High Speed Cutting Inconel 718 with Coated Carbide and Ceramic Inserts

High speed machining (HSM) technology is one of important aspects of advanced manufacturing technology. Nickel-based superalloys have been widely used in the aircraft and nuclear industry due to their exceptional thermal resistance and the ability to retain mechanical properties at elevated temperatures of service environment over 700 ℃. However, they are classified as difficult-to-cut materials due to their high shear strength, work hardening tendency, highly abrasive carbide particles in the microstructure, strong tendency to weld and form built-up edge and low thermal conductivity. They have a tendency to maintain their strength at high temperature that is generated during machining. The Inconel 718 workpiece material used in the experiment was in the hot forged and annealed condition. The commercially available inserts (all inserts were made by Kennametal Inc.) were selected for the tests, a PVD TiAlN coated carbide, a CVD/PVD TiN/TiCN/TiN coated carbide and a CVD Al 2O 3/TiC/TiCN coated carbide were used at the cutting speed range about 50～100 m/min. Three kinds Sialon grade inserts with various geometry and cutting angles were used at the cutting speed range from 100 m/min to 300 m/min. For evaluating the inserts machinability when high speed cutting Inconel 718, Taylor Formula within certain cutting speeds, an high speed cutting experiment of tool life was carried out to establish the models of tool life by means of rapid facing turning test. The conclusions drawn from the turning of Inconel 718 with silicon nitride based ceramic; PVD and CVD coated carbide inserts are as follows: Studies on tool wear in high speed machining. The thorough investigations and studies were made on the tool wear form, wear process and wear mechanism in high speed cutting of difficult-to-machine materials with ceramic tools and with coated carbides. The major wear mechanisms of nickel-based alloys are interactions of abrasive wear, adhesion wear, micro-breakout and chipping. Optimization analysis on the application of high speed machining. Based on the experimental results, the optimal cutting parameters were determined for machining of Inconel 718 at high speed. The recommendation of tool inserts for high speed cutting inconel 718 were ceramic inserts of KY2000 with negative rake angle and KY2100 with round type, the PVD coated carbide insert KC7310 was recommended for its lower price.

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.

Dry Milling of the Ultra-High-Strength Steel 30CrMnSiNi2A with Coated Carbide Inserts

The ultra-high-strength steel （UHSS） plays an important role in the mechanical industry because of their special performances. The machinability of 30CrMnSiNi2A steel was studied in dry milling with two different coated tools in the present work. This paper introduced that 30CrMnSiNi2A steel was a kind of diffficult-to-machine materials. The results showed that the cutting force components of feed direction and cutting width direction, i.e. Fx and Fy, increased slightly with increasing the cutting speed and feed rate. The values of axial force component Fx were much larger than Fx and Fy, and increased obviously with increasing the milling speed. The workpiece surface had the minimum roughness at the cutting speed of 150 m/min. The physical vapor deposition （PVD） coated （（Ti, A1）N-TiN） insert was more suitable for machining 30CrMnSiNi2A steel than the chemical vapor deposition （CVD） coated （Ti（C, N）-Al2O3） insert. Moreover, the main failure modes of PVD-coated insert were micro-chipping and coating spalling. The wear modes of CVD-coated insert were ploughing, coating spalling, and cratering. The serious adhesive wear and the abrasion with some adhesion were the main wear mechanism of PVD- and CVD-coated inserts, respectively.

Comparative investigation towards machinability improvement in hard turning using coated and uncoated carbide inserts： part Iexperimental investigation

The investigation of low cost uncoated andcoated carbide insert in the hard turning of hardened AISID2 steel （≥55 HRC） will definitely open up a new arena asan economical alternative suitable to industrial machiningsectors. Thus, this paper reports the comparative machin-ability assessment for the hard turning of AISI D2 steel（（55 ± 1） HRC） by coated and uncoated carbide insert in adry environment. Micro hardness and abrasion tests werecarried out to assess resistance capability against wear. Theabove test results confirmed the greater wear resistanceability of AIaO3 coated carbide insert over uncoated car-bide. Based on the extensive investigation of comparativemachinability, the coated carbide insert （TiN-TiCN-A12O3）outperformed the uncoated carbide insert with regard tosurface roughness, flank wear, chip-tool interface temper-ature, and chip morphology. Abrasion and diffusion wereobserved as the principal tool wear mechanisms in theinvestigated range. The uncoated carbide failed completelydue to the severe chipping and quick dulling of the cuttingedge, which led to its unsuitability for machining hardenedsteel.

Low Temperature Preparation of Carbide Coated Carbon for Refractory Castable Applications

Titanium carbide （ TiC ） coated graphite flakes （GF） and carbon black （CB） powders were prepared at relatively low temperatures （ 750 - 950 ℃ ） using a no- vel molten salt synthesis technique. The in-situ formed TiC coatings were homogeneous and crack-free and their thicknesses could be readily controlled/tailored by simply adjusting the Ti/C ratio. Compared to their uncoated counterparts, as prepared TiC coated GF and CB showed much improved water-wettability/dispersivity and rheological properties, and thus could be potentially used to prepare carbon-containing refractory castables.

Vanadium Carbide Coating Growth on Die Steel Substrate in Borax Salt Bath

Vanadium pentoxide, borax, boron carbide and sodium fluoride were used to grow vanadium carbide coating on die steel（Cr12, Cr12MoV） surface at 950 ℃ by TD process, which extended the life period of Cr12 and Cr12MoV as punching die. Kinetics of vanadium carbide coating growth was brought forward and verified by comparison of the mathematical model with the experimental results. The thickness of coating was illustrated by SEM. The chemical constituent of coating and remnants were tested by XRD. To increase the thickness, rare earths （FeSiRe23） were added to the borax salt bath. The electronic probe microanalysis （EPMA） revealed that the addition of rare earths could decrease carbon concentration in the coating and increase the depth of vanadium carbide coating.

Influence of particle size and surfactants on uniformity and quantity of silicon carbide particles in electrodeposited nickel-silicon carbide coatings

The electrodeposition of nickel-silicon carbide coatings on a copper electrode was done by mixing SiC particles in the nickel electrodeposition solution.The influence of surfactants and silicon carbide particle size on uniformity and quantity of silicon carbide particles in nickel-silicon carbide composite coatings was investigated.It was found that particle size affects the nucleation overpotential,with 40 nm silicon carbide nanoparticles more effective in promoting nickel nucleation than 500 nm particles due to an increase in active nucleation sites.In terms of surfactants,anionic surfactant sodium dodecyl sulfate(SDS)produced better dispersion of 40 nm silicon carbide particles than cationic surfactant cetyltrimethyl ammonium bromide(CTAB),but little difference was found between the two when 500 nm silicon carbide particles were used.Thus,although the suspension of silicon carbide particles can be improved and their co-deposition can be promoted with a cationic surfactant CTAB,it is less effective than an anionic surfactant SDS in terms of surface finish.

Growth Characteristics and Kinetics of Niobium Carbide Coating Obtained on AISI 52100 by Thermal-reactive Diffusion Technique

Niobium carbide coating was produced by thermal-reactive diffusion technique on AISI 52100 steel in salt bath at 1 123 K, 1 173 K, and 1 223 K for 1, 2, 4, and 6 hours. The salt consisted of borax, sodium fl uoride, boron carbide, and niobium pentoxide. The presence of NbC phase on the steel surface was confi rmed by X-ray diffraction analysis. Microscopic observation showed that niobium carbide coating formed on the substrate was smooth and compact. There was a distinct and fl at interface between the coating and substrate. The micro-hardness of niobium carbide coating was 2892±145HV. The thickness of coating ranged from 1.6 μm to 14μm. The forming kinetics of niobium carbide coating was revealed. Moreover, a contour diagram derived from experimental data was graphed for correct selection of process parameters. Some mathematical equations were built for predicting the coating thickness with predetermined processing temperature and time. The results showed that these mathematical equations are very practical as well as the kinetics equation.

Microstructure and Properties of Plasma Spraying Boron Carbide Coating

Microstructure of plasma spray boron carbide coating was studied by SEM and TEM. Its physical, mechanical and electrical properties were measured. The results showed that high microhardness, modulus and low porosity of B4C coating were manufactured by plasma spray. It was lamellar packing and dense. The B4C coating examined here contained two principal structures and two impurity phase besides major phase. The relatively small value of Young's modulus, comparing with that of the bulk materials, is explained by porosity . The Fe impurity phase could account for the relatively high electrical conductivity of boron carbide coating by comparing with the general boron carbide materials.

High-Speed Machining of Malleable Cast Iron by Various Cutting Tools Coated by Physical Vapor Deposition

The coating material of a tool directly affects the efficiency and cost of machining malleable cast iron.However,the machining adaptability of various coating materials to malleable cast iron has been insufficiently researched.In this paper,turning tests were conducted on cemented carbide tools with different coatings(a thick TiN/TiAlN coating,a thin TiN/TiAlN coating,and a nanocomposite(nc)TiAlSiN coating).All coatings were applied by physical vapor deposition.In a comparative study of chip morphology,cutting force,cutting temperature,specific cutting energy,tool wear,and surface roughness,this study analyzed the cutting characteristics of the tools coated with various materials,and established the relationship between the cutting parameters and machining objectives.The results showed that in malleable cast iron machining,the coating material significantly affects the cutting performance of the tool.Among the three tools,the nc-TiAlSiN-coated carbide tool achieved the minimum cutting force,the lowest cutting temperature,least tool wear,longest tool life,and best surface quality.Moreover,in comparisons between cemented-carbide and compacted-graphite cast iron machined under the same conditions,the wear mechanism of the coated tools was found to depend on the cast iron being machined.Therefore,the performance requirements of a tool depend on multiple factors,and selecting an appropriately coated tool for a particular cast iron material is essential.

Preparation and Property of Chromium Carbide Thermal Diffusion Coating on Cold Working Die Materials

Thermal diffusion （TD） salt bath chromizing of cold working dies was studied. Firstly, it obtained an ideal salt bath formula by comparing with a variety of formulas, and then obtained the influence rule of coating thickness based on studying of some process parameters. The microstructure morphologies and phase structures of the TD chromizing coating were investigated by X-ray diffraction （XRD）, energy-dispersive spectrometry （EDS） and other modern analysis methods. Meanwhile, it carried out a system of testing and analysis of coating, such as hardness, wear resistance, etc.

EFFECT OF CARBON ACTIVITY IN MATRIX ON DYNAMICS OF CARBIDE DIFFUSION COATING

The increase of thickness of carbide layer during carbide diffusion coating is proportional to the root of carbon activity in various steels. Thus it was demonstrated that the controlling fac- tor of the dynamics of carbide layer growth is carbon activity in steel matrix, but not carbon concentration.

Comparing the Effectiveness of Coatings on Carbide andCermet Cutting Tool Inserts

A series of metal cutting experiments was performed on a CNC lathe to evaluate the performance of various coatings on different tool substrates. The workpiece material was plain medium carbon steel and the cutting tool materials were carbide and cermet inserts coated with various single as well as multilayer coatings. Machining was done under various cutting conditions of speed and feed-rate, and for various durations of Cutting. The output parameters studied were the cutting forces (axial, radial and tangential), the surface roughness of the workpiece, as well as the tool wear (crater and flank wear). From these results, the performances of the various cutting inserts are evaluated and compared. Results show that cutting forces are significantly lower when using coated cermets than when using coated carbides although different coatings on the same substrate also result in different cutting forces. However, there is less difference in the surface roughness of the finished workpiece for the various coatings and substrates.

Microstructure, mechanical properties, and milling performance of arc-PVD AlTiN–Cu and AlTiN/AlTiN–Cu coatings

AlTiN,AlTiN–Cu and AlTiN/AlTiN–Cu coatings were prepared on WC–6%Co substrates by cathode arc evaporation deposition technology.Two kinds of nitrogen pressures were used to deposit both AlTiN–Cu and AlTiN/AlTiN–Cu coatings.Surface and cross-sectional morphologies of films were observed by scanning electron microscopy(SEM).Crystal structure of films was analyzed by X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).Hardness and adhesion of films were measured by nano-indentation and nano-scratch tester.Cutting tests were performed under milling conditions during wet machining of TC4 alloy.The results show that with addition of Cu,more droplets occur on AlTiN coating surface,but the grain size of it is refined,and the hardness decreases but the toughness is improved.Under higher N2 pressure,the defects on the surface of AlTiN–Cu and AlTiN/AlTiN–Cu coatings diminish,and the hardness of them is enhanced,while the adhesion is reduced.Compared to AlTiN coated cemented carbide tool,the lifetimes of AlTiN–Cu and AlTiN/AlTiN–Cu coated tools under the same N2 pressure are improved by 11%and 24%,respectively.

Phase Formation and Process Analysis of SiC-Al_2O_3-Al_6Si_2O_(13) Composite Powder via Carbothermal Reduction of Fly Ash at 1 550 ℃

Silicon carbide（SiC）-alumina（Al_2O_3）-mullite（Al_6Si_2O_（13）） composite powder was successfully synthesized at 1 550 ℃ for 5 h via carbothermal reduction reaction,and the effects of various mass ratios of active carbon to fly ash（0.38,0.44 and 0.58） on the phase composition and microstructure of products were investigated,and the formation process of the powder was also analyzed in detail.The products mainly consist ofβ-SiC,α-Al_2O_3,Al_6Si_2O_（13） and FeSi.Increasing carbon content favors the decomposition of Al_6Si_2O_（13） and formation of SiC.The average particle size of β-SiC andα-Al_2O_3 is about 1 μm and that of Al_6Si_2O_（13） is 5-10μm.The formation process of SiC-Al_2O_3-Al_6Si_2O_（13）powder includes the decomposition of mullite in fly ash and formation of SiC.

Interface strengthening for thermal sprayed WC-10Co4Cr coating subjected to pulsed magnetic treatment

The reliability of the coated industry components demands ideal fatigue properties of the coating,and it is mainly determined by the performance of the interfaces.In this study,pulsed magnetic treatment(PMT)was applied to the thermal sprayed WC-10Co4Cr coating,and the fatigue lifetime of the coated bolt increased by 219.82%under an imitation of the operating mode condition.Scratch tests further proved that both the adhesion and cohesion strength were improved after PMT,and they benefit from the interface strengthening effects.The formation of coherent WC/Co interfaces was characterized by in-situ transmission electron microscopy(TEM),and the molecular dynamic simulations indicate that the work of separation of these interfaces is much higher than the original disordered ones.Residual stress was relaxed and distributed more homogeneously after PMT,and it mainly contributes to the coating/substrate strengthening.This work provides a new post-treatment method focusing on the interfaces in the WC-based coating and gives insight into its mechanism so that it is hopeful to be applied to other kinds of coatings.