Key Engineering Materials Vol. 1016

Abstract: This study aims to investigate the effects of Minimum Quantity Lubrication (MQL) independent pulse parameters, which are the intervals between two pulses (1, 2, and 3 seconds) and the duration of the lubricant application (1, 2, and 3 seconds), in the turning of AISI 1040 steel. MQL pulse parameters supplying the best lubrication in terms of cutting force, cutting temperature, and surface roughness were 1 second interval between pulses and 3 seconds duration of lubricant application. These parameters provided 10.7%, 43.6%, and 65.5% improvement in cutting force, cutting temperature and surface roughness values, respectively, compared to dry cutting conditions. When the MQL pulse parameters were compared among themselves, an improvement of 6.7%, 38.3% and 61.7% was achieved in the cutting force, cutting temperature, and surface roughness values, respectively, in the conditions that gave the worst and the best results. According to ANOVA (Analysis of variance) results, the duration of the lubricant application was determined as the most important parameter on the surface roughness and resultant force whereas the interval between two pulses was obtained the most important parameter on the cutting temperature.

Abstract: This paper presents an experimental study on the influence of solidification cooling rate on the evolutions of microstructural morphologies of a high strength low alloy steel. To this end, solidification samples (cylindrical form with 10 mm diameter and 120 mm length) were prepared from 30 cm below the ingot/hot-top interface, at the center, of a 40 MT (Metric Ton) ingot. Solidification experiments were carried out by using Gleeble^® 3800 thermo-mechanical simulator. Two solidification cooling rates of 1 and 50°C/s were chosen. For microstructural characterization, samples were prepared by mounting, polishing and etching with 3% Nital solution. Also, an optical microscope was employed for microstructural observations. The obtained results showed that for 1°C/s, the microstructure is composed with dendrites and grains. Here, the grain morphology is the dominant one. In the case of 50°C/s, the dendrites were localized at the sample surface and the grains were present more into the depth of the sample. Moreover, the increase of solidification cooling rate results in finer dendrites. The results are discussed in the framework of solidification mechanisms.

Abstract: Plasma nitriding (ion nitriding) is a plasma-supported thermochemical cementation of steel, during which the hardness of the surface and resistance to wear and fatigue of the material increases due to the formation of a hard layer. The process of plasma nitriding is very variable, which makes it possible to nitride all types of steel, but the result depends primarily on the chemical composition and process tech-nique. In this way, for example, cement, construction, tool steels, high-strength and stainless steels, as well as cast iron, are nitrided. Structural steel belongs to a group of very important and diverse materi-als, it has versatile use in many areas of industry such as machines, vehicles, buildings, bridges, etc. Corrosion of materials is a common phenomenon that cannot be completely eliminated. This degrada-tion is often classified as one of the main reasons for material loss. The article presents the benefit of plasma nitriding on the corrosion resistance of structural steels. Experiments were carried out for select-ed three types of structural steels, on which plasma nitriding was performed and then a corrosion test in a mist of neutral sodium chloride solution. The achieved results confirmed that plasma nitriding has a significant effect on increasing the corrosion resistance of structural steels.

Abstract: The paper presents the use of integral methods of surface texture evaluation of structural steel samples used in armaments production for the analysis of the functional behaviour of gear surfaces. The aim of the paper is to evaluate the relationship between the quality of the ground surface and the surface after the plasma nitriding process and the functional properties of the surface using unconventional characteristics. These characteristics include Amplitude Distribution and Material Ratio, Autocorrelation Function (ACF), Frequency Spectrum (FS) and Power Spectral Density (PSD). These characteristics can, for example, reveal small changes in surface texture caused by both the cutting tool and surface treatments, such as diffusion nitriding technology, which show only slight changes in standard parameters. Thus, these characteristics can be used as a suitable diagnostic tool for evaluating changes in the functional properties of surfaces. These changes can usually be characterized by wavelength profile inequalities and statistical and spectral properties. In this paper, the surfaces of C45, 15NiCr13, 18CrNiMo7-6 and 16MnCr5 steels after the finishing operation of grinding and further after plasma nitriding are evaluated. Measurement of the standard parameter, i.e. the arithmetic mean height Ra, of ground and nitrided surfaces resulted in the same or slightly higher values after diffusion technology. Using integral characteristics, changes in surface texture were found to be directly related to the functional behaviour of surfaces in interaction and can predict, for example, noise levels, wear and lubrication properties.

Abstract: The growing demand for advanced materials with enhanced surface properties has driven significant research into various surface modification techniques. Among these, plasma treatment emerges as a versatile and effective method for improving the characteristics of different materials [1-10]. Plasma technology offers unique benefits, such as the ability to modify surfaces without the need for harsh chemicals or excessive energy inputs. This study focuses on two specific materials: Aluminum alloy 2024, recognized for its high strength-to-weight ratio, excellent corrosion resistance, and widespread application in aerospace and automotive industries, and unvulcanized rubber compounds, which provide flexibility and resilience essential for various applications, including seals and gaskets. Utilizing dielectric barrier discharge (DCSBD) technology for surface modification presents a novel approach to activating and cleaning the surfaces of these materials [11,12]. DCSBD plasma operates at atmospheric pressure, making it a cost-effective alternative to traditional cleaning and activation methods that often rely on corrosive chemicals or mechanical abrasion. The versatility of DCSBD plasma allows for fine-tuning of various parameters, such as voltage, treatment time, and gas composition, enabling tailored modifications to achieve desired surface properties. This research aims to investigate the effects of plasma application on Aluminum alloy 2024, particularly in terms of enhancing surface energy and wettability. Increasing surface energy is critical for improving adhesion properties, particularly for applications that involve coating or bonding processes [13]. The plasma treatment process results in enhanced surface energy, significantly reducing the contact angle of testing liquids on treated surfaces compared to their untreated counterparts. This enhanced wettability can lead to improved adhesive bonding and overall performance of coated or bonded materials [14-17]. The study evaluates how variations in treatment parameters such as voltage, exposure time, and airflow rate affect the surface properties of both materials. Furthermore, the impact of varying distances between the plasma source and the treated surfaces is examined, as this distance significantly influences the efficacy of the surface modification process. Understanding the relationship between these variables is essential for optimizing plasma treatment conditions. Previous studies have highlighted the potential of plasma treatment to improve the adhesion of coatings to Aluminum alloy 2024 [18-20]. This research asserts that atmospheric pressure plasmas provide a compelling alternative to conventional surface preparation techniques, such as acid etching or mechanical abrasion, which can be harmful to both the environment and the materials being treated. Moreover, the comparative surface modification effects on the two distinct materials: shape-stable Aluminum alloy 2024 and shape-unstable unvulcanized rubber offer valuable insights into the plasma treatment process. The findings from this research are expected to elucidate the intricate relationship between plasma treatment parameters and the resulting surface characteristics. By systematically varying the distance between the plasma source and the material surfaces, this study aims to identify optimal conditions for effective surface modification. Ultimately, this research contributes to a better understanding of plasma technology's capabilities, paving the way for enhanced applications across various industries. Experimental data suggest that the plasma process significantly reduces contaminants and enhances the alloy’s wettability. Another study examined how plasma treatment can improve the adhesion of paint films by pre-treating Aluminum 2024 surfaces. To improve adhesive bonding on Aluminum 2024, further research demonstrated that atmospheric-pressure plasmas offer a viable alternative to acid treatments or abrasive techniques for preparing surfaces before bonding [18]. Exposure times for Aluminum 2024 surfaces differ based on the plasma-generating device; one study applied exposure times from 1 to 10 seconds at 330 [W] using a DCSBD system [21]. Another essential factor in plasma-based surface modification is the material-to-plasma distance, as seen in research where wood surfaces were exposed to plasma for 10 seconds with spacers to control the separation distance at 0.15 [mm], 0.45 [mm], and 1 [mm] [22]. Comparable studies using DCSBD plasma technology at 400 W applied exposure times from 5 to 60 seconds, under varying atmospheric gases such as O₂, CO₂, N₂, and Ar, with separation distances from 0.1 to 0.2 [mm] [23]. This work aims to investigate the potential of DCSBD plasma to treat flat materials, specifically Aluminum 2024 alloy and unvulcanized rubber compound (UnRB). The study seeks to compare plasma’s surface modification effects on shape-stable (AA2024) and shape-unstable (UnRB) flat materials. Prior studies have shown that adjusting the distance between the plasma source and the surface significantly impacts surface energy and cleanliness. Here, we focus on evaluating how distance influences the effectiveness of plasma surface modification on AA2024 and UnRB, aiming to determine the maximum distance at which effective surface modification can be achieved. Evidence of plasma efficacy includes a notable increase in surface energy and fluorescence changes, clear indicators of the plasma’s cleaning effect. Given that UnRB is less dimensionally stable than aluminum alloy, comparing these materials at varying distances from the plasma source offers fresh insights into how different surfaces respond to plasma treatment. The findings simulate conditions where materials are at various distances from the plasma-generating ceramic dielectric, providing deeper understanding of plasma’s cleaning and energy effects on different surface types.

Abstract: Metallic materials with poor plasticity are usually difficult to get effective surface strengthening. To solve this problem, an innovative surface deformation technology called magnetic-assisted ultrasonic nanocrystal surface modification (MA-UNSM), was used to process Ti64 alloy in this study. It has been demonstrated that MA-UNSM leads to higher hardness, deeper plastic deformation layer, and residual stresses with higher magnitude and greater depth compared with UNSM. Specifically, the external magnetic field increased the hardness from 427.6 HV for traditional UNSM to 493.8 HV for MA-UNSM and the surface compressive residual stress (CRS) from 641 MPa to 757 MPa. It is believed that by lowering the resistance between dislocations and pinning obstacles, the magnetic field enhances the plasticity of the material, and thus more effective surface hardening.

Abstract: In the article, the authors describe the WC coatings deposited by the High Power Impulse Magnetron Sputtering (HiPIMS) method. Industrial equipment was used to prepare the charges. A mixture of argon and krypton (Ar+Kr) gases was used as the working gas. Three coatings were deposited where the frequency was varied in the range from 1000 Hz to 2500 Hz. The thickness ranged from 2.8 µm to 6.8 µm was achieved. The thickness increased with the frequency of the coating process. The authors further evaluated mechanical properties such as roughness, hardness and Young's modulus and tribological properties such as coefficient of friction and wear. The measured properties were compared with the authors' published results in the articles of renowned scientific journals. The measured results compared with published results in scientific journals showed that the increase in frequency has an effect on the kinetic energy of the incident Ar+Kr ions. This causes a greater amount of dusted WC particles from the target, which results in a greater thickness of the deposited coating.

Abstract: Water or moisture contained in any form in hydraulic oil is not desirable in a hydraulic system. It can cause emulsification of the oil, which results in deterioration or rupture of the lubricating film, as well as corrosion of metal parts in this system. This corrosion can cause damage to metal parts and impair their functionality. Regular control of the amount of water in hydraulic oil is therefore a very important part of hydraulic oil diagnostics. The article presents a case study of monitoring the condition of hydraulic oil for water content values, which were determined according to the Karl Fischer method. The analysis of hydraulic oil in the article was also an experimental drop analysis for monitoring water in hydraulic oil, which we classify as a quick and simple chemical method aimed at indicatively demonstrating the presence of water in oil and the degree of oil contamination. This analysis belongs to non-dismantling technical diagnostics. Its greatest advantage is that with its help, oil analysis is faster and cheaper compared to analyses performed in laboratories.

Abstract: Advanced high-strength steels (AHSS) have their current applications directed mainly to the automotive industry, where they use modern metallurgical techniques to develop microstructures with retained austenite, which leads to an improvement in the combination of strength and ductility through transformation-induced-plasticity (TRIP). The main priority of the research work will be a detailed examination and optimization of the heat treatment parameters of medium-manganese steels, specifically by the Quenching and Partitioning (Q&P) method and the expansion of experimental data related to the increase of wear resistance of these materials. The issue of the application of medium-manganese high-strength AHSS steels in the field of tribology is currently very relevant. Mid-manganese AHSS steels, which show significant wear resistance, have the potential to replace traditional Hadfield Mn steels that contain 10-14 wt. % manganese. With the help of specifically designed heating and cooling cycles, it is possible to improve their wear resistance through metastable retained austenite, which has significant potential in demanding industrial environments. This scientific study examines the possibilities of increasing the economic efficiency of the production and use of AHSS steels in various industrial areas and at the same time reducing costs compared to expensive wear-resistant steels. A key aspect of the research is the experimental evaluation of heat treatment optimization to maximize resistance to mechanical damage and extend the life of materials in various applications.