Structure, Mechanical and Tribological Properties of HVOF Sprayed (WC-Co+Al) Composite Coating on Ductile Cast Iron

The paper presents the results of examinations of WC-Co coating sprayed on ductile cast iron by high velocity oxygen fuel spray process (HVOF) with powder containing Al particles in an amount of 10%. The impact of Al particles added to the tungsten carbide coating on the structure, mechanical and tribological properties in the system of (WC-C)/ductile cast iron was examined. The microstructure of the thermal sprayed WC-Co+Al coating was characterized by light, scanning electron (SEM) and transmission electron (TEM) microscopes as well as the analysis of chemical and phase composition in micro areas (EDS, XRD). It was found that by supersonic thermal spraying with WC-Co powders with the addition of Al particles, the coatings of low porosity, high hardness, a very good adhesion to the substrate, compact structure with molten Al particles and finely fragmented WC particles embedded in a cobalt matrix, reaching the nanocrystalline sizes were obtained.Moreover, the results were discussed in reference to examination of bending strength considering cracking and delamination in the system of (WC-Co+Al)/ductile cast iron as well as hardness and wear resistance of the coating. It was found that the addition of Al particles was significantly increase resistance to cracking and wear behaviour in the studied system

The High-Speed 6xxx Aluminum Alloys in Shape Extrusion Industry

This chapter describes and analyzes the 6xxx aluminum alloys used in the shape extrusion sector dedicated to automotive and construction industry. The division and application of 6xxx aluminum alloys are performed. The precipitation hardening of 6xxx (Al-Mg-Si) alloys is presented as these alloys easily undergo deformation and present the potential for new kinds of alloys for high-speed extrusion. The mechanisms of strengthening are shown with the evolution of precipitation sequences. Also some examples of industry applications of 6xxx aluminum alloys are presented

INFLUENCE OF CORROSION ON MECHANICAL PROPERTIES AND MICROSTRUCTURE OF 3XXX, 5XXX, AND 6XXX SERIES ALUMINUM ALLOYS

Growing demands imposed on passenger car producers concerning the reduction of exhaust emission to the environment are forcing a search for new materials and design solutions. One of the most-important factors that can reduce this emission is the low mass of a vehicle, leading to a decrease in its average fuel consumption. A reduction in weight can be obtained by the use of aluminum elements instead of steel; e.g., in air conditioning pipes, decreasing the specific weight of the construction by nearly three times. In the present study, the influence of the SWAAT corrosion test on A/C piping made from 3xxx, 5xxx, and 6xxx series aluminum alloys was investigated. The study focused on changes in the mechanical properties of samples before and after a SWAAT test determined by a tensile test and Vickers hardness measurements. Additionally, microstructure examinations were performed with the use of optical and scanning microscopy. Corrosion products on the surface of pipes were identified by Energy Dispersive X-ray Spectroscopy. Pipes made from the EN AW 6063 alloy revealed an almost 50% decrease in its strength properties after the tests. The largest decline in plastic properties was observed in pipes made from the EN AW 6060 alloy

APPLICATION OF COATINGS MADE BY PLASMA SPRAY AND PVD METHODS FOR PROTECTION OF GRAPHITE MOULDS

The results of our research on the application of coatings for protecting industrial casting molds are presented. Tests were carried out on graphite molds with deposited Al2O3 coatings containing the addition of glassy carbon and with W/Zr/DLC coatings, both examined after the process of pouring molds with molten aluminum bronze. The coatings were applied by two different methods; i.e., plasma spraying in the case of Al2O3 + glassy carbon coating and PVD in the case of W/Zr/DLC coating. Reference tests were also conducted on graphite molds without coating. The use of protective coatings on graphite molds seems to be an effective solution. Studies have shown that coatings have good resistance during the casting process. The liquid metal sticking to the surface did not penetrate deep inside the graphite mold. The use of coating technology reduces the amount of downtime necessary to replace worn molds and increases the efficiency of the casting process.Application of coatings made by plasma spray and PVD methods for protection of graphite mould

Wybrane aspekty podejmowania decyzji w sytuacjach kryzysowych. Studium przypadku

This article is a study of research on factors influencing decision-making under risk. An important management competence is the ability to make rational decisions. In reality, however, decisions are made with limited rationality or using heuristic methods. The right decisions are the basic factor affecting the condition of an enterprise and determining its development. Typically, the decisions made are influenced by the decision-maker's personality, experience and emotions. However, in professional life, decisions are also influenced by formal and legal regulations and rules as well as the rules and methodology adopted in a particular company. By confronting the ways in which decisions are made in both professional and personal life, it is possible to infer the tendencies that drive decision-makers. The article presents the results of an extensive literature analysis on governance and the influence of personality on decisionmaking. In the research part, a survey of a selected group of people was conducted and the results obtained were analysed comparatively in relation to the gender of the respondents. The results showed a greater tendency for men to take risks. Women were better at assessing the consequences of their decisions. Both women and men were cautious in estimating risks in professional decisions

Fucoidan Does Not Exert Anti-Tumorigenic Effects on Uveal Melanoma Cell Lines

Background. The polysaccharide fucoidan is widely investigated as an anti-cancer agent. Here, we tested the effect of fucoidan on uveal melanoma cell lines. Methods. The effect of 100 µM fucoidan was investigated on five cell lines (92.1, Mel270 OMM1, OMM2.3, OMM2.5) and of 1 µg/mL–1 mg/mL fucoidan in two cell lines (OMM1, OMM2.3). Cell proliferation and viability were investigated with a WST-1 assay, migration in a wound healing (scratch) assay. Vascular Endothelial Growth Factor (VEGF) was measured in ELISA. Angiogenesis was evaluated in co-cultures with endothelial cells. Cell toxicity was induced by hydrogen-peroxide. Protein expression (Akt, ERK1/2, Bcl-2, Bax) was investigated in Western blot. Results. Fucoidan increased proliferation in two and reduced it in one cell line. Migration was reduced in three cell lines. The effect of fucoidan on VEGF was cell type and concentration dependent. In endothelial co-culture with 92.1, fucoidan significantly increased tubular structures. Moreover, fucoidan significantly protected all tested uveal melanoma cell lines from hydrogen-peroxide induced cell death. Under oxidative stress, fucoidan did not alter the expression of Bcl-2, Bax or ERK1/2, while inducing Akt expression in 92.1 cells but not in any other cell line. Conclusion. Fucoidan did not show anti-tumorigenic effects but displayed protective and pro-angiogenic properties, rendering fucoidan unsuitable as a potential new drug for the treatment of uveal melanoma

SELECTION OF PROTECTIVE COATINGS OBTAINED BY PLASMA-SPRAYING METHOD FOR FOUNDRY INDUSTRY

This article presents results from the studies of protective coatings applied to industrial graphite molds used for the casting of non-ferrous metals. The selection of coatings was based on the results of measurements of surface wettability by liquid copper and microstructure examinations. The study involved industrial graphite molds with single-layer protective coatings of Al2O3 + 30%C and ZrO2-Y2O3 + 30%C as well as two-layer protective coatings of Al2O3 + 30%C /glassy carbon and ZrO2-Y2O3 + 30%C /glassy carbon

INFLUENCE OF WELDING TECHNIQUES ON MICROSTRUCTURE AND HARDNESS OF STEEL JOINTS USED IN AUTOMOTIVE AIR CONDITIONERS

Austenitic steels belong to a group of special-purpose steels that are widely used in highly aggressive environments due to their enhanced anticorrosive behavior and high mechanical properties. The good formability and weldability of these materials has made them very popular in automotive AC systems. This study presents the results of hardness tests and microstructure observations on plasma- and laser-welded joints. The examined joints consisted of two different stainless steel components; i.e., a nipple made from corrosion-resistant AISI 304 steel and a corrugated hose made from 316L steel. Microplasma welding was carried out on a workstation equipped with an MSP-51 plasma supply system and a BY-100T positioner. The laser-welded joint was made on a numerically controlled workstation equipped with an Nd:YAG laser (without filler material) with 1 kW of maximum power; the rotational speed of the welded component was n = 4 rpm. Microstructural observations were performed using a scanning electron microscope and an optical microscope. Vickers hardness was measured with a hardness tester. The obtained results proved that both the microplasma- and laser-welded joints were free from any visible welding imperfections. In the micro areas of the austenitic steel weld, crystals of intercellular ferrite appeared against a background of austenite. The crystallization front (depending on the welding technology) was running from the fusion line towards the weld axis. The grain size depended on the distance from the fusion line

SELECTION OF OPTIMAL CONDITIONS FOR SOLID BONDING OF THE AlSi11 ALUMINIUM ALLOY

In the present work, the optimal conditions for solid bonding of fragmented aluminum alloy were determined. The research was conducted on metal chips from the AlSi11 TM aluminum alloy after the turning process. The selection of proper bonding conditions was based on the results of tensile tests and surface quality analysis of as-extruded profiles. The extrusion process was conducted within a temperature range of 350–500°C, with a ram speed of 13 mm/s. Extrusion ratio λ was 25. As a reference material, a sample from the solid AlSi11IM alloy has been extruded under the same conditions.The influence of temperature during direct extrusion on both maximum force and surface quality of obtained profiles has been determined. With reference to tensile test results, no significant influence of temperature on the mechanical properties has been noticed. Profiles extruded at 500°C were characterized by visible cracks on the surface, oriented perpendicular in the direction of extrusion. Moreover, surface flaws were also noticed in profiles extruded at 350°C. A tensile testrevealed a strong relationship between the extrusion conditions and plasticity of solid bonded rods. A shiny and smooth surface was obtained only in profiles extruded at a temperature range of 400–450°C.Selection of optimal conditions for solid bonding of the AlSi11 aluminium allo

Effect of rapid solidification aluminum alloys with different Si content on mechanical properties and microstructure

Rapid solidification is a relatively new and effective way of ultrafine grained UFG aluminum alloys production with enhanced mechanical properties. Due to significant cooling rate close to almost 106 K/s it is possible to obtain material with grain size far below 100 nm. In the present study RS aluminum alloys with Si content in a range of 5-10 wt.% were produced during melt spinning. As a result, materials in a form of ribbons were produced. As-received flakes were subjected to cold pressing into a cylindrical billets with diameter of 40 mm. Hot extrusion of pre-compacted material was subsequently performed at the temperature of 450 °C with press ram speed of 3 mm/s and extrusion ratio of λ=25. In this work influence of brittle phases on mechanical properties of as-extruded rods will be examined. Both tensile and microhardness tests were performed in order to determine mechanical properties of obtained profiles. It has been showed that brittle phases refinement during melt spinning significantly influences mechanical properties of tested materials