Adhesion evaluation of thin ceramic coatings on tool steel

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1、H6il#OLOTELSEVIERSurfaceandCoatingsTechnology78(1996)87-102Adhesionevaluationofthinceramiccoatingsontoolsteelusingthescratchtestingtechnique*FouadAttara,ThomasJohannessonbaLinkdpingUniversity,DepartmentofMechanicalEngineering,DivisonofEngineeringMaterials,S-

2、58I83Link6ping,SwedenbLundUniversity,DivisionofEngineeringMaterials,S-221O0Lund,SwedenReceived27June1994;acceptedinfinalform14November1994AbstractCoatingsofcarbides(TiCandTiC/CrC)andnitrides(TiNandCrN)weredepositedontotwotypesofcoldworktoolsteelusingphysical

3、vapourdeposition(PVD)andchemicalvapourdeposition(CVD).Theadhesionstrengthwasmeasuredusingtwoversionsofthescratchtestingtechnique(stepwiseandlinearlyincreasingload).TheadhesionstrengthrepresentedbythecriticalloadforcoatingremovalLcandthecoefficientoffrictiona

4、tthecriticalloadgcwasdetermined.ThestepwiseincreasingloadresultedinlowerLcandhigher/~ccomparedwiththelinearlyincreasingload.Theformationofdifferentregularcrackpatternsinthecoatingsduringthecontactbetweenscratchindenterandexposedcoatingsurfacesispresentedsche

5、maticallyandtheformationmechanismisexplainedandanalysed.HigherresidualstresseswereobservedinPVDcoatingsdepositedontosubstratesofgreaterroughness,owingprobablytothehighgrainboundaryconstraintduringgrowth.FortheCVDcoatings,thesurfaceroughnessofthesubstratedidn

6、otaffectthecoating'sresidualstressesbecausestressformationisduetothedifferenceinthecoefficientsofthermalexpansion.Modelsoftheworkofadhesionbetweenthecoatingandsubstratearereviewedcriticallyandexpanded.Keywords:Adhesion;Thincoatings;Scratchtesting;Residualstr

7、ess;CrackbehaviourNotationW~workofadhesionatthecriticalstepwiseincreasingload(Jm-2)W1workofadhesionatthecriticallinearlyLnormalload(N)increasingload(Jm-2)LanormalloadatwhichthefirstcrackappearsO'pploughingstress(MPa)atthesurface(N)O-intinternalstress(MPa)lin

8、earlyincreasingloadatwhichthefirst~ttensilestress(MPa)flakingoccurs(criticalload)(N)shearstress(MPa)stepwiseincreasingloadatwhichthefirstflakingoccurs(criticalload)(N)Ffrictional(horizontal)forc