Machining performance of pearlitic–ferritic nodular cast iron with coated carbide and silicon nitride ceramic tools

This paper concerns the fundamental cutting characteristics obtained in the turning of the pearlitic–ferritic nodular iron (EN-GJS-500-7 grade with UTS=500 MPa) when using carbide tools coated with single TiAlN and multilayer TiC/Ti(C,N)/Al₂O₃/TiN coatings, as well as silicon nitride (Si₃N₄) based ceramic tools. As a competitor, a P20 uncoated carbide grade was selected. The fundamental process readings include cutting and feed forces, the tool–chip interface temperature, Peclet number, friction coefficient and the tool–chip contact length as functions of cutting parameters. In particular, the measurements of cutting temperature were carried out using conventional tool–work thermocouple method and IR thermography. It is concluded based on many process characteristics that multilayer coated and ceramic tools can substantially improve the performance of nodular iron machining.     

Wear behavior of Al2O3/Ti(C,N)/SiC new ceramic tool material when machining tool steel and cast iron

Design, fabrication and application of ceramic cutting tools are one of the important research topics in the field of metal cutting and advanced ceramic materials. In the present study, wear resistance of an advanced Al₂O₃/Ti(C,N)/SiC multiphase composite ceramic tool material have been studied when dry machining hardened tool steel and cast iron under different cutting conditions. Microstructures of the worn materials were observed with scanning electronic microscope to help analyze wear mechanisms. It is shown that when machining hardened tool steel at low speed wear mode of the kind of ceramic tool material is mainly flank wear with slight crater wear. The adhesion between tool and work piece is relatively weak. With the increase of cutting speed, cutting temperature increases consequently. As a result, the adhesion is intensified both in the crater area and flank face. The ceramic tool material has good wear resistance when machining grey cast iron with uniform flank wear. Wear mechanism is mainly abrasive wear at low cutting speed, while adhesion is intensified in the wear area at high cutting speed. Wear modes are dominantly rake face wear and flank wear in this case.     

Machinability of hardened steel using alumina based ceramic cutting tools

Alumina based ceramic cutting tool is an attractive alternative for carbide tools in the machining of steel in its hardened condition. These ceramic cutting tools can machine with high cutting speed and produce good surface finish. The wear mechanism of these ceramic cutting tools should be properly understood for greater utilization. Two types of ceramic cutting tools namely Ti[C,N] mixed alumina ceramic cutting tool and zirconia toughened alumina ceramic cutting tool are used for our investigation. The machinability of hardened steel was evaluated by measurements of tool wear, cutting forces and surface finish of the work piece. These alumina based ceramic cutting tool materials produce good surface finish in the machining of hardened steel. In this paper an attempt is made to analyse the important wear mechanisms like abrasive wear, adhesive wear and diffusion wear of these ceramic cutting tool materials and the performance of these ceramic cutting tools related to the surface finish is also discussed here.     

Mechanical property and cutting performance of yttrium-reinforced Al2O3/Ti(C,N) composite ceramic tool material

Effects of yttrium on the mechanical property and the cutting performance of Al₂O₃/Ti(C,N) composite ceramic tool material have been studied in detail. Results show that the addition of yttrium of a certain amount can noticeably improve the mechanical property of Al₂O₃/Ti(C,N) ceramic material. As a result, the flexural strength and the fracture toughness amount to 1010 MPa and 6.1 MPam^1/2, respectively. Cutting experiments indicate that the developed ceramic tool material not only has better wear resistance but also has higher fracture resistance when machining hardened #45 steel. The fracture resistance of the yttrium-reinforced Al₂O₃/Ti(C,N) ceramic tool material is about 20% higher than that of the corresponding ceramic tool material without any yttrium additives.     

Effect of temperature of annealing below 900 °C on structure, properties and tool life of an AlTiN coating under various cutting conditions

In this study the cemented carbide cutting tools with a nano-crystalline Al_0.67Ti_0.33N hard PVD coating deposited by cathodic arc evaporation were annealed within a range of temperatures 700-800 °C during 2 h in vacuum. The changes in structure and properties of the coating vs. temperature have been analyzed using TEM as well as high temperature nano-indentation methods. Cutting tools with the annealed AlTiN coating have been run through a number of cutting tests with varying conditions. The conditions were as following: 1) continuous cutting: turning of annealed 1040 steel (HB 220); 2) interrupted cutting: turning of 4340 steel (HRC 40); 3) end milling: ball nose end milling of hardened H13 steel (HRC 50). The cutting tool life has been investigated before and after annealing of the Al_0.67Ti_0.33N coatings at different temperatures. The relations between high temperature hardness and plasticity of the Al_0.67Ti_0.33N coating and tool life under varying cutting conditions was outlined.     

Advanced coated ceramic tools for machining superalloys

The main limitation on the use of nickel-base superalloys, such as INCONEL 718, is the difficulty in conventional-type machining. The use of high cutting speed to achieve both machining adiabatic conditions and high productivity is necessary for their applications. This non-conventional type machining results in a short life-span of tools, even for those expensive ceramic ones with reinforced SiC whiskers (SiC_w) suitable for use at high cutting speeds. The aim of the paper is to present the results of a new idea proposed by the authors to obtain an increase in tool life at high cutting speed by minimizing the temperature effects on composite reinforcement mechanisms. The 2090 SiC whiskers reinforced A1₂O₃ tools were CrN and (Ti,AI)N coated using the PVD technique, and comparative machining tests on INCONEL 718 were carried out using uncoated and coated tools. After machining, the tools were observed with a scanning electron microscope (SEM), and EDAX (X-ray) semiquantitative analyses were performed. The behaviour of the CrN and (Ti,AI)N layers using various cutting conditions was analysed and different wear mechanisms along the tool chip contact length were observed. The cause and the mechanisms of wear were deduced and mathematic models linking tool life with process parameters were suggested.     

Experimental investigation on tool wear characteristics of PVD and CVD coatings during face milling of Ti6242S and Ti-555 titanium alloys

Ti6242S and Ti-555, as two typical titanium alloys, are often used to manufacture high-temperature aeroengine parts and landing gear components, respectively. They have different chemical composition and microstructure, which make them have different mechanical properties, and also affect their machinability. In this paper, face milling experiments were carried out to evaluate the wear performance by using CVD-Ti(C, N) + Al₂O₃ + TiN, PVD-(Ti, Al)N + TiN coated and uncoated tools. The results show that Ti-555 has the worse machinability than that of Ti6242S. When milling Ti6242S, all tools suffered adhesive wear and diffusion wear; the wear of Ti(C, N) + Al₂O₃ + TiN coated tool was more serious than that of other tools due to the blunt cutting edge; (Ti, Al)N + TiN coated tool suffered micro chipping and coating peeling with the minimal wear loss. When milling Ti-555, uncoated tool suffered serious chipping, abrasive wear and adhesive wear; Ti(C, N) + Al₂O₃ + TiN coated tool suffered serious chipping and coating peeling with short tool life; (Ti, Al)N + TiN coated tool suffered coating peeling, adhesive wear and diffusion wear. Overall, (Ti, Al)N + TiN coated tools have the longest tool life and are preferred for face milling of Ti6242S and Ti-555 titanium alloys.     

Self-lubrication of sintered ceramic tools with CaF2 additions in dry cutting

An Al₂O₃/TiC ceramic cutting tool with the additions of CaF₂ solid lubricant was produced by hot pressing. The fundamental properties of this ceramic cutting tool were examined. Dry machining tests were carried out on hardened steel and cast iron. The tool wear, the cutting forces, and the friction coefficient between the tool–chip interface were measured. It was shown that the friction coefficient at the tool–chip interface in dry cutting of hardened steel and cast iron with Al₂O₃/TiC/CaF₂ ceramic tool was reduced compared with that of Al₂O₃/TiC tool without CaF₂ solid lubricant. The mechanisms responsible were determined to be the formation of a self-lubricating film on the tool–chip interface, and the composition of this self-lubricating film was found to be mainly CaF₂ solid lubricant, which was released and smeared on the wear track of the tool rake face, and acted as lubricating additive between the tool–chip sliding couple during machining processes. The appearance of this self-lubricating film contributed to the decrease of the friction coefficient. Cutting speed was found to have a profound effect on this self-lubricating behavior.     

Development of Technology and Strategies for the Machining of Ceramic Components by Sinking and Milling EDM

This paper investigates the manufacturability of B₄C, SiC, Si₃N₄-TiN by milling EDM and the performance of it has been compared to conventional sinking EDM. It is shown that due to the good flushing conditions, milling EDM performs well, even for the machining of ceramic materials with a rather low electrical conductivity (B₄C, SiC). Because the used milling EDM technique removes material in a layer by layer fashion (2D-machining), a new strategy for the machining of complex 3D-shapes in ceramic material has been developed. It consists of a milling EDM pre-machining step, followed by one or more finishing sinking EDM steps. The developed strategy has been validated on an industrial example and compared to a pure sinking EDM strategy. Time reductions of more than 50% were obtained.     

Cutting performance and failure mechanisms of an Al2O3/WC/TiC micro- nano-composite ceramic tool

An Al₂O₃-based composite ceramic tool material reinforced with WC microparticles and TiC nanoparticles was fabricated by using hot-pressing technique. The cutting performance, failure modes and mechanisms of the Al₂O₃/WC/TiC ceramic tool were investigated via continuous and intermittent turning of hardened AISI 1045 steel in comparison with those of an Al₂O₃/(W, Ti)C ceramic tool SG-4 and a cemented carbide tool YS8. Worn and fractured surfaces of the cutting tools were characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results of continuous turning revealed that tool lifetime of the Al₂O₃/WC/TiC ceramic tool was higher than that of the SG-4 and YS8 tools at all the tested cutting speeds. As for the intermittent turning, tool life of the Al₂O₃/WC/TiC ceramic tool was equivalent to that of YS8, but shorter than that of the SG-4 at lower cutting speed (110 m/min). However, tool life of the Al₂O₃/WC/TiC ceramic tool increased when the cutting speed increased to 170 m/min, becoming much longer than that of the SG-4 and YS8 tools. The longer tool life of the Al₂O₃/WC/TiC composite ceramic tool was attributed to its synergistic strengthening/toughening mechanisms induced by the WC microparticles and TiC nanoparticles.     

Documentation of tool wear progress in the machining of nodular ductile iron with silicon nitride-based ceramic tools

Nowadays, the HPM of cast irons is based on silicon nitride ceramic and CBN cutting tools. This paper characterizes and correlates several outputs of the cutting process of nodular cast iron using uncoated and Al₂O₃/TiN coated Si₃N₄ ceramic tools resulting from wear progress and destruction of tool faces. Investigations include tool wear curves, tribological behaviour of the tool–chip interface and tool wear mechanisms occurring on contact surfaces. The image-based characterization of worn surfaces employs such techniques as SEM, BSE and EDX analysis. The occurrence of various wear mechanisms, such as abrasive, adhesive and chemical wear was revealed.     

Oxidation post-treatment of hard AlTiN coating for machining of hardened steels

In this study, cemented carbide ball nose end mills with nano-crystalline Al_0.67Ti_0.33N hard PVD coatings deposited by cathodic arc evaporation were annealed at 700 °C during 2 h in a controlled atmosphere environment (argon + oxygen mixture) and in vacuum. The changes of structure and properties of the treated coating surfaces have been analyzed using both cross-sectional scanning electron microscopy (SEM) and x-ray absorption spectroscopy (XAS) of the N-K and O-K edges. Cutting tools have been run through ball nose end milling of hardened H13 steel (HRC 50) where temperature or stress dominating phenomena control tool life. The data obtained indicate that an AlTiN coated cutting tool can be modified upon annealing at low temperature conditions and should be considered as a composite surface engineered material. It is shown that increased tool life could be achieved if annealing of AlTiN is performed in an oxygen-containing atmosphere. A variety of different characteristics should be optimized to achieve better wear resistance of the cutting tools with annealed Al_0.67Ti_0.33N coating under high temperature and stress cutting conditions.     

Cutting performance and wear mechanism of nanoscale and microscale textured Al2O3/TiC ceramic tools in dry cutting of hardened steel

Nanoscale and microscale textures with different geometrical characteristics were fabricated on the surface of the Al₂O₃/TiC ceramic tool, and molybdenum disulfide (MoS₂) solid lubricants were burnished into the textures. The effect of the textures on the cutting performance was investigated using the textured self-lubricated tools and conventional tools in dry cutting tests. The tool wear, cutting force, cutting temperature, friction coefficient, surface roughness and chip topography were measured. Results show that the cutting force, cutting temperature, friction coefficient and tool wear of nanoscale and microscale textured self-lubricated tools are significantly reduced compared with the conventional tool, and the developed tool with wavy microscale textures on the rake face is the most effective in improving the cutting performance. The textured self-lubricated tools increase the surface roughness of machined workpiece, while they can reduce the vibration for a stable cutting and produce more uniform surface quality. The chip topography is changed by the textured self-lubricated tools. As a result, the nanoscale and microscale textured self-lubricated tools effectively improve the cutting performance of conventional Al₂O₃/TiC ceramic tool, and they are applicable to a stable dry cutting of the hardened steel.     

Model of quality management of hard coatings on ceramic cutting tools

For the development and introduction of new coated cutting tools (i.e. new combinations of cutting materials and hard coatings), it is necessary to carry out a number of studies with the purpose of optimizing the coatings composition and processing procedures, and also to test new tools under working conditions. The aim of this paper is to establish a common model for environmentally oriented quality management in the use and development of coated ceramic cutting tools with new coating systems. The paper also presents an investigation of the results of tribological and cutting properties of the coatings deposited with the PVD and CVD techniques on cutting inserts made from (Al₂O₃ + TiC) tool ceramics. Tests were carried out on ceramic inserts, uncoated and PVD or CVD-coated, with gradient, mono-, multi- (nano) layers and multicomponent hard wear resistant coatings composed of TiN, Ti(C, N), (Ti, Al)N, (Ti, AlSi)N and Al₂O₃ layers.     

Investigating the correlation between nano-impact fracture resistance and hardness/modulus ratio from nanoindentation at 25-500 °C and the fracture resistance and lifetime of cutting tools with Ti1−xAlxN (x = 0.5 and 0.67) PVD coatings in milling operations

A novel laboratory technique, nano-impact testing, has been used to test Ti_1−xAl_xN (x = 0.5 and 0.67) PVD coated WC-Co inserts at 25-500 °C. Cutting tool life was studied under conditions of face milling of the structural AISI 1040 steel; the end milling of hardened 4340 steel (HRC 40) and TiAl6V4 alloy. A correlation was found between the results of the rapid nano-impact test and milling tests. When x = 0.67 improved resistance to fracture was found during milling operations and also in the nano-impact test of this coating compared to when x = 0.50. The coating protects the cutting tool surface against the chipping that is typical for cutting operations with intensive adhesive interaction with workpiece materials such as machining of Ti-based alloys. The results give encouragement that the elevated temperature nano-impact test can be used to predict the wear and fracture resistance of hard coatings during milling operations. At 500 °C nanoindentation shows there is a lower H/E_r ratio for the PVD coatings compared to room temperature, consistent with reduced fracture observed at this temperature in the nano-impact test.     

Surface integrity generated by oblique machining of steel and iron parts

In this study the surface integrity produced by oblique turning of a range of iron-based materials including C45 carbon, 41Cr4 low-alloy hardened, X6CrNiTi18-10 stainless steels and EN-GJS-500-7 spheroidal iron was quantified by means of 2D and 3D surface roughness parameters, strain-hardening effects and associated residual stresses. Surfaces were produced by a special straight-edged cutting tool with large inclination angle of 55° equipped with carbide and mixed Al₂O₃–TiC ceramic cutting tool inserts. It was documented that oblique machining performed with relatively higher feed rate allows obtaining lower surface roughness and, in general, better bearing characteristics. Moreover, compressive stresses with the maximum value located close to the machined surface and parabolic profile can be induced into the surface layer. The magnitude of stresses depends on the strain-hardening rate of the surface layer.     

Development of a Elliptical Vibration Milling Machine

A unique elliptical vibration milling machine is developed by utilizing a double-spindle mechanism. The developed machine generates circular vibratory motion of the cutting tool mechanically by rotating an eccentric sleeve with a built-in motor. The radius and the maximum frequency of the circular vibration are set to 0.5 mm and 167 Hz respectively. The developed machine is applied to elliptical vibration planing by clamping the tool spindle, and also to elliptical vibration end milling by rotating the inner tool spindle as well at the same time. The machining tests of hardened steel with CBN and coated carbide tools are carried out, and it was proved that the elliptical vibration cutting shows better results as compared with conventional cutting without elliptical vibration motion. A mirror surface on hardened steel with a roughness of about 0.11 μm Ra was obtained by elliptical vibration planing by employing a single crystal diamond tool.     

Performances of micro-textured WC-10Ni3Al cemented carbides cutting tool in turning of Ti6Al4V

Cutting performances of micro-textured WC-10Ni₃Al cutting tools compared with micro-textured WC-8Co cutting tools in turning of Ti6Al4V was investigated in this study. Cutting forces, cutting temperature, and tool life based on the criterion of a 300 μm flank wear were measured. The wear tracks of the rake face and flank face for micro-textured WC-10Ni₃Al cutting tools were analyzed. It is found that WC-10Ni₃Al cutting tools had smaller heat damages during LST compared with WC-8Co cutting tools, which was benefit for avoiding premature tool failure during Ti6Al4V machining process. Micro-textures on the rake face could effectively reduce cutting forces, cutting temperature, adhesion on the rake face, and hence increase tool life, especially at higher cutting speed.     

新型陶瓷刀具的发展与应用

回顾了陶瓷刀具的发展简况及其意义,重点介绍了Si3N4基和TiCN基复合陶瓷刀具的研制、性能和应用.复合Si3N4陶瓷刀具有较高的耐磨性和抗冲击性,特别适合于各类铸铁件的粗精加工,也能进行铣削、刨削等冲击力很大的加工,其切削效率可提高3～10倍;复合TiCN金属陶瓷刀具具有很高的硬度和耐磨性,特别适合于各类高硬高强钢(如淬硬钢等)的加工,可对高硬材料实现"以车代磨"干切削,免除退火工艺和冷却液,大幅度提高生产效率.新型复合陶瓷刀具已经在我国冶金、水泵、矿山机械、轴承、滚珠丝杠、汽车、军工等十几个行业得到应用.     

Al2O3/WB2 composite ceramic tool material reinforced with graphene oxide self-assembly coated silicon nitride

Graphene oxide coated silicon nitride coated powder was prepared by electrostatic self-assembly technique. Microstructure analysis shows that GO is uniformly coated on the surface of silicon nitride and evenly dispersed in the matrix material. The microstructure analysis and performance tests were carried out on ceramic tools with different volume contents of Si₃N₄@GO coated powder. The results show that when the content of Si₃N₄@GO is 7. 94 vol%, the comprehensive mechanical properties of Al₂O₃/WB₂/(Si₃N₄@GO) ceramic tool materials are the best, with the Vickers hardness, flexural strength and fracture toughness 18.7GPa, 740 MPa and 8 .2MPa·m^1/2, respectively. Compared with the Al₂O₃/WB₂ ceramic tool material, the ceramic tool with Si₃N₄@GO coated powder increased the flexural strength and fracture toughness by 30.3% and 36.7%.