Metal Toughened Magnetron Sputtering TiB2_ Hard Coatings: Preparation, Structure And Performance Studies

Hard coatings are widely used, because of their high hardness, wear resistance, corrosion resistance and thermal stability, in the fields of surface protection such as cutting tools and engines. However, these hard coatings are intrinsically brittle and usually exhibit abrupt fracture failure. Therefore, toughening hard coatings is of very importance from either scientific or practical perspectives. The traditional way to toughen was to manipulate the bonding structure in the electronic scale, i.e., to improve the intrinsic toughness. By this way, the hardness was usually reduced when the toughness was increased. Different from the traditional method, we improved the growth structure of hard coatings, in the microstructure scale, to improve the extrinsic toughness, by which way the hardness and the toughness of the hard coatings can be right balanced.We prepared two-metals(Ti and Ni) toughening TiB2 coatings, respectively, bymagnetron co-sputtering from two targets. And then we studied the structure and deformation behavior of TiB2-Ti coatings with different Ti content, and the structure, deformation behavior, and tribological behavior of Ti B2-Ni coatings with different substrate bias. Various characterization methods were used to evaluate toughness of these two coatings. Main results are as follows:(1) TiB2-Ti coatings have a dense structure in SEM and TEM.(i) When Ti<30 vol. %, the coatings were dominated by the ceramic phase and exhibited high stress(-2.8 GPa), high hardness(~40 GPa), and high H/E* ratios(0.12). In addition, these coatings showed low ?H values and brittle deformation.(ii) When Ti>40 vol.%, the coatingsweredominatedbythemetalphaseandexhibitedlowerstress(~0gpa),hardness(~20gpa),and<0.1h/e*values.thesecoatingshavehigher?hvaluesandcouldhavehighertoughness.throughtheabovestudiesoftib2-ticoatingsandti-bequilibriumphasediagram,weachievedtheti-bmetastablephasediagram.thetoughnessoftib2-ticoatingswasinvestigatedbyvickersindentation,scratchandnanoscratchtests.theresultsshowedimprovedtoughnesswithincreasingticontent.wesuggestthatthemaintougheningmechanismsareasfollows:theadditionofductilephaseexpendstheplasticzoneofcracktipsandincreasestheintrinsictoughness;whilethespecialgrowthstructureincreasesextrinsictoughnessofcoatings.(2)tib2-nicoatingsalsohaveadensegrowthstructure.underlowerbias(30v),thecoatingstendtobeamorphousinxrdandsaed.bycontrast,thecoatingswithhighbiashavegoodcrystallization.andthesecoatingshavelowroughnessandresidualstress.thehardnessofthesecoatingswere>40gpa.withincreasingthenegativebiasfrom30vto110 v,thetoughnessandadhesionincreasedsimultaneously.furthermore,thefrictioncoefficientagainsttheal2o3wasbetween0.5~0.6andthewearratewasatthesameorderof10-15m3/nmmagnitude.theerosionrateofthetib2-nicoatingswasmuchlowerthanthatofthesubstrate,m42 steel.