The primary purpose of this work was to study the effectiveness of using diamond-like coatings (DLC) to increase the wear resistance of carbide end mills and improve the surface quality of the processed part when milling aluminum alloy and low-carbon steel. The functional role of forming an adhesive sublayer based on (CrAlSi)N immediately before the application of the external DLC film by plasma-enhanced chemical vapor deposition (PECVD) technology in the composition of a multicomponent gas mixture containing tetramethylsilane was established in the article. The article shows the degree of influence of the adhesive sublayer on important physical, mechanical, and structural characteristics of DLCs (hardness, modulus of elasticity, index of plasticity, and others). A quantitative assessment of the effect of single-layer DLCs and double-layer (CrAlSi)N/DLCs on the wear rate of end mills during operation and the surface roughness of machined parts made of aluminum alloy AlCuMg2 and low-carbon steel 41Cr4 was performed.

The main purpose of this paper was to study the efficiency of using diamond-like carbon (DLC) coatings based on a-C:H:Si with a pre-formed CrAlSiN sublayer to increase the cutting ability of ball end mills made of KFM-39 cemented carbide at a speed of 150–250 m/min in milling aircraft-grade Inconel 718, and to assess the DLC coating effect on the quality of the machined surface. DLC coating performance was quantified against uncoated carbide ball end mills and the proven TiN–AlN–TiAlN gradient multilayer coating at elevated temperatures measured by the natural thermocouple method. The temperature near the cutting edge is the factor determining the wear intensity in the tool contact surfaces in milling hard-to-machine nickel alloys to the greatest extent. Thermo-EMF (electromotive force) was recorded and converted into temperatures by calibration charts. The behavior of CrAlSiN–DLC and TiN–AlN–TiAlN coatings was compared with the results of high-temperature tribological tests on a ball-on-disc friction machine. For the CrAlSiN–DLC coating at cutting speeds of 150 and 200 m/min (<650 °C), the milling time until critical flank face wear (0.4 mm) was more than 67 and 50 min, respectively (1.4–1.5 times longer than an uncoated tool and about 1.3 times longer than the TiN–AlN–TiAlN coating). The CrAlSiN–DLC coating was characterized by a minimum adhesion amount.