FABRICATION OF DLC COATED COBALT-CEMENTED TUNGSTEN CARBIDE MICRO-DRILLS AND THEIR CUTTING PERFORMANCE

In machining the particle reinforced aluminum based composite material with high Si content using the cobalt-cemented tungsten carbide micro cutting tools, diamond like carbon （DLC） films are deposited on cobalt-cemented tungsten carbide micro-drills with two-step pretreatment method. Characteristics of DLC coated tools are investigated in bias-enhanced HFCVD system with the optimized hot filament arrangement. The optimization deposition technology is obtained and the wear mechanism of cutting tools is analyzed. The drilling performance of DLC coated tools is verified by the experiments of cutting particle reinforced aluminum based composite material （Si 15% in volume） compared with uncoated ones. Experimental results show that the two-step pretreatment method is appropriate for complex shaped cemented carbide substrates and ensures the good adhesive strength between the diamond film and the substrate. The cutting performance of DLC coated tool is enhanced 10 times when machining the Si particle reinforced aluminum based metal matrix composite compared with that of uncoated ones under the same cutting conditions.

Cutting performance of multilayer diamond coated silicon nitride inserts in machining aluminum-silicon alloy

Aluminum-silicon （Al-Si） alloy is very difficult to machine and diamond tools are considered by far the best choice for the machining of these materials. Experimental results in the machining of the Al-Si alloy with diamond coated inserts are presented. Considering the fact that high adhesive strength and fine surface morphology play an importance role in the applications of chemical vapor deposition （CVD） diamond films, multilayer technique combining the hot filament CVD （HFCVD） method is proposed, by which multilayer diamond-coating on silicon nitride inserts is obtained, microcrystalline diamond （MCD）/ nanocrystalline diamond （NCD） film. Also, the conventional monolayer NCD and MCD coated inserts are produced for comparison. The as-deposited diamond films are characterized by field emission scanning electron microscopy （FE-SEM） and Raman spectrum. All the CVD diamond coated inserts and uncoated insert endure the aluminum-silicon alloy turning to estimate their cutting performances. Among all the tested inserts, the MCD/NCD coated insert exhibits the perfect behavior as tool wear due to its very low flank wear and no diamond peeling.

Relationship Between Thermal Shock Behavior and Cutting Performance of a Functionally Gradient Ceramic Tool

Based on the deep understanding of the requirements of cutting conditions on ceramic tools, a design model for functionally gradient ceramic tool materials with symmetrical composition distribution was presented in this paper, according to which an Al 2O 3-TiC functionally gradient ceramic tool material FG-1 was synthesized by powder-laminating and uniaxially hot-pressing technique. The thermal shock resistance of the Al 2O 3-TiC functionally gradient ceramics FG-1 was evaluated by water quenching and subsequent three-point bending tests of flexural strength diminution. Comparisons were made with results from parallel experiments conducted using a homogeneous Al 2O 3-TiC ceramics. Functionally gradient ceramics exhibited higher retained strength under all thermal shock temperature differences compared to homogeneous ceramics, indicating the higher thermal shock resistance. The experimental results were supported by the calculation of transient thermal stress field. The cutting performance of the Al 2O 3-TiC functionally gradient ceramic tool FG-1 was also investigated in rough turning the cylindrical surface of exhaust valve of diesel engine in comparison with that of a common Al 2O 3-TiC ceramic tool LT55. The results indicated that the tool life of FG-1 increased by 50 percent over that of LT55. Tool life of LT55 was mainly controlled by thermal shock cracking which was accompanied by mechanical shock. While tool life of FG-1 was mainly controlled by mechanical fatigue crack extension rather than thermal shock cracking, revealing the less thermal shock susceptibility of functionally gradient ceramics than that of common ceramics.

Cutting Performance and Mechanism of RE Carbide Tools

The research of rare earth elements (RE), added into cemented carbide tools, is one of the recent developments of new types of tool materials in China. Systematic experiments about RE carbides YG8R. (K30), YT14R (P20) and, YW1R (M10) were made to study on the cutting performance in comparison with non-RE carbides YG8, YT14 and YW1. The cutting experiments were as follows: tool life, cutting force, tool-chip friction coefficient and interrupted machining. The action of RE on the carbide materials and the cutting mechanism of the RE carbide tools in the cutting process were verified with the aid of SEM and energy spectrum analysis. Experimental results show that the RE carbide tools have a good overall performance.

MULTI-SCALE AND MULTI-PHASE NANOCOMPOSITE CERAMIC TOOLS AND CUTTING PERFORMANCE

An advanced ceramic cutting tool material Al2O3/TiC/TiN （LTN） is developed by incorporation and dispersion of micro-scale TiC particle and nano-scale TiN particle in alumina matrix. With the optimal dispersing and fabricating technology, this multi-scale and multi-phase nanocomposite ceramic tool material can get both higher flexural strength and fracture toughness than that of A1203/TiC （LZ） ceramic tool material without nano-scale TiN particle, especially the fracture toughness can reach to 7.8 MPa . m^0.5. The nano-scale TiN can lead to the grain fining effect and promote the sintering process to get a higher density. The coexisting transgranular and intergranular fracture mode induced by micro-scale TiC and nano-scale TiN, and the homogeneous and densified microstructure can result in a remarkable strengthening and toughening effect. The cutting performance and wear mechanisms of the advanced multi-scale and multi-phase nanocomposite ceramic cutting tool are researched.

Research on the Cutting Performance of Cubic Boron Nitride Tools

There were only two kinds of superhard tool material at the past, i.e. diamond and cubic boron nitride (CBN). Manmade diamond and CBN are manufactured by the middle of 20th century. Various manufacturing methods and manmade superhard materials were developed later. They were widely used in different industry and science areas. Recently, a new kind of superhard tool material, C 3N 4 coating film, had been developed. American physical scientists, A. M. Liu and M. L. Cohen, designed a new kind of inorganic compound C 3N 4 with the theory of molecule engineering. According to calculation, it can reach or even exceed the hardness of diamond, so material scientists and technique circles draw their attention to it. A high speed steel twist drill coated with C 3N 4 film is applied to the drilling hole process on steel workpiece in cutting tests, the tool life is increased greatly. When the C 3N 4 film is coated on the cemented carbide inserts, the cutting performance is improved, but is not good enough. The data of mechanical performance and cutting tests about this kind of new tool material is given in this paper, it shows that C 3N 4 has a promising future. The anti-wear ability of cutting tool increases sharply after C 3N 4 being coated on HSS tool. Coated HSS drill also has some benefit after being reground. The tool life prolongs after C 3N 4 being coated on cemented carbide inserts, but is not so long as that of C 3N 4 coated HSS tool. When machining PRCM with C 3N 4 thin-film coated cemented carbide tool, the cutting performance is poor and it is much better when machining PRCM with PCBN, PCD compound plates and CVD thick-film coated cutting tool. Some relative aspects need to be deeply discussed and researched, e.g. the existing coating techniques is not good enough and should be improved in the future, the film thickness should be optimized and try to find out the most effective value, the binding force and mutual effect between coated film and substrate need to be studied furtherly, etc.

Research on the cutting performance and the wear mechanism of the cermet cutter in high speed turn-milling

When machining D60 steel by high speed turn-milling under the different cooling and lubricating conditions, the cutting performance and the wear mechanism of the cermet cutter are researched. With water soluble cooling fluid, the wear performance of the cermet cutter is bad, and does not adapt to the requirements of machining. However, when machining D60 by high speed turn-milling is under dry conditions, the wearing performance of the cermet cutter is very good and the cutting time lasts almost 3 hours. The wear mechanism of the cermet cutter under the water soluble cooling fluid is different from the dry condition. With the water soluble cooling fluid, a great deal of little chap units are formed since high frequency alternates heat stress. The crash and desquamate of these chap units is the main cause of the cutter wearing. Under dry cutting conditions, it is the main cause of cermet cutter wear in the felting phase intenerating causing rigid phase grains to fall.

COATED CARBIDE TOOL'S CUTTING PERFORMANCE AND ITS DATA BASE

The development and application of coated cemented carbide made in China are pres-ented. Three aspects of the coated carbide tool's performance: cutting forces, surface finish and toollife are studied. Furthermore speed-correcting coefficients of the tool are given. On the basis of thework, a data base for coated carbide tools has been built on a microcomputer. It consists of fivemodules. essential data base, tools' comparison and inquiry, recommending cutting regimes, exper.imental curve base and an expert system for tool selection.

Cutting performance of saw blades with microtextured rougher and finisher sawteeth

The problems of severe sawtooth wear,harsh sawing noise,and low surface quality during the processing of circular saw blades need to be solved.To improve the cutting performance of TiC-based cermet saw blades,microtextures parallel to the cutting edge were fabricated on rough and fine sawteeth by laser machining.The cutting tests were performed on a sawing platform under lubricated conditions.Models of the sawing arc length and working sawtooth cutting force variations were developed for sawing steel pipes,and the accuracy of the sawing force model was verified experimentally.The results indicate that the variations in the sawing force are proportional to the sawing arc length.The circular saw blades with microtextures that did not penetrate the sawtooth rake face exhibited the lowest cutting force,sawing noise,and highest machined surface quality.Furthermore,the worn-out distance of the rougher and finisher sawteeth was reduced by approximately 7.4%and 44.1%,respectively,compared with conventional circular saw blades.The main failure modes of sawteeth were tip wear,rake face adhesion,and oxidative wear.In addition,the mechanism by which the textures improve the cutting and wear properties of TiC-based circular saw blades was discussed.This study provided a significant concept for enhancing the cutting performance of circular saw blades and improving the machined surface quality.

Cutting performance of surgical electrodes by constructing bionic microstriped structures

Surgical electrodes rely on thermal effect of high-frequency current and are a widely used medical tool for cutting and coagulating biological tissue.However,tissue adhesion on the electrode surface and thermal injury to adjacent tissue are serious problems in surgery that can affect cutting performance.A bionic microstriped structure mimicking a banana leaf was constructed on the electrode via nanosecond laser surface texturing,followed by silanization treatment,to enhance lyophobicity.The effect of initial,simple grid-textured,and bionic electrodes with different wettabilities on tissue adhesion and thermal injury were investigated using horizontal and vertical cutting modes.Results showed that the bionic electrode with high lyophobicity can effectively reduce tissue adhesion mass and thermal injury depth/area compared with the initial electrode.The formation mechanism of adhered tissue was discussed in terms of morphological features,and the potential mechanism for antiadhesion and heat dissipation of the bionic electrode was revealed.Furthermore,we evaluated the influence of groove depth on tissue adhesion and thermal injury and then verified the antiadhesion stability of the bionic electrode.This study demonstrates a promising approach for improving the cutting performance of surgical electrodes.

Analysis and experiment on cutting performances of high-stubble maize stalks

In the cold areas of Northeast China,maize high-stubble cutting is a novel stalk conservation tillage method,in which the maize stalks are under a unilaterally-fixed no-support cutting status.Thus,reducing the cutting resistance and power consumption of maize stalks under this status is very significant for the development of high-efficiency high-stubble cutting devices.Based on a self-designed testing system that highly restored the maize high-stubble cutting conditions and by means of experimental design and mathematic statistics,the effects of working parameters(blade angle,blade shape,cutting speed and cutting angle)on the maximum cutting resistance and power consumption were studied.By analyzing stress conditions during the stalk cutting process,six mathematic models were built to express the relationships between individual factors and the maximum cutting resistance or cutting power consumption.Through model optimization,the parameter combination for optimal cutting performance of maize stalks under unilaterally-fixed no-support cutting status was obtained:blade angle is 18°,blade shape is isosceles triangle,cutting speed is 9.5 m/s,and cutting angle is 75°.Field validation experiments under this parameter combination showed that the maximum cutting resistance was(55.23±3.50)N(declined by 11.04%),and power consumption was(11.41±1.04)J(declined by 16.65%).The research findings can be a reference for the design and development of maize high-stubble cutting devices.

Comparative Study on Cutting Performance of Chaser and Triangle-Shaped Inserts in Inconel 718 Turning

The effect of cutting teeth number on the cutting force,surface roughness,tool wear rate and the cutting chip shape charac teristics is systematically evaluated.A novel five tee th chaser insert(C tool)which could turn the workpiece at five cutting points simultaneously is involved in comparison with the standard triangle shaped insert(T tool),in the purpose of solving the problems of cutting heat concentration and rapid tool failures in the Inconel 718 machining process.Comparative orthogonal cut ting experimen ts of the C tool and T tool show that the cut ting depth is the significant influencing factor of the cutting forces.Meanwhile,the five cut ting teeth of the C tool show the effec tiveness of dispersing the cut ting forces as well as improving the cut ting efficiency.The feed rate is the significant factor to affect the root-mean-square surface roughness(Ra)of workpiece machined by the T tool,while the significant influencing variable of Ra for the C tool is the cutting depth due to its unique tool geome try(0°rake angle)in the axial feeding process.Moreover,due to the dispersing effect,the cut ting edges on the C tool exhibits lower tool wear rate than that of the T tool under the same axial feed.The chips are regular continuous long chips for the T tool,while the irregular continuous chips with the characteristic of saw-toothed profile are obtained due to its unique 0°rake angle.The C tool shows the valid potential for effectively dispersing the cut ting heat and slowing down the tool wear rate in the Inconel 718 machining process.

Influence of Coolant on Cutting Tool Performance

This paper reports a Study carried out to substantiate or refute the belief that when coolant is applied, the cutting performance is actually improved. Experiments on cutting forces and chip geometry were conducted in which AISI 1050 Steel was machined by turning using P30 uncoated tungsten carbide tools. Experiments were performed on a CNC Okuma LH35-N lathe undermachining conditions commonly used in workshops in Singapore and many other parts of the world.

INVESTIGATION ON NEW TYPE OF DOUBLY BLENDING ABRASIVE WATER JET NOZZLE SYSTEM WITH HIGHER PERFORMANCE

Based on the two existing abrasive water-jet（AWJ） systems, the dia-jet （or pre-jet） and the post-jet, a new type of abrasive water-jet system is put forward, which combines the dia-jet＇s advantage, low operating system pressure, slender stream jet, and more concentrative abrasive in the blended stream, with merits of post-jet, the less sophisticate apparatus, successive supply of abrasives. The theoretic analysis is brought out in detail, and the nozzle system structure is concisely illustrated. Its relevant experiment results are demonstrated, proving that this new system is effective in various aspects, enlarging penetrating capability without raising system pressure, saving machining power supply, lessening energy loss, etc.

Progress on Bionic Textured Cutting Tools:A Review and Prospects

Cutting tools are known as the“productivity”of the manufacturing industry,which affects the production efficiency and quality of the workpiece,and has become the focus of research and attention in academia and industry.However,traditional cutting tools often suffer from adhesion or wear during the cutting process,which considerably reduces the cutting efficiency and service life of the tools,and makes it difficult to meet current production requirements.To solve the above problems,scholars have introduced bionics into the tool’s design,applying the microscopic structure of the biological surface to the tool surface to alleviate the tool’s failure.This paper mainly summarizes the research progress of bionic textured cutting tools.Firstly,categorize whether the bionic texture design is inspired by a single organism or multiple organisms.Secondly,it is discussed that the non-smooth surface of the biological surface has five characteristics:hydrophilic lubricity,wear resistance,drag reduction and hydrophobicity,anti-adhesion,and arrangement,and the non-smooth structure of these different characteristics are applied to the surface of the tool is designed with bionic texture.Furtherly,the cutting performance of bionic textured cutting tools is discussed.The anti-friction and wear-resisting mechanism of bionic textured cutting tools is analyzed.Finally,some pending problems and perspectives have been proposed to provide new inspirations for the design of bionic textured cutting tools.

Rock excavation using surface miners: An overview of some design and operational aspects

Surface miner, a continuous mining machine, is being manufactured in India and abroad owing to enhanced demand of production in various mining industries like coal, limestone, gypsum, bauxite etc. Different types of surface miners are manufactured today based on cutting drum placement and design specifications. Selective mining without drilling and blasting, high production and small size products are some of the prominent attractive features obtained with these moving marvels. This machine can be used with good efficiency in soft to medium hard rock (100-120 MPa). This paper synthesizes the different applications, equipment models, features offered, operating methods, cutting performance assessment models as well as typical production performance of surface miner in coal and limestone mines of India. Engine hour metre reading, diesel and pick consumptions are linearly influenced by production. The emphasis for future research is also brought out.

Development of Diamond-Coated Drills

Compared with the sintered polycrystalline diamond, the deposited thin film diamond has the great advantage on the fabrication of cutting tools with complex geometries such as drills. Because of their low costs for fabrication equipment and high performance on high speed machining non-ferrous metals and alloys, metal-compound materials, and hard brittle non-metals, diamond-coated drills find great potentialities in the commercial application. However, the poor adhesion of the diamond film on the substrate becomes the main technical barriers for the successful development and commercialization of diamond-coated tools. In this paper, diamond thin films were deposited on WC-Co based drills by the electron aided hot filament chemical vapor deposition (EACVD). A new multiple chemical pre-treatment technology including microwave oxidation, reaction in alkaline solution and cleaning by ultrasonic treatment in acid solution was developed and affects on the diamond adhesion strength, nucleation and surface morphology were investigated. At the same time, a special setup to fabricate diamond-coated drills was also developed and then the novel CVD process based on the varied parameters controlling model was presented, therefore the uniform quality and homogenized thickness of diamond coating could be available. From practical utilization viewpoint, the cutting performance of the diamond-coated drill was studied by drilling SiC particle reinforced aluminum matrix composite. The satisfied wear resistance and decrease of torque and thrust led to the long life of this kind of drill. This paper exhibited the meaningful work for the development of cutting tools with complex geometries and further extended the application of diamond material.

Adherent coating on gradient cemented carbide with ultrafine Ti(C_(0.5),N_(0.5))

Gradient cemented carbide is usually employed as the snbstrate for coated carbide insert. In this work, gradient cemented carbide with ultrafine Ti（C0.5,N0.5） was prepared and its microstructure and properties were researched. Moreover, this novel substrate was coated to investigate cutting performance. It is found that the average WC grain size in the gradient zone is larger than that in the bulk. Owing to ultrafine Ti（C0.5,N0.5） introduction, gradient cemented carbide prepared by vacuum sintering exhibits full densification. By contrast, the gradient cemented carbide with ultrafine Ti（C0.5,N0.5） shows higher transverse rupture strength （TRS） and hardness than the homogenous one. Gradient cemented carbide suffers small TRS reduction after coating, and the bonding between coatings and gradient substrate is tidy and compact. The coated gradient cemented carbide shows much better endurance and impact resistance than the coated homogenous one. It confirms the superiority of gradient cemented carbide when used as the substrate for coating inserts.

Microstructure and properties of YG8 cemented carbide with different pulse currents

In order to study the effect of pulse current treatment on the mechanical properties,microstructure and cutting performance of YG8 cemented carbide,experiments were carried out by using self-made pulse current treatment device to treat cemented carbide samples with different current densities(J=5,10 and 15 A·mm^-2)After the treatment of pulse current,when the current density increased from 5 to 15 A·mm-2,the hardness of the sample was improved to HV 1605,HV 1629 and HV 1653from HV 1574;the transverse rupture strengths of the sample were 2136,2289 and 2364 MPa,which were all higher than that of the untreated sample(2062 MPa)increasing by 3.6%,11.0%and 14.6%,respectively;the corresponding cutting performance was increased by10.1%,13.9%and 19.4%,compared to that of the untreated tool.The tool’s life was also improved.After the treatmen of pulse current,pulse current provided the driving force for dislocation motion,making it more likely for the dislocation to multiply and slip,the dislocation density was increased,and the mechanical properties were significantly improved.

Using air curtains to reduce short-range infection risk in consulting ward: A numerical investigation

Air curtains is promising in reducing the short-range infection risk in hospitals.To quantitatively evaluate its performance,this paper explores air curtains equipped on normal consulting desk to avoid doctor’s direct exposure to the patient exhaled pollutants.A numerical investigation is conducted to evaluate the effects of supply air velocity and angle on cutting off performance.Simulation results show that the average mass fraction of exhaled pollutants decreases significantly(70%–90%)in the consulting ward,indicating satisfying performance of air curtains.Increasing supply air velocity is demonstrated to be conducive in forming full air curtains,whereas an excessively high supply air velocity may be of adverse effects by entraining exhaled flow.Besides,the supply air angle is also critical due to its coupling with supply air velocity.It is found that larger angle(0°–40°)is better where velocity is less than 3 m/s,otherwise a small angle(20°)is preferable where velocity is larger than 3 m/s.Exhaled flow could be well suppressed at the supply air angle 20°but moves over air curtains at 40°.This study can provide effective and intuitive guidance in applying air curtains in consulting wards.