Nikhil Ranjan Dhar

Machining of AISI 4140 steel under cryogenic cooling—tool wear, surface roughness and dimensional deviation

Abstract Increase in cutting velocity and feed for machining with high productivity is generally restricted by the elevated cutting temperature which causes rapid tool failure. In precision machining also, the major problem is the high cutting temperature, which impairs the dimensional and form accuracy of the product, its surface integrity by inducing tensile residual stresses and surface and subsurface cracks. Application of conventional cutting fluid often cannot control the high cutting temperature in high production machining. Besides, they are the major source of pollution from machining industries. Cryogenic cooling is an environment friendly clean technology for desirable control of cutting temperature. The present work investigates the role of cryogenic cooling by liquid nitrogen jet on average chip–tool interface temperature, tool wear, dimensional accuracy and surface finish in turning AISI 4140 steel under industrial speed–feed conditions.

Response surface and neural network based predictive models of cutting temperature in hard turning

Graphical abstract

Wear behavior of uncoated carbide inserts under dry, wet and cryogenic cooling conditions in turning C-60 steel

Environmental pollution, inconveniences and health hazards due to conventional application of cutting fluids essentially required for cooling and lubrication have been a great concern of the industries and the modern societies. Further they are also ineffective in controlling the high cutting temperature and rapid tool wear. One of the possible and potential techniques to overcome such problem is application of cryogenic cooling particularly by liquid nitrogen specially where the cutting temperature is a major constraint in achieving high productivity and job quality. The present work deals with experimental investigation in the role of cryogenic cooling by liquid nitrogen jets on tool wear, dimensional deviation and surface finish in turning of C-60 steel at industrial speed-feed combination by uncoated carbide inserts (SNMG and SNMM) of different geometric configurations. The results have been compared with dry and wet machining. The results of the present work indicate substantial reduction in tool wear, which enhanced the tool life, dimensional accuracy and surface finish. This may be mainly attributed to reduction in cutting zone temperature and favourable change in the chip-tool interaction. Further it was evident that machining with soluble oil cooling failed to provide any significant improvement in tool life, rather surface finish deteriorated. Furthermore, it provides environment friendliness and improves the machinability characteristics.

Effects of cryogenic cooling by liquid nitrogen jets on tool wear, surface finish and dimensional deviation in turning different steels

High production machining at high cutting velocity and feed generates large amount of heat and high cutting temperature, which shortens the tool life and deteriorates the job quality. This problem becomes more acute when the jobs are difficult to machine and are to be used under dynamic loading. The conventional cutting fluids are not that effective in such high production machining particularly in continuous cutting of materials like steels. Further, the conventional cutting fluids are not environment friendly. The disposal of the cutting fluids often leads to local water pollution and soil contamination. Recycling and reuse of conventional cutting fluids are problems in the future. In this decade, with increased environmental awareness, the researchers are striving to develop environment friendly machining technology; one such technology is to use cryogenic cooling with liquid nitrogen. This paper deals with experimental investigation in the role of cryogenic cooling by liquid nitrogen jets on tool wear, surface finish and product quality in turning of Ni–Cr steel, and 42CrMo4 steel at different cutting velocities and feeds by two types of carbide inserts of different geometry. Compared to the dry machining, cryogenic machining performed much superior mainly due to substantial reduction in cutting zone temperature enabling favourable chip formation and chip–tool interaction. It also provides reduction in cutting forces and substantial reduction in tool wears, which enhanced the tool life, dimensional accuracy and surface finish. Furthermore, it provides environment-friendliness and improves the machinability characteristics.

Influence of single and dual cryogenic jets on machinability characteristics in turning of Ti-6Al-4V

Based on the necessity of a solid study on the orientation of liquid nitrogen jets in turning, this study investigates the specific cutting energy, surface roughness, chip morphology, chip–tool interface temperature, tool life, and wear of coated carbide tool under the single and duplex jets liquid nitrogen for congenial turning of a hard-to-cut superalloy (Ti-6Al-4V). The single jet was aimed at rake face, whereas the duplex jets were impinged at rake and flank surfaces, simultaneously. Results showed that the later coolant employment method ensured the most favorable machining characteristics, which can be accredited to the extreme cooling by liquid nitrogen jets, in terms of reduced specific cutting energy, temperature, roughness, and admittedly, an increased life of tools. The duplex liquid nitrogen jets prolonged tool life by 60% and 30% compared to dry and single jet assistance, respectively. However, no visible difference in chip formation has been noticed. In recapitulation, the duplex liquid nitrogen jets are established as sustainability promoter as—tool life is increased thus tool cost is reduced, required energy is lessened, temperature is pacified, surface quality is improved, and above all, favorable machinability of Ti-6Al-4V superalloy is attained.

Effects of cutting parameters and machining environments on surface roughness in hard turning using design of experiment

Hard turning is gradually replacing the time consuming conventional turning process, which is typically followed by grinding, by producing surface quality compatible to grinding. The hard turned surface roughness depends on the cutting parameters, machining environments and tool insert configurations. In this article the variation of the surface roughness of the produced surfaces with the changes in tool insert configuration, use of coolant and different cutting parameters (cutting speed, feed rate) has been investigated. This investigation was performed in machining AISI 1060 steel, hardened to 56 HRC by heat treatment, using coated carbide inserts under two different machining environments. The depth of cut, fluid pressure and material hardness were kept constant. The Design of Experiment (DOE) was performed to determine the number and combination sets of different cutting parameters. A full factorial analysis has been performed to examine the effect of main factors as well as interaction effect of fact...

Effects of minimum quantity lubrication (MQL) by vegetable oil-based cutting fluid on machinability of AISI 9310 steel

The growing demands for high productivity of machining need use of high cutting speed and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluids changes the performance of machining operations because of their lubrication, cooling and chip flushing functions but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimisation of cutting fluid leads to economical benefits by way of saving lubricant costs. This paper presents the effects of minimum quantity lubricant (MQL) by vegetable oil-based cutting fluid on the cutting performance of AISI 9310 steel, as compared to dry and wet machining. Compared to the dry or wet machining, MQL machining performed much superior mainly due to substantial reduction in cutting temperature enabling favourable chip formation and chip-tool interaction. It also provides substantial reduction in tool wear, which enhanced the tool life and surface finish.

Experimental study on hard turning of hardened medium carbon steel with carbide insert under high-pressure coolant condition

A basic difference of hard turning from conventional turning lies in its larger specific cutting forces requirements which in turn can be lowered by applying no cutting fluid. The beneficial effects of hard turning can be offset by excessive temperature generation which causes rapid tool wear or premature tool failure if the brittle cutting tools required for hard turning are not used properly. Under these considerations, the concept of high-pressure coolant (HPC) presents itself as a possible solution for high speed machining in achieving slow tool wear while maintaining cutting forces at reasonable levels, if the high pressure cooling parameters can be strategically tuned. This paper deals with an experimental investigation of some aspects of the turning process applied on hardened steel (HRC 56) using coated carbide tools at high cutting speeds under high-pressure coolant, comparing it with dry cut. The results indicate that the use of high-pressure coolant leads to reduced surface roughness, delayed tool flank wear, and lower cutting temperature, while also having a minimal effect on the cutting forces.