Microstructure And Properties Of WC-Co HVAF Coatings Obtained From Standard, Superfine And Modified By Sub-Micrometric Carbide Powders

In this paper, microstructure and some properties of various coatings based on WC-Co obtained by the High Velocity Air Fuel technique are discussed. Initially, two WC-Co 83-17 powders of standard and superfine size were examined as a feedstock for a coatings deposition on a steel substrate. A standard Amperit 526.074 powder and an Inframat superfine powder were applied. Then three different sub-micrometric powders, WC, Cr3C2 and TiC were applied to modify the microstructure of WC-Co (Amperit 526.074). The aim of the investigations was to compare the microstructure and basic properties of coatings deposited from different components. The influence of sub-micrometric additions on mechanical properties of basic coatings was analyzed. Microstructure characterization of powders by using SEM and characterization of their technological properties as well, are presented. For all manufactured coatings obtained by a High Velocity Air Fuel method, the microhardness, porosity, adhesion to a substrate, and fracture toughness were determined. An improvement in WC-Co coating properties, as a result of sub-micrometric carbides addition, was revealed

Mikrostruktura i odporność na ścieranie modyfikowanych powłok typu WC-Co

Results of investigations related to microstructure and wear resistance characterization of three types of WC-17Co coatings obtained by a high velocity process were showed in this article. The first type of coating was obtained by spraying standard powders of WC-17Co types. The second one was from “superfine powder” with the same chemical composition. The third type of coating consists of standard powders, as in first case, but with additions of sub-microcrystalline carbides of different types. The process of powder modifications rely on simple mechanical blending of standard WC-17Co powder with 5% wt. of carbide modifier. The presented investigations included the characterization of the microstructure of coatings. Evaluation of porosity, thickness, and especially the morphology of the matrix of coatings were made. The matrix microstructure description was an interesting problem, especially due to the localization and morphology of modifier particles in the Co base phase. Final investigations consisted of the characterization of the wear resistance of the analysed coatings.W artykule przedstawiono wyniki badań dotyczących charakterystyki mikrostruktury oraz odporności na ścieranie dwóch typów powłok węglikowych WC-Co natryskanych metodą naddźwiękową. W pierwszym przypadku analizowano powłoki otrzymane ze standardowych proszków WC-Co. Drugi rodzaj powłok to powłoki modyfikowane za pomocą submikrokrystalicznych cząstek węglików różnego typu. Zmodyfikowane proszki uzyskano w wyniku prostego mieszania proszku bazowego z dodatkiem 5% wagowych modyfikatora. Wykonano badania obejmujące ocenę mikrostruktury powłok, ich grubość oraz porowatość. Szczególny nacisk położono na analizę osnowy metalicznej powłok celem określenia lokalizacji i morfologii cząstek modyfikatorów. W badaniach końcowych dokonano oceny odporności na ścierania analizowanych powłok

Tribological behavior of WC-Co HVAF-sprayed composite coatings modified by nano-sized TiC addition

The method of improving the properties of WC-Co thermally sprayed coatings by addition of nanostructured reinforcement for mechanical strengthening was explored in this research. Nanostructured WC-Co coatings were characterized by higher hardness than commercial counterparts, but wear tests in the literature have shown contrasting results, whereas bimodal coatings, where nanostructured components are mixed with conventional, micrometer-sized WC grains, exhibited enhanced abrasive and friction wear resistance, in comparison to coatings obtained exclusively from nano-sized powders. A mixed effect of matrix reinforcement by nanoparticles and strong fixing of the micron-sized WC grains was proposed as a possible reason for the enhanced wear resistance of bimodal coatings. A conventional, agglomerated and sintered WC-Co (83-17) feedstock powder was therefore blended with nano-sized TiC (40–100 nm) particles to obtain multimodal coatings containing a nanostructured reinforcement. The amount of TiC added into the powder mixture was in the range of 1–7 wt%. Powder mixtures were deposited onto carbon steel substrate using a High Velocity Air Fuel (HVAF) process. The dry sliding tribological behavior of the coatings was evaluated via ball-on-disk tests against Al2O3 counterparts. The tests were performed at room temperature as well as at 400 °C, with a sliding speed of 0.1 m/s, a sliding distance of 5000 m and a normal force of 10 N. The wear rates of the coatings and of the Al2O3 counterparts were measured separately, and friction coefficients were recorded during each test. The influence of TiC nano-particles on the sliding wear mechanisms was discussed in this work, based on an analysis of wear scars and wear debris through SEM + EDX and micro-Raman spectroscopy

Influence of nano-sized WC addition on the microstructure, residual stress, and tribological properties of WC-Co HVAF-sprayed coatings

Selective Laser Melting (SLM) opens new opportunities for the use of Al-Si alloys in mechanical parts. Besides simplifying the fabrication of complex components, this Additive Manufacturing technique also helps improve the mechanical properties of Al- Si alloys, making them attractive for applications where low or moderate load carrying capacity is required and significant weight reduction is desirable. However, the tribological properties of these components are generally inadequate and the optimization of dedicated post-processing protocols and coating strategies becomes mandatory. This work tests the possibility of depositing self-lubricating Diamond Like Carbon (DLC)-based films on an AlSi10Mg alloy built by SLM, with methods suitable for large-scale production. The resulting wear resistance and frictional behavior are evaluated under various applied loads, using substrates prepared with different pre- treatments. Cast samples are also considered for comparison. The applied coatings are multilayer architectures produced with industrial techniques, consisting of an electroless nickel-phosphorus buffer layer deposited on the AlSi10Mg surface plus a DLC top thin film grown by Plasma Assisted - Chemical Vapor Deposition (PA-CVD). The buffer layer assists coating adhesion while the DLC termination lends improved tribological performances. At 1 N load, the friction coefficients stabilize in the range 0.18-0.22 for different coating-substrate combinations whose surface roughness (Sq) varies between 0.47 and 4.6 μm. Even lower values are obtained when increasing the load to 10 N, similarly to what is found for the counterpart wear rate, which passes from 10-6-10-5 to 10-7-10-6 mm3/(N∙m). These results indicate that DLC-terminated coating architectures are extremely efficient on conventionally made samples as well as on SLM grown samples even in the presence of significant roughness. At the same time, industrial processes such as PA-CVD prove to be a viable solution for depositing on SLM components after standard finishing procedures have been applied on their surfaces

Preface

The 8th International Conference of Computational Methods in Engineering Science (CMES’2023), held on November 23rd-25th, 2023 in Puławy, Poland, is organized by the Polish Society for the Promotion of Knowledge, the Lublin University of Technology (Faculty of Mechanical Engineering, Faculty of Electrical Engineering and Computer Science, Faculty of Management, and Faculty of Environmental Engineering), and the Polish Air Force University (Faculty of Aviation). The conference is an excellent opportunity to present and learn how computational methods can be applied in scientific disciplines like mechanical, materials, and civil engineering, management, environmental engineering, mining and energy, computer engineering, and innovative products launched by companies. The interdisciplinary nature of the conference facilitates knowledge sharing among Polish and foreign research centers that represent different engineering and technical sciences disciplines. This edition creates opportunities for plenary sessions and presentations of companies that solve engineering problems with modern computational methods and tools