Ductile Iron Research Articles

Experimental and FEM Studies of Continuous Drive Friction Welding of Ferritic Spheroidal Graphite Cast Iron

Experimental and FEM studies of the friction welding process of spheroidal graphite cast iron (SGCI) are presented. A coupled thermal and mechanical 2.5 D FEM model was used to simulate the continuous drive friction welding (CDFW) process. The FE model predicted the peak temperature of the joint, effective stress, axial shortening, and the weld flash size. Additionally, the friction force on the axial shortening of specimens was studied. The peak temperatures were measured both on the axis and at the surface of the specimen. The predicted maximum temperatures in the axis, ½ radius, and 2 mm from the surface of the sample amounted to 1162 °C, 1177 °C, and 1061 °C, respectively. The maximum temperature of the spheroidal graphite cast iron joint was below the melting temperature of the base material (~1350 °C). The predicted temperature curves, outbursts, and shortening of welded elements indicated a good match with real models.

Linking the microstructure with strain-life curves for improved utilization of the lightweight potential of thick-walled nodular cast iron

The assessment of the fatigue life of critical, highly stressed component areas is an important aspect in the design of thick-walled components for wind turbines made of nodular cast iron. With the demand for resource efficiency through lightweight design combined with a certain capability to withstand extreme loads and special events, this issue is becoming increasingly important. However, there are still gaps in the description of local strain-based material behaviour. For the design and local strain-based fatigue assessment of large cast components, possibilities to determine the fatigue life as accurately as possible must be provided by standards and guidelines. The paper aims to provide a wide range of material and fatigue data from one common source for general design interests. During research projects at Fraunhofer LBF, material properties for the PRAM-based fatigue life assessment and the elastic-plastic material behaviour have been derived from 9 nodular cast iron grades with 44 microstructural variations. To describe the influence of the technological size effect on cyclic stress-strain and PRAM-N curves the quasi-static parameters (tensile strength and elongation at break) and the microstructure (nodularity and graphite particle density) are considered. In addition, suggestions for scatter bands in the strain-based design approach are given to the designers of thick-walled GJS components.

Effect of Austempering Holding Time Variations of 30, 60, and 90 Minutes at 300 °C on The Microstructure and Toughness of Nodular Cast Iron

The phases of the nodular cast iron matrix are similar to those of steel. Therefore, heat treatment of steel can be applied to nodular cast iron. A potential heat treatment for nodular cast iron is austempering. This study aimed to determine the effect of austempering holding time at 300 °C on the microstructure and toughness of nodular cast iron. The austempering process begins with austenitizing at a temperature of 850 °C for 60 minutes, then the quenching process is carried out in a salt bath until a temperature of 300 °C is held with variations of 30, 60, and 90 minutes, then cooled to room temperature. Metallographic testing was conducted to determine the phase change before and after the austempering process using a Scanning Electron Microscope (SEM). Meanwhile, impact testing was carried out to determine changes in toughness before and after the austempering process. At a holding time of 30 minutes, metallographic testing on the raw material produced a gray coarse pearlite phase, black nodular graphite surrounded by white ferrite. After the austempering process, gray fine pearlite and black nodular graphite appeared. At the holding time of 60 and 90 minutes, the graphite sizes were bigger. Austempering withholding times of 30, 60, and 90 minutes resulted in impact energy of 4.2, 10, and 11 Joule. From the results of the study, it was concluded that an increase in holding time would increase the size of the graphite and the toughness of nodular cast iron.

Effects of ferrite and graphite phases on scratch characteristics of nodular cast iron

In this work, we conduct micro-scratch tests of nodular cast iron with Vickers indenter under constant normal load and investigate the effects of individual phases (i.e., ferrite and graphite phases) on the scratch characteristics of nodular cast iron. Using a bimodal Gaussian model to fit the experimental data of penetration depth, residual depth, elastic recovery rate, and scratch hardness, we calculate the contribution percentages of individual phases to scratch variables. The scratch variables are independent of the scratch speed used in this work, while the penetration depth increases linearly with increasing the normal load. There exists a large difference between the contribution percentages and the volume fractions calculated from SEM images and XRD pattern. Such a large difference suggests that the bimodal Gaussian distribution analysis does not include the effect of the interaction between two phases on the scratch characteristics of dual-phase materials with significantly distinct mechanical properties and geometrical dimensions. A more refined method taking into account the interaction between two phases needs to be developed for the analysis of the scratch characteristics of dual-phase materials.

Revealing the strength and toughness mechanisms of ductile iron in three heat‐treatment processes

AbstractMicrostructural characteristics and mechanical properties of the ductile iron in three heat treatment processes (normalizing, quenching + high‐temperature tempering and isothermal quenching) were investigated in this paper. The pearlite and ferrite with large‐sized spherical graphites can be obtained in the normalized sample, and the spherical graphites with relatively large size can still be observed in the mechanical mixture of tempered martensite and acicular ferrite for the quenched‐tempered sample. Meanwhile, the lower bainite accompanied with the relatively fine spherical graphites are existed in the isothermal‐quenched sample. The difference of tensile strength is mainly caused by the phase composition, distribution and size of the spherical graphites and the effect of the solid solution strengthening. The weaker degree of the debonding damage, higher proportion of high‐angle grain boundaries will improve the impact toughness of the ductile iron. In a word, the optimum combination of strength and toughness is acquired by using isothermal quenching, and the tensile strength and impact toughness are ~1350 MPa and ~10.62 J, respectively.

Optimization of car crankshaft strength with ductile iron material through Solidworks simulation

This study aims to provide crucial insights into the performance of crankshaft designs under various loads and operational conditions. The method employed in this research is finite element analysis, facilitated by SolidWorks software, utilizing Ductile Iron material. Crankshafts crafted from ductile Iron are typically employed in vehicle engines due to their commendable mechanical properties and cost efficiency. The force exerted by the piston on the crankshaft generally ranges from 4500 N to 7500 N. The Factor of Safety within the crankshaft denotes the ratio between its material strength and the maximum stress it experiences during operation. The findings of this research indicate that the highest recorded maximum von Mises stress utilizing ductile iron material is 4.658 MPa, with a corresponding Factor of Safety in the crankshaft of 118.4. Consequently, the resilience of ductile iron crankshafts under varying loads and operational conditions can be ensured through meticulous analysis of crankshaft geometry.

In-situ observation and kinetics study on shrinkage defect corrosion of ductile iron in NaCl solution

The corrosion propagation and kinetics of shrinkage defects in ductile iron in NaCl solution were investigated by in-situ observation based on time-lapse microscopy and confocal laser scanning microscopy. Immersion experiments reveal that shrinkage defects endure notably harsher corrosion compared to the matrix, exhibiting an average depth increase of 52.38μm within a single day. The depth loss rate, a crucial indicator for corrosion kinetics, inversely correlates with the square root of immersion time, underscoring the substantial role of shrinkage defects in expediting early-stage corrosion. The corrosion process predominantly involves longitudinal extension, with sharply shaped defects experiencing the most significant depth increases.

GCD700 구상흑연주철의 주조조직 생성에 미치는 냉각속도와 Sn 첨가의 영향

GCD700 구상흑연주철의 주조조직 생성에 미치는 냉각속도와 Sn 첨가의 영향

Study of the Wear Resistance Plasma Nitrided GGG60 by Optimization of Surface Treatment Conditions Using Response Surface Methodology

AbstractIn this study, the wear performance of spheroidal graphite cast iron subjected to plasma nitriding at different temperatures and treatment durations was investigated. The plasma nitriding parameters were optimized by response surface methodology (RSM) due to the output performance. Plasma nitriding was applied at three different temperatures (400, 450, 500 °C) and three different heat treatment durations (0.5, 2, 4 h). Wear tests were performed by ball-on-disk method for 60 minutes and for three different wear loads (10, 20, 30 N). The specimens were investigated for hardness, microstructure and wear performance. The RSM model was then created by using the wear resistance features. Plasma nitriding showed better wear performance than the untreated specimen for all treatment conditions. Hardness, nitrided layer thickness and wear performance remarkably improved with increasing temperature and process duration. The parameter that affects volume loss the most is wear load with 70.66% according to RSM modeling results. The most effective parameter in the wear rate change was found to be treatment duration at 42.85%. The model was able to predict the results with an error of 2.11% for volume loss and 9.14% for wear rate. The prediction results are very close to the experimental results. This clearly shows that the model can be used to determine the plasma nitriding parameters.

Effects of Ti addition and wall thickness on microstructure, hardness, and wear properties of spheroidal graphite cast irons

Spheroidal graphite cast irons (SGCIs) have been commonly used in automotive and energy sectors where superior mechanical strength and wear resistance are required. This paper investigated the performance of the SGCIs under severe wear conditions as a function of Ti content and cooling rate. SGCIs alloyed with various Ti content (0, 0.1, 0.2, 0.3, and 0.5 wt%) were produced by green sand-casting process in different section sizes (10, 30, and 50 mm). Ball-on-disk type wear equipment with an Al2O3 ball was used to determine the wear rates of the SGCI samples. With increasing Ti content, up to 45% of nodular graphite turned into vermicular graphite, depending on the Ti addition and section sizes. Carbide precipitation was observed in the matrix due to the carbide-forming effect of Ti. The hardness and wear resistance of the SGCIs were improved by adding Ti owing to the combined effects of increasing pearlite and TiC particles precipitated in the matrix. Thinner-wall castings provided a faster cooling rate, which improved hardness and wear resistance. Alloying with 0.5 wt% Ti decreased the wear rates up to 35%.

An HVOF-Sprayed (Cr3C2-NiCr+Co) Composite Coating on Ductile Cast Iron: Microstructure, Mechanical Properties, and Scratch Resistance.

High-velocity oxy-fuel (HVOF) thermally sprayed Cr3C2-NiCr coatings have been shown to be effective in shielding important machinery and equipment components from wear in harsh, high-temperature conditions. In this investigation, the HVOF thermal spray coating technique was used to deposit Cr3C2-NiCr powder with 10% Co particles onto ductile cast iron. The effect of the Co particles on the mechanical, tribological, and microstructure characteristics of a Cr3C2-NiCr/ductile cast iron system was investigated. The microstructure analysis employed various techniques, including light microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). Scratch tests were applied to analyze the coating quality and adhesion. The coatings created using the HVOF spray method with Cr3C2-NiCr powders mixed with Co particles exhibited a dense structure containing large Co particles, partially melted, and very fine Cr3C2 particles embedded into the NiCr alloy matrix. Additionally, they possessed high hardness and excellent adhesion to the substrate. The results of bending strength tests were also presented, together with information on the coating's microhardness and fracture toughness. These included an analysis of the cracks and delamination in the Cr3C2-NiCr/ductile cast iron system. It was observed that the addition of Co particles significantly increased the resistance to cracking and wear behavior in the studied system.

Wear reduction mechanism in modulated turning of nodular graphite iron with coated carbide tool

Modulation-assisted machining (MAM) is used for turning nodular graphite iron (NGI) with coated carbide tools and compared with conventional machining (CM) at the cutting speed of 350 m/min in dry and wet conditions. Significant reductions in flank wear are achieved using MAM as compared to CM turning, in both dry and wet conditions. Dry MAM results in even lower wear than wet MAM condition. The substantial wear reduction in dry MAM is due to the formation of two material layers (i.e., the MgO deposition layer and the stagnated iron layer) and their unique arrangement on the flank face of the tool. The protective effect of these layers and the MAM conditions conducive to the formation of these layers are discussed.

A comparative study of flake graphite iron and compacted graphite iron in austempered condition for directional control valves

Demand for lighter materials with the right qualities is unavoidable in the present era of engineering. Compacted graphite iron is a type of cast iron gaining momentum nowadays in foundries due to its distinct characteristics that fall between gray cast iron/flake graphite iron and spheroidal graphite iron. It becomes the right candidate to replace flake graphite iron in many applications. In this research, flake graphite iron (FC −30) and compacted graphite iron-300 grades were studied to enhance its properties through austempering heat treatment process. Initially, the as-cast (non-austempered) flake graphite iron and compacted graphite iron were subjected to microstructural study and mechanical testing. Subsequently, the flake graphite iron and compacted graphite iron were subjected to austempering heat treatment. The various austempering temperatures selected are 270, 320, and 370 °C for different soaking time periods of 30, 60, 90, and 120 min. As cast flake graphite iron specimen (FC-30) exhibited lesser tensile strength (293 N/mm2) than as cast compacted graphite iron (528 N/mm2) and austempered compacted graphite iron (652 N/mm2). With respect to hardness measurement, austempered compacted graphite iron specimens yielded higher hardness of up to 415 BHN. However, the compacted graphite iron specimen austempered at 370 °C for 90 min measured an optimum hardness value of 373 BHN and tensile strength of 630 N/mm2 with less retained austenite (0.3%). This hardness value is considered to be more suitable in machining operation for making hydraulic directional control valves exposed to constant abrasion.

Mechanical Properties and Fracture Toughness Prediction of Ductile Cast Iron under Thermomechanical Treatment

Temperature has a great influence on the mechanical properties of ductile cast iron or nodular cast iron. A thermomechanical treatment was carried out at various elevated temperatures of 450 °C, 750 °C and 850 °C using a universal testing machine with a tub furnace. Specimens were held at these temperatures for 20 min to ensure a homogeneous temperature distribution along the entire length of the specimen, before a tensile load was applied. Specimens were deformed to various levels of uniform strain (0%, 25%, 50%, 75%, and 100%). These degrees of deformation were measured with a dial gauge attached to a movable cross plate. Three strain rates were used for each specimen and temperature: 1.8×10−4 s−1, 9×10−4 s−1 and 4.5×10−3 s−1. A simple analytical model was extracted based on the CT tensile test geometry and yield stress and a 0.2% offset strain to measure the fracture toughness (JIC). To validate the analytical model, an extended finite element method (XFEM) was implemented for specimens tested at different temperatures, with a strain rate of 1.8×10−4 s−1. The model was then extended to include the tested specimens at other strain rates. The results show that increasing strain rates and temperature, especially at 850 °C, increased the ductility of the cast iron and thus its formability. The largest percentage strains were 1 and 1.5 at a temperature of 750 °C and a strain rate of 1.8×10−4 s−1 and 9×10−4 s−1, respectively, and reached their maximum value of 1.7 and 2.2% at 850 °C and a strain rate of 9×10−4 s−1 and 4.5×10−3 s−1, respectively. In addition, the simple and fast analytical model is useful in selecting materials for determining the fracture toughness (JIC) at various elevated temperatures and different strain rates.

Laser Remelting of Ductile Cast Iron to Achieve a Graphite-Free Surface Layer for Enabling a Manual High-Gloss Finish

Laser remelting is being explored as a viable technique for obtaining a graphite-free, defect-free surface layer on cast iron EN GJS 400-15. The goal is to obtain a large remelted layer along with a low surface roughness to enable a subsequent manual high-gloss surface finish. The impact of the laser remelting process parameters is evaluated by using samples with three different cooling rates, resulting in different graphite microstructures. By utilizing four passes and a laser power of 300 W, the smallest roughness and largest remelting depth are achieved. The remelted layer is mostly devoid of graphite particles. Subsequent manual polishing is performed to evaluate the potential for achieving a high-gloss finish with a roughness of Sa < 0.05 µm. Laser remelting alone does not improve visual appearance or reduce roughness. However, after manual polishing, the roughness of the laser-remelted surfaces with Sa = 0.018 µm is one order of magnitude smaller than the manually polished initial state. Graphite removal during laser remelting therefore makes it possible to achieve a conventional and high-gloss polish, overcoming the previous limitations of GJS materials.

Application of Arc Furnace Flue Ash in Casting Heat Insulation Riser

Iron black commonly employs in thermal insulation riser sleeves due to its ability to react with aluminum powder, generating heat. However, the complex production process and unstable composition of iron black lead to high production costs. The potential of using arc furnace flue ash (AFFA) as a complete substitute for iron black and MnO2 and KNO3 oxidizing agents in conventional riser sleeves was investigated in this study. Waste material can be transformed into a valuable resource, while production costs can be reduced by utilizing arc furnace flue ash. The research examined the impact of varying types and amounts of arc furnace flue ash on riser sleeve temperature and holding time by conducting single-factor and orthogonal optimization experiments. The orthogonal optimization experiment determined that the optimum ratio of each oxidant was 6 % arc flue ash, 3 % MnO2 and 6 % KNO3. At this time, the highest temperature was 1512 ℃ and the holding time was 244 s. Results indicated that different types of arc furnace flue ash used as an oxidizing agent demonstrated superior holding capacity and heat generation performance compared to iron black. Additionally, a comparative analysis of factory casting experiments using ductile iron 600-3 (IS) revealed that both arc furnace flue ash and iron black risers effectively countered shrinkage. However, arc furnace flue ash risers exhibited improved mechanical properties, as evidenced by the hardness of the castings.

SEM/EDS Investigation of Aluminized Deformable Austempered Ductile Iron with Al and AlCr Particle Slurries Before and After High-Temperature Oxidation

SEM/EDS Investigation of Aluminized Deformable Austempered Ductile Iron with Al and AlCr Particle Slurries Before and After High-Temperature Oxidation

On the stress- and strain-based fatigue behavior of welded thick-walled nodular cast iron

Nodular cast iron (GJS) represents one of the most widely used materials for vehicle, energy and heavy machinery industry. Nevertheless, foundries struggling with the influence of local material defects in GJS like pores, shrinkages and dross often leading to a locally reduced fatigue strength of the entire component. One measure to tackle those negative effects is the welding of the affected areas. This measure is then successful when locally achieved material strengths and surface qualities are higher than the component with the casting defect. Unfortunately, data for the lifetime and fatigue assessment of welded GJS are not present right now. Thus, the research project »nodularWELD« assessed the local stress- and strain-based fatigue data of different thick-walled GJS grades for building a basis for a successful usage even of defect affected components. So, three ferritic and pearlitic GJS grades were investigated in the heat-affected zone, the base material, the welding filler and more over in an integral material state comprising all those three aforementioned states based on axial and bending investigations. Additionally metallographic and fractographic analysis were conducted.

Repair feasibility and performance enhancement analysis of Fe-based alloy coating on ductile iron surface by high-speed laser cladding

In this paper, high-speed laser cladding technology with a scanning speed of 40 mm/s was used to clad the ductile iron surface with the Fe-based alloy coating. The coatings' microstructure, element distribution, crystallographic structure, wear resistance, and corrosion resistance were investigated by using an optical microscope, SEM, XRD, friction and wear testing machine, super depth-of-field microscope, and electrochemical workstation. The results show that the microstructure of the coating is mainly γ-Fe solid solution and carbide eutectic structure. The phases of the coating are FCC phase (γ-Fe dominated), BCC phase, and carbide. The elemental distribution of the coating cross-section elements is uniform, and no quality obvious defects such as large gas pores and cracks are found. The coating mass loss was 60.0% and 47.1% of the substrate for different friction parameters and the more significant coating oxide build-up phenomenon with increased loading force. The self-corrosion rate of the coating was 0.006 g/m2·h, and the substrate was 0.042 g/m2·h; the maximum impedance value of the coating (1.34×104 Ω·cm2) was increased 20 times based on the substrate (619.2 Ω·cm2). In summary, Fe-based coatings with these process parameters can repair failed ductile iron parts and significantly extend their service life.

An Experimental Study on Nodular Iron Machined Surfaces Utilizing a Capable 2D Finite Element Model for Precise Surface Roughness Estimation

Nodular iron plays a crucial role in various industries, especially in large-scale applications such as gearboxes. Ensuring that nodular iron remains free from oil leakage and that contact surfaces are properly aligned is essential, given its operational requirements. Achieving flat contact faces through precise machining is therefore of utmost importance. As surface roughness and flatness are closely linked, it is vital to investigate the machining process parameters involved. This study focuses on addressing surface quality issues with EN-GJS-600-3 cast iron by optimizing machining parameters. CMM measurements were utilized to analyze the relationship between surface roughness and flatness, with a surface profile used to assess flatness. Furthermore, a new 2D surface roughness estimation method (2D-SRET) was created and tested with experimental data in order to improve the precision of assessing the discrete flat surface machining procedure.