Investigation on wear behaviour of cryogenically treated TiAlN coated tungsten carbide inserts in turning

Cryogenic treatment has been ascribed as a way of improving the cutting life of tungsten carbide turning inserts. Most of the research conducted till date has not reported any effort to excavate the effect of cryogenic treatment on the performance of coated tungsten carbide inserts in terms of adhesion strength of coatings deposited on tungsten carbide substrate. In order to understand the effect of cryogenic treatment on the adhesion strength of coatings, a comparative investigation of the wear behaviour and machining performance of cryogenically treated coated tungsten carbide inserts in orthogonal turning has been carried out in this study. The commercially available TiAlN coated square shaped tungsten carbide inserts (P25) were procured and subjected to cryogenic treatment at two levels −110 °C (shallow treatment) and −196 °C (deep treatment) of temperature independently. The criterion selected for determining the turning performance was based on the maximum flank wear (0.6 mm) as recommended in ISO 3685-1993. The results showed that shallow cryogenically treated coated tungsten carbide inserts performed significantly better as compared with deep cryogenically treated and untreated inserts. Major outcome of the present study includes a substantial decrease in tool life of deep cryogenically treated inserts as compared to untreated inserts indicating the destructive effect of deep cryogenic temperature (−196 °C) on TiAlN coated inserts which is further supported by VDI-3198 indentation test.     

Wear behaviour of cryogenically treated tungsten carbide inserts under dry and wet turning conditions

Cryogenic treatment has been acknowledged as a means of extending the life of tungsten carbide inserts but no study has been reported in open literature regarding the effect of coolant on the performance of cryogenically treated tungsten carbide inserts in turning. In order to understand the effect of coolant, a comparative investigation of the wear behaviour of cryogenically treated tungsten carbide inserts in dry and wet orthogonal turning has been carried out in this study. The commercially available uncoated square-shaped tungsten carbide inserts with chip breakers were procured and cryogenically treated at ?196 °C and the cutting tests were executed in accordance to the International Standard Organisation, ISO 3685-1993 for continuous and interrupted machining mode. The criterion selected for determining the tool life was based on the maximum flank wear (0.6 mm) and the selection of cutting conditions was made to ensure the significant wear at a suitable time interval. The results showed that cryogenically treated tungsten carbide inserts performed significantly better in wet turning conditions under both continuous and interrupted machining modes especially at higher cutting speeds. A considerable increase in tool life was also recorded in interrupted machining mode as compared with continuous machining mode.     

The effect of the multi-layer surface coating of carbide inserts on the cutting forces in turning operations

In this paper, the effects of the multi-layer hard surface coating of cutting tools on the cutting forces in steel turning are presented and discussed, based on an experimental investigation with different commercially available carbide inserts and tool geometries over a range of cutting conditions. The cutting forces when turning with surface coated carbide inserts are assessed and compared qualitatively and quantitatively with those for uncoated tools. It is shown that hard surface coatings reduce the cutting forces, although the reduction is marginal under lighter cutting conditions. The cutting force characteristics for surface coated tools are also discussed and shown to have similar trends to those of uncoated tools.     

Experimental Investigations to Study the Effects of Microwave Treatment Strategy on Tool Performance in Turning Operation

In the present study, microwave treatment has been used to enhance the tribological properties of single-point tungsten carbide (WC) cutting tool inserts such as wear resistance and hardness. The tool hardness and cutting parameters were considered to evaluate the performance of microwave-treated WC inserts in turning operation. The optimum cutting parameters were identified using response surface method (RSM)-based desirability approach. The relationship between cutting parameters and output responses, viz. flank wear, cutting force and surface roughness, was developed using the RSM. The investigations revealed that the increase in tool hardness due to complex carbide formation results in a significant reduction in tool wear, cutting forces and improvement in the surface finish of workpiece. Further, the statistical models results were validated with the experimental results. Metallurgical properties of treated and untreated tool inserts were analyzed using scanning electron microscope, x-ray diffraction method and Vickers microhardness tests. The results highlighted the importance of microwave treatment in enhancing the machining performance in turning operation.     

Investigation of the effects of cryogenic treatment applied at different holding times to cemented carbide inserts on tool wear

Cutting tool costs is one of the most important components of machining costs. For this reason, tool life should be improved using some methods such as cutting fluid, optimal cutting parameters, hard coatings and heat treatment. Recently, another one of the methods commonly used to improve tool life is cryogenic treatment. This study was designed to evaluate the effects of different holding times of deep cryogenic treatment on tool wear in turning of AISI 316 austenitic stainless steel. The cemented carbide inserts were cryogenically treated at −145 °C for 12, 24, 36, 48 and 60 h. Wear tests were conducted at four cutting speeds (100, 120, 140 and 160 m/min), a feed rate of 0.3 mm/rev and a 2.4 mm depth of cut under dry cutting conditions. The wear test results showed that flank wear and crater wear were present in all combinations of the cutting parameters. However, notch wear appeared only at lower cutting speeds (100 and 120 m/min). In general, the best wear resistance was obtained with cutting inserts cryogenically treated for 24 h. This case was attributed to the increased hardness and improved micro-structure of cemented carbide inserts. These improvements were confirmed through hardness, image processing, and XRD analyses.     

Impact of the cooling system on the cutting of medical cobalt chromium with ceramic cutting inserts

This paper presents a study of tool life, process forces and surface integrity. The focus is on the continuous turning of biocompatible cobalt chromium using ceramic cutting inserts and different cooling systems. The goal when using cooling lubricants with tungsten carbide tools is on the one hand to extend tool life time and on the other hand to achieve a better surface quality on the workpiece. When using ceramic cutting tool materials usually cooling lubricants are dispensable. The heating of the component and thus the reduction in strength is desired, since the ceramic cutting materials withstand higher temperatures. Tool life of ceramic cutting materials without cooling lubricants is often rather low. Therefore, cooling lubricants should help to extend the tool life. It will also be investigated how the different cooling systems affect the surface integrity of the workpiece. The investigations were performed under constant cutting parameters.     

Effects of cryogenic treatment and refrigerated air on tool wear when machining medium density fiberboard

Cooling of cutting tools with liquid coolants and lubricants is impractical when machining dry wood or wood composites. This study examines the combined effect of cryogenic tool treatment and using refrigerated air for cooling tools on reducing tool wear. A total of four, double-flute, solid, tungsten carbide router bits were used to machine medium density fiberboard with a CNC router. Three of the four tools were cryogenically treated to below −149 °C. During cutting, refrigerated air was applied to two tools, while the other two cut at ambient temperature. All tools were examined under the stereo light microscope to capture images in order to measure tool wear. Elemental analysis was performed using scanning electron microscopy to determine the percentage of specific elements present on clearance faces of tools after cutting was completed. Results show that less tool wear occurs when using refrigerated air and cryogenic treatment, thereby increasing tool life when cutting medium density fiberboard.     

Effects of deep cryogenic treatment on the wear development of H13A tungsten carbide inserts when machining AISI 1045 steel

In this study, the effects of deep cryogenic treatment (93 K) on the surface and sub-surface wear development of H13A cobalt-bonded tungsten carbide cutting inserts during the wet machining of AISI 1045 steel were investigated. Cutting inserts were subjected to short periods (171–553 s) of turning at cutting speeds of 50–140 m/min, during which time mass measurements were taken and the worn edges were imaged and scanned, by optical microscopy and light interferometry, at regular intervals. Sections were taken following machining so that sub-surface features could be observed by scanning electron microscopy. It was determined that cryogenic treatment resulted in a 9.2 % increase in hardness and an increase in abrasive wear resistance, although microstructural changes and sub-surface behaviours suggested a corresponding decrease in toughness may have occurred.     

Influence of cryogenic heat-treatment soaking period and temperature on performance of sintered carbide cutting tools in milling of Inconel 718

Cryogenic heat treatment is an innovative heat treatment applied to improve the mechanical properties of sintered carbide cutting tools. In this study, the effect of cryogenic heat treatment used at different temperatures and soaking periods on the mechanical properties of carbide cutting tools was investigated. Cryogenic heat treatment was applied at two different temperatures, −145 °C and − 196 °C, for 24 and 36 h soaking periods. The microstructure of the cryogenic heat-treated cutting tool was investigated as microhardness and grain size. As a result of microstructure analysis, heat treatment soaking period was found to be more effective than heat treatment temperature. Milling tests of the Inconel 718 superalloy were performed under dry conditions using cryogenic heat-treated cutting tools and non-heat treated tools. The effect of heat treatment on cutting tool performance was studied in terms of the amount of tool wear, cutting force, surface roughness values. According to the results obtained, the cryogenic heat treatment applied to the cutting tools has a positive effect on cutting performance. In addition, in the examinations carried out on worn cutting tools, effective wear mechanisms were found to be oxidation, adhesion and abrasion.     

Tool flank wear prediction in CNC turning of 7075 AL alloy SiC composite

Flank wear occurs on the relief face of the tool and the life of a tool used in a machining process depends upon the amount of flank wear; so predicting of flank wear is an important requirement for higher productivity and product quality. In the present work, the effects of feed, depth of cut and cutting speed on flank wear of tungsten carbide and polycrystalline diamond (PCD) inserts in CNC turning of 7075 AL alloy with 10 wt% SiC composite are studied; also artificial neural network (ANN) and co-active neuro fuzzy inference system (CANFIS) are used to predict the flank wear of tungsten carbide and PCD inserts. The feed, depth of cut and cutting speed are selected as the input variables and artificial neural network and co-active neuro fuzzy inference system model are designed with two output variables. The comparison between the results of the presented models shows that the artificial neural network with the average relative prediction error of 1.03% for flank wear values of tungsten carbide inserts and 1.7% for flank wear values of PCD inserts is more accurate and can be utilized effectively for the prediction of flank wear in CNC turning of 7075 AL alloy SiC composite. It is also found that the tungsten carbide insert flank wear can be predicted with less error than PCD flank wear insert using ANN. With Regard to the effect of the cutting parameters on the flank wear, it is found that the increase of the feed, depth of cut and cutting speed increases the flank wear. Also the feed and depth of cut are the most effective parameters on the flank wear and the cutting speed has lesser effect.     

Modes of failure of cemented tungsten carbide tool bits (WC/Co): A study of wear parts

Cemented tungsten carbide (WC/Co) holds a successful past as abrasion and wear-resistant components in mining industries for their wonderful combination of very high hardness and good fracture toughness as well as comparatively extraordinary wear resistance. Generally, the tungsten carbide drill bits/blades are used in rock drilling, mineral cutting, gas oil drilling and even tunneling industries. The service environments of the WC/Co tool bits are terribly complicated because of totally different hardness of the drilling objectives at different working conditions, consequence various movement patterns of the WC/Co drill bits. As a result, the failure mechanism of the tool bits is quite different. The mechanism of hole drilling and different mining operation and processes, a tool-bit gradually degrades till it breaks at the end of its life. Replacing a drill-bit once its breakage is often expensive in certain special applications. At the same time an early tool replacement decision could lead to cause of lower tools life. This type of claims is marking the ways that modify the accurate prediction of tool failures. In circumstances, where degradation signals using the appropriate features are utilized to make the tool replacement decision. Intensive investigation of the performance of tungsten carbide tools in hard metal industries and tool industries is being conducted worldwide. Tungsten carbide alloyed with cobalt (WC/Co) shows unique characteristics like high strength at elevated temperature and high mechanical and chemical resistance that makes carbide tools appropriate for cutting, drilling, mining and machining operation. A whole failure study is revealed within the paper. This study also discusses the failure mode of a tungsten carbide tools, its prediction and remedies.     

A study of micropool lubricated cutting tool in machining of mild steel

This paper presents an experimental study of the performance of micropool lubricated cutting tool in machining mild steel. Microholes are made using femtosecond laser on the rake face of uncoated tungsten carbide (WC) cutting inserts. Finite element analysis is conducted to assess the effect of microholes on the mechanical integrity of the cutting inserts. Liquid (oil) and solid (tungsten disulfide) lubricants are used to fill the microholes to form micropools. A comparative study is conducted between micropool lubricated (surface-textured) cutting tools and dry/flood-cooled conventional (untextured) cutting tools. Three cutting force components are measured and compared. Tool–chip contact length and chip morphology are examined using optical microscope. It is found that the mean cutting forces (F_f, F_t, and F_c) are reduced by 10–30% with micropool lubrication. The chip–tool contact length is reduced by about 30%. Coiling chips are produced with micropool lubricated cutting tool while long and straight chips are formed with the conventional cutting tool. Liquid and solid lubricants are found to be equally effective in reducing the contact length and coefficient of friction at the chip–tool interface. There is no adverse effect on the performance of the insert with microholes on the rake face.     

Cryogenic properties of some cutting tool materials

Cutting tool materials belong to a group of nonductile materials. Chipping and breaking of the cutting edge and fracturing of the tool are common types of tool failure even under conventional machining conditions. This leads to a concern about whether cutting tool materials are able to maintain their strength and toughness and withstand the low-temperature thermal shock during cryogenic machining. The objective of this investigation was to study the behaviors of these kinds of materials at cryogenic temperatures. The results will also serve as a basis in selecting the suitable cutting tool materials for cryogenic machining and in determining the cryogenic strategy and optimum cutting conditions. Several representative cutting tool materials, such as five grades of commercial carbide-cobalt alloys and M46 highspeed steel, are investigated in terms of microstructural observation, impact testing, transverse rupture strength measurement, and indentation testing. It has been shown that carbide tool materials generally retain their strength and toughness as the temperature decreases to liquid nitrogen temperature. The behaviors of carbide tool materials at cryogenic temperatures can be explained in terms of the temperature effects on the binder phase.     

Relationship between metal cutting performance and material properties of TiC-coated cemented carbide cutting tools

The performance of TiC-coated cemented carbide cutting tool inserts was evaluated in steel turning and cast iron milling. The machining behavior was correlated with the properties of the coating and the chemical vapor deposition parameters. It is shown that improved performance can be obtained by controlling the grain size and orientation of the coating, and by choosing appropriate parameters to minimize the formation of the substrate.     

超细晶硬质合金刀具车削不锈钢的切削温度研究

超细晶硬质合金刀具由于具有更高的硬度和抗弯强度,可以满足现代制造业的更高要求,在难加工材料高速切削领域显示出明显优势。在不锈钢材料的加工过程中,切削温度对刀具的磨损有极大的影响,而多数实验方法很难测得刀具表面具体的温度分布。借助DEFORM仿真分析软件,模拟超细晶硬质合金刀具对304不锈钢的车削过程;依据正交试验方法,分析切削用量三要素切削速度、进给量和背吃刀量对刀具温度的影响规律;通过实际车削实验与仿真结果进行比较,并与普通晶粒硬质合金刀具进行对比。结果表明:与普通晶粒硬质合金刀具加工相似,切削速度对超细晶粒硬质合金刀具温度的影响程度最大,其次是进给量,最后是背吃刀量;超细晶粒硬质合金比普通晶粒硬质合金刀具具有更好的散热性,尤其在较高速度条件下切削,优势更加明显。     

Cutting conditions for finish turning process aiming: the use of dry cutting

To avoid the use of cutting fluids in machining operations is one goal that has been searched for by many people in industrial companies, due to ecological and human health problems caused by the cutting fluid. However, cutting fluids still provide a longer tool life for many machining operations. This is the case of the turning operation of steel using coated carbide inserts. Therefore, the objective of this work is to find cutting conditions more suitable for dry cutting, i.e., conditions which make tool life in dry cutting, closer to that obtained with cutting with fluid, without damaging the workpiece surface roughness and without increasing cutting power consumed by the process. To reach these goals several finish turning experiments were carried out, varying cutting speed, feed and tool nose radius, with and without the use of cutting fluid. The main conclusion of this work was that to remove the fluid from a finish turning process, without harming tool life and cutting time and improving surface roughness and power consumed, it is necessary to increase feed and tool nose radius and decrease cutting speed.     

Some aspects of machining cast Al-SiCp composites with conventional high speed steel and tungsten carbide tools

An attempt was made to evaluate machining of eutectic Al-Si (LM6) and hypoeutectic Al-Si (LM25) alloys reinforced with 10, 15, and 20% SiCp of two particle sizes using conventional high-speed steel (HSS) and tungsten carbide (WC) tools by varying cutting speed, feed, depth of cut, and environment. Machining of metal matrix composites (MMCs) is a difficult task using HSS and WC tools. The tool life of both these conventional tools was observed to decrease with increasing percentage and coarseness of SiCp in the composites. Tungsten carbide tools had a longer tool life than HSS under all the different conditions studied. Contrary to the known phenomenon of enhanced tool life in machining monolithic alloys with the use of cutting fluid, the tool life of WC/HSS tool in machining composites with cutting fluid was only 10 to 20% of that without cutting fluid.     

Evaluation of machinability in turning of microalloyed and quenched-tempered steels: Tool wear,statistical analysis,chip morphology

The machinability of microalloyed steel (30MnVS6) and quenched-tempered (QT) steels (AISI 1045 and AISI 5140), at different cutting condition, is presented in the paper. An experimental investigation was conducted to determine the effects of cutting speed, feed rate, hardness, and workpiece material on the flank wear land and tool life of coated cemented carbide inserts in the hard turning process. It was tried that for any test condition the hardness of these steels became almost identical by using appropriate heat-treatment processes. The statistical analysis was used for evaluation of different factors on cutting forces. Chips characteristics and chip/tool contact length were also investigated. The different sections (shear plane, microcrack, thickness and edge) of the chip were examined by scanning electron microscope (SEM). Shear planes and microcracks of the chips in microalloyed steel show that the chips of microalloyed steel are regular and discontinuous. Crater wear of the tools was studied by using video microscope in turning process. The results showed that the tool life and machinability of the microalloyed steel is better than the QT steels at identical cutting condition.     

Tool wear and machining performance of cBN–TiN coated carbide inserts and PCBN compact inserts in turning AISI 4340 hardened steel

PCBN is the dominant tool material for hard turning applications due to its high hardness, high wear resistance, and high thermal stability. However, the inflexibility of fabricating PCBN inserts with complex tool geometries and the prohibitive cost of PCBN inserts are some of the concerns in furthering the implementation of CBN based materials for hard turning. In this paper, we present the results of a thorough investigation of cBN plus TiN (cBN–TiN) composite-coated, commercial grade, carbide inserts (CNMA 432, WC–Co (6% Co)) for hard turning applications in an effort to address these concerns. The effect of cutting speed and feed rate on tool wear (tool life), surface roughness, and cutting forces of the cBN–TiN coated carbide inserts was experimented and analyzed using analysis of variance (ANOVA) technique, and the cutting conditions for their maximum tool life were evaluated. The tool wear, surface roughness, and cutting forces of the cBN–TiN coated and commercially available PCBN tipped inserts were compared under similar cutting conditions. Both flank wear and crater wear were observed. The flank wear is mainly due to abrasive actions of the martensite present in the hardened AISI 4340 alloy. The crater wear of the cBN–TiN coated inserts is less than that of the PCBN inserts because of the lubricity of TiN capping layer on the cBN–TiN coating. The coated CNMA 432 inserts produce a good surface finish (<1.6 μm) and yield a tool life of about 18 min per cutting edge. In addition, cost analysis based on total machining cost per part was performed for the comparison of the economic viability between the cBN–TiN coated and PCBN inserts.     

PCBN刀具切削性能和磨损机理研究综述

聚晶立方氮化硼(PCBN)刀具是继聚晶金刚石刀具之后的又一种超硬刀具,以其独特的“以车代磨”、“硬态加工”、“干式切削”等方式被誉为21世纪的绿色环保刀具。PCBN刀具在金属切削方面具有广泛的应用,主要用来加工各种淬硬钢、耐磨铸铁等铁基材料。本文介绍了PCBN刀具成分、几何形状、切削参数等对其切削性能的影响,在此基础上分析了不同材料加工时刀具的主要磨损机理,还简单对比了硬质合金和PCBN刀具切削性能上的差异。