Gray Iron Research Articles

Fatigue failure analysis of grey cast iron water pipes accounting for fatigue strength variation

Fatigue cracking is thought to be a critical failure mode for Grey Cast Iron (GCI) water pipes; however, this failure mechanism is poorly understood. Using a novel approach to sourcing GCI pipe material for testing, the variation in fatigue strength between pipes from the same batch was experimentally quantified. These results were used to assess the impact of fatigue strength variation on a hypothetical but realistic GCI water pipe years-to-failure scenario. Full-pipe sections were used during fatigue testing and the observed failure mode gave physical meaning to the years-to-fatigue-failure predictions for the first time. The accumulation of fatigue damage was predicted to represent a terminal and very small part of a GCI pipe’s life, so the loads applied to a GCI pipe early in its life are likely to have a limited impact on its remaining life and so do not need to be included in predictive modelling. For the scenario considered here, the predicted variation in lifetime was an 8.6-year range about an average of 59.4 years. GCI pipes in the UK are all > 50 years old, so this is a significant variation for asset and investment planners to account for as these pipes approach the end of their lives.

Tribological properties under dry and lubricated sliding conditions of TiSiN and AlTiCrN coatings deposited on gray cast iron

In internal combustion engines, the majority of friction losses and wear occur between the cylinder liners and piston rings. Hard coatings applied to cylinder liners can increase the efficiency of internal combustion engines by improving tribological properties. The gray cast iron cylinder liner was coated with TiSiN and AlTiCrN employing the cathodic arc deposition process. The coatings were examined using nanoindentation tests, scratch tests, an optical profilometer, a scanning electron microscope, an X-ray diffractometer, and energy dispersive analysis to assess their hardness, adhesion, and structural characteristics. The reciprocating test was carried out to assess the coatings' wear and friction characteristics under lubricated and dry sliding with a ball at varying normal loads. The hardness of the TiSiN and AlTiCrN coatings was 45 GPa and 18 GPa, respectively. The cohesion strength, adhesion strength, and crack propagation resistance of AlTiCrN coating were approximately 2, 1.3 and 2.5 times higher than those of TiSiN coating, respectively. Both coatings exhibited remarkable wear performance at high normal loads. Under dry sliding conditions at 25 N normal load, the wear rate of AlTiCrN and TiSiN coatings were nearly 33 and 20 times, respectively, lower than the uncoated substrate. Under dry sliding conditions, the TiSiN coating exhibited the lowest wear rate at low normal loads (5 N and 15 N), while the AlTiCrN coating performed best at high normal loads (25 N). In lubricated sliding conditions, the AlTiCrN coating consistently showed the lowest wear rate across all normal loads.

Origin and evolution of soil materials of the Paleo-Chadian linear-dune landscape in the Far North Region of Cameroon

The mineralogy and micromorphology of associated red Arenosols and both yellow and grey Gleysols of the Paleo-Chadian linear-dune landscape of the Far North Region of Cameroon were studied in order to obtain information about depositional environments and pedogenic processes. Differences between the red soils and both others include a significant difference in clay content, which is much higher in the grey and yellow soils. The composition of the clay fraction is also different, with kaolinite and illite as main mineral phases in the red soils, whereas smectite is strongly predominant in the grey soils and a major phase in the yellow soils. Mössbauer spectroscopy analysis reveals a predominance of hematite as iron oxide mineral in the red soils, in contrast to goethite-predominance in the yellow soils. Thin section observations reveal poor sorting of the coarse fraction, differences in feldspar content, and an absence of reworked clay aggregates, as well as the presence of pore-related carbonate features in the grey soils and iron oxide nodules in the grey and yellow soils. The obtained results indicate that the red soils are derived from a different parent material than the other soils. The grey soils developed on flood-related fluvial deposits in interdune depressions, whereas the red soils formed on aeolian sands and the yellow soils show a mixed origin. In the interdune depressions, hydromorphic conditions led to iron reduction and pedogenic carbonate enrichment.

Tribology and airborne particle emissions from grey cast iron and WC reinforced laser cladded brake discs

Laser cladding (LC) is a promising technique to overlay a protective coating on grey cast iron (GCI) brake discs to enhance the wear and corrosion resistance. This study utilized a pin-on-disc tribometer in an aerosol chamber to investigate the tribology and airborne particle emissions from tungsten carbides (WC) reinforced coating overlayed onto GCI substrate through laser cladding. Uncoated GCI brake discs served as reference material, while low-metallic (LM) and non-asbestos organic (NAO) brake pads were used as counterparts. The results indicate that LC coating exhibited slightly higher coefficient of friction and significantly lower wear than uncoated GCI discs. Abrasive wear is the dominant wear mechanism for both uncoated GCI brake discs and LC coatings. LC coatings substantially decreased the particle mass concentrations. All three friction pairs displayed a mass weighted size distribution with a major peak around 2–3 μm. The number size distribution was dominated by a mode below 1 μm. Emissions by number were generally low. Meanwhile, all three friction pairs emitted sheared off and agglomerated particles, with iron being the dominant element. Tungsten was identified in the particles emitted from LC coatings, indicating that the hard coating has a potential to wear off and become airborne particles.

Enhancing Tribological Performance of Gray Cast Iron by Laser Surface Texturing of Micro-grooves and Micro-crosshatches

Enhancing Tribological Performance of Gray Cast Iron by Laser Surface Texturing of Micro-grooves and Micro-crosshatches

Influence of Casting Materials on the Microstructure and Mechanical Properties of Gray Cast Iron for Cylinder Liners

Influence of Casting Materials on the Microstructure and Mechanical Properties of Gray Cast Iron for Cylinder Liners

Casting Production in Poland Versus European Trends in 21st Century

This article presents changes of the total casting production volumes and of the production of castings made from basic casting alloys in Poland, in Europe and worldwide in years 2001–2021. Analogous casting production parameters were compared for Poland, Europe and countries being the leading European and global manufacturers in years 2001, 2011 and 2021. The leading casting manufacturers in Europe (with the manufacturing volume exceeding 1 million tons in the mentioned years) include Germany, Italy, the Ukraine, France and Spain. For years, the largest casting manufacturer worldwide has been China. In 2001–2021, global casting production increased from ca. 68 million tons to ca. 97 million tons (i.e. by ca. 42%), whereas the European one decreased from ca. 17 million tons to ca. 12 million tons (i.e. by close to 30%). In the analyzed period, the Polish production volume grew from ca. 0.75 million tons to ca. 0.88 million tons (i.e. by ca. 17%). The presented data reveal the decreasing importance of gray cast iron and cast steel and the increasing one of ductile cast iron and aluminum alloys. However, the Polish average annual growth rate for aluminum alloy casting production was 10.3%, whereas the global one was 3% and the European one 0.7%.

Enhanced tribological performance of MoS2 and hBN-based composite friction materials: Design of tribo-pair for automotive brake pad-disc systems

This research comprehensively analyzes the friction and wear behavior of composite friction materials when dry sliding against grey cast iron and laser-clad nickel-based (LC1) and iron-based (LC2) alloy discs. The composite friction materials (P1, P2, P3, P4, P5, and P6) under investigation contain graphite, MoS2, and hBN-based solid lubricant synthesized through the powder metallurgy technique. Tribological tests were conducted using a pin-on-disc configuration to simulate the dynamic interaction between the composite materials and the laser-clad grey cast iron discs. The tests were performed at a 60 N load, 6283.19 m sliding distance, and 2.094 m/s sliding velocity under dry sliding conditions. The results provide valuable insights into the effectiveness of MoS2 and hBN-based solid lubricant composites in reducing friction and wear when in contact with iron and nickel alloy-based laser-clad grey cast iron surfaces. The study elucidates the mechanisms governing tribological behavior, including the formation of friction plateaus and the role of laser-clad counter-discs in reducing wear. The specific wear rate of the nickel-based laser-clad counter disc (LC1) and iron-based laser-clad (LC2) system improved by 63.76 % and 48.32 %, respectively, compared to the conventional grey cast iron disc system when using the hBN-based pin (P6). Additionally, the specific wear rate of the hBN-based pin was 38.49 % lower than the conventional graphite-based pin when sliding against the grey cast iron counter-disc. Artificial Neural Network (ANN) was used to validate the wear rate of the best-performing tribological pair, namely the hBN-based pin (P6) and LC2 counter discs, through supervised learning.

Compound Castings for the Coke Industry.

In this paper, issues related to the technology of compound castings composed of two parts, i.e., the working layer and the supporting part, made of X46Cr13 high-chromium steel and EN-GJL-HB 255 grey cast iron, respectively, in a liquid-solid system by pre-installing a monolithic insert in the mould cavity are presented. As a part of the research, the mechanism of formation of transitional zones in the bonding area of the above-mentioned two alloys was identified and described. It was shown that the phenomenon that determines the formation of a permanent bond between the joined materials is the transport of C and heat from the "high-carbon and hot" material of the supporting part poured into the mould in the form of liquid cast iron to the "low-carbon and cold" material of the working layer placed in the form of a steel monolithic insert inside the mould cavity. In the paper, the suitability of the compound castings technology developed for use in the coke industry is also presented. Full-size high-chromium steel-grey cast iron compound casting plates designed for the coke quenching car lining were positively verified in real coke plant operating conditions.

Design and Control of the Natural Frequency of Brake Discs in the Aspect of the Gray Cast Iron Production Process.

The results of research on the influence of the chemical composition of cast iron and its potential changes in the production cycle on the elastic properties and the correctness of numerical simulations of the natural frequency of ventilated brake discs are presented. The tests were carried out for three grades of gray cast iron with flake graphite with a eutectic saturation coefficient ranging from 0.88 to 1.01. A quantitative metallographic assessment of the pearlitic cast iron matrix and graphite precipitates was carried out, and the hardness and compressive/tensile strength of individual cast iron grades were determined, taking into account the limit contents of the alloying elements. Next, ultrasonic tests were performed, and the elastic properties of cast iron were determined. Based on the obtained data, a numerical modal analysis of brake discs was performed, the results of which were compared with the actual values of an FRF frequency analysis. The error of the computer simulations was estimated at approx. 1%, and it was found that the accuracy of the calculations of the first natural frequency did not depend on the dimensions (size) of the discs and the chemical composition of the cast iron from which they were cast. The functional relationships between the chemical composition of cast iron, its strength and elasticity and the first natural frequency of the disc vibrations were determined, and a database of the material parameters of the produced cast iron grades was developed. An implementation example showed the validation of the brake disc design with natural frequency prediction and demonstrated a high convergence of the experimental results with the simulated values. Using I-MR control cards, both the effectiveness of designing and predicting the natural vibrations of brake discs based on the implemented material database as well as the stability of the gray cast iron production and disc casting processes were confirmed.

Дослідження впливу параметрів процесу хонінгування силікатними брусками на якість обробленої поверхні

Numerous studies have shown that the kinematics of the honing process, which determines the trajectory of the cutting grain during machining, has a major impact on the parameters of macro- and microrelief. The complex working movement during honing of holes creates favourable conditions for the fuller use of the cutting capacity of the bars and uniform wear of the tool, which positively affects the machining performance and accuracy of the geometric shape of the surface. It is shown that, in this regard, there is a need to investigate the influence of the parameters of the honing process with silicate bars on the quality of the machined surface. The paper presents the results of a study of the effect of the contact pressure of the bars and the axial and circumferential speeds on the quality of the treated surface. The study was performed on a vertical single-spindle honing machine. The samples used were cylinder liners of car engines made of grey alloy cast iron. The evaluation was based on the roughness of the machined surface and the mass removal of metal during machining. The best performance was achieved by those bars that resulted in the lowest roughness of the samples. It was found that with an increase in the circumferential speed, the surface quality improves, and with an increase in the axial speed, it deteriorates after processing with diamond, abrasive and silicate stones. With an increase in the contact pressure of the bars, the surface quality deteriorates after machining with diamond bars and improves after machining with abrasive and silicate bars. It has been proven that the high surface quality after treatment with silicate blocks is due to the formation of amorphous silica during honing, which, under the influence of abrasive grains, falls into the cavities of the treated surface and adheres to the surface, thus saturating the treated surface with silicon oxide. It has been established that with an increase in the axial speed of the bars, metal removal increases, and with an increase in the circumferential speed, it decreases after machining with diamond, abrasive and silicate bars. With an increase in the contact pressure of the stones, metal removal increases after machining with diamond stones and gradually decreases after honing with abrasive and silicate stones. It was found that the metal removal after machining with silicate stones is 2 times less than after honing with diamond stones. It is proposed to set the allowance for finishing honing with silicate stones for cylinder liners made of alloy cast iron (HB 240) within 0.01-0.02 mm.

Microstructure, mechanical and electrochemical behavior of magnetron-sputtered carbothermic reduced iron-boride ceramic coatings

In this study, magnetron sputtered carbothermic reduced iron boride (FeB) coatings were developed on grey cast iron (GCI) substrates at different substrate temperatures. The impact of substrate temperature on structural, mechanical, and corrosion behavior was examined for two FeB deposition scenarios: FeB coatings deposited at room temperature (RT) and at 500 °C substrate temperature. The evolution of phases and microstructure was studied using XRD and FESEM, respectively. The mechanical properties, creep, deformation behavior, and adhesion strength (scratch test) of the deposited coatings were investigated using nanoindentation at ambient temperature. The highest hardness and Young’s modulus of 16 GPa and 231 GPa respectively, were achieved at 500 °C due to microstructural enhancement. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of the coatings. The results show that substrate temperature strongly influences the surface morphology of the coatings, which in turn governs the mechanical and corrosion behavior of the FeB coating. The FeB-coated GCI at 500 °C substrate temperature showed higher resistance to scratching, better mechanical properties, and improved corrosion resistance which is attributed to the enhanced adhesive strength, refined microstructure, and formation of protective oxide layers of FeB on the surface of the coatings.

Composition and Structure of Surface Layer in Composite Castings from Gray Cast Iron Formed Using Chromium-Ferroboron Master Alloys

Composition and Structure of Surface Layer in Composite Castings from Gray Cast Iron Formed Using Chromium-Ferroboron Master Alloys

Improving tension fatigue performance of gray cast iron by LSPwC-induced gradient structure and carbon diffusion

HT250 Gray cast iron (GCI) commonly utilized in diesel engine cylinders, is susceptible to fatigue failure under alternating stress conditions. To address this issue, the investigation involved the application of laser shock peening without coating (LSPwC) on HT250 GCI to assess its impact on the high cycle tension fatigue properties of the material. Both experimental and simulation methodologies were employed to analyze the effects of LSPwC on residual stress, microhardness, and microstructure in HT250 GCI. The LSPwC resulted in a substantial 29% enhancement in the high cycle tension fatigue limit of the HT250 GCI, which is attributed to a synergistic combination of factors induced by LSPwC, including high-amplitude compressive residual stresses, elevated microhardness, grain refinement, and carbon diffusion. This study contributes valuable insights into the reinforcement of complex cast components.

The phenomenon of thermodiffusion in liquid and solid metals in the works of O. M. Skrebtsov

The year 2024 marks the 100th anniversary of a world-renowned scientist, our countryman, Professor Olexandr Mikhailovich Skrebtsov. In addition to research on the use of radioactive isotopes in metallurgy and the development of the theory of the liquid state of metal melts, he paid considerable attention to the phenomenon of thermodiffusion in liquid and solid metals. This paper is devoted to the analysis of this part of the scientific heritage of O. M. Skrebtsov. The movement of atoms under the action of a temperature gradient (thermodiffusion) occurs during various natural phenomena and in many technological processes. However, when studying the driving forces and mechanisms of thermodiffusion, as a rule, the academic approach prevailed. This allowed the theory of thermodiffusion to be well enough developed concerning gases, salt solutions, and solid metals. This article is focused on the analysis of research aimed at the possibility of practical use of this phenomenon to improve the service life of parts operating under conditions of a temperature gradient and optimize processes occurring with a temperature gradient. Such processes occur in metallurgical units, accompanying bimetallic casting, welding, surfacing, etc. Based on the analysis of the experimental data available in the literature, a relationship between the heat of thermodiffusion and the ratio of the atomic radii of the diffusing elements, Rd, and the base metal, Rb, was found. The fundamental possibility of using thermodiffusion for controlling the desulfurization processes in liquid cast iron and creating protective coatings on gray cast iron parts during their operation at high temperatures was also shown

The effect of niobium carbide coating on wear behavior of grey cast iron via thermo-reactive diffusion process

Wear is the limit for grey cast iron (GCI), which is utilized extensively in today’s industries. Coating the surface of a material can enhance its ability to withstand wear. In this study, thermo-reactive diffusion (TRD) process was used to coat the surface of grey cast iron with niobium carbide (NbC). The coatings were applied for 2, 4 and 6 hours at 950ºC and 1050ºC. The coated samples were subjected to metallographic examination to investigate the microstructure of the coating zone. For this purpose, optical microscopy examinations were carried out. Microhardness tests were carried out to assess the mechanical properties of the samples. The coated surfaces were analyzed using energy-dispersive X-ray spectrometry (EDS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Wear tests were carried out on the coated surfaces to measure the volumetric wear loss, the wear rate and the changes in the coefficient of friction. Coating thickness rose as furnace waiting time increased, according to optical microstructures of coated surfaces. The hardness of the coated surfaces increased with a longer coating duration. Depending on the duration and temperature of the coating process, the layer thickness ranged from 6 to 52 µm. The lowest microhardness and the highest microhardness values of the coatings were determined at 950ºC for 2 hours and at 950ºC for 6 hours, respectively. Compared to the uncoated samples, the coated samples had a 6-9 times higher hardness value. In the abrasion tests, the loss of wear volume increased with increase in load.

Analysis of the possibilities of reducing the levels of residual stresses in casting produced from synthetic cast iron

In the production of castings, residual stresses arise in the cooling process, the level of which is often unknown. Their significance in engineering practice is very important because they are superposed on the stresses from the service load and are often the primary cause of material failure leading to failure of the equipment or structure. Their quantification using numerical simulations is rather difficult because many variables enter into the calculation simulating technological processes. Therefore, residual stress levels are most often determined in such cases by experimental measurement and, if possible, by monitoring and evaluating the history of parameter changes due to changes in the input parameters.In the present paper, the results of experimental measurements of residual stresses in synthetic cast iron castings are presented, where the effect of Ti microalloying on residual stress levels was assessed. Based on the comparison of the results obtained experimentally on castings made from grey cast iron, it can be concluded that the addition of Ti metal reduced the residual stress levels while maintaining the tensile strength and hardness HB.

Study of the process parameters influence on crack formation in laser alloying of grey cast iron

This study aimed to investigate the influence of process parameters on crack formation in laser alloying or cladding of grey cast iron. For this purpose, the effects of laser power and feeding rate of Ni-based alloying powders were examined. The microstructure and hardness of the coating and the interface of the coating with cast iron (bonding zone) were studied. The results showed that the dilution ratio is crucial in crack formation, explaining the challenges in achieving a defect-free laser alloying coating on cast iron. The higher dilution ratio of laser alloying resulted in higher dissolved carbon and bigger (Nb, Ti)C carbides formation than in laser cladding coatings. In this study, cracks appeared in the coating due to the combination of the high amount of carbide in the layer and a sharp hardness gradient at the interface with the cast iron substrate. An empirical relation was proposed for dilution ratio as a function of specific energy density, which combined the most critical process parameters on crack formation.

Properties of Laser-Alloyed Stainless Steel Coatings on the Surface of Gray Cast Iron Discs

The influence of laser-alloyed stainless steel coatings on the properties of the surfaces of cast iron discs, such as friction-induced vibration and noise, friction coefficient, residual stress, hardness, and corrosion resistance, was investigated in this study. The experimental results show that after laser alloying, the surface hardness of the cast iron discs increased significantly. The residual stresses on the surfaces of the laser-alloyed discs changed from tensile to compressive residual stresses, while any compressive residual stresses increased by more than six times. Most of the laser-alloyed discs demonstrated better performance in friction-induced vibration and noise damping and friction reduction. Metallographic observation and XRD (X-ray diffraction) analysis results show that the laser-alloyed layer is mainly a mixture of acicular martensite and dendritic material, while the phase composition of laser-treated discs is mainly martensitic, [Fe, Ni], Fe3Si, Cr23C6, and austenite, which plays a significant role in the improvement of the properties of the laser-alloyed cast iron in physics, tribology and corrosion resistance. This research has significance for the laser surface treatment of various cast irons and steels, which is an increasingly important manufacturing technology in the vehicle friction brake industry.

Theory and practice of inoculation for high-grade gray cast iron railway castin

JSC “Cheboksary Aggregate Plant” has mastered the production of high-strength gray cast iron "wedge friction" railway castings (grade SCH30) intended for freight wagon bogies. According to the casting's technical specifications, the presence of interdendritic graphite and cementite in the vertical and sloping walls of the casting is not allowed. However, in separate batches, interdendritic graphite and up to 10 % cementite were found in the controlled walls of the castings. To solve the problem of obtaining castings with a blemish-free microstructure, the iron modification technology was changed. Instead of ferrosilicon FS 75, a more effective composite dispersed inoculant was developed and implemented. The advantages of the latter, which consisted of chemically treated ultrafine modifier (USM) and a by-product of organosilane production (KSM), were theoretically substantiated. The advantages of the developed modifier over FS75 were confirmed by modeling the behavior of inoculant’s particles when filling the “wedge friction” cavities in the FLOW-3D program. USM and KSM particles were evenly distributed throughout the volume of the castings at all observed heights of the controlled casting walls. They served as graphite crystallization centers throughout the solidification time of the castings, ensuring the absence of blemishes in the castings. The introduction of the developed material into production allowed reducing the modifier consumption by 6.25 times, ensuring the absence of blemishes in the castings, achieving the required mechanical properties of the iron, and an economic effect of over 4 million rubles