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Results of cutting tool life research of replaceable inserts (replaceable polyhedral plates) with wear-resistant coating and stressed-deformed condition of their cutting wedge are presented. Investigations have been executed in steel (0.40 % C, 1 % Cr) machining. Components of cutting force were measured by means of the dynamometer Kistler, magnitude and distribution of contact stresses have been defined according to earlier executed research in this area with use of a method of a sectional (split) cutting tool. Calculation of stresses in a cutting insert has been executed with use of program ANSYS which has displayed reduction of internal stresses in a base material of the insert with an antiwear coating in comparison with the insert without it. In the antiwear coating equivalent stresses more than in the insert without a coating and rich 1821 MPa. Experimental data on influence of various kinds of coats on cutting tool life and strength of replaceable inserts are presented.

The paper presents data about distribution of contact stresses on a rake surface and flank-land of a cutter in free orthogonal turning of a disk made from a titanium alloy (Ti-6Al-2Mo-2Cr). On the cutting edge of the bar blade, there is a normal force Nρ, directed perpendicularly to a transient surface, with a large magnitude of specific linear force qN r= 182.6 N/mm, but the tangential force on the cutting edge Fρis equal to zero. On the rake surface, there are uniformly distributed shear contact stresses with very small magnitude of τ ≈ const ≈ 25 MPa, irrespective of feed rate, which speaks about plastic character of the contact on the rake surface. The greatest normal contact stress on the rake surface σmax≈ 1009 MPa, irrespective of feed rate. The greatest magnitude of normal contact stresses on the flank surface chamfer near the cutting edge σh max= 3400-2200 MPa confirms the hypothesis about recovery of a transient surface sag after separation of a formed element of a chip, and explains increased wear of the cutting tool on the flank surface at initial time. Normal σhand shear τhcontact stresses on the flank surface chamfer are essentially diminish with a distance from the cutting edge. It explains working ability of the cutting tool even at very large wear on the flank surface (hf> 3 mm). Our experimental data allows calculating the components of cutting force and contact stresses on the rake and flank surfaces of cutting tools during titanium alloy (Ti-6Al-2Mo-2Cr) machining.

In this paper different contact conditions between tool, chip and work material are analyzed. Experimental and theoretical studies of contact load distribution on the artificial flank wear land of the cutter in free orthogonal turning of a disk made from titanium alloy (Ti-6Al-2Mo-2Cr) are described. Investigations of cutting with various feed rate and cutting speed show that the greatest contact loads are observed immediately at the cutting edge. It is associated with the discontinuous character of titanium alloy chip and the elastic recovery of the transient (machined) surface at the moment when generated chip element is separated. The main influence of the variable chip thickness ratio of the discontinuous chip on the value of the greatest normal contact load near the cutting edge is shown that confirms the author’ hypothesis about a sag of the transient surface in the cutting edge region.Abbreviation and symbols: m/s – meter per second (cutting speed v); mm/r – millimeter per revolution (feed rate f); MPa – mega Pascal (specific contact load as stress σ or τ); hf– the width of the flank wear land of the cutting tool, flank wear land can be natural or artificial like in this paper [mm]; xh– distance from the cutting edge on the surface of the flank wear land [mm]; σh– normal specific contact load on the flank land [MPa]; τh– shear (tangential) specific contact load on the flank land [MPa]; HSS – high speed steel (material of cutting tool); Py r– radial component of cutting force on the rake face [N]; Pz– tangential component of cutting force [N]; γ – rake angle of the cutting tool [°]; α – clearance angle of the sharp cutting tool [°]; αh– clearance angle of the flank wear land [°]; b – width of a machined plate or disk [mm]; a – the thickness of the layer being removed (uncut chip thickness) [mm]; a1– chip thickness [mm]; Ka– chip thickness ratio (Ka= a1/a) as a degree of plastic deformation in chip formation zone; Ka2– variable chip thickness ratio, Ka2= a2/a1, where а2– distance from the rake face surface of the chip to the contact point of two neighbouring elements of the chip [mm]; Φ – shear angle [°]; hd– value, which determines the depth of deformation, for an ordinary task it is equal to the thickness of the machined part or the radius r of the machined disk [mm]; q – intensity of loading in the chip formation region [MPa].

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