Staff

Abstract:
This work compares experimentally measue properties of W-Al-B thin films with mechanical properties, density, and thermal conductivity values calculated using DFT methods. Theoretical modelling was conducted to simulate two WB2 stable structures alloyed with varying amounts of aluminium: α-WB2 (P6/mmm) and ω-WB2 (P63/mmc), as well as α-AlB2 (P6/mmm). Using the HiPIMS-DC magnetron sputtering technique, films with α-WB2 structure and varying aluminium contents were deposited at 400 °C. When layers are composed with x = 1.4% aluminium (where x = at%Al / (at%Al + at%W)), their microstructure changes from amorphous to crystalline columnar. A back transformation to an amorphous microstructure occurs when the amount of aluminium exceeds x = 7.3%. An original method was used for the film density studies, which combined mass measurements and microscopic observation. These measurements were then used to determine the layers' thermal conductivity using the thermoreflectance method. The measured conductivity of the deposited ceramic films range from 3 to 6 W/(mK). Moreover, the obtained films are very hard, e.g. H = 36.1 ± 1.7 GPa for x = 1.4% Al, but exhibit a much lower Young's modulus than the theoretical values. The relatively high H/E⁎ ratio > 0.1 for films with low aluminium content indicates anmore elastic character. Ab-initio calculations showed that, based on the criteria of Cauchy pressure (C12-C44) and Pugh's ratio (B/G), the α-WB2 structure may have a ductile nature in contrast to the other structures. However, the deposited films are rather brittle in nature, resulting from an excess of boron. The fracture toughness measurements show higher KIC values for low aluminium content. They are 3.8 MPa√m for WB2, 2.8 MPa√m for x = 1.4%, and 3 MPa√m for x = 7.3% aluminium

Keywords:
thin films, high-power impulse magnetron sputtering, density, thermal conductivity, fracture toughness, stiffness tensor

Abstract:
In this work, tantalum-doped tungsten boride ceramic coatings were deposited from a single sputtering target with the radio frequency (RF) and high-power impulse magnetron sputtering (HiPIMS) methods. Two-inch torus targets were synthesised from pure elements with the spark plasma sintering (SPS) method with a stoichiometric composition of W1-xTaxB2.5 (x = 0, 0.08, 0.16, 0.24). Films were deposited with RF and HiPIMS power suppliers at process temperatures from RT to 600 °C. The substrate heating and the energy of the ionised material impacting the substrate increase the surface diffusivity of adatoms and are crucial in the deposition process. The results of SEM and XRD investigations clearly show that the addition of tantalum also changes the microstructure of the deposited films. The coatings without tantalum possess a finer microstructure than those with 24% of tantalum. The structure of films is homogeneous along the film thickness and composed mainly of columns with a (0001) preferred orientation. Deposited coatings are composed mainly of P6/mmm α-WB2 structures. The analysis of nanoindentation results allowed us to determine that ceramic coatings obtained with the HiPIMS method possess hardness above 41 GPa and a ratio of hardness to reduced Young modulus above 0.1. The thickness of HiPIMS-deposited films is relatively small: only around 60% of the RF magnetron sputtered coatings even when the average power input was two times higher. However, it has been shown that the RF coatings require heating the substrate above 400 °C to obtain a crystalline structure, while the HiPIMS method allows for a reduction of the substrate temperature to 300 °C.

Keywords:
RF magnetron sputtering, HiPIMS magnetron sputtering, Superhard ceramic coatings, Transition metal borides, Deposition temperature

Abstract:
The article presents research on finishing treatment applied to components made of Inconel through 3D printing by Laser Powder Bed Fusion method. Vibration-abrasive machining was carried out using a supporting fluid and various shapes of abrasive. The effects of the processing conditions were analysed based on the surface roughness of the samples and mass loss. The obtained collective results were subjected to comparative analysis with the effects of vibratory-abrasive processing without the use of a processing fluid, as presented in the article. The research has shown that using vibration-abrasive processing, it is possible to reduce the height of surface irregularities by more than three times after four hours of treatment. The intensity of processing was the highest in the first hour of the process. The lowest roughness heights Ra = 1.8 μm were obtained using ceramic balls in the presence of a supporting fluid.

Keywords:
vibration-abrasive processing, IN939, roughness, additive manufacturing, 3D printing post-processing

Keywords:
HiPIMS magnetron sputtering, DC magnetron sputtering, coatings

Keywords:
Ternary transition metal diboride thin films, Mechanical properties, HiPIMS/DC magnetron sputtering, wear resistance and adhesion, DFT Methods