Engineering ceramics are commonly used as coating materials in machining steel and in the non-ferrous alloys industry, mainly to increase the durability tools working in different operating conditions. Coatings based on borides, nitrides, or carbides have high hardness and good tribological properties at room and at elevated temperatures. TiB2 is a unique material characterized by the low affinity to aluminium and its alloys. Such properties justify its successful use in the production of thin anti-wear films dedicated to increasing the durability of tools used in the non-ferrous metal processing industry. This compound is also considered to be superhard materials (hardness up to 30 GPa). Titanium diboride hardness, depending on process parameters and production methods, is in the range of 30 - 40 GPa. Unfortunately, this material has high brittleness, which create the limits of the area of its application.The paper presents the influence of negative substrate polarization on mechanical properties (HV, E) and fracture toughness (KIc) of TiB2 coatings. All coatings were obtained using the magnetron sputtering method on samples of SW7M steel heat treated to hardness 59 HRC. The result of the increase of negative substrate polarization is the increase in hardness and Young modulus. The fracture toughness obtained in the coatings remained at a constant level of 0.6 MPa·m1/2. This means that the coatings are very brittle. In the case of polarization UBIAS = -75 V, the authors achieved a 3 times higher brittleness index KIc and an increase of hardness to 36 GPa simultaneously.Keywords: TiB2 coatings, fracture toughness, magnetron sputtering, PVD
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