Borides in Thin Film Technology

Ultrahard (hardness greater than 4000 HV 005) coatings derived from TiB2 were investigated as thin, wear-protective coatings for cutting tools Deposition methods were based on non-reactive as well as reactive sputter deposition employing dc magnetron sputtering from TiB2 targets Coatings were deposited onto molybdenum, niobium and cemented carbide substrates Very fine-columned films with an (001)-oriented TiB2 phase are formed by means of non-reactive sputtering of TiB2 targets Coatings deposited reactively in Ar-N2-C3H8 atmospheres exhibit very fine-grained to fracture-amorphous structures In the case of reactive sputtering in Ar-N2 gas mixtures a hexagonal TiB2−xNy phase appears at low N2 flows An increase of the N2 flow results in the formation of an additional phase based on TiN Reactive deposition in Ar-C3H8 atmospheres leads to the existence of mixed-phase structures with phases based on TiB2 and TiC Quarternary films grown in Ar-N2-C3H8 mixtures show multiphase structures consisting of phases based on TiB2 as well as TiC and TiN Vickers microhardness measurements on coatings 3 - 5 μm thick on cemented carbide inserts gave the following maximum HV 005 values: Ti-B films 4000; Ti-B-N 4800; Ti-B-C 4000; Ti-B-C-N 4200 Stresses were found to be compressive with values up to 4 GPa The results of scratch tests indicate very good adherence Ti-B-coated cemented carbide inserts have been tested in the turning of aluminum alloys with promising results

Sputter deposition of ultrahard coatings within the system Ti-B-C-N

Surface and interface characterization of heat- treated (Ti, Al)N coatings on high speed steel substrates☆

Titanium carbide and chromium carbide multilayer coatings with varying individual layer thicknesses were synthesized by the co-evaporation of titanium, chromium, and carbon (through tungsten) ingots by electron beam-physical vapor deposition. The adhesion of the multilayer coatings was found to be greater than 50 N. The hardness of the titanium carbide/chromium carbide multilayer coatings was found to increase from 1302 VHN 0.050 to 2052 VHN 0.050 by decreasing the thickness of the individual layer from 1.2 to 0.1 μm. In addition, the average grain diameter was also found to decrease from 3.315 to 0.356 μm by decreasing the thickness of the individual layers. The fracture toughness of the TiC/CrC multilayer coatings decreased from 4.179 to 1.411 MPa-m 1 2 with decreasing layer thickness. Lastly, the amount of compressive stress in both the TiC and CrC layers within the multilayer coating was found to decrease with decreasing individual layer thickness. The samples were characterized by various techniques including Vicker's hardness, X-ray diffraction, scanning electron microscopy, scratch testing and fracture toughness, with the results being presented.

Synthesis of titanium carbide/chromium carbide multilayers by the co-evaporation of multiple ingots by electron beam physical vapor deposition

Titanium carbide (TiC), in addition to other transition metal carbides, has excellent wear-resistant properties in machining of stainless and high speed tool steels. TiC was successfully deposited on 304 stainless steel by reactive ion beam-assisted electron beam–physical vapor deposition (RIBA, EB–PVD). The hardness values ranged from 1100 to 3500 VHN 0.050 depending on the processing parameters. The surface morphology and degree of texturing were correlated with the processing conditions. Ion bombardment resulted in strong surface and growth texture in primarily the (111) orientation. A change from the (111) orientation to the (200) was observed at high substrate temperatures. Vickers hardness, scanning electron microscopy (SEM), X-ray diffraction (XRD) and electron probe microanalysis (EPMA) were used to characterize these films.

W. Dunford

Papers

Structure and properties of refractory compounds deposited by electron beam evaporation