0 WZL/Fraunhofer IPTCutting materials, tools and coolants for machining with geometrically defined cutting edges part 1Manufacturing Technology ILecture 4Laboratory for Machine Tools and Production EngineeringChair of Manufacturing TechnologyProf. Dr.-Ing. Dr.-Ing. E.h. F. Klocke1Seite 1 WZL/Fraunhofer IPTContents of the lectures 4 and 5 tool steels cemented carbides coatings ceramics tool design cooling lubricants Lecture 4 Lecture 52Seite 2 WZL/Fraunhofer IPTStructure Introduction classification according to hardness and toughness nomenclature and classification of cutting materialsTool steelsCemented carbidesCoatingsSummary3Seite 3 WZL/Fraunhofer IPTMain requirements on tool materials Hardness Abrasion Toughness Heavy cuts ( high feed values and depth of cut, high cutting forces) Interrupted cuts High dynamics Heat resistance Diffusion High cutting speed (heat generation) Heat shock resistance4Seite 4 WZL/Fraunhofer IPTClassification of cutting materialstoughness, flexural strength and feedCutting speed,Wear resistance, thermal resistanceDPoptimal cutting material1BN1 in consideration of hardness2 in consideration of hardnessand temperatureDP:2fine and ultra fine graincementedcarbideAl2O3+ TiCCermetcoatedCermetCoated cemented carbideSi3N4-ceramicAl2O3 -ceramiccemented carbide basedon tungsten carbidecoated HSSHSS5Seite 5 WZL/Fraunhofer IPTClassification of cutting materialscold working steelhigh speed steelWC-CoTiC/TiN - Co,NiWC-(Ti,Ta,Nb)C-Cooxide ceramicsilicium-nitride ceramiccomposite ceramicsboron nitridediamondtool steelcemented carbidesceramicssuper hard cuttingmaterialscutting materials for processing with geometrically defined cutting edge6Seite 6 WZL/Fraunhofer IPTApplication GroupsP Group WC-(Ti,Ta,Nb)C-Cohigh heat resistance, reduced toughnessMGroupKGroup(WC, Co)high toughness, reduced heat resistance7Seite 7 WZL/Fraunhofer IPTcemented carbidesdenotation cemented carbide groupHWuncoated cemented carbide, main content tungsten-carbide (WC) with grain size 1 mHT 1)uncoated cemented carbide, main content titanium carbide (TiC) or titanium nitride (TiN) or bothHC cemented carbide as above, coated1)these cemented carbides are also called "Cermets"HFuncoated cemented carbide, main content tungsten-carbide (WC) with grain size < 1 mClassification and application of hard cutting materials (DIN ISO 513)8Seite 8 WZL/Fraunhofer IPTClassification and application of hard cutting materials (DIN ISO 513)ceramicdenotation group of ceramicCAoxide ceramic,major content aluminum oxide (Al2O3)CMcomposite ceramic, major content oxide ceramic(Al2O3), also non-oxide ceramicCNnitride ceramic, major content silicon nitride (Si3N4)CRoxide ceramic,major content aluminum oxide (Al2O3)reinforcedCCoxide ceramic as above, but coateddiamonddenotation diamond groupDPpoly-crystalline diamond DMmono-crystalline diamondboron nitridedenotation boron nitride groupBLcubic-crystalline boron nitride with low content of boron nitrideBHBCcubic-crystalline boron nitride with high content of boron nitridecubic-crystalline boron nitride as above, but coated9Seite 9 WZL/Fraunhofer IPTdenotation colorP blueMKhard cutting materialsapplication groupwork piece materialyellowredP01P10P20P30P40P50P05P15P25P35P45M01M10M20M30M40M05M15M25M35K01K10K20K30K40K05K15K25K35aincreasing wear resistance of the cutting material, increased cutting speeds possiblebincreasing toughness of the cutting material, increased feed rates possibleaaabbbmachining main group (Source: DIN ISO 513)steel:all kinds of steel and cast steel,except rustproof steel with austenitic microstructurestainless steel:stainless austenitic and austenitic-ferriticsteel and cast steelcast iron:cast iron with flake graphite, cast iron with spherical graphite, annealed cast ironApplication of cutting materials (DIN ISO 513)10Seite 10 WZL/Fraunhofer IPTApplication of cutting materials (DIN ISO 513)NSHgreenbrowngreyN01N10N20N30non-ferrous metal:aluminum and other non-ferrous metals, non-metal work materialsN05N15N25S01S10S20S30special alloys and titanium:high-temperature special alloys based upon iron, nickel and cobalt, titanium and titanium alloysS05S15S25H01H10H20H30hard work materials:hardened steel, hardened cast iron materials, chilled cast ironH05H15H25denotation color hard cutting materials work piece materialaaabbbmachining main group (Source: DIN ISO 513) application groupaincreasing wear resistance of the cutting material, increased cutting speeds possiblebincreasing toughness of the cutting material, increased feed rates possible11Seite 11 WZL/Fraunhofer IPTStructureIntroduction Tool steels unalloyed tool steels alloyed tool steels high speed steel (HS)Cemented carbidesCoatingsSummary12Seite 12 WZL/Fraunhofer IPTMain design features of tool steelsOrdinary tool steelsMatrix: Martensite, primary carbidesHigh speed steelMatrix: Martensite, primary carbides, secondary carbides13Seite 13 WZL/Fraunhofer IPTExamples of unalloyed cold working steelsunalloyed cold working steelcomposition [%] applicationC Si Mn Cr Mo V Whammer, axe, shear, screw driver, chiselwood saw, hand saw, solid of composite saw bladesfile, scraper, paper shearall kind of chiselsfile, scraper, paper shearcutting tools, shear for steel cutting, broaching tools0,80-0,900,25-0,400,50-0,701,20-1,350,10-0,300,10-0,35-0,500,40-0,400,15-0,800,600,42-0,470,20-0,300,85-1,01,7-1,90,25-0,30 0,051,10-1,250,15-0,300,20-0,400,5-0,8--0,07-0,120,15-0,452,0-2,250,10-0,4011,0-12,0----0,6-0,8C45W1.1730C85W1.1830C125W1.156345CrMoV71.2328115CrV31.2210X210CrW121.2436alloyed cold working steeldenotationNr.14Seite 14 WZL/Fraunhofer IPTVariations and applications of high speed steelscutting steel atmedium load maximum loadcompo-sitiondenotationW - Mo - V - Co< 850 N/mm2 > 850 N/mm2 roughing finishing18% WHS18-0-1HS18-1-2- 5+----+--12% WHS12-1- 4- 5HS10-4- 3- 10----(+)(+)++6% W + 5% MoHS6-5-2- + - -HS6-5- 3- - (+) +HS6-5-2- 5- - + -2% W + 9% MoHS2-9-1HS2-9-2HS2-10-1-8+---+---+---IIIIIIIVHigh-speed steels are notated with the letters HS and the indication of the percentalamount of alloying additions inthe sequence W-Mo-V-Co, e.g. HS10-4-3-10. The classification of high-speed steels is raised by their W- and Mo-concentraion intofour alloy- and performance groups.15Seite 15 WZL/Fraunhofer IPTMain applications of the most important high speed steelssteel groupdenotation according toDIN EN ISO 4957HS6-5-2HS6-5-3HS6-5-2-5HS10-4-3-10HS2-9-2HS2-9-1-8mater-ialNr.1.33431.33441.32431.32071.33481.3247applicationstandard material for roughing and finishing, twist drills, tapping tools, milling tools, broaching tools, reaming tools, countersinker, hobbing tools, saws, forming toolshigh performance tapping and reaming tools, high performance millingtools, broaching tools, twist drillshigh performance milling tools, turning and hobbing tools, high performancetwist drills and tapping tools, cold working tools, roughing tools with high tenacityuniversal roughing and finishing tools, turning and high performance millingtools, free cutting steel, tools for wood machiningtwist drill and tapping tools, milling tool, reaming tool, broaching toolend milling tools, turning tools for free cutting operations, twist drills, tapping tools16Seite 16 WZL/Fraunhofer IPTProduction of high speed steel by melting02004006008001000120014001600melting and foundingblock turningblock annealing forging rolling final annealingtemperature T / Ctime t / hdenotation HS18-1-2-5 HS10-4-3-10 HS12-1-4-5 HS12-1-4 HS6-5-2hardening temperature C 1280 1240 1240 1240 1230annealing at 0,5 1 h3 560 C2 570 C1 550 C2 570 C2 560 C2 540 C17Seite 17 WZL/Fraunhofer IPTHeat treatement of high speed steel1. annealing2. annealingoil / airair air air airheating in vacuum furnaceannealing time in each case: 1 2 htime t / hslow furnacedown coolingtemperature T / Ccompensating temperatureheatingaustenizeannealingstress relief annealingpre machiningfinishing3. annealingABCDEFGA 600 - 650 C B 1. pre-heating stage ca. 400 C (in salt bath)C 2. pre-heating stage 850 C D 3. pre-heating stage 1050 CE hardening temperature ~1200 CF salt bath 500 - 600 CG 50-80CTo realize their endhardness HSS-Tools are preapared by a heattreatment. In a first stepthey are hardend ( heated, held on austenite temperature and cooled down with high speed), afterwards several times tempered. 18Seite 18 WZL/Fraunhofer IPTTemperature dependent effects on the hardness in tempering HS~ 600 ASMA1A2M1M2~ 66 temper temperature T / Chardness / HRCTempering of high-speed-steel takes place bei temperatures between 540 580 C and isfor this reason in the temperature range of secondary harndess. This pickup of hardnessleads under normal hardening- and temperconditons to hardness values, which can beclearly higher then these after quenching.The cutting material hardness resulting from the overlay of the different processes isshown as a sum graph S depending on the tempering temperature.19Seite 19 WZL/Fraunhofer IPTTools made of high speed steel - examplessource: Forstsource: Sandviksource: PWStools for gear shapingcylinder gearspline shaft chain wheelinternal gear broaching tools forinternal broachingexternal broachinghard broachingtools fordrillingmillingtapping thread millingthread forming20Seite 20 WZL/Fraunhofer IPTStructureIntroductionTool steel Cemented carbide WC-Co-based cemented carbide (HW) TiN/TiC-based cemented carbide cermet (HT) fine grain cemented carbideCoatingsSummary21Seite 21 WZL/Fraunhofer IPTMilestones in the development of cemented carbidespatent for manufacturing of WC.Co-HM,K. SchrterSpring Fair Leipzig: 1. WC-Co-HMManufacturer Krupp, Denotation WIDIACarboloy (General Electric)WC-TIC-Co cemented carbidesTiC-Mo2C-Ni (1. cermet-generation )Manufacturer Plansee, denotation Titanit STitanit (Plansee), Bhlerit (Bhler)Coromant (Sandvik)presentation of coated cemented carbidesfine grain Spinodal - Cermet ( 1. Cermet with TiN )increased development of Cermetsultrafine and nanocrystalline grainhardness HV30flexural strength N/mm2mean grain diameter mstandard (1,4 - 1,8)fine grain (< 1)ultra fine grain (< 0,5)uncoatedmulti layer0 1000 2000 3000 4000tool life1923100%360%19271928193119341937194268/691970197373/741993( )22Seite 22 WZL/Fraunhofer IPTProduction process of cemented carbide components23Seite 23 WZL/Fraunhofer IPTInfluences on wear resistance and toughness of cemented carbidesWith regard to the wear- and performance abillity of uncoated and coated cementedcarbides the features of cemented carbide substrates play a key role24Seite 24 WZL/Fraunhofer IPTMicrostructure of conventional cemented carbide and cermetIn conventional cemented carbides based on WC the tungsten carbides mostly exist in prism shape with a triangular base. The carbide skeleton is filled up with the bindingphase. The structure of cermets is only made of chamfered mixed carbonitrides. Characteristiclyfor their microstructure is the core-shell-structure of the hard material.25Seite 25 WZL/Fraunhofer IPTComposition and properties of conventional WC-Co cemented carbidescemented carbide classificationsource: DIN ISO 513HW - K05 HW - K10 HW - K25 HW - K40sort WC - 4Co WC - 6Co WC - 9Co WC - 12Co15,1 14,9 14,6 14,21730 1580 1420 12905700 5400 5000 45001600 2000 2350 2450650 630 590 5806,9 9,6 12,3 12,70,21 0,22 0,22 0,2280 80 70 655,0 5,5 5,6 5,9source: ISO 3369source: ISO 3878source: ISO 4506source: ISO 3327source: ISO 3312density / (g/cm-3)hardness HV 30compression strength(cyl.-specimen) / (N/mm2)flexural strength / (N/mm2)Youngs Modulus/ (103N/mm2)fracture toughness / (Nm1/2/mm2)Poisson ratiothermal conductivity / (Wm-1K-1)thermal expansion coefficient (293 K1073 K) / (10-6K-1)Cemented carbides of this group exist almost completely out of hexagonal tungstenmonocarbide and the binding phase cobalt. They can contain up to 0,8 mass% VC and/orCR3C2 and/or up to 2 mass% (TaNb)C as doping additives to controle the grain size and constancy.26Seite 26 WZL/Fraunhofer IPTMicrostructure of micro grain and sub micro grain cemented carbidesturning of chilled cast iron( 80 shore )024681014mintool lifestandard micro grain sub micronstandardmicro grainsub micronWC - 6-Co carbides(H): hardness HV30(B): flexural strength N/mm2source: Krupp Widiavc = 16 m/minf= 0,1 mmap = 1,0 mminsert:SPGN 120308sharp cornered,= 7527Seite 27 WZL/Fraunhofer IPTDependency of grain size, hardness and toughnesssource: Widia nano: < 200 nm fine:0,8 - 1,3 m super fine: 0,5 - 0,8 m ultra fine: 0,2 - 0,5 m1000120014001600180020002400hardnessHV30500100015002000250030004000flexural strengthN/mm4 6 8 10 12 16cobalt content / % 1428Seite 28 WZL/Fraunhofer IPTCutting edge after hard milling 55 HRCconventional cemented carbide 9.5% Comilling time 90 minultra fine cemented carbide 7.5% Comilling time 175 min29Seite 29 WZL/Fraunhofer IPTApplication of ultra fine grain cemented carbide - micro millingwork piece: X5CrNi18-10cutting speed: 6 m/minrevolutions: 8000 min-1feed per tooth: 1 to 5 mdepth of cut: 64 mwidth of cut: 254 m1 mm30Seite 30 WZL/Fraunhofer IPTComposition and properties of WC-(Ti,Ta,Nb)C-Co cemented carbidescemented carbide classification source: DIN ISO 513HW - P10 HW - P15 HW - P25 HW - P30 HW - M10 HW - M15composition (mass-%)WC(Ti, Ta, Nb)CCo31,060,09,025,564,510,017,372,710,010,078,511,59,584,56,011,082,56,510,6 11,7 12,6 13,0 13,1 13,31560 1500 1490 1380 1700 15504500 5200 4600 4450 5950 55001700 2000 2200 2250 1750 1900520 500 550 560 580 5708,1 9,5 10,0 10,9 9,0 10,50,22 0,23 0,22 0,23 0,22 0,2225 20 45 60 83 907,2 7,9 6,7 6,4 6,0 6,0source: ISO 3369source: ISO 3878source: ISO 4506source: ISO 3327source: ISO 3312density / (g/cm-3)hardness HV 30compression strength(cyl.-specimen) / (N/mm2)flexural strength / (N/mm2)Youngs Modulus/ (103N/mm2)fracture toughness / (Nm1/2/mm2)Poisson ratiothermal conductivity / (Wm-1K-1)thermal expansion coefficient (293 K1073 K) / (10-6K-1)Cemented carbides of this group contain besides tungsten mixed carbides (MC) out of titanium- tantalum- niobium- and/or zirconiumcarbide. Compared to the WC-Co-cemented carbides they show improved high temperature abbilities.31Seite 31 WZL/Fraunhofer IPTsource: Pulvermetallurgie der Hartmetallecermet group source: DIN ISO 513HT P05 HT P10 HT P20composition (mass-%)carbon nitrideadditional carbidesCo/Ni89,00,610,485,70,813,582,31,016,7source: ISO 33696,1 7,0 7,0source: ISO 38781650 1600 1450source: ISO 45065000 4700 4600source: ISO 3327 2000 2300 2500source: ISO 3312 460 450 4407,2 7,9 10,00,21 0,22 0,219,8 11,0 15,79,5 9,4 9,1density / (g/cm-3)hardness HV 30compression strength(cyl.-specimen) / (N/mm2)flexural strength / (N/mm2)Youngs Modulus/ (103N/mm2)fracture toughness / (Nm1/2/mm2)Poisson ratiothermal conductivity / (Wm-1K-1)thermal expansion coefficient (293 K1073 K) / (10-6K-1)Composition and properties of CermetsIn comparison with conventional cemented carbides cermets show a lower density. Significant differences compared to WC-based cemented carbides are the clearly lowerheat conductivity and at the same time higher thermal extension.32Seite 32 WZL/Fraunhofer IPTTurning of steel using cermetsDue to the high edge strength, the high resistance against abrasive wear, and littleadhesive wear cermets are particularly suited for finishing steels.33Seite 33 WZL/Fraunhofer IPTMilling with Cermetsend mill,carbide K25Pend mill,cutting speed vc34Seite 34 WZL/Fraunhofer IPTApplication of different cemented carbide qualitiesWC-Co-carbide: + high hardness and wear resistance because of tungsten carbide(K-group) + high edge toughness because of high solubility of WC in the WC-Co binder- reduced heat resistance because of diffusionWC-(Ti,Ta,Nb)C-Co: + high heat resistance, resistance against oxidation and (P-group) diffusion because of high content of TiC, TaC and NbC- reduced edge toughness because of poor solubility of carbidesin the bindercermet (TiC/TiN) : + high heat resistance, high resistance against oxidation and diffusion + high surface quality because of low adhesion - low toughness- low thermal shock resistance35Seite 35 WZL/Fraunhofer IPTStructureIntroductionTool steelCemented carbide Coatings Chemical vapour deposition (CVD) Physical vapour deposition (PVD)Summary36Seite 36 WZL/Fraunhofer IPTWear phenomena on coated cutting toolsdiffusionoxidationabrasiondelaminationadheasionsurface effectsvolume effectsstressesfracture formationoutbreakbreakPrimary task of the hard material layer is to prevent the contact between work material and tool during machining in order to reduce the tool wear caused by adhesion, abrasion, diffusion and oxidation at the surface of the cutting material. 37Seite 37 WZL/Fraunhofer IPTDesign of a CVD coating installationCHH2H2+TiCl4liquidTiCl4evaporatorgas exitcoating furnacegas entranceH2To produce a TiC-layer for example Titantetrachlorid??? (TiCl4) is vaporized and lettogether with methane to a reaction vessel which can hold a couple of thousands of cutting inserts. Thereby the titaniumcarbide is produced in a chemical reaction at a temperature between 900 C and 1100 C and a pressure below atmospheric pressure. 38Seite 38 WZL/Fraunhofer IPTTTT-curve of a WC Co alloy at coating temperaturesWC Eta Eta'Co3W200400600800100012000,01 0,1 1,0 10 100 1000temperatureT / Ctime t / hCo - 5 W - 0,23 CHT-CVDMT-CVDP-CVDPVDTime-Temperature-Transformation chart of a cobalt aloy. Listed are typical coatingtemperatures and times for the processes HAT-CVD, MT-CVD, PA-CVD and PVD. The figure shows that in the classical HT-CVD and middle temperature-CVD-process thearea of eta-phase-precipitation is run through respectively affected.Compared to that in low temperature processes like PA-CVD- and PVD-processes no changes of constitution is to be expected. 39Seite 39 WZL/Fraunhofer IPTCoating process and flexural strength14,52,6FPA-CVDPVDPVDCVDchangeof flexuralstrength/ %10100-10-20-30-40-50-600 2 4 6 8700C550C1000C400Ccoating thickness / mTiNTiN/Ti(C,N)PVDCVD PVDPVDPA-CVDThe comparing examination of the bending strength of thin, differently coated WC-Co cemented carbides shows which influence the coating temperature and layer thicknesshave on this important paramater of toughness performance.40Seite 40 WZL/Fraunhofer IPTCoating method and cutting performance10000050000100005000100050010060 80 100 200 400 300impactsncutting speed vc/ (m/min)work mat.:42CrMo4+QTRm= 980 N/mm2substrate:P30/40SPUN 120312f = 0,2 mmap= 2,5 mmMT-CVDuncoatedArc-PVDThe MT-CVD- as well as the PVD-coated cemented carbide are clearly superior in theirperformance compard to the uncoated cemented carbide.Coming to lower cuttingspeeds the PVD-layer shows advantages.41Seite 41 WZL/Fraunhofer IPTCommonly used layer structuretypical multi-layer with functionalIntermediate layersmultilayer (nano-structure)graded layermonolayer (thin hard layer)t = 0.5 ... 50 mt = 0.5 ... 10 mt = few atomic cells ... 100 nmhard and soft compounds(MoS2, WC/C, graphite etc. .)hard film + solid lubricantfilm(a-Me-C:H)super hard coatings(CVD-DP / BN)42Seite 42 WZL/Fraunhofer IPTIncreased tool life using Middle-Temperature-CVD-coatings43Seite 43 WZL/Fraunhofer IPTPerformance of Plasma-CVD coated cemented carbidecarbide P25 / TiN, PA-CVD - coateddisk millingwork material: 60WCrV8,220 HBcutting material: HW-P25vc= 80 m/minfz= 0,08 mmae= 42 mmap= 6 mm type of coatingworktravellf/ mPA-CVD none HT-CVD0412168The attributes of PA-CVD-coated cemented carbides have a positive affect on theirperformance in machining higher-strength steel workmaterials in interupted cut.The sensitivity of the composite against Kammrissbildung ??? and failure throughdecomposotion is much smaller compared to HAT-CVD-coated cutting materials.44Seite 44 WZL/Fraunhofer IPTImproved wear resistance and tenacity using multilayer coatings010203040607080%1001 m / 9 m4 m / 6 m6 m / 4 mAlONTiNAlONTiNAlONTiNAlONTiN3 mprobability of tool breakagesingle layer thickness Al2O3 /TiCPVDCVDPVDP-CVDCVDwearresistancetenacitycoating thicknesstransientcoatingsubstrateCVD -coatingAl2O3 / TiCtotal coating thickness for all tools 10 msource: Widia, SumitomoWith rising coat thickness the wear resistance of CVD-coated cemented carbidesincreases, at the same time however the bending strength and therewith the toughnessdecreases.45Seite 45 WZL/Fraunhofer IPTIncreased fracture resistance using graded subsurfaces360%P 251000 1200 1400 1600hardness HVmultilayercoating ongradedsubsurface100%tool lifeworkpiece: C25vc=200 m/minf=0,15 - 0,3 mmap=0,5 - 1,5 mmgradedsubsurfacehardness10 mmultilayer coating46Seite 46 WZL/Fraunhofer IPTImprovement of edge stability using Ti(C,N)-transition layers47Seite 47 WZL/Fraunhofer IPTCVDmultilayer-coatings with ZrSEM-picturecarbidecalotte crater48Seite 48 WZL/Fraunhofer IPTC-based coatingshydrogen-contenthardnesscrystal latticeof graphitecrystal lattice of diamondclassification of C-based coatings basedon hydrogen-content and hardnessdiamondgraphiteplasma-poymeramorphous carbon(DLC)49Seite 49 WZL/Fraunhofer IPTCVD-diamond thin-film coatingsmicro-crystalline (standard) nano-crystalline (even) multi-layer (even)micro-crystallinenano-crystallinesource: CemeCon50Seite 50 WZL/Fraunhofer IPTReduced adhesion and abrasion by smooth CVD-diamond coating100 m5 m900 m900 mrake face900 m900 msevere adhesions900 msevere adhesionsflank facePVD-TiB2CVD-diamond coated tool (coating thickness 4m)New lc= 40 m lc= 40 mvc= 200 m/minfz= 0,15 mm dry HC-K20 end mill with two teethd = 10 mmap= 3 mmslot milling51Seite 51 WZL/Fraunhofer IPTPhysical Vapour Deposition (PVD) coatings ~500C instead of 1000C (CVD) limited chemical bonding with substrate preservation of compressive stresses during the substrate grinding process sharp edges preservation of the toughness in the substrate material HS coatable lower layer thicknesses compared to CVD52Seite 52 WZL/Fraunhofer IPTPVD-process vacuum platinggas inletinert processgasreaction gasvacuum plating device- electrical heatingor- electron beam (EB-PVD)vacuum pumpenergy supplyevaporatorspecimen holder,bias voltagewater cooledrecipientelectron beam (EB-PVD)target materialmetal ionsplasmaandreaction gas ionscoatingBeim Vakuumverdampfen wird das Schichtmaterial in einem Tiegel im Hochvakuum verdampft. Die Dampfatome weisen bei diesen Drcken mittlere freie Weglngen von bis zu mehreren Metern auf. Sie treten deshalb i. Allg. nicht in Wechselwirkung miteinander und gelangen geradlinig zum Substrat. Da dieses erheblich klter ist als der Dampf, kondensieren die Teilchen auf dem Substrat. Aufgrund des geradlinigen Teilchenflugs muss der Substratwerkstoff in der Beschichtungskammer bewegt werden, um Abschattungseffekte und ungleichmige Schichtdicken zu vermeiden. 53Seite 53 WZL/Fraunhofer IPTPVD-process sputteringvacuum pumpadditionalmagnet systemsputter device- without additionalmagnetic field:diode-sputter-source- with additionalmagnetic field:magnetron-sputter-source1-5 kVelectrode as additionalion source- +gas inletinert processgasreaction gasmetal ionsplasmaandreaction gas ionscoatingspecimen holder,bias voltageevaporatortarget materialIn einem Niederdruckplasma wird ein Inertgas (z.B. Argon) durch Anlegen einer Hochspannung ionisiert. Die positiv geladenen Inertgasionen werden auf das als Kathode geschaltete Target (Schichtwerkstoff) hin beschleunigt und schlagen dort durch Impulsaustausch Atome, Atomgruppen und Molekle des Beschichtungsmaterials heraus.54Seite 54 WZL/Fraunhofer IPTPVD-process Arc-ion platinggas inletinert processgasreaction gasvacuum pumpmagnets for arc stabilizingresp. steering rotating arcplasma channel105000 V - +bias voltagespecimen holdermetal ionsplasmaandreaction gas ionscoatingBeim Ionenplattieren wird das Substrat mit einer negativen Spannung, die sog. Biasspannung, beaufschlagt. Der Metalldampf wird durch im Gasraum angeordnete Elektroden und elektromagnetische Felder ionisiert. Ein Teil der ionisierten Teilchen wird zum Substrat hin beschleunigt. 55Seite 55 WZL/Fraunhofer IPTExample for a coating machine56Seite 56 WZL/Fraunhofer IPTCoating prevents built-up edges0,2 mm0s005 9 0 35mPVD - TiN - coatedvC = 63 m/min broaching oil vC = 63 m/min dryvC = 63 m/min dry vC = 63 m/min dryworkpiece material:17CrNiMo 6 BGtool material: WC 6 Corise per tooth:h - 0,1 mmcutting tool geometrie:Becaue of the use of PVD-TiN- coated instead of uncoated cemented carbides the built-up-edge formation is supressed in the complete examined cutting speed area of vc= 10 63 m/min because of the decreased adhesion between the chip and cutting material. 57Seite 57 WZL/Fraunhofer IPTPhysical and chemical properties of coatings*data for the cubic NaCl-structure at 50% TiC/TiN or TiN/AlNverygoodverygoodmean good mean chemical resistance8,0 9,4 7,7coefficient of thermal exspansion 25/1000/ 10-6/K-1675,7 -156,3* -260,0* -337,6 -184,1enthalpy of forming H298K / kJ/mol23002400 -33002600 -34002300 3100micro hardness/ HV 0,05 -Al2O3(Ti,Al)N Ti(C,N) TiN TiC58Seite 58 WZL/Fraunhofer IPTNotch Wear and AbrasionHW-P10HC-P10(TiAlN)Dry Synthetic Ester SubstrateSpalling100mNotch= 37 minVBN= 0,2 mmProcess:Turning (external)Material:42CrMo4VInserts:HW-P10, HC-P10(SPUN 120304)Cutting parameter:vc= 150 m/minf = 0,12 mmap= 1,0 mmAbrasion= 69 min= 48 min = 23 min59Seite 59 WZL/Fraunhofer IPTOxidation Resistant Coating Systemsester with additivesoverviewwear of minor cutting edge600 m300 mVBNmax(Ti,Al)N/Al2O3tc= 57 minProcess:Ext. cyl. turningMaterial:X5CrNi18-10Cutting material: :HC-K20(SPUN 120308)Cooling lubricant::Ester without add.Cutting parameters::vc= 150 m/minf= 0,12 mmap= 2,5 mm050100150200mWidthof wearland VB Nmax, VB Nn(Ti,Hf,Cr)N (Ti,Al)N-Reference-VBNntc= 40 min tc= 57 min VBNmaxVBNnVBNmax60Seite 60 WZL/Fraunhofer IPTStructureIntroductionTool steelCemented carbideCoatings Summary61Seite 61 WZL/Fraunhofer IPTQuestions Which are the main components in high speed steel (HS), WC-Co-based cemented carbides (HW) and cermets (HT)? Why are complex tools such as broaching and gear hobbing mills often made of high speed steel (HS)! Why do cermets (HT) have a higher thermal strength than WC-Co-based cemented carbides (HW)? A given finishing turning process does not deliver the required surface finish. The surface obtained is too rough. What measures can be taken to increase the surface finish. Cemented carbides from the P-group have high content of TiC, TaC and NbC carbides, low content of WC. What is the benefit of this composition, what are the disadvantages? What are the advantages of CVD-coatings compared to PVD-coatings? A high speed steel has to be coated. What type of process (CVD, PCD) do you consider. What wear effects can be influenced by a coating? What are main failure effects of coating?62Seite 62 WZL/Fraunhofer IPTQuestions How does particle size in cemented carbides influence toughness What can be done to overcome build up edges What are the main conditions to promote adhesive wear What can be done to prevent adhesion Which material more sensitive to adhesion (compare against tool steel): Aluminum, carbon steel (0,6% C) or grey cast iron (GG 15) Show for K - grade carbides the dependence of grit size and cobalt contend on toughness Show for K - grade carbides the dependence of grit size and cobalt contend on hardness