An investigation of tool wear in high-speed turning of AISI 4340 steel

A commercially available insert has been used to turn an AISI 4340 steel at speeds placed between 325 and 1000 m/min. The flank wear was measured in connection to cutting time. This is to determine the tool life defined as the usable time that has elapsed before the flank wear has reached the criterion value.It is shown that an increase in cutting speed causes a higher decrease of the time of the second gradual stage of the wear process. This is due to the thin coat layer which is rapidly peeled off when high-speed turning.The investigation included the realization of a wear model in relation to time and to cutting speed. An empirical model has also been developed for tool life determination in connection with cutting speed.On the basis of the results obtained it is possible to set optimal cutting speed to achieve the maximum tool life.     

Investigations on surface integrity of AISI 1045 using LPB tool

Low plasticity burnishing (LPB) is relatively a new method of surface enhancement, which raises the burnishing to the next level of sophistication. LPB can provide deep stable surface compression for improved surface integrity characteristics. The present study focuses on the surface roughness, microhardness, surface integrity and fatigue life aspects of AISI 1045 work material, using full factorial design of experiments. The assessment of the surface integrity aspects on work material was done, in terms of evaluating the interaction effects of parameters, identifying the predominant factor amongst the selected parameters, their order of significance and setting the levels of the factors for minimizing surface roughness and/or maximizing surface hardness and fatigue life. Mathematical expressions were developed for surface characteristics of importance as response variables. Subsurface microhardness studies were also done to assess the depth of compression, altered material zone and correlate fatigue life with surface roughness and surface hardness. The process can be applied to critical components effectively, as the LPB process today has significant process cycle time advantages, and lower capital cost. Additional cost reduction will be realized by introducing proven high speed machining concepts into the LPB process.     

Influence of cryosoaking period on wear characteristics and surface topography of M35 tool steel

Cryogenic treatment affects tool steels wherein alteration in microstructural features like phases, uniform precipitation of carbides is observed. In this work, improvement in wear resistance of cryotreated material with microstructural features and surface roughness of material has been correlated. Samples of AISI M35 steel were hardened at 1200°C, followed by triple tempering at 555°C in the salt bath, subsequently subjected to cryogenic treatment at minus 185°C for varying cryosoaking period (4–32?h) followed by soft tempering at 100°C. Such samples were characterized for hardness, microstructure, carbide density, wear rate and surface roughness. A correlation of carbide density and roughness has been established with wear resistance.     

Numerical analysis of the effect of tool wear on surface integrity during hard turning

Journal of Mechanical Science and Technology - The white layer formed during hard turning deteriorates surface integrity, thereby severely affecting the fatigue life of machined parts. A 2D...     

Evaluating the effect of coolant pressure and flow rate on tool wear and tool life in the steel turning operation

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and workpiece in machining processes. High fluid pressure allows for better penetration of the fluid into the cutting zone, enhancing the cooling effect, and decreasing tool wear through lubrication of the contact areas. The main objective of this work is to understand how tool wear mechanisms are influenced by fluid pressure under different cutting speeds in the finish turning of AISI 1045 steel using coated carbide tools. The main finding was that the use of a lower cutting speed (v _c ?=?490 m/min) in dry cutting resulted in tool life close to that obtained with cutting fluid, but when the cutting speed was increased (v _c ?=?570 m/min), the high-pressure coolant was effective in prolonging the life of the cutting tool. It was also concluded that, regardless of the cutting speed and cooling/lubrication system, the wear mechanisms were the same, namely abrasion and attrition.     

Experimental investigations of vegetable based cutting fluids with extreme pressure during turning of AISI 304L

Experimental studies on the performances of both new developed environmental friendly vegetable based cutting fluids (refined sunflower and canola oils) including different percentage of extreme pressure (EP) additive and two commercial cutting fluids (semi-synthetic and mineral cutting fluids) in turning processes were reported in this work. Performances of cutting fluids were compared with respect to surface roughness, cutting and feed forces and tool wear during longitudinal turning of AISI 304L. Experimental results were also compared with dry cutting conditions. The results indicated that 8% of EP included canola based cutting fluid performed better than the rest.     

Experimental investigations of vegetable based cutting fluids with extreme pressure during turning of AISI 304L

Experimental studies on the performances of both new developed environmental friendly vegetable based cutting fluids (refined sunflower and canola oils) including different percentage of extreme pressure (EP) additive and two commercial cutting fluids (semi-synthetic and mineral cutting fluids) in turning processes were reported in this work. Performances of cutting fluids were compared with respect to surface roughness, cutting and feed forces and tool wear during longitudinal turning of AISI 304L. Experimental results were also compared with dry cutting conditions. The results indicated that 8% of EP included canola based cutting fluid performed better than the rest.     

Analysis of tool wear and surface finish in hard turning

Hard turning is a profitable alternative to finish grinding. The ultimate aim of hard turning is to remove work piece material in a single cut rather than a lengthy grinding operation in order to reduce processing time, production cost, surface roughness, and setup time, and to remain competitive. In recent years, interrupted hard turning, which is the process of turning hardened parts with areas of interrupted surfaces, has also been encouraged. The process of hard turning offers many potential benefits compared to the conventional grinding operation. Additionally, tool wear, tool life, quality of surface turned, and amount of material removed are also predicted. In this analysis, 18 different machining conditions, with three different grades of polycrystalline cubic boron nitride (PCBN), cutting tool are considered. This paper describes the various characteristics in terms of component quality, tool life, tool wear, effects of individual parameters on tool life and material removal, and economics of operation. The newer solution, a hard turning operation, is performed on a lathe. In this study, the PCBN tool inserts are used with a WIDAX PT GNR 2525 M16 tool holder. The hardened material selected for hard turning is commercially available engine crank pin material.     

The effect of surface topography on the wear of steel

The pattern of roughness and wear has been obtained by varying the speed, the number of passes and the pre-roughness of the samples in both dry and lubricated sliding conditions. Three-dimensional graphs of wear versus speed versus sliding time and roughness of the worn surfaces were produced and a linear relation between the variation of the roughness and the amount of wear at a high number of passes has been determined. The initial dry wear rate is influenced by the prior surface roughness. In the case of lubricated conditions the influence of prior roughness is not pronounced. In dry sliding the smooth surfaces in the running-in stage roughen and the rough surfaces become smoother, while in lubricated conditions both surfaces become smoother in the first few passes. Sliding perpendicular to the lay produces rougher surfaces and more wear than is the case in the parallel direction.     

The dependence of tool overhang on surface quality and tool wear in the turning process

In the turning process, the importance of machining parameter choice is increased, as it controls the surface quality required. Tool overhang is a cutting tool parameter that has not been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the workpiece and when using the hole-turning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the workpiece and tool wear. For this purpose, we used workpieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the workpiece and tool wear were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.     

Some studies on hard turning of AISI 4340 steel using multilayer coated carbide tool

Hard turning with multilayer coated carbide tool has several benefits over grinding process such as, reduction of processing costs, increased productivities and improved material properties. The objective was to establish a correlation between cutting parameters such as cutting speed, feed rate and depth of cut with machining force, power, specific cutting force, tool wear and surface roughness on work piece. In the present study, performance of multilayer hard coatings (TiC/TiCN/Al₂O₃) on cemented carbide substrate using chemical vapor deposition (CVD) for machining of hardened AISI 4340 steel was evaluated. An attempt has been made to analyze the effects of process parameters on machinability aspects using Taguchi technique. Response surface plots are generated for the study of interaction effects of cutting conditions on machinability factors. The correlations were established by multiple linear regression models. The linear regression models were validated using confirmation tests. The analysis of the result revealed that, the optimal combination of low feed rate and low depth of cut with high cutting speed is beneficial for reducing machining force. Higher values of feed rates are necessary to minimize the specific cutting force. The machining power and cutting tool wear increases almost linearly with increase in cutting speed and feed rate. The combination of low feed rate and high cutting speed is necessary for minimizing the surface roughness. Abrasion was the principle wear mechanism observed at all the cutting conditions.     

AISI 304不锈钢铣削加工刀具磨损实验研究

AISI 304不锈钢具有低导热性和高韧性等特性,切削加工性较差。研究采用复合涂层硬质合金铣刀,对AISI 304不锈钢进行了端铣实验研究,考察后刀面磨损情况。实验表明,进给率对磨损的影响大于切削速度。针对刀具后刀面磨损,给出了相对较好的切削条件组合。     

Experimental research on micro mill-grinding AISI 1045 steel with a cold spraying compound micro cutting tool

Journal of Mechanical Science and Technology - Micro mill-grinding is a novel compound machining process. This article presented a novel micro mill-grinding tool fabricated by cold spray...     

Machinability investigation in hard turning of AISI D3 cold work steel with ceramic tool using response surface methodology

The hard turning process has been attracting interest in different industrial sectors for finishing operations of hard materials. In this paper, the effects of cutting speed, feed rate, and depth of cut on surface roughness, cutting force, specific cutting force, and power in the hard turning were experimentally investigated. An experimental investigation was carried out using ceramic cutting tools, composed approximately with (70 %) of Al₂O₃ and (30 %) of TiC, in surface finish operations on cold work tool steel AISI D3 heat-treated to a hardness of 60 HRC. Based on 3³ full factorial designs, a total of 27 tests were carried out. The range of each parameter is set at three different levels, namely, low, medium, and high. Analysis of variance is used to check the validity of the model. Experimental observations show that higher cutting forces are required for machining harder work material. This cutting force gets affected mostly by feed rate followed by depth of cut. Feed rate is the most influencing factor on surface roughness. Feed rate followed by depth of cut become the most influencing factors on power; especially in case of harder workpiece. Optimum cutting conditions are determined using response surface methodology (RSM) and the desirability function approach. It was found that, the use of lower depth of cut value, higher cutting speed, and by limiting the feed rate to 0.12 and 0.13 mm/rev, while hard turning of AISI D3 hardened steel, respectively, ensures minimum cutting forces and better surface roughness. Higher values of depth of cut are necessary to minimize the specific cutting force.     

Influence of the tool corner radius on the tool wear and process forces during hard turning

Hard turning has become an alternative machining process for grinding processes of hardened steels. One challenge during hard turning is the increasing wear during the operation time of the tool and the hereby influenced workpiece surface and subsurface properties. This causes unfavorable changes of the microstructure and residual stress state or rather damages of the subsurface. Important factors are the contact conditions between the tool and the workpiece. The width of flank wear land influences the size of the passive force significantly. This has a direct impact on the subsurface properties of the workpiece. One solution is to modify the contact conditions and thereby the specific mechanical and thermal loads that are applied to the tool as well as to the workpiece. This article presents an experimental approach of modified corner radius geometry of cutting tools for hard turning processes. Hereby, the size and direction of the contact length of the cutting edge are adjusted as well as the load impact during machining. The aim is to reduce the tool wear performance. The results show the potential of the load-specific tool design concerning the tool wear and the workpiece subsurface properties. Furthermore, a new approach for predicting the process forces during hard turning is presented.     

Modeling and predicting for surface topography considering tool wear in milling process

This paper presents a model for the prediction of surface topography considering tool wear during the milling process. First, the cutting edge path equation, which can be transformed into equivalent polynomial equations and solved for discrete positions along the feed direction, is established including the effect of tool wear. Then, cutting edge is divided into a series of cutting points and an algorithm is proposed to determine the range of divided position angle. Finally, surface topography model is established based on the established cutting path equation, the range of position angle, the calculated cutting time, and spiral lag angle. By using this model, surface topography generation is simplified with respect to other models in literature and the modeling method of surface topography does not need to mesh the workpiece and the model can easily be extended to include other factors on surface generation. Based on the established surface topography model, an algorithm is proposed to simulate generation of surface profile in milling operation. Experimental work and validation of the established model is performed on a five-axis milling center by using stainless steel 1Cr18Ni9Ti and cemented carbides milling cutter. Cutting test results about the topography generation of the plane and cylindrical surface show good agreement with model predictions.     

Effects of tool overhang on selection of machining parameters and surface finish during diamond turning

In precision machining leading to nano-metric surface finish, selection of the suitable machining parameters is a critical task. To ensure the desired surface quality, one needs to optimally select the machining parametric matrix. Towards this effort, this paper adds another critical parameter in terms of tool overhang. A well-defined set of machining exercises is carried out with different tool overhangs and machining parameters. In this investigation, an attempt has been made to locate the optimum range of tool overhang with minimum tool vibrations. The interaction between tool overhang with other parameters is also thoroughly investigated. Another important focus of this study is to find out the optimum machining parameters for the situations where it is not possible to select an optimum tool overhang. One such situation occurs when a steep concave parabolic surface needs to be fabricated. In this case a large tool overhang has to be selected. Power spectral density distribution analysis of surface roughness for different tool overhangs is performed to find out significant parameters and their degree of contribution to surface roughness. Analysis of variance is also applied to ascertain statistically significant factors contributing to surface roughness. To model the surface roughness, response surface methodology is being used. The model has been verified by conducting a series of experiments and a steep concave parabolic surface is developed by following the predictions of the developed model.     

Microstructural characterization of laser surface melted AISI M2 tool steel

We describe the microstructure of Nd:YAG continuous wave laser surface melted high‐speed steel, namely AISI M2, treated with different laser scanning speeds and beam diameters on its surface. Microstructural characterization of the remelted surface layer was performed using light optical and scanning electron microscopy and X‐ray diffraction. The combination of the three techniques provided new insights into the substantial changes induced by laser surface melting of the steel surface layer. The advantage of the method is that it avoids the difficult and tedious work of preparing samples of this hard material for transmission electron microscopy, which is the technique normally used to study these fine microstructures. A melted zone with a dendritic structure and a partially melted zone with a heterogeneous cellular structure were observed. M₂C carbides with different morphologies were identified in the resolidified surface layer after laser melting.     

Online monitoring and measurements of tool wear for precision turning of stainless steel parts

Online monitoring and measurements of tool wear were carried out using cutting forces for precision turning of stainless steel parts. The best combination of features was selected from 14 features extracted from force signals by using a Sequential Forward Search algorithm. Back-propagation neural networks (BPNs) used two features for online classification. When the adaptive neuro-fuzzy inference system (ANFIS) was applied, seven features were needed for the classification. For online measurements, only one feature is needed for BPN. Three features are needed for ANFIS for online measurements. For online classification of turning tool conditions, a 2?×?20?×?1 BPN can achieve a success rate of higher than 86% while a 7?×?2 ANFIS can reach a success rate of higher than 96%. For online measurements of tool wear, the estimation error can be as low as 1.37% when a 1?×?20?×?1 BPN was used while the error can be as low as 0.56% using a 3?×?3 ANFIS. Therefore, the 3?×?3 ANFIS can be used first to predict the degradation of tool conditions during the turning process. It can also be used to measure the tool wear online so as to take feedback control action to enhance accuracy of the process. Once the detected tool wear is close to the worn-out threshold, the 7?×?2 ANFIS will be then applied to classify the tool conditions in order to stop the turning operation on time automatically so as to assure the quality of products and to avoid catastrophic failure.