Crater Wear Rate Research Articles

Study on thermal-mechanical characteristics and crater wear of cemented carbide tools during the milling 508III steel

The water chamber head is made of 508III steel with high strength and hardness. The cemented carbide tool bears a large thermal-mechanical load during the cutting process, which leads to severe insert wear and damage as well as low tool life. Firstly, the milling experiments and finite element (FE) simulation were carried out to study the thermal-mechanical characteristics of tools. Secondly, the thermal-mechanical coupling simulation was carried out to explore the temperature field, strain, total deformation of the milling cutter, and the deformation and strain of the rake face of the milling insert respectively. Finally, the tool wear experiment was carried out, and the form, morphology, and energy spectrum of tool wear were analyzed, and the parameters of the crater wear were measured. The proposed crater wear rate was used as the characterization variable of tool wear, and the crater wear rate model was established to explore the wear evolution process of inserts preliminarily. The research results can provide theoretical support and experimental basis for the in-depth study of the tool failure mechanism and tool optimal design of the high-efficiency milling water chamber head.

Wear of Mo- and W-alloyed TiAlN coatings during high-speed turning of stainless steel

This study investigates the wear of W- and Mo-alloyed Ti1-x-yAlxMeyN coatings (Me = W, Mo) with x ≈ 0.55 and y ≈ 0.10 during high-speed turning of stainless steel 316L. A difference in the crater wear rate was observed between TiAlN and Ti1-x-yAlxMeyN coatings. The wear behavior in the sliding area is characterized in detail for two different regions by scanning and transmission electron microscopy and energy dispersive X-ray spectroscopy. A thin adhered layer constituted of elements from the workpiece material is observed on the top of all coatings, followed by diffusion of species from the stainless steel 316L into the coatings. Co from the cemented carbide substrate also diffuses through column boundaries of the coating. The temperature varies in the sliding area. The presence of Mo or W retards the spinodal decomposition and the formation of h-AlN as compared to TiAlN coatings, leading to lower crater wear rate in alloyed coatings.

On the mechanism of crater wear in a high strength metastable β titanium alloy

The primary wear mechanism of WC-Co tools when machining aerospace titanium alloy components is crater wear. The diffusion controlled dissolution and thus the crater wear rate is more apparent when machining the high strength, fatigue resistant metastable β titanium alloys: an expensive class of titanium alloy used in aerostructural components such as twin aisle aircraft landing gear parts. To characterise the mechanistic process of crater wear progression, outer diameter turning trials were conducted on the metastable β alloy, Ti-5553. Uncoated WC-Co inserts were used for time steps of 30, 60 and 900 s at a cutting speed of 70 m/min. The crater region was analysed using high-resolution SEM, X-EDS, WDS and STEM/TEM. Such targeted characterisation enabled the detailed mechanism of progressive crater wear in titanium machining to be further understood. In the crater wear process, rapid diffusion of Co into adhered Ti-5553 occurs within the crater zone, proceeded by decarburisation of the WC (hcp). Thermodynamic modelling and high-resolution imaging of the interface suggests Co facilitates the formation of Ti2Co, and possibly a liquid, within prior Co rich regions at WC grain boundaries. Subsequently, this creates regions that exhibit similar characteristics to a Kirkendall morphology due to accelerated C depletion and W–Ti dissolution. The formation of abrasive titanium carbides in the workpiece material increases as C is made available from the WC transforming to W (bcc) and through binder regions. Once the W (bcc) layer is formed the rapid decarburisation process is concentrated at prior Co-rich (heavily β stabilised) Ti regions, this degradation dictates the crater wear rate during the machining of Ti-5553. Now an understanding of the crater wear mechanism has been characterised for Ti-5553, tooling manufacturers can engineer the Co-binder volume fraction and distribution, to improve tool life and provide significant cost savings when machining metastable β titanium alloy components.

Reliability of PVD-coated single-layer TiAlN carbide tool during turning of hardened AISI 4340 alloy steel

Reliability of a cutting tool in terms of tool wear is of foremost importance in metal cutting owing to its direct impact on the surface quality of the machined surface, and its dimensional accuracy, and consequently, on the economics of machining operations. With this view, in the present work, reliability of single layer PVD-coated TiAlN carbide tool is assessed during turning of hardened AISI 4340 steel (35 HRC) at various cutting conditions. Dry cutting tests were carried out with cutting speeds of 142, 265, 345 and 487 m/min and feed and depth of cut values of 0.125 mm/rev and 0.8 mm, respectively. Flank wear and its growth was monitored at regular intervals of length of cut using a digital microscope with a maximum magnification of 230X. Reliability of cutting tool obtained at different cutting conditions is compared with a view to understand the progression of tool wear and wear mechanisms at different stages of tool life. Environmental scanning electron microscope (ESEM) with energy dispersive X-ray spectroscopy (EDAX) system was used to understand tool wear and wear mechanisms. It has been observed that a better reliability of a PVD- coated tool could be obtained by limiting the cutting speed 200-250 m/min as at higher cutting speeds lower cutting tool reliability resulted due to the weakening of the cutting edge by an accelerated crater wear rate.

Reliability of Coated Carbide Tool During Turning Hardened Steel

Reliability of a cutting tool in terms of tool wear is of foremost importance in metal cutting owing to its direct impact on the surface quality of the machined surface, and its dimensional accuracy, and consequently, on the economics of machining operations. With this view, in the present work, reliability of single layer PVD-coated TiAlN carbide tool is assessed during turning of hardened AISI 4340 steel (35 HRC) at various cutting conditions. Dry cutting tests were carried out with cutting speeds of 142, 265, 345 and 487 m/min and feed and depth of cut values of 0.125 mm/rev and 0.8 mm, respectively. Flank wear and its growth was monitored at regular intervals of length of cut using a digital microscope with a maximum magnification of 230X. Reliability of cutting tool obtained at different cutting conditions is compared with a view to understand the progression of tool wear and wear mechanisms at different stages of tool life. Environmental scanning electron microscope (ESEM) with energy dispersive X-ray spectroscopy (EDAX) system was used to understand tool wear and wear mechanisms. It has been observed that a better reliability of a PVD-coated tool could be obtained by limiting the cutting speed 200-250 m/min as at higher cutting speeds lower cutting tool reliability resulted due to the weakening of the cutting edge by an accelerated crater wear rate.

Influence of tool surface topography on the material transfer tendency and tool wear in the turning of 316L stainless steel

The influence of tool surface topography on the initiation and build-up of transfer layers in the orthogonal turning of 316L austenitic stainless steel have been studied under well controlled conditions. Tool materials include CVD Ti(C,N)-Al2O3-TiN and PVD (Ti, Al)N-(Al,Cr)2O3 coated cemented carbide inserts prepared using different grinding and polishing treatments. Post-test characterization of the inserts was performed using high resolution scanning electron microscopy and energy dispersive X-ray spectroscopy.The results show that the transfer tendency of work material is strongly affected by the surface topography of the rake face. For both types of inserts, the initial transfer and the build-up of transfer layers are localised to microscopic surface irregularities on the rake face. Consequently, an appropriate surface treatment of the cemented carbide substrate before coating deposition and the as-deposited CVD and PVD coating can be used in order to reduce the transfer tendency and the mechanical interaction between the mating surfaces. Also, an improved surface finish was found to reduce coating wear and consequently the crater wear rate of the inserts investigated. This can most likely be explained by the reduced tendency to discrete chipping of coating fragments in the contact zone and the formation of a thin transfer layer composed of Al, Si, Ca, O with beneficial friction properties which are promoted by a smooth coating surface.

Characteristic of Wear, Force and their Inter-relationship: In-process Monitoring of Tool within Different Phases of the Tool Life

This paper mainly concentrates on mapping and understanding of the inter-relationship between the tool wear and cutting force/s in view of in-process monitoring of the tool during turning within the different phases of the tool life. Inter-relationship between the tool wear and cutting forces was studied using two different industrial state-of-the-art tool coatings; PVD-applied (Ti,Al)N and CVD-applied TiCN/Al2O3/TiN during turning of AISI 4340 steel. The experimental results show that the feed component and radial component are more influenced by tool wear and increase sharply when rapid deterioration of the cutting edge takes place. Gradual growth of flank wear, rapid deterioration of the cutting edge and catastrophic failure due to increased crater wear rate was correctly sensed by the force signals and boost up the existence of a strong interrelationship between the cutting force- wear-time within the different phases of tool life. This paper also presents mathematical modeling of the force-wear characteristic for better understanding of the relationship.

A Cobalt Diffusion Based Model for Predicting Crater Wear of Carbide Tools in Machining Titanium Alloys

In machining titanium alloys with cemented carbide cutting tools, crater wear is the predominant wear mechanism influencing tool life and productivity. An analytical wear model that relates crater wear rate to thermally driven cobalt diffusion from cutting tool into the titanium chip is proposed in this paper. This cobalt diffusion is a function of cobalt mole fraction, diffusion coeficient, interface temperature and chip velocity. The wear analysis includes theoretical modeling of the transport-diffusion process, and obtaining tool–chip interface conditions by a nonisothermal visco-plastic finite element method (FEM) model of the cutting process. Comparison of predicted crater wear rate with experimental results from published literature and from high speed turning with WC/Co inserts shows good agreement for different cutting speeds and feed rate. It is seen that wear rates are independent of cutting time.

Modelling of CBN tool crater wear in finish hard turning

The wear of cubic boron nitride (CBN) cutters, commonly used now in the finish turning of hardened parts, is an important issue that needs to be addressed for hard turning to be a viable technology due to the high costs of CBN cutters and the down-time for tool change. Chipping and tool breakage, which lead to early tool failure, are both prone to take place under the effect of crater wear. The objective of this study is to develop a methodology to model the CBN tool crater wear rate to both guide the design of CBN tool geometry and optimise cutting parameters in finish hard turning. First, the wear volume losses due to the main wear mechanisms (abrasion, adhesion, and diffusion) are modelled as functions of cutting temperature, stress, and other process attributes respectively. Then, the crater wear rate is predicted in terms of tool/work material properties and cutting configuration. Finally, the proposed model is experimentally validated in finish turning of hardened 52100 bearing steel using a low CBN content insert. The comparison between the prediction and the measurement shows reasonable agreement and the results suggest that adhesion is the main wear mechanism over the investigated range of cutting conditions .

ＢＮ添加鋼の被削性 第３報 断続切削における被削性

This paper deals with machinability of BN added steels in face milling. In this study, work materials including different content levels of Al, B and N were cut with a carbide tool P10, a TiN cennet tool, a TiC cermet tool and a TiCN coated carbide tool. When face milling the steels with the carbide tool P10 and the cermet tools at the cutting speed over 200 m/min, steels containing Al, B and N caused much smaller flank wear but larger crater wear than S45C. While in face milling of BN added steels by the TiCN coated tool at the cutting speed of 300 m/min, the crater wear rate was drastically reduced than that of S45C. In the cace of face milling in low oxygen atmosphere, crater wear of the carbide tool were also reduced. It was concluded that the machinability of BN added steels in face milling was influenced by tool materials, Al, B and N content of work materials and cutting atmosphere.

Effect of grain size on wear behaviour of alumina cutting tools

Pure alumina inserts with grain sizes of 0.83, 2.94 and 6.33 μm were produced by slip casting and pressureless sintering. They were used to turn medium carbon steel in dry, continuous cutting conditions, at a cutting speed of 450 m min -1. Examination of the flank face showed that the flank wear land was characterized by long and parallel ridges at short machining times, with the ridges becoming wavier as the grain size of the insert increased. The initial volume flank wear rate increased with increasing grain size of the insert and is consistent with grain spallation being the primary wear mechanism, although the wear rate was moderated by the subsequent smearing of spalled grains onto the tool surface by single glide. After the attainment of a critical width of flank wear land, a transition in wear feature to a two-zone wear feature with spikes nearer the cutting edge and ridges further away occurred; shortly after which the volume flank wear rate decreased appreciably. A similar two-zone wear feature was also observed on the crater of the tool even with short machining times. Although the size of the spikes observed in the crater varied with the grain size of the insert, crater wear rate, expressed as time rate of change of the maximum crater depth, is grain-size independent. This is because the maximum depth of the crater occurred in the region covered with spikes, where material loss is controlled by plastic deformation-induced necking of asperities, a process known to be grain-size independent.

Transitions in wear mechanisms of alumina cutting tools

Alumina inserts were used to turn medium carbon steel bars in dry, continuous cutting conditions at a cutting speed of 450 m min−1. Three wear mechanisms were identified: plastic deformation-induced necking of asperities; grain spallation; and bulk plastic deformation of alumina. The crater wear land was characterized by spikes nearer the cutting edge and ridges further away because the temperatures and compressive stresses were higher nearer the cutting edge. The crater wear-rate, as measured by the maximum crater depth, was controlled by plastic deformation-induced necking, which was also responsible for the formation of the spikes. The flank wear land was characterized by ridges during the initial stage of machining, formed by the spallation of grains and their subsequent smearing by single glide. As the temperatures and compressive stresses on the flank wear land increased with increasing width of the wear land and machining forces, a transition to a two-zone wear feature (TF) characterized by spikes and ridges occurred, similar to that observed on the rake face. Seizure then followed and a transition in wear rate (TR) was observed in that further increases in the width of the flank wear land occurred by bulk plastic deformation of the to material at a much reduced rate. The present work shows that there exists a transition zone (from TF to TR) in flank wear, sepa the rapid wear mechanism of grain spallation from the slower mechanism of bulk plastic deformation, defined by both machining time and a critical flank wear land width.

コーテッド工具のすくい面摩耗予測

No matter what wear mechanism controls tool wear, tool wear rate can be expressed as functions of stress and temperature on the tool face. Thus stress and temperature distributions on the rake face were measured with split tools and with thermocouples respectively to obtain wear equations. Specific crater wear rate of coated tools was linear with normal stress and increased exponentially with temperature. Using the wear equations, crater wear of coated tools was predicted through cutting temperature analysis by the newly proposed finite difference method. The calculated results for the tools with single and double coating layers were in good agreement with experimental results. The analysis for predicting crater wear of coated tools showed that thermal conductivity of substrate has a great influence on tool wear rate.

サーメット工具のすくい面摩耗に関する研究 高速切削時の摩耗機構の一考察

The purpose of this study is to clarify the wear mechanism at high speed cutting, that is, high tool face temperature where mutual diffusion at interface comes to active. The relation is investigated and discussed between the crater wear rate and the condition of diffusion layer by cutting test and dynamic diffusion test, for reference. Combination of materials is cermet tool of TiC type to plain carbon steel of 0.45% C. In the cutting test by turning, cutting speed varied from 2.5 m/s to 7.5 m/s. In the dynamic diffusion test, both samples, contacting each other with a plane inclined at 5 degrees under axial load, were kept for 30 minutes in argon gas at various temperatures from 1 273 K to 1 473 K. The surface of samples was observed and analyzed with SEM and EPMA. The main results obtained are as follows : (1) At tool face temperature over 1 300 K, wear rate depends strongly upon that temperature. (2) In that case, there is observed the Ti-rich layer on worn surface, which is hard and brittle layer of several gm thick. (3) A model is considered in which wear proceeds by repetition of formation and tearing off of the layer. (4) the layer is produced as a result of diffusion at interface and squeeze of binding material of Ni by pressure. (5) Also in the diffusion test, Ti-rith layer is observed.

サーメット工具のすくい面摩耗機構に関する研究

The purpose of this paper is to clarify the wear mechanism at high cutting speed where mutual diffusion at interface comes to active.The relation between the crater wear rate and the condition of diffusion layer by cutting test and dynamic diffusion test, for reference, was investigated and discussed. Combination of materials was cermet tool of TiC type to plain carbon steel of 0.45%C. In the cutting test by turning, cutting speed was varied from 2.5 m/s to 7.5 m/s. In the dynamic diffusion test, the contact planes of both samples inclined at 5 degrees under axial load, were kept at high temperature ranging from 1273 K to 1473 K for 30 minutes in argon gas environment. The surface of samples was observed and analyzed using SEM and EPMA. The main results obtained are as follows:(1) At a tool face temperature over 1300 K, the wear rate depends strongly upon the temperature.(2) In this circumstance, a Ti-rich layer on the worn surface of tool is observed, which is hard and a brittle layer of several um thick.(3) A model can be proposed in which the wear proceeds by the repetition of formation and tearing off of the layer.(4) The layer is produced as a result of diffusion at interface and squeeze of binding material of Ni by pressure.

S45Cの正面フライス切削時のセラミック工具の損傷

In order to investigate the application of ceramic tools in intermittent cutting, face milling test was conducted on 0.45% carbon steel with several ceramic, carbide and cermet tools. The wear patterns, the wear rates and the tool life were measured and also crater wear was observed precisely with an optical and an electron microscope. Obtained data were analysed to evaluate the wear characteristics of ceramic tools in comparison with those of carbide and cermet tools. Main results obtained are : 1. Ceramic tools are applicable for face milling without tool failure under the selected cutting conditions. 2. Crater wear rate of ceramic tools in face milling is much higher than those of another machining methods. Consequently, 50 μm of maximum crater wear depth is considered to be the suitable tool life criteria from the view point of tool failure. 3. Thermal cracks parallel and normal to the cutting edge are observed in the crater wear region of ceramic tools. Since these cracks in ceramic tools are not so deep as those of carbide and cermet tools, it is considered that they are not essential for the tool failure.

The effect of thermal conductivity of tool material on cutting forces and crater wear rate

As the thermal conductivity of the tool material is related to tool-chip contact length, the influence of the thermal conductivity of the tool material on the cutting forces and crater wear was investigated by studying changes in the contact length.