Thermal conductivity is an important property for cast components produced from different types of cast iron. Development of a general widely-accepted thermal conductivity model for compacted and lamellar graphite irons poses a research challenge. The present study extends the modeling approach introduced earlier for pearlitic lamellar graphite iron toward compacted graphite iron and ferritic lamellar graphite iron. The proposed thermal conductivity model of the bulk material is based on the alloy microstructure and Si segregation between eutectic cells and non-cell regions, at the main assumption that the heat paths in the eutectic cells are formed by connected graphite phases surrounded by ferrite phases. The overall thermal resistance of these heat paths is determined by the hydraulic diameter of the interdendritic region. The uncertainties both for the modeled and for experimentally derived thermal conductivities have been estimated. The importance of considering the Si segregation in the model has been discussed. For the investigated samples, the agreement between modeled and measured thermal conductivities has been achieved within 4% on the average, at the same value of the single fitting parameter found for pearlitic, pearlitic–ferritic lamellar, and compacted graphite iron alloys. The results contribute to the understanding of the material microstructure effects on the cast iron thermal conductivity.

The aim of the present study is to elucidate the influence of individual microstructural parameters, such as pearlite fraction, nodularity, and eutectic cell size, on the tensile strength (UTS) of cast irons. The UTS model was built by integrating the rule of mixtures for each microstructural component, and the UTS was described as a function of the aforementioned factors. The UTS and the required microstructure parameters for the model calculation were obtained experimentally. In the model, two coefficients were introduced to quantify the influence of the eutectic cell size and the interaction terms for the mixed two components. These coefficients were determined through fitting the experimental data, and the model's accuracy was validated using data not included in the fitting process. The results exhibited reasonable agreement, confirming the model's reliability. The model, thus, offers insights into the influence of each microstructural factor on UTS and serves as a guide for designing alloys to achieve the desired UTS through microstructure modifications.

Thermal conductivity is an important property for many iron cast components, and the lack of widely accepted thermal conductivity model for cast iron, especially grey cast iron, motivates the efforts in this research area. The present study contributes to understanding the effects alloy microstructure has on thermal conductivity. A thermal conductivity model for a pearlitic cast iron has been proposed, based on the as-cast alloy composition and microstructural parameters obtained at different solidification rates. According to the model, available parallel heat transfer paths formed by connected graphite flakes across eutectic cells are determined by the space between dendrite arms. The uncertainties both for model inputs and for validation measurements have been estimated. Sensitivity analysis has been conducted to result in better understanding of the model behaviour. The agreement between modelled and measured thermal conductivities has been achieved within 5% on the average for the investigated samples.

An evaluation method for the initial penetration of molten cast iron into the sand mold was suggested based on the laboratory-scale penetration experiments for the cast iron. The horizontal penetration depth of the molten cast iron into the sand core was analyzed using the capillary model. The early stage of the penetration was discussed, and it was clarified that the penetration is not stopped by the solidification but is stopped by the decreasing of the equivalent pore radius. It was explained that the equivalent pore radius decreases with increasing the penetration depth, and the penetration is stopped when the critical pressure, i.e., the pressure required for the penetration, becomes higher than the pressure which is acting on the penetration front. Based on the analysis, an evaluation method of the penetration of depth at the early stage of the penetration was suggested. The analysis method was applied for the other type of metals (mercury and steel) as well, and reasonable results were obtained. A simplified finite-element model of liquid iron penetration into a sand core was developed, accounting for heat exchange between the melt and the porous medium, at different pore geometries.

Predicting the permeability of different regions of foundry cores and molds with complex geometries will help control the regional outgassing, enabling better defect prediction in castings. In this work, foundry cores prepared with different bulk properties were characterized using X-ray microtomography, and the obtained images were analyzed to study all relevant grain and pore parameters, including but not limited to the specific surface area, specific internal volume, and tortuosity. The obtained microstructural parameters were incorporated into prevalent models used to predict the fluid flow through porous media, and their accuracy is compared with respect to experimentally measured permeability. The original Kozeny model was identified as the most suitable model to predict the permeability of sand molds. Although the model predicts permeability well, the input parameters are laborious to measure. Hence, a methodology for replacing the pore diameter and tortuosity with simple process parameters is proposed. This modified version of the original Kozeny model helps predict permeability of foundry molds and cores at different regions resulting in better defect prediction and eventual scrap reduction.

Accurate kinetic parameters are vital for quantifying the effect of binder decomposition on the complex phenomena occurring during the casting process. Commercial casting simulation tools often use simplified kinetic parameters that do not comprise the complex multiple reactions and their effect on gas generation in the sand core. The present work uses experimental thermal analysis techniques such as Thermogravimetry (TG) and Differential thermal analysis (DTA) to determine the kinetic parameters via approximating the entire reaction during the decomposition by multiple first-order apparent reactions. The TG and DTA results reveal a multi-stage and exothermic decomposition process in the binder degradation. The pressure build-up in cores/molds when using the obtained multi-reaction kinetic model is compared with the earlier approach of using an average model. The results indicate that pressure in the mold/core with the multi-reaction approach is estimated to be significantly higher. These results underscore the importance of precise kinetic parameters for simulating binder decomposition in casting processes.

Understanding and evaluating the performance of different powder and substrate materials combined in the laser cladding/alloying layer is prioritised by process and material engineers to obtain high-quality durable surfaces. The surface quality is usually determined by the combination of various process parameters, such as laser power, powder feeding rate, and scanning speed, that result in different dilution ratios. Furthermore, process parameter calibration highly depends on the surface geometry and alignment of the deposited tracks. The application of simulation tools for the manufacturing process design tends to reduce experimental efforts. However, laser surface cladding and alloying represents a complex manufacturing process, where powder deposited on the surface of a material solidifies and forms an alloy with the substrate. Full-scale process simulation is often not feasible for parametric studies aiming at tuning the process parameters.  

The present work introduces an experimentally validated simulation methodology, including a simplified three-dimensional finite-element heat transfer model of the laser surface cladding/alloying process, Figure 1. Cladding/alloying of a nickel-based superalloy powder on the grey cast iron substrate has been studied. With the help of laser cladding experiments and measurements on cross-section images, it has been shown that the model is capable to predict the actual laser power to obtain the desired penetration depth into the substrate, heat-affected zone size and dilution ratio. It is shown by introducing a laser power scaling factor that the model input and comparison data can be obtained from a single cladding/alloying experiment. 

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.

This paper describes and validates a methodology for implementation of full-scale sand-casting simulation in a general-purpose finite element software, including mold filling, heat transport, solidification kinetics, chemical microsegregation and prediction of microstructure and material properties. The solidification model, customized for gray cast iron, includes novel methods for handling interaction between parallel dendritic and eutectic solidification modes and its impact of their interaction on the final microstructure. The validation involves a previously published gray iron casting experiment and involves comparison of simulated and experimental cooling curves, microstructure parameters and tensile strength. We believe that this is valuable to researchers and engineers seeking to improve the state of the art of casting simulation tools.