Search Results (157)

Thermal analysis (TA) has been a valuable tool for controlling the carbon equivalent (CE) of cast irons. Additionally, this technique can provide enhanced control over melt quality, allowing for the avoidance of defects such as undesirable graphite morphology and the formation of carbides. To obtain the most valuable information from the TA, it is necessary to minimize the variations in the filling operation of the TA cups. However, the mass and pouring temperature of TA cups can vary in TA’s typical foundry operations. A design of experiments was performed to determine whether specific parameters of cooling curves used for quality control can distinguish the inoculation effect in the melt when the mass and the pouring temperature of TA cups are varied. The minimum temperature of the eutectic arrest proved to be a robust inoculation potential control parameter when variations in the cup’s mass were within a range of 268–390 g and were filled at any pouring temperature between 1235 and 1369 °C. Lighter cups under 268 g and poured at a low temperature are not suitable for controlling inoculation potential by TA; however, they remain helpful in controlling CE. These later cups are related to cooling times of less than 180 s, which can serve as a criterion for discarding unsuitable samples. A bimodal population of cell surfaces was revealed in the samples, with the population of small cells being proportionally more numerous in samples with lower TE_min values. Full article

Nodular cast iron is one of the most widely used materials in the machine building industry. The main reasons for this are its strength, elongation, and competitive price compared to other steels and metals. The possibility to have a high strength and elongation together is thanks to the spheroidal shape of the graphite inserts in the metal structure of the iron. To exploit these advantages, special treatments such as adding magnesium are used after the melting process but before pouring the metal in the casting mold. Classic technology is called tundish/sandwich technology when ferrosiliconmagnesium alloy in bulk is placed at the bottom of a ladle before filling it with liquid cast iron. In the present article, an alternative technology will be presented where a fesimg alloy is filled in a steel wire and inserted automatically into a ladle. The advantages of this technology will be described in detail. Full article

Laser surface treatment (LST) has been employed on ductile cast iron (DCI) parts to obtain a good performance and a long service life. There is a need to understand the laser surface-treated microstructure and hardening ability of DCIs with different matrix structures to facilitate the scientific selection of DCI for specific applications. In this study, a Laserline-LDF3000 fiber-coupled semiconductor laser with a rectangular spot was used to harden the surface of ductile cast irons (DCIs) with different pearlite contents. The hardened surface layer having been solid state transformed (SST) and with or without being melted–solidified (MS) was obtained under various process parameters. The microstructure, hardened layer depth, hardness and hardening ability were analyzed and compared as functions of pearlite contents and laser processing parameters. The results show that the MS layers on the DCIs with varied pearlite contents have similar microstructures consisting of fine transformed ledeburite, martensite and residual austenite. The microstructure of the SST layer includes martensite, residual austenite and ferrite, whose contents vary with the pearlite content of DCI. In the pearlite DCI, martensite and residual austenite are found, while in ferrite DCI, there is only a small amount of martensite around the graphite nodule, with a large amount of unaltered ferrite remaining. There exists no significant difference in the hardness of MS layers among DCIs with different pearlite contents. Within the SST layer, the variation in the hardness value in the pearlite DCI is relatively small, but it gradually decreases along the depth in the ferrite DCI. In the transition region between the SST layer and the base metal (BM), there is a steep decrease in hardness in the pearlite DCI, but it decreases gently in the ferrite DCI. The depth of the hardened layer increases slightly with the increase in the pearlite content in the DCI; however, the effective hardened depth and the hardening ability increase significantly. When the pearlite content of DCI increases from 10% to 95%, its hardening ability increases by 1.1 times. Full article

Metallographic evaluation of nodular cast iron is crucial for quality control in the foundry industry. Traditionally, this process relies on experts who visually interpret microscopic images. This study introduces HawkEye, a comprehensive software solution that automates metallographic analysis using advanced computer vision and deep learning models. Specifically, HawkEye software dynamically adapts its processing workflow based on the input image and its typological classification. The software supports both etched and non-etched specimens and automates the segmentation and classification of graphite nodules, gathering their morphological descriptors; it identifies microstructural phases and provides a global quality assessment. All these functions are embedded into a user-friendly interface designed for both laboratory and industrial use. Nevertheless, the key contribution of this work is the replacement of subjective evaluation with a reproducible, AI-driven approach, which significantly enhances the objectivity, traceability, and scalability of metallurgical analysis. In fact, the proposed approach achieves 99% accuracy in nodule classification compared to manual expert assessment, reduces manual image processing steps, and introduces a novel method for ferrite/perlite measurement in combination with carbide detection using YOLO and SAM models. Full article

The significance of the matrix morphology of vermicular cast iron for the alloy’s thermal shock resistance was determined. The study included vermicular cast iron subjected to heat treatment in order to obtain an ausferritic matrix. Heat treatment involved austenitization at 960 °C for 90 min, followed by two different austempering variants at 290 °C and 390 °C, each for 90 min. Austempering at 390 °C resulted in a higher content of retained austenite compared to austempering at 290 °C. A test stand was used to determine thermal shock resistance, enabling repeated heating and cooling of the samples. The samples were heated inductively and subsequently cooled in water at a constant temperature of approximately 30 °C. The total length of cracks formed on the wedge-shaped surfaces of the tested samples was adopted as a characteristic value inversely proportional to the material’s thermal shock resistance. The samples heated to 500 °C were subjected to 2000 heating–cooling test cycles. It was found that in as-cast iron, structural changes were minor, whereas in the heat-treated material, changes in the structure were more noticeable. Under the influence of thermal shocks, ausferrite transforms into ferrite with carbides. Among the analyzed materials, the most resistant cast iron was the one austempered at 290 °C. Oxide precipitates were observed near cracks and graphite regions. Full article

This work investigated changes in the microstructure and local mechanical properties after the application of selected heat treatments to EN-GJL-300 grey cast iron. The main goal was to optimize heat treatment to achieve increased mechanical properties and subsequently wear resistance. The heat and heat–mechanical treatment were investigated by using a dilatometer as a physical simulator of treatment on real samples. Continuous cooling with three different rates and two other non-continuous treatments (austempering and ausforming) were used to treat the experimental samples. The research was focused on modification of the matrix microstructure, initially pearlitic. No change in the shape or morphology of the graphitic lamellae was required to preserve the damping properties. The results showed that, in terms of the specified conditions, heat treatment with continuous cooling at a rate of 10 °C s⁻¹ appeared to be optimal. This variant showed the presence of bainite and martensite in the microstructure with high hardness measured by nanoindentation as well as the optimal value of general Brinell hardness. Full article

This paper presents an experimental study of uniform and variable texture patterns on a honed EN-GJS 400-15 spheroidal graphite cast iron surface. Textured samples were fabricated using a CNC electrochemical jet machining technique and tested against a 52100 G5 roller countersurface featuring a rectangular 1 mm × 13 mm contact area. Tribological tests were conducted in a fully flooded PAO4 lubricant bath at 30 °C on a TE-77 reciprocating sliding tribometer with a 25 mm stroke length. Frictional behaviour was assessed at test frequencies from 12 to 18 Hz under two loads, 11 N and 50 N, covering mixed and hydrodynamic lubrication regimes. Experimental results demonstrated that EJM textured surfaces were accurately fabricated within a ±2.50 µm standard error in depth, with chemical etching effects reducing the $R_q$ roughness of initial grinding marks by 0.223 µm. Textured surfaces exhibited a more pronounced friction performance at 50 N than at 11 N, exhibiting a consistent friction reduction of up to 18.8% compared to the untextured surface. The variable textured surface outperformed the uniform textured surface under the mixed lubrication regime due to the enhanced secondary lubrication effect. Optical and SEM analyses revealed that textured surfaces reduced plastic deformation and two-body abrasion. Full article

With the global shift in energy structure and the advancement of the “double carbon” strategy, methanol has gained attention as a clean low-carbon fuel in the engine sector. However, the corrosion–wear coupling failure caused by acidic byproducts, such as methanoic acid and formaldehyde, generated during combustion severely limits the durability of methanol engines. In this study, we employed a systematic approach combining the construction of a corrosion liquid concentration gradient experiment with a full-load and full-speed bench test to elucidate the synergistic corrosion–wear mechanism of core friction pairs (cylinder liner, piston, and piston ring) in methanol-fueled engines. The experiment employed corrosion-resistant gray cast iron (CRGCI), high chromium cast iron (HCCI), and nodular cast iron (NCI) cylinder liners, along with F38MnVS steel and ZL109 aluminum alloy pistons. Piston rings with DLC, PVD, and CKS coatings were also tested. Corrosion kinetic analysis was conducted in a formaldehyde/methanoic acid gradient corrosion solution, with a concentration range of 0.5–2.5% for formaldehyde and 0.01–0.10% for methanoic acid, simulating the combustion products of methanol. The results showed that the corrosion depth of CRGCI was the lowest in low-concentration corrosion solutions, measuring 0.042 and 0.055 μm. The presence of microalloyed Cr/Sn/Cu within its pearlite matrix, along with the directional distribution of flake graphite, effectively inhibited the micro-cell effect. In high-concentration corrosion solutions (#3), HCCI reduced the corrosion depth by 60.7%, resulting in a measurement of 0.232 μm, attributed to the dynamic reconstruction of the Cr₂O₃-Fe₂O₃ composite passive film. Conversely, galvanic action between spherical graphite and the surrounding matrix caused significant corrosion in NCI, with a depth reaching 1.241 μm. The DLC piston coating obstructed the permeation pathway of formate ions due to its amorphous carbon structure. In corrosion solution #3, the recorded weight loss was 0.982 mg, which accounted for only 11.7% of the weight loss observed with the CKS piston coating. Following a 1500 h bench test, the combination of the HCCI cylinder liner and DLC-coated piston ring significantly reduced the wear depth. The average wear amounts at the top and bottom dead centers were 5.537 and 1.337 μm, respectively, representing a reduction of 67.7% compared with CRGCI, where the wear amounts were 17.152 and 4.244 μm. This research confirmed that the HCCI ferrite–Cr carbide matrix eliminated electrochemical heterogeneity, while the DLC piston coating inhibited abrasive wear. Together, these components reduced the wear amount at the top dead center on the push side by 80.1%. Furthermore, mismatches between the thermal expansion coefficients of the F38MnVS steel piston (12–14 × 10⁻⁶/°C) and gray cast iron (11 × 10⁻⁶/°C) resulted in a tolerance exceeding 0.105 mm in the cylinder fitting gap after 3500 h of testing. Notably, the combination of a HCCI matrix and DLC coating successfully maintained the gap within the required range of 50–95 μm. Full article

This study enhanced the performance of gray cast iron through the precise control of the partial austenitizing temperature combined with an isothermal quenching process. The study investigated the effects of three austenitizing temperatures, namely 810 °C, 850 °C, and 900 °C, on the microstructure and mechanical properties of gray cast iron. With the increase in austenitizing temperature, the transformation of pearlite to ausferrite was promoted, and the ausferrite content increased from 8.0% at 810 °C to 91.2% at 900 °C. Mechanical property tests showed that the specimen treated at 850 °C had the best comprehensive performance. Its tensile strength reached 332 MPa, an increase of 78.6% compared with the as-cast state. The elongation increased by 51.8%, and the wear depth under a 20 N load decreased from 250 μm to 2 μm. Specimens with a high ausferrite content exhibited stable low-friction characteristics due to the uniform hardness and the suppression of adhesive wear. However, an excessively high austenitizing temperature of 900 °C would lead to an increase in residual stress in the casting and deformation of the graphite structure, reducing the wear resistance. Under the established austenitizing temperature conditions, this study explored the relevant mechanisms for the performance improvement of gray cast iron by means of various testing methods, providing a theoretical basis and process reference for optimizing the material performance of explosion-proof equipment under harsh mining conditions. Full article

This research presents an innovative method for revisiting heterogeneous nucleation in the formation of spheroidal graphite during the production of ductile cast iron. This study incorporates controlled melting at a temperature of 1200 °C, followed by a rapid cooling process, to increase the likelihood of revealing and subsequently observing the graphite nuclei. Given the slow dissolution rate of spheroidal graphite, this sequence produces finer graphite nodules associated with residual graphite that has partially dissolved. Furthermore, the investigation explores diverse configurations of treatment agents to reexamine their effects during the nucleation of nodular graphite. The findings revealed that the graphite nucleus comprised oxides, sulfides, carbides, nitrides, and carbo-nitrides, confirming the reliability of the approach considered in this study. Additionally, the research highlights the crucial role of magnesium in the nucleation of nodular graphite structures. Several mechanisms are expected to be used in conjunction with distinct treatment agents. It involves segregation and solubility dynamics, desulfurization and deoxidation, and inclusions as heterogeneous nucleation sites. Full article

Lamellar graphite pearlitic grey cast irons are frequently used in the manufacturing of components that operate under cavitation erosion conditions. Their poor performance regarding cavitation erosion limits their use in intense cavitation environments. The physical modification of the surface layer offers a flexible and cost-effective way to combat cavitation attacks without altering the core properties. This paper comparatively analyzes the effects of four technological processing methods on the cavitation erosion resistance of grey cast irons. Cavitation erosion tests were conducted on a vibrating device with piezoceramic crystals in accordance with the ASTM G32-2016 standard. Surface hardness tests were carried out using a Vickers hardness tester, while roughness measurements were performed using a Mitutoyo device. The microstructures generated by the applied technologies and the surface wear mechanisms were analyzed using optical microscopy and scanning electron microscopy (SEM). The results indicated that the TIG local surface remelting process provides the most significant improvement in cavitation erosion resistance. Full article

High-temperature-resistant materials, such as stainless steel and cast steel, are widely used in industrial applications. While cast steel has a lower casting ability, cast iron demonstrates a superior casting performance but suffers from structural instability in thin sections, in which its phase structure tends to shift from graphite to cementite. This limits its applicability in thin-walled components. This study aims to characterize thin-walled ductile cast iron with improved high-temperature resistance. The focus is on evaluating the effects of Fe-Mg inoculation with the addition of nickel on the microstructure and mechanical properties of the material. Gray cast iron was cast and inoculated with Fe-Mg and nickel. Mold designs incorporated thickness variations of two, three, four, and five mm. Chemical composition testing was performed in the liquid state using a CE meter and in the solid state using a spectrometer, following ASTM A536 standards for ductile cast iron. A microstructural analysis was conducted using a scanning electron microscope (SEM) JEOL JSM-IT500 SEM (JEOL Ltd., Tokyo, Japan), and hardness was measured using the Vickers method. The results demonstrated that Fe-Mg inoculation with the nickel addition improved the microstructure and hardness of the thin-walled ductile cast iron. These enhancements contribute to increased high-temperature resistance and structural integrity, providing significant benefits for industrial casting processes. The findings have implications for improving the quality of small and medium industry (SMI) products, including the development of advanced metal molds. Full article

Metal matrix composites (MMCs) produced through the unique liquid pressing infiltration (LPI) process exhibit significant industrial potential. In this study, TiC/FC250 metal matrix composites were fabricated using the liquid pressing infiltration process, and the effects of austempering and quenching–tempering heat treatments on the microstructure and wear characteristics were investigated in comparison to as-cast specimens of both the FC250 gray cast iron matrix material and the TiC/FC250 metal matrix composites without heat treatment. The results indicated that the quenching–tempering heat treatment effectively enhanced the dry sliding friction and wear characteristics compared to the as-cast condition. The heat-treated specimens, under optimal conditions, demonstrated superior properties compared to other heat treatments and the matrix material. Although the metal matrix composites were successfully produced via the liquid pressing infiltration process and optimal heat treatment, some graphite morphology transformed from a flake to a spherical shape due to the high temperature and slow cooling rate during the process. With the quenching–tempering heat treatment, the wear resistance increased by approximately 41.53% in the matrix material and by 53.38% in the metal matrix composites compared to the as-cast specimens. The TiC/FC250 metal matrix composite heat-treated under optimal conditions exhibited an approximate 58.28% reduction in the friction coefficient compared to the FC250 gray cast iron. Full article

The electrochemical corrosion of a single-suction centrifugal water pump impeller made of gray cast iron operating at 85 °C was investigated in two industrial water media, i.e., groundwater extracted from a borehole and treated wastewater. Open circuit potential (OCP) measurement plus potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques elucidated the electrochemical corrosion performance and inductively coupled plasma-optical emission spectroscopy (ICP-OES) characterized the water samples. The retired and brand-new impellers were studied using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and visual and metallographic examinations. Impeller trailing edges were vulnerable to corrosion damage due to increased total fluid pressure, velocity, and temperature. The groundwater was more contaminated with Ca, Mg, Na, Si, and S elements and possessed higher conductivity, pH, and suspended solids than the treated wastewater. The impeller was more susceptible to graphitic corrosion in the groundwater due to emerging microgalvanic cells. A kinetic control electrochemical mechanism was elucidated as the corrosion rate-controlling step in the wastewater. A mixed kinetic and diffusion control mechanism was predominant in the groundwater because a short Warburg impedance element emerged. This study showcased the significance of integrated industrial water management and treatment strategies to protect pumps’ integrity and uptime in critical industrial units implementing a zero-liquid discharge program. Full article

This paper presents possible modifications to the properties of grey cast iron by laser heat treatment. These modifications are analyzed especially with regard to wear properties as a result of graphite content, which is a well-known solid lubricant. Examples of applications of grey cast iron in cases where good wear resistance is required are presented. Laser hardening from the solid state, laser remelting, and laser alloying are characterized. In this study, changes in the surface layer caused by these treatments were analyzed (especially the influence on the microstructure—including graphite content—and wear properties). It was shown that all of these treatments enable the wear resistance of the surface layer to be enhanced, mostly due to the increase in the hardness and microstructure homogeneity. It was also proven that it is possible to retain the graphite phase (at least partially) in the modified surface layer, which is crucial in the case of friction wear resistance. In particular, laser hardening from the solid state does not eliminate graphite. Laser remelting and alloying cause the dilution of carbon from the graphite phase to the melted metal matrix, but, in the case of nodular cast iron, it is possible that not all of the valuable graphite in the surface layer is lost. Full article