Proceedings of SerbiaTrib '13

In order to provide both high parts quality andmaximum tools life one should calculate so called«optimal cutting speed» v О . Optimal cutting rates(v О , S О ) correspond to the optimal cuttingtemperature. It is constant magnitude for the definecombination work – tool material [1]. Whenmachining with this temperature, maximum toolslifetime, minimal roughness of machined surfaceRa, minimal amount of surfaces defects have beenoccurred. Therefore these cutting rates should beused, when finishing work was performed for parts,which work in corrosive medium and hightemperature, because the surface layer has to containminimal amount of defects. For estimating of theoptimal cutting speed the equation is obtained byprof. Silin S. S. [1]:vOCO⋅ a ⎛ a b c ⎞a⎜1 ⋅ 1 ⋅ ρ ⋅θ=Pz⎟ , (1)1 ⎝ min ⎠where a 1 , b 1 – is the thickness and the width of cutrespectively [m]; а – is the coefficient of the temperatureconductivity of the work material [m 2 /s]; сρ – is thespecific heat capacity per unit volume[J/(m 3 · s · degree)]; θ – is the temperature in the cuttingarea, °С; n, C o – are coefficients, which depend on theproperties of work material; Pz min – is a minimalstabilized cutting force [N].But very often there is a need to select a cuttingcondition, which differs from the optimal ones.Therefore the opportunity to estimate thetechnological conditions of turning with taking intoconsideration the tribological properties of coatedtools, will provide the required quality and serviceproperties of parts at the stage of machining.The analysis of the mathematical models forestimating of the parameters of cutting process andquality of the surface level has shown, that themore important variable quantities are the shearplane angle β 1 and the adhesive component of thenfriction coefficient f M . Thus the main tasks of thescientific research were:1. To investigate the influence of tribologicalcharacteristics of coated tools on cutting process andthe parameters of surface layer.2. To define optimal cutting speed for tools withdifferent coatings.3. EXPERIMENTAL CONDITIONSThe wide range of cutting rates, different workmaterials and coated tools were selected forperforming of experiments (Table 1).In the capacity of tools were used the replaceableinserts 120412, material – VK6R (chemicalcomposition: Co – 6%, basis – WC) and TT7K12(chemical composition: Co – 12%, TiC – 1 %, TaC –7%, basis – WC). The different compositenanolaminated ion-plasmous coatings weredeposited on the replaceable inserts: (Ti;Si)N,(Ti,Si,Zr)CN and (Ti;Si;Al)N. Other groupreplaceable inserts was modified by implanting ofnanoparticle TiB 2 , Al 2 O 3 , Ta 2 O 3 and ZrB 2 in worksurface of tools. All selected coatings have beencharacterized by the minimal adhesive of the toolssurfaces with work material, and also they have beenprovided maximum tools lifetime. The machiningwas performed by the regular engine lathe NH 22.The temperature was measured by means of adynamic thermocouple of work material – toolingmaterial. The normal component of a cutting forcePz was measured by using the tool dynamometerDyna-Z, which was connected with personalcomputer (Figure 1). The tool dynamometer Dyna-Zis a self-sufficient measurement system, which canuse without an additional power source, atensometric station and DAQ board. And a precisionmeasured signal can be shown and saved in a veryuseful for operator form [3].Table 1. Experimental conditionsChanging parametersToolsgeometryCuttingrateWork materialHeat-resistant alloy(CrNi77ТiAlW)EI437Stainless steel(05Cr12Ni2Co3Мo2WV)EK26Cutting angle, γ° 5 8 0Relief angle, α° 10 12 10Lead angle, φ, φ 1 ° 45Nose radius, r, [mm] 1,2Titanium alloyOT4Deph t [mm] 0,25; 0,5; 0,75; 1Feed S [mm/rev] 0,07; 0,14; 0,2; 0,32Speed v [m/min] 14-170 33-190 15-130Tool material –VK6R TT7K12 VK6R ТТ7К12 VK6Rcarbide materialNanostructured coating (Ti,Si)N Ta 2 O 3 (Ti,Si)N Ta 2 O 3 (Ti,Si)N(Ti,Si,Al) ZrB 2 (Ti,Si,Al)N ZrB 2 (Ti,Si,Zr)CNNTiB 2 TiB 2 ZrB 2Al 2 O 3 Al 2 O 3 Al 2 O 313 th International Conference on Tribology – Serbiatrib’13 199