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.