Machining hardmetal with CVD diamond direct coated ceramic tools: effect of tool edge geometry (original) (raw)
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Wear resistant CVD diamond tools for turning of sintered hardmetals
Diamond and Related Materials, 2003
Sintered hardmetals are very hard materials that are usually machined using diamond grinding wheels and electro-discharge machining. Dry cutting with super-hard cutting tools like cubic boron nitride (c-BN), polycrystalline diamond (PCD) and chemical vapour deposition (CVD) diamond is an ecological alternative to reduce operation times and, therefore, to improve the productivity. In the present work, cylindrical forging dies of WC-27 wt.% Co hardmetal grade were turned at fixed operating parameters (cutting speeds15 mymin; depth-of-cuts0.2 mm; feed rates0.03 mmyrev.) using CVD diamond tipped hardmetal inserts. Commercial PCD and c-BN inserts were tested for comparison. The cutting tool behaviour was studied in terms of both the tool wear and the finishing quality of the workpiece. The tool damage was evaluated using a special probe for edge roughness evaluation, together with scanning electron microscopy observations. The CVD diamond tools survived the task showing slight cratering, whereas flank wear was the main wear mode for the other superhard tools. Amongst all the tested tools, PCD presented the worst performance in terms of tool wear and workpiece surface quality. Furthermore, the operation time was reduced to one tenth with respect to conventional diamond wheel grinding. ᮊ
Cutting forces evolution with tool wear in sintered hardmetal turning with CVD diamond
Diamond and Related Materials, 2004
The cutting forces evolution is investigated during the dry turning of sintered hardmetal (WC-25 wt.%Co) with chemical vapour deposition (CVD) diamond brazed tools. The effect of the cutting speed (v), feed (f) and depth of cut (d) in the cutting forces is analysed, being found a clear relationship between tool forces, tool wear and workpiece surface finishing. The chosen test conditions (vs40 m min , fs0.03 mm rev. and ds0.1 mm) allow to set up a threshold main cutting force value of 35 y1 y1 N below which excellent workpiece finishing is assured with low cutting tool damage. Flank tool wear, besides cratering on the rake tool face and hardmetal deposition on the tool surface, are the main damage modes of the cutting tools.
Diamond and Related Materials, 2006
Very smooth CVD diamond films are used as direct coatings on Si 3 N 4 tool substrates. By adjusting deposition parameters, namely Ar/H 2 and CH 4 /H 2 gas ratios, and substrate temperature, nano-(27 nm) and submicrometric (43 nm) crystallite sized grades were produced in a hot filament reactor. Also, a conventional 5 and 12 μm micrometric grain size types were produced for comparison. Normalized coated inserts were tested for dry turning of WC-25 wt.% Co hardmetal. All the CVD diamond grades endured the hardmetal turning showing slight cratering, having the flank wear as the main wear mode. Their turning performance was distinct, as a consequence of morphology and surface roughness characteristics. Among all the tested tools, the more even surface and the submicrometric grade presented the best behaviour regarding cutting forces, tool wear and workpiece surface finishing. For this coating, the depth-of-cut force attained the lowest value, 150 N, the best combination of wear types (KM = 30 μm, KT = 2 μm and VB = 110 μm) and workpiece surface finishing (Ra = 0.2 μm).
2005
This work presents results obtained for the performance evaluation of cutting tools produced by brazing a thick diamond film on a tungsten carbide substrate. The evaluation was based on the machining of aluminum-silicon alloys. The diamond films, approximately 500 μm thick, were produced at LAPMA-IF-UFRGS in a microwave plasma CVD reactor (Astex A5000 – 5 kW). The brazing process was optimized in order to promote a strong adhesion between the diamond film and the substrate, using a CuAg(Ti) brazing filler in-between them. The performance of the cutting tools was evaluated through the wearing of the cutting edge, related to the quality of the machined surface (roughness). The results obtained for the produced cutting tools were also compared to the results obtained for the machining with a a commercial diamond tool, considered as a reference. These results show that the performance of the cutting tools produced by brazing a diamond film on a tungsten carbide substrate for machining n...
This paper investigates the effects of different surface pretreatments on the adhesion and performance of CVD diamond coated WC–Co turning inserts for the dry machining of high silicon aluminum alloys. Different interfacial characteristics between the diamond coatings and the modified WC–Co substrate were obtained by the use of two different chemical etchings and a CrN/Cr interlayer, with the aim to produce an adherent diamond coating by increasing the interlocking effect of the diamond film, and halting the catalytic effect of the cobalt present on the cemented carbide tool. A systematic study is analyzed in terms of the initial cutting tool surface modifications, the deposition and characterization of microcrystalline diamond coatings deposited by HFCVD synthesis, the estimation of the resulting diamond adhesion by Rockwell indentations and Raman spectroscopy, and finally, the evaluation of the dry machining performance of the diamond coated tools on A390 aluminum alloys. The experiments show that chemical etching methods exceed the effect of the CrN/Cr interlayer in increasing the diamond coating adhesion under dry cutting operations. This work provided new insights about optimizing the surface characteristics of cemented carbides to produce adherent diamond coatings in the dry cutting manufacturing chain of high silicon aluminum alloys.
Single Point Diamond Turning of CVD Coated Silicon Carbide
Manufacturing Science and Engineering, Parts A and B, 2006
Scratching experiments, using diamond styli and single point diamond tools, were performed to simulate Single Point Diamond Turning (SPDT). The results of these experiments were used to determine if a ductile response is possible, and then to determine the critical depth of cut or penetration depth for the ductile to brittle transition (DBT). The depths of the scratches produced at different loads were measured and correlated to the ductile and brittle response of the material. The DBT depth for Chemically Vapor Deposited (CVD) coated Silicon Carbide (SiC) samples was determined. The analysis for the critical depth (DBT) did confirm the possibility for SPDT of CVD coated SiC in the ductile regime. These results were further used for SPDT of CVD SiC.
CVD Diamond Coated Tungsten Carbide (WC) Tool Inserts
Journal of Engineering Research, 2021
In this paper a self-developed polycrystalline diamond coating was done on tungsten carbide (WC) tool insets by using simple thermal chemical vapor deposition technique. The growth of these diamond films has been carried out at ~900 ºC temperature. The as-grown polycrystalline diamond films on the surface of tungsten carbide tool inserts have been characterized using Raman spectrometer and scanning electron microscope (SEM). The morphological studies reveal that the as-grown diamond films are of high crystalline quality. The as-grown diamond films possess compressive stress. The micro-hardness indentation test of the as-grown diamond films on WC tool inserts and bare have also been done and it has been found that the Vicker’s hardness of the as-grown diamond WC tool inserts is found to be 1423.32 HV which is 29% better than the un-coated tools.
3D characterisation of tool wear whilst diamond turning silicon
Wear, 2007
Nanometrically-smooth infrared silicon optics can be manufactured by the diamond turning process. Due to its relatively low density, silicon is an ideal optical material for weight sensitive infrared (IR) applications. However, rapid diamond tool edge degradation and the effect on the achieved surface have prevented significant exploitation. With the aim of developing a process model to optimise the diamond turning of silicon optics, a series of experimental trials were devised using two ultra-precision diamond turning machines. Single crystal silicon specimens <1, 1, 1> were repeatedly machined using diamond tools of the same specification until the onset of surface brittle fracture. Two cutting fluids were tested. The cutting forces were monitored and the wear morphology of the tool edge was studied by scanning electron microscopy (SEM).
Vacuum, 2008
Silicon-aluminium alloys (Al-Si), with Si contents up to 20%, are important materials in automotive and aeronautical industries due to their low density and high wear resistance. The turning of these alloys has been done mainly by superhard tools like polycrystalline diamond (PCD). CVD diamond either as thin coatings on silicon nitride ceramics or as thick brazed tips on hard metals is alternative material. In this work, CVD diamond thin films were grown on Si 3 N 4 ceramic substrates and thick CVD diamond plates were brazed onto WC-Co tools. These different inserts were used in dry turning of silicon-aluminium alloys with 12 wt% and 18 wt% Si. Both directly diamond coated and brazed tools are able to machine the Al-12 wt% Si alloy with negligible wear. In turning of Al-18 wt% Si, sharp edged tools yield lower cutting forces than the chamfered ones, with the occurrence of tool failure at about 500 and 100 m, respectively. CVD brazed tools proved to be able for dry turning this hypereutectic alloy, keeping the cutting forces below 60 N. Minimal wear was observed after 1500 m of cutting length, mainly caused by diamond chipping at the flank face.
In the present study investigation was done to analyze the tool life by analyzing the change in surface roughness with time during machining of silicon (infrared crystal) at optimized parameters with a single crystal diamond tool. Silicon has low mass density, low cost & low coefficient of thermal expansion. Due to these properties it is used in microelectro, micro-mechanical & weight sensitive infrared applications where surface roughness is a major criteria for the acceptance of the fabricated part. A contact type mechanical profilometer was used to measure the surface roughness of silicon.