5 mm^3/Nm during the dry sliding condition. On comparing with the dry condition, coefficient friction was lowered by 4.3%, 12.9%, 15% and 17.2% for wet with conventional cutting fluid, nano-cutting fluid TiO2, nano-cutting fluid Al2O3and cryogenic cooling with LN2 respectively. On comparing with a dry condition, specific wear rate was lowered by 22.5%, 29.5%, 37.92% and 98.5% for wet with conventional cutting fluid, nano-cutting fluid TiO2, nano-cutting fluid Al2O3and cryogenic cooling with LN2 respectively. ` xvii Surface roughness, flank wear length, cutting force, temperature, machining time and chip compression ratio were found at 1.85μm, 245μm, 110N, 127°C, 49.31seconds and 2.3 respectively during dry turning and declined by 30.27%, 54.28%, 49.09%, 53.54%, 30.26% and 54.35% during cryogenic cooling on comparing with respective values during dry machining condition. It was found that values of machining properties were higher during dry machining condition and followed by decreasing pattern as (i) dry, (ii) wet, nano-cutting fluid with TiO2, nano-cutting fluid with Al2O3 and cryogenic cooling with LN2. It has been found that wastage is associated with liquid nitrogen due to its property and boiling point temperature of -196°C. During experimentation, the contact of liquid nitrogen with the atmosphere at room temperature created white fumes. This gave a need for the development of an alternative cooling process. A controlled and localized process was developed for supplying the conventional cutting fluid and nano-cutting fluids drop by drop at the interface of pin-on-disc tribometer and cutting insert-workpiece on lathe machine. The results of rigorous experiments showed that nano-cutting fluid with Al2O3 was better than dry, wet, nano-cutting fluid with TiO2 and cryogenic LN2. The wastage of nano-cutting fluid has been found very low or negligible as compared with cryogenic cooling with LN2.