Search Results (147)

Nodular Cast Iron (NCI, also known as ductile iron) is widely used in important components such as crankshafts for automotive engines and internal combustion engines, as well as storage and transportation containers for spent fuel in nuclear power plants, due to its good comprehensive mechanical properties such as strength, toughness, and wear resistance. The effect of temperature on the fracture behavior of NCI was investigated using compact tensile (CT) specimens at different temperatures. The results showed that the conditional fracture toughness parameter (K_Q) of the NCI specimens firstly increased and then decreased with decreasing temperature. The crack tip opening displacement δ_m shows a significant ductile–brittle transition behavior with the decreasing of temperature. δ_m remains constant in the upper plateau region but sharply decreases in the ductile–brittle region (−60 °C to −100 °C) and stabilizes at a smaller value in the lower plateau region. Multiscale fractographic analysis indicated that the fracture mechanism changed from ductile fracture (above −60 °C) to ductile–brittle mixed (−60 °C to −100 °C) and then to completely brittle fracture (below −100 °C). As the temperature decreased, the fracture characteristics changed from ductile dimples to dimple and cleavage mixed and then to brittle cleavage. 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

Recycled aluminum–silicon alloys provide significant environmental benefits by reducing the consumption of raw materials and lowering carbon emissions. However, their industrial application is limited by the presence of iron-based intermetallic compounds and the insufficient investigation in the literature regarding their effects on mechanical behavior. This study focuses on a recycled EN 42000 alloy, comprising 95% recycled aluminum, with a focus on the effect of its elevated iron content (0.447 wt%) on aging behavior and mechanical performance. Laboratory-scale specimens were produced through gravity die casting and subjected to T6 heat treatment, consisting of solution, quenching, and artificial aging from 160 °C to 190 °C for up to 8 h. To investigate overaging, analyses were conducted at 160 °C and 170 °C for durations up to 184 h. Tensile tests were conducted on specimens aged under the most promising conditions. Based on innovative quality indices and predictive modeling, aging at 160 °C for 4.5 h was identified as the optimal condition, providing a well-balanced combination of strength and ductility (YS = 258 MPa, UTS = 313 MPa, and e% = 3.9%). Mechanical behavior was also assessed through microstructural and fractographic analyses, highlighting the capability of EN 42000 to achieve properties suitable for high-performance automotive components. Full article

In this study, cavitation erosion tests were conducted to investigate the effects of the presence of coolant additives and chlorides on the corrosion and cavitation erosion of cylinder liners in marine diesel engines. Electrochemical experiments were conducted to evaluate the corrosion characteristics of ductile cast iron (DCI), and the corrosion potential and corrosion current density were measured. In addition, weight loss, surface roughness, and maximum surface damage depth were quantified as a function of cavitation exposure time. Furthermore, to investigate the erosion and erosion–corrosion characteristics induced by cavitation attack, the damaged surface morphology was closely examined using a scanning electron microscope (SEM) after the cavitation erosion tests. The results revealed that the coolant additive effectively protected the DCI from corrosion caused by aggressive chlorides. In particular, when an appropriate amount of additive was added to a coolant containing 100 ppm of chloride, the corrosion current density of DCI was reduced by approximately 31.7 times, significantly improving corrosion resistance. Therefore, different surface damage mechanisms corresponding to cavitation erosion and cavitation erosion–corrosion were identified depending on the presence or absence of the coolant additive during the cavitation erosion tests. Full article

This study aims to evaluate the corrosion behavior of ductile cast iron (FCD-500) under simulated marine engine operating conditions and to determine the optimal corrosion inhibitor conditions under chloride contamination. Experiments were conducted at 50 °C and 80 °C, with different Cl⁻ concentrations (0–500 ppm) and sodium nitrite (NaNO₂)-based inhibitor concentrations (0; 9000; 15,000; 17,000 ppm). Immersion and electrochemical tests were performed to analyze the microstructural corrosion characteristics and inhibitor efficiency. The results indicated that as the Cl⁻ concentration increased, proportionally higher levels of inhibitor were required to maintain surface stability. The maximum inhibition efficiency, approximately 97.3%, was achieved with an inhibitor concentration of 17,000 ppm, at a Cl⁻ concentration of 100 ppm. Full article

In this study, as-cast ductile iron was austempered to produce austempered ductile iron (ADI). A CrAlSiN film was then deposited on the surface of ADI specimens using the cathodic arc deposition (CAD) method. The gas flow ratio of Ar/N₂ varied (2, 2.5, and 3) under different processing parameters, designated as S1, S2, and S3, respectively. The composition, structure, hardness, adhesion, and wear resistance of the coated specimens were analyzed to evaluate the effect of the gas flow ratio on surface hardness and abrasion resistance. The experimental results indicated that CrN/Al(Si)N nano-multilayered films were successfully synthesized using oppositely positioned dual targets (Cr and AlSi) reacting with N₂ gas during the CAD process. The coatings significantly enhanced the surface hardness and wear resistance of ADI. A comparison of the three coating conditions with varying gas flow ratios revealed that as the Ar/N₂ gas flow ratio decreased (i.e., N₂ gas flow increased), the surface hardness of the coated ADI specimens increased while the abrasion rate decreased. Among the tested conditions, S1 exhibited the highest hardness (1479 HV_0.1) and the lowest wear rate (1.6 × 10⁻⁶ g/m). Full article

The development of high-strength cast irons with multiphase metal matrix structures is one of the new areas of modern materials science and mechanical engineering. This is so because of the high dissipative properties of such materials, which, in turn, ensure an improvement in their functional characteristics. It is known that one of the effective methods for obtaining alloys with a heterogeneous structure is a multi-stage heat treatment. Therefore, this study aimed to enhance the corrosion and friction properties of high-strength cast irons by combining different processing methods to create a bainite-martensitic matrix. High-strength cast irons with high ductility micro-alloyed with boron were chosen as the object for research. The experiments studied the effect of various types of multi-stage heat treatment on the structural features, tribological properties, hardness and corrosion resistance. The cast irons were quenched in water or liquid nitrogen after a controlled duration of isothermal exposure at different temperatures. It was established that cooling of isothermally hardened samples in liquid nitrogen makes it possible to effectively engineer the morphology and amount of the formed martensitic phase. It was observed that the high-strength cast irons with 10–15% lower bainite, residual austenite and martensite have the best frictional characteristics. This innovative method allowed the quenching of cast iron directly into liquid nitrogen without violent cracking. Full article

The HVOF (High Velocity Oxy-Fuel) thermal spraying method is widely used in surface engineering to produce coatings with high hardness, low porosity, and excellent crack resistance. Composite coatings with chromium carbide (Cr₃C₂) in a nickel–chromium (NiCr) matrix are commonly applied in demanding environments, such as the energy and transport sectors. This study compares the microstructure, mechanical, tribological, and corrosion properties of two coatings—Cr₃C₂-25(Ni20Cr)-10(Ni) and Cr₃C₂-25(Ni20Cr)—deposited on ductile cast iron using HVOF. The addition of 10 wt.% Ni enhances coating integrity, mechanical performance, and environmental resistance by improving ductility, reducing residual stress, enhancing wettability, and balancing hardness with improved crack, wear, and corrosion resistance. Microstructure analysis via LM (Light Microscopy) and SEM (Scanning Electron Microscopy), along with chemical and phase characterization using EDS (Energy Dispersive X-ray Spectroscopy) and XRD (X-ray Diffraction), revealed that the Ni-enriched Cr₃C₂-25(Ni20Cr)-10(Ni) coating exhibited a denser structure, lower porosity, and high hardness. Its microstructure consists of large, partially melted Ni particles and fine Cr₃C₂ and Cr₇C₃ carbides embedded in the NiCr matrix, some at submicron scales. Performance tests, including indentation (H_IT, E_IT, K_IC), scratch, and corrosion resistance assessments, confirmed that Ni addition improves crack resistance, wear durability, and corrosion protection. Consequently, these coatings demonstrate superior operational durability, making them more effective in challenging environments. 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

To address the failure issue of local wear in QT400-18 transition shafts used in high-speed trains, laser cladding remanufacturing of a ductile cast iron surface was carried out using 45 wt.%Fe + 55 wt.% Inconel625 powder. The phase composition, microhardness, interfacial bonding strength, and wear resistance of the cladding layer were analyzed. The results show that the cladding layer is primarily composed of a γ (Ni, Fe) solid solution and a small amount of eutectic carbides. The microstructure of the cladding layer forms columnar dendrites, cellular dendrites, and equiaxed crystals from bottom to top. The microstructure of the single-layer, single-pass interface consists of ferrite, acicular martensite, and ledeburite, while the multi-layer, multi-pass interface consists of ferrite, granular pearlite, and discontinuous ledeburite. The average microhardness of the single-layer, single-pass cladding layer is approximately 350 HV_0.5, and the hardness of the fine-grained and coarse-grained regions of the multi-layer, multi-pass cladding layer is approximately 330 HV_0.5 and 250 HV_0.5, respectively. The interfacial bonding strength reaches 96.5% of the base material strength. The wear mechanism of the cladding layer is mainly mild abrasive wear, with significantly better wear resistance than the base material. 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

The foundry industry is an industry with a large production of waste. One such type of waste is fine-grained to dust-like waste, depending on the stage of the foundry process in which it is generated. As part of this research, dust samples were collected from three Slovak foundries producing castings from gray iron, ductile iron, and steel. The aim of the experiments was to recycle iron from dust materials in the foundry process. Based on the chemical composition of the dust, samples with the highest iron content were selected and added to the charge of the electric induction furnace (EIF). Since it was not possible to add dust material directly into the EIF, the dust was modified by pelletizing and briquetting using three types of binders selected according to the foundries’ requirements. Pellets were prepared using dust from only one type of foundry waste and were used as part of the charge in the EIF. In the case of briquetting, different binder contents in the briquette mixture were tested to evaluate their effect on the strength and disintegration of the briquettes. Based on the foundries’ requirements that the binder had to be low-cost and that we had to not contaminate the melt (thus requiring a minimal amount), not affect the furnace operation, and not degrade the properties of the produced cast iron, briquettes with the best properties were selected and used as part of the charge for cast iron production. Samples of the cast iron produced this way were taken for chemical analysis, and specimens were prepared for tensile strength testing. The results showed that the use of briquettes, in limited amounts, did not have a negative impact on the chemical composition of the cast iron, the melting process, or its tensile strength. Full article

Based on actual service environment parameters, this experiment investigated the change in the corrosion rate of nodular cast iron (DCI) in an environment containing organic (triethanolamine phosphate, PTEA) and inorganic (hexametaphosphate, SHMP) inhibitors, and analyzed the effects of both inhibitors and the pH value of the solution on the corrosion behavior of DCI. Additionally, a variable flow rate device was used to conduct immersion tests, enabling the accurate evaluation of the materials’ corrosion resistance in an actual service environment. After a certain period, the corrosion of the DCI surface was observed, and the weight loss corrosion rate of the materials was calculated to analyze the differences in corrosion resistance under varying environmental parameters. It was found that the inhibitory effect of both inhibitors on DCI increased with the immersion time, and the inhibitory effect of the SHMP inhibitor was more pronounced under alkaline conditions. Based on the electrochemical and flow rate immersion test results, it can be concluded that, in the solution environment used in this experiment, the inhibitory effect of the SHMP inhibitor on DCI is stronger than that of the PTEA inhibitor. Full article

Cyclic failure problems in layered ductile iron are evident in a wide range of elements in transportation and mining equipment and depend on production technology and operating conditions. The aim of this study was to analyze the effect of residual stresses on the behavior of cyclic and static failure. The stress intensity factor, crack initiation, propagation patterns, static tension diagrams, and fracture behavior of compact tension (CT) specimens were determined. The samples used in this study were made from base cast iron, some of which were subjected to a special localized heat treatment. Experimental and analytical methods were used to conduct this study. The experiments were performed using original testing methods that adhered to the American Society for Testing and Materials (ASTM) regulations. The deformations of the partially heat-treated specimens due to residual stresses were determined using the grid method. The limiting stress intensity coefficient and the failure threshold under cyclic loading were determined in accordance with ASTM recommendations for various crack depths and openings. The results show that the heat treatment process readily produces residual stresses of different magnitudes, stress redistribution, different structures, and layer positions. Residual stresses affect the crack initiation and propagation. The stress intensity factor depends on the depth of the crack, the position of the layers, and the magnitude of the residual stresses. Full article

Among the materials used for components subjected to abrasive wear, chromium cast iron, hardfaced layers, martensitic steels and Hadfield steel should be singled out. Each of these types of materials exhibits a different morphology of structure and strength properties. Hadfield steel, characterized by an austenitic microstructure, shows the ability to strengthen the subsurface layers by cold work, while maintaining a ductile core. Hardox steels belong to the group of low-alloy martensitic boron steels. However, it should be noted that increasing hardness does not always translate into low wear values due to a change in the nature of wear. In view of the above, the authors decided to subject selected Hardox steels and Hadfield cast steels in the post-operational condition to abrasive wear tests in the presence of loose abrasive. The study showed that Hardox Extreme steel exhibits the highest resistance to abrasive wear (value of the coefficient k_b is equal to 1.39). In the case of Hadfield steel, the recorded values are slightly lower (k_b = 1.32 and 1.33), while the above ratios remain higher compared to Hardox 600 and Hardox 500 steels. The main wear mechanism of high-manganese steels is microploughing, plastic deformation and breakouts of larger fragments of material. In the case of Hardox 450 and Hardox 500 steels, the predominant wear mechanisms are microploughing and breaking out of material fragments. As the hardness of the steel increases, the proportion of wear by microcutting and scratching predominates. Full article