J.S. Dureja

Design optimization of cutting conditions and analysis of their effect on tool wear and surface roughness during hard turning of AISI-H11 steel with a coated—mixed ceramic tool

Abstract The present study is an attempt to model the tool wear and surface roughness, through response surface methodology (RSM) during hard turning of AISI-H11 steel with TiN-coated—mixed ceramic inserts. The effect of machining parameters — i.e. cutting speed, feed rate, depth of cut, and workpiece hardness — on the response factors, viz. flank wear and surface roughness, have been investigated by applying analysis of variance (ANOVA) and through factor interaction graphs in the RSM. The non-linear quadratic models best fit the experimental data points. The desirability function approach has been used for multiple response factors optimization. The confirmation experiments carried out to check the validity of developed models predicted response factors within 5 per cent error. The feed rate, depth of cut, and workpiece hardness are observed to have a statistically significant impact on the flank wear, whereas feed rate and workpiece hardness are the significant factors affecting the surface roughness. The tool wear was monitored with a toolmakers microscope, and wear characterization of some of the representative inserts was carried out using scanning electron microscope/energy dispersive X-ray (SEM-EDX) analysis. The tool appears to be worn out by abrasion, notch wear, and chipping of the tool surface owing to rubbing and impingement of hard particles in the work material and also by adhesion wear.

Wear mechanisms of coated mixed-ceramic tools during finish hard turning of hot tool die steel

Abstract The present study aims to investigate the wear mechanisms of a TiN-coated mixed ceramic tool prevalent under different machining conditions during hard turning of hot tool die steel. The different wear mechanisms observed are abrasion wear at low cutting speed, low feed rate, and highest work piece hardness; formation of protective layer and built-up edge (BUE) resulting from tribochemical reactions between constituents of tool and work piece material at moderate speed. High temperature accompanied by high cutting speed resulted in the removal of the protective layer and suppressed the BUE formation. Hard carbide particles of work material at a higher feed rate severely gouged the tool flank land. Chipping and brittle fractures were observed at very low and high depth of cut. Adhesion of work piece material followed by plastic deformation and notching was clearly visible at low work piece hardness. The influence of cutting speed, feed rate, depth of cut, and work piece hardness on the progressive tool flank wear, and flank wear rate (VBr-μm/km) in the steady wear region was also analysed.

Wear mechanisms of TiN-coated CBN tool during finish hard turning of hot tool die steel

Abstract The aim of the present investigation was to identify the wear mechanisms of TiN-coated CBN tools prevalent under different machining conditions during hard turning of hot tool die steel. The different wear mechanisms observed were abrasion wear at low cutting speed, low feed rate, and high workpiece hardness; formation of a transferred layer resulting from tribochemical reactions between constituents of the tool and workpiece material at high speed; and the formation of built-up edges at moderate cutting speed. Hard carbide particles of the work material at higher feed rate severely abraded the tool flank land, resulting in shallow grooves due to the detachment of CBN grains. At greater depth of cut, the built-up edges and transferred layer reduced friction and tool wear. Excessive adhesion of workpiece material followed by plastic deformation and notching were clearly visible at low workpiece hardness (47 HRC). The influence of cutting speed, feed rate, depth of cut, and workpiece hardness on the progressive tool flank wear, i.e. flank wear rate (VBr, μm/mm) in the steady wear region, was also analysed. The flank wear rate was observed to decrease with increase in cutting speed, depth of cut, and workpiece hardness, but after an initial decrease it increased with increase in feed rate.

A review of empirical modeling techniques to optimize machining parameters for hard turning applications

There has been a tremendous development in the field of modeling and optimization methods starting from Taylor’s tool life model. Use of costly tools such as polycrystalline cubic boron nitride, polycrystalline diamond and ceramics in high-end computer numerical control machining forces the researcher to minimize the experimental runs to achieve the best cutting conditions with minimum tool wear and overall production cost. Machining process optimization to achieve said objectives comprises selecting optimum cutting parameters by applying low-cost mathematical models. This article attempts to evaluate the applicability of various modeling and optimization methods to specific response parameters in hard turning problems. Various empirical modeling techniques such as linear regression modeling, artificial neural networks, polynomial and fuzzy modeling along with process optimization through Taguchi, response surface methodology and genetic algorithm for hard turning applications have been discussed in length to provide the production engineers a ready database to compare relative merits and suitability of these techniques for a particular machining application. Also, article discusses integration of different modeling and optimization techniques to achieve desired goals when a single optimization technique is not able to provide the acceptable solution. The last part of the article highlights the current trends in hard turning applications and research priorities for future work.

Performance Evaluation of Milling of Inconel-625 Under Minimum Quantity Lubrication

Abstract In the present investigation an attempt has been made to explore the potential of MQL milling of Inconel-625 with coated carbide tool. The performance is compared in terms of surface roughness and tool flank wear in MQL milling with dry and wet milling operation of Inconel-625. The milling under MQL condition gives superior results over wet and dry milling operations. Factorial design of experiments ANOVA analysis was applied to investigate the statistically significant parameters. RSM-Desirability function optimization was applied to find out optimal setting of parameters to minimize tool wear and surface roughness in MQL machining of Inconel-625.

A review of near dry machining/minimum quantity lubrication machining of difficult to machine alloys

Cutting fluids cool and lubricate the cutting tool and machined area, wash away chips thereby increasing material removal rate, lengthen tool life and improve dimensional accuracy. However, strict environmental regulations prohibit liberal use of conventional coolants due to environment, health hazards and economic reasons. But, dry cutting although environmental friendly is not feasible under all machining applications. Some materials, when machined dry, tend to stick to tool face, spoiling tool and machined surface finish, can be efficiently machined under near dry machining (NDM) or under minimum quantity lubrication (MQL) conditions; in which cooling and lubrication in the cutting zone can be achieved by a tiny amount of cutting oil applied to tool tip with compressed air in mist form, thereby addressing the negative impact of flooded coolant machining. This paper, attempts to critically review research progress and current state of affairs in machining of difficult to machine alloys under NDM/MQL.

Investigating wear mechanisms of CBN and mixed-ceramic tools during finish hard turning of low-medium hardness AISI H11 steel

The principal aim of this paper is to identify the wear mechanisms of CBN and mixed-ceramic tools during finish hard turning of low to medium hardness (42–52 HRC) AISI H11 steel under different machining conditions. The effect of machining parameters viz. cutting speed, feed rate, depth of cut and work hardness on wear pattern of these tools have been investigated. The prominent wear modes observed for CBN tool are abrasion wear, formation of transferred layer resulting from tribochemical reactions between constituents of tool, and workpiece material, built up edge, adhesion of workpiece material followed by plastic deformation and notching clearly visible at low workpiece hardness (47 HRC). The different wear mechanisms observed for mixed ceramic tool are abrasion wear, notch wear, chipping and brittle fractures of tool surface due to rubbing and impingement of hard particles in the work material, built up edge and adhesion followed by plastic deformation. The tool wear was characterised through optical microscopy and scanning electron microscope accompanied with energy dispersive analysis through X-ray.