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Abstract: High power pulsed magnetron sputtering (HPPMS), substrate pretreatments and adhesive interlayers can enhance tool life significantly. In the conducted research, TiAlN PVD-films and W-, Ti- or Cr-adhesive nanointerlayers were deposited by HPPMS on different superficially treated hardmetal inserts. The mechanical properties of the coatings were determined via nanoindentations and mathematical analysis. Additionally, inclined impact tests and milling investigations were performed to examine the substrate pretreatment and interlayer effects on film adhesion and wear behaviour. The results reveal that HPPMS jointly with an appropriate substrate pretreatment and a Cr-nanointerlayer lead to significant adhesion and cutting performance improvement. [Copyright &y& Elsevier]

We review results on the growth of metastable Ti 1− x Al x N alloy films by hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) using the time domain to apply substrate bias either in synchronous with the entire HIPIMS pulse or just the metal-rich portion of the pulse in mixed Ar/N 2 discharges. Depending upon which elemental target, Ti or Al, is powered by HIPIMS, distinctly different film-growth kinetic pathways are observed due to charge and mass differences in the metal-ion fluxes incident at the growth surface. Al + ion irradiation during Al–HIPIMS/Ti–DCMS at 500 °C, with a negative substrate bias V s = 60 V synchronized to the HIPIMS pulse (thus suppressing Ar + ion irradiation due to DCMS), leads to single-phase NaCl-structure Ti 1− x Al x N films ( x ≤ 0.60) with high hardness (> 30 GPa with x > 0.55) and low stress (0.2–0.8 GPa compressive). Ar + ion bombardment can be further suppressed in favor of predominantly Al + ion irradiation by synchronizing the substrate bias to only the metal-ion-rich portion of the Al–HIPIMS pulse. In distinct contrast, Ti–HIPIMS/Al–DCMS Ti 1 − x Al x N layers grown with Ti + /Ti 2 + metal ion irradiation and the same HIPIMS-synchronized V s value, are two-phase mixtures, NaCl-structure Ti 1− x Al x N plus wurtzite AlN, exhibiting low hardness (≃ 18 GPa) with high compressive stresses, up to − 3.5 GPa. In both cases, film properties are controlled by the average metal-ion momentum per deposited atom < p d > transferred to the film surface. During Ti–HIPIMS, the growing film is subjected to an intense flux of doubly-ionized Ti 2+ , while Al 2+ irradiation is insignificant during Al–HIPIMS. This asymmetry is decisive since the critical < p d > limit for precipitation of w -AlN, 135 [eV-amu] 1/2 , is easily exceeded during Ti–HIPIMS, even with no intentional bias. The high Ti 2 + ion flux is primarily due to the second ionization potential (IP 2 ) of Ti being lower than the first IP (IP 1 ) of Ar. New results involving the HIPIMS growth of metastable Ti 1− x Al x N alloy films from segmented TiAl targets are consistent with the above conclusions. [ABSTRACT FROM AUTHOR]

Abstract: High Power Pulsed Magnetron Sputtering (HPPMS) techniques jointly with the deposition of a graded Cr/CrN-nanointerlayer on cutting inserts can increase the film adhesion and consequently the tool life. These improvements depend on the roughness of the employed cemented carbide substrates. The investigations described in the present paper intend to explain the effect of Cr/CrN-interlayer thickness and substrate roughness on the coating adhesion and cutting performance. To attain various roughnesses, the applied cemented carbide inserts were superficially treated. These treatments were grinding at a medium roughness level, or grinding with subsequent polishing for enhancing the surface integrity and finally, in all cases, micro-blasting by fine Al2O3 grains. After Ar-ion etching, graded Cr/CrN adhesive layers with different thicknesses were deposited by HPPMS technology on the variously pretreated substrates. Subsequently, an approximately 3μm thick (Ti,Al)N film was deposited by HPPMS PVD on all used inserts. Rockwell C indentations and inclined impact tests were performed to assess qualitatively and quantitatively the films'' adhesion. The cutting performance of the coated tools was investigated in milling of 42CrMo4 QT. FEM supported calculations of the developed stresses during the material removal process contributed in explaining the obtained tool wear results. In these calculations, the adhesion, dependent on the substrate roughness characteristics and on the adhesive interlayer thickness, was taken into account. The results revealed that the effectiveness of HPPMS adhesive graded Cr/CrN-nanointerlayer strongly depends on the substrate surface integrity and on the interlayer thickness. Thus, the film adhesion and consequently the cutting performance can be significantly improved if the interlayer thickness is adapted to the substrate roughness. [Copyright &y& Elsevier]

Abstract: Recent advantages in PVD coatings for cutting tools enable high speed and dry machining with superior cutting parameters in commercial manufacturing sectors. For this reason hard coatings with high oxidation resistance and thermal stability are used for economically justifiable machining. In this regard nc-(Ti,Al)N/a-Si3N4 films were sputtered on tungsten carbide cutting tools and WC/Co samples by using the high power pulse magnetron sputtering (HPPMS) technology. Coating composition, microstructure and applied properties were investigated by using X-ray diffraction, scanning electron microscope and nanoindentation. The hardness value was about 29GPa for a Si content of 3.3at.%. The grain size was about 6nm. As this study focuses on the thickness uniformity of the coatings, SEM pictures of the cross-section have been taken around the cutting edge to determine the deposition rate and the film growth. The coatings morphology has been compared to middle frequency and direct current sputtered nanocomposite (Ti,Al,Si)N films. The results demonstrate the enhanced HPPMS coatings properties, including a denser structure, a smoother surface and a favourable thickness uniformity. [Copyright &y& Elsevier]

Abstract: Hard coatings with high hardness, high oxidation resistance and thermal stability are used for economical machining. In this regard nanostructured (Cr,Al)N and nc-(Cr,Al)N/a-Si3N4 films were sputtered on tungsten carbide tools and WC/Co samples by using the HPPMS (High Power Pulse Magnetron Sputtering) technology. The relationship between coating composition, microstructure and mechanical properties was investigated by using X-ray diffraction, Scanning Electron Microscopy (SEM), and Nanoindentation. The maximum hardness value was about 40 GPa. For the coatings the Al-content was varied from 10–90 at.% while the silicon content was about 5 at.% for the (Cr,Al,Si)N. As this study focuses on oxidation behaviour of the deposited coatings, annealing tests were carried out in air at 1000 °C. HPPMS is a promising technology to ensure a uniform coating distribution, especially for complex shaped substrates like cutting tools or moulds. SEM pictures of the cross section have been taken around the cutting edge to determine the deposition rate and the film growth. The coatings morphology has been compared to m. f. (middle frequency)- and d. c. (direct current)-sputtered nanocomposite (Cr,Al,Si)N films indicating enhanced properties due to the application of the HPPMS-technology with regard to denser structure, higher hardness, favourable surface topography and better thickness uniformity. [Copyright &y& Elsevier]