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Streszczenie:
The limited lifetime of hot forging tools, caused by severe wear mechanisms such as abrasion, adhesion, thermal fatigue, and plastic deformation, remains a major challenge in forging operations. The study encompasses the entire process, from concept to industrial implementation. It begins with basic laboratory tests of the innovative material, followed by the application of protective coatings on an industrial scale to forging dies, which were then successfully used in production. The research presents the development and evaluation of novel hybrid surface treatments combining plasma nitriding with nanocomposite coatings based on tungsten boride alloyed with either tantalum (W-Ta-B) or titanium (W-Ti-B). The coatings were deposited using High Power Impulse Magnetron Sputtering (HiPIMS) from SPS-fabricated ternary targets. Laboratory characterization included structural, mechanical, tribological, and oxidation resistance analyses. The W-Ti-B films exhibited superhardness above 40 GPa and superior wear resistance, while the W-Ta-B coatings demonstrated enhanced oxidation resistance and adhesion. Both coatings revealed fine columnar microstructures and favorable H/E* and H³/E² ratios, indicating high resistance to plastic deformation and cracking. Industrial trials under hot forging conditions confirmed their effectiveness, with tool life extended by up to 80% compared with conventional nitrided tools. These findings demonstrate the strong potential of HiPIMS-deposited W-based boride coatings to significantly improve tool performance in demanding thermal and mechanical environments.

Słowa kluczowe:
HiPIMS, Boride coatings, Hot forging tools, Nanocomposites, Durability

Streszczenie:
The forging of lead-free brass alloys is characterized by low tool durability, presenting a significant challenge in industrial applications. To address this issue, unique magnetron-sputtered coatings based on WB and with the addition of Tantalum, were employed to increase tool life. These coatings were produced from proprietary sintered targets using the SPS-HiPIMS technology. Initially, the coatings underwent laboratory testing, where their microstructure, adhesion to the substrate, and mechanical properties were tested and evaluated. The next phase involved testing these coatings on tools used in hot flashless forging processes. The experiments were conducted on dies that were preliminarily gas-nitrided to provide a suitable substrate for the coating application. The results were compared with those of only nitrided dies.
The study involved the use of nitrided dies, dies with WB2.5 and with W0.76Ta0.24B2.5 coatings. After forging, the tools were observed to assess the wear mechanisms. Surface scans were performed to measure material loss by comparing the surface profiles before and after forging. Scanning Electron Microscopy (SEM) was used to analyze the contribution of various wear mechanisms, such as abrasive wear, thermo-mechanical fatigue, and plastic deformation, to the overall tool wear.
The results confirmed the beneficial impact of these coatings on enhancing tool durability. In certain cases, the service life of the tools was extended by up to 50 %. This study demonstrates that the application of newly developed W0.76Ta0.24B2.5 coating which can significantly improve the durability of tools used in the flashless forging of lead-free brass alloys, offering a promising solution for industrial manufacturing challenges.

Streszczenie:
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.

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