In hot forming processes of steel, oxide scale layers are formed in dependence of the occurring process conditions. As remaining oxide scale can weaken the formed workpiece, it has to be removed at the end of the process. Through this, the oxide scale formation can lead to a mass loss of up to 3

In hot forming processes and during heat treatment, scale layer formation occurs on the surface by temperatures over 570 °C. The structure of the scale layer depends on many different parameters, such as temperature, time, atmosphere and the alloying elements of the material. The aim of this work is to characterise the scale layer forming on steels with different carbon and chromium contents. Focus is on phase analysis using EDX and correlation of the iron oxide phases with hardness using nanoindentation. In addition to the well-known iron oxide phases and the three-layer-structure a fourth layer, called subscale, was identified, which primarily consists of chromium and silicon oxides. As this layer is the interface with the base material, it could influence the adhesion of the scale layer. The hardness measurements show high values in the area of the subscale, which indicates brittle fracture behaviour. The thickness of the subscale and the primary elements it contains depend on the alloying elements of the base material. For an unalloyed steel, the subscale thickness was reduced, compared to the low-alloy steels.

This fundamental research delineates new developments in cooling rate subroutines and heat source models in GMAW multi-pass welding simulations, the outcomes are then compared with the experimental result. The software used to perform the welding simulation is MSC Marc, one of the nonlinear finite elements analysis software used to simulate the behavior of complex materials and interactions. This research uses S235 material structural steel as a specimen, which is widely used in construction and uses ER70S-6 for filler material. Before the actual welding process begins, an initial analysis is needed to design the geometry, in which the physical and mechanical material properties are required. The cooling time and material must also be determined using a subroutine, as these features are not available in the simulation software. After modeling and formulation are completed, the Goldak double ellipsoid heat source model (HSM), cylindrical HSM, and rectangular HSM are used for the simulation. A subroutine is also included in the simulation so that material hardness can be obtained as a simulation result. This research produces a simulation process that provides values very close to the actual welding process, as demonstrated by the comparison between the simulation methods and the experimental method. The subroutine developed in this research can be used as a reference for conducting actual welding processes in predicting weld material hardness as an impact of cooling time and microstructural changes due to multipass GMAW welding.

In this work, Fe-2Cu-0.8C-CaF 2 self-lubricating composites with calcium fluoride solid lubricant (3 □ 12 wt.%) were examined for their friction and wear at 5 and 10 m/s, at 500 °C. Addition of CaF 2 decreased density and hardness of composites. During sliding, materials gained weight due to oxidation. Compared to the base matrix (Fe-2Cu-0.8C), composites showed lower weight gain and lower coefficient of friction. Increase in porosity with CaF 2 content increased oxidation resulting in higher weight gain and increased friction due to wear debris abrasion. Increase in speed reduced weight gain due to higher material loss. Adhesion was the dominant wear mechanism in base matrix; delamination and wear debris abrasion in composites. Temperature rise at sliding surfaces was theoretically estimated. Increase in speed increased temperature, which reduced friction due to softening and shearing of solid lubricant. Composite with 3 wt.% CaF 2 showed least surface damage and 6 wt.% showed lowest coefficient of friction, i.e., lower by 16% and 10% at 5, 10 m/s than base matrix. Tribological response of the composites to a broad range of applied parameters, viz. speed, load and temperature taken from earlier works and present work is briefly summarized. The study suggests the dominant role of CaF 2 content and the wear debris in altering the tribological response. Further, the stability of the developed composites at high temperature and high load conditions was also established. The study suggests that the developed composites could serve high-load and high-temperature applications for heavy machinery such as bearings, shafts and gears.

During hot forming of steel oxide scaling occurs at higher temperatures caused by reactions with oxide containing atmospheres. Three characteristic iron oxides exist for steel at temperatures above 570 degrees C: Wustite (FeO), magnetite (Fe3O4) and hematite (Fe2O3). Scale layer formation is influenced by various process parameters, such as temperature, process time and furnace atmosphere. Additionally, the base material with different alloying elements (e.g. C, Cr, Si and Ni) also affects the scale layer formation. Therefor oxide scales are very difficult to handle in the entire manufacturing process. The aim of this work is to examine and evaluate the influence of temperature, time and the alloying elements C and Cr in association with the layer growth, layer composition and thermophysical properties for scale layers. Based on the achieved correlations, a model is developed, which is able to predict the scale formation and scale properties, depending on temperature, time and alloying elements. With rising temperature and time increasing layer thicknesses were observed. Further, the additional Cr ensured lower layer thicknesses compared to the unalloyed steels. The iron oxide distribution changed with rising temperature to higher oxide containing phases like magnetite and hematite. The mathematical model, developed based on this results, is able to calculate the resulting layer structure, thickness and thermophysical properties depending on temperature, time and chemical composition of the material.

Cold spraying has great potential for additive manufacturing, especially of oxidation-sensitive metals, because the material is not melted and significantly higher deposition rates can be achieved than with conventional additive manufacturing processes such as selective laser melting or direct metal deposition. Titanium is regarded as a high-performance engineering material due to its unique combination of properties, including good corrosion resistance, biocompatibility and high strength at comparatively low density. However, due to its high price, it appears reasonable for many applications to use material compounds in which titanium is only used on the surface of the workpiece, while less expensive materials such as aluminum are used for the remaining volume. In the present work, cold sprayed pure titanium coatings were deposited on Al substrates and then formed to defined 3-dimensional final contours by die forging and rotary swaging. Different porosities were selectively set in order to evaluate their influence on the coating adhesion and cohesion in the forming process. Pre-consolidation of the coatings and the use of Al/Ti interlayers proved to be promising strategies.

The development of new materials or material systems is always accompanied by the development of processing technologies suitable for the material. The reduction of process steps, the saving of material and the optimization of material properties are aims of forming processes. The basis for this is the comprehensive characterisation of the thermos-physical and thermos-mechanical technologically relevant material behaviour, taking into account the real process conditions. In the present work, the material-specific process limits were determined by means of experimental simulation and used in the numerical simulation in order, on the one hand, to identify the forming steps for optimizing the manufacturing conditions and, on the other hand, to be able to set the final material properties. It was essential to homogenize the casting microstructure for the forming processes and to adjust it to globulitical grains by solution annealing. The previously limited forming behaviour of the cast AlSi9Mg alloy with 20 vol.-

Nanostructured materials, when compared to typical micro-phase materials, have the potential to provide considerable improvements in mechanical and biological performance by reducing the grain to the nanoscale. Comparing them to their larger counterparts, nanomaterials (NMs) show distinct physicochemical and biological characteristics. The majority of human tissues and organs in the body also contain nanoscale components, which are made up of tiny units of protein, lipid, and amino acids. The biomimetic structure of nanoscale materials is exceptional. NMs can interact with biomolecules and cells significantly depending on their size, shape, chemical content, surface structure, charge, aggregation, solubility, etc. Implants still fail due to fracture, infection, corrosion, and excessive load despite the fact that extensive research has been done over the past decade to develop medical implants for bone regeneration and repairing body tissues. This chapter addresses the thermal-sprayed coating (i.e., high-velocity oxy-fuel coating, HVOF) and sol-gel sprayed nanocoatings’ deposition typically on metallic substrates for biomedical applications and also discusses the effect of post heat treatment on hydroxyapatite (HA) coatings. This article explores in detail the various problems encountered in the selection of suitable biomaterials for particular applications. The explanations pertaining to the superiority of nano-HA to micro-HA along with the influence of TiO2 in nano-HA coatings have also been brought forth. Several properties of the developed coatings, such as fracture strength, osteoblast adhesion, antimicrobial properties, corrosion, etc., have also been discussed. Finally, a comparison has been drawn from HVOF and sol-gel coating techniques based on microstructure and nanostructure HA coatings.

PurposeThis paper aims to numerical and experimental analysis on substrate deformation and plastic strain induced by wire arc additive manufacturing.Design/methodology/approachThe component has the form of a hollow, rectangular thin wall consisting of 25 deposition layers of SS316L on an SS304 substrate plate. Thermo-mechanical finite element analysis was applied with Goldak’s double-ellipsoidal heat-source model and a non-linear isotropic hardening rule based on von Mises’ yield criterion. The layer deposition was modelled using simplified geometry to minimize overall pre-processing work and computational time.FindingsA new material modelling of SS316L was obtained from the chemical composition of the evolved component characterized by scanning electron microscope/energy dispersive X-ray and further generated by an advanced material-modelling software JMatPro. In defining heat-transfer coefficients, transient thermometric analysis was first performed in the bead and on the substrate, which was followed by an adjustment of the heat-transfer coefficients to reflect the actual temperature distribution. Based on the adjusted model and boundary conditions, sensitivity analysis was conducted prior to the ultimate simulation of substrate deformation and equivalent plastic strain. Furthermore, this simulation was verified by conducting a series of automated wire + arc additive manufacturing tests using robotic gas Metal arc welding with distortion measured by coordinate-measurement machine and equivalent plastic strain measured by optical three-dimensional-metrology measurements (Gesellschaft für Optische Messtechnik).Originality/valueIt can be concluded that a proper numerical computation using the adjusted model and property-evolved material exhibits a similar trend with acceptable agreement compared to the experiment by yielding an error percentage up to 30% for deformation and up to 21% for equivalent plastic strain at each individual measurement point.

This fundamental research deals with the investigation of material property model influences on distortion induced by multi-layered Wire Arc Additive Manufacturing (WAAM) with synergic-pulsed gas metal arc welding (P-GMAW) process which was modelled and simulated by means of non-linear numerical computation. The material property models of stainless steel SS316L component to be compared stem from three different sources namely existing database, initial wire and evolved component. The new property models were generated with advanced material modelling software JMATPRO based on chemical compositions analysed at initial wire and component using SEM–EDX. The flow curve for each material model was taken with the strain rates ranging from 0.001 to 1.0 s−1. In the numerical simulation, a coupled thermomechanical solution was adopted including phase-change phenomena defined in latent heat. Goldak’s double ellipsoid was applied as heat source model and simplified rectangular bead with hexagonal element type and meshing was developed to avoid extensive pre-processing effort and to reduce the computational time at post-processing level. Temperature behaviour due to the successive layer deposition was simulated considering heat transfer effect coupled to mechanical analysis. The adjustment of simulative transient to experimental thermal distribution lead to new fitted heat transfer coefficient. Prior to execution of numerical simulation, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards maximum reached temperature. It can be concluded based on the adjusted model, selected mesh size and experimental validation that numerical computation of substrate distortion with evolved material property of component and initial wire of SS316L yield closer average result within the relative error ranging between 11 and 16% compared to database material giving more than 22%.

This research focuses on investigating major imperfection in coupled processes of ““Welding-to-Forming”” and “Forming-to-Welding” which are frequently found in parts production in automotive industries. Finite Element Method (FEM) based Virtual Manufacturing (VM) approach is used to predict final dimensional change in both welding and forming processes through the utilization of specialized FEM software Simufact.Welding and Simufact.Forming. This research is to demonstrate the accuracy in predicting final geometry in both coupled processes where the physical properties from the first process serves as the initial condition for the later process. Low carbon steel S235 with thickness of 2 mm along with filler material ER70s mild steel is selected as material for both coupled process simulations. This study incorporates thermo-mechanical FEM as the solver for computational process as well as assign Goldak’s Double Ellipsoid Heat Source model on welding simulation that serves as moving heat source, while in forming process, a sheet metal bending process with hydraulic press is incorporated. For each coupled process, the result of the first manufacturing process will be transferred with legitimate procedure proposed by Simufact software and will serve as the initial condition for the subsequent manufacturing process. The FEM-based VM simulation was successfully conducted for both coupled process and shows in simulation result, that the average final displacement due to spring-back effect on coupled processes of “Welding-to-Forming” is 1.52 mm, while on “Forming-to-Welding” simulation results, the average final distortion yields the value of 1.12 mm.

This paper presents an investigation of austenitic stainless steel grain growth kinetics of SS316L under different heating temperature ranges and holding times. The main variables such as apparent activation energy (Q), rate constant (K), and kinetic exponent (n) were analyzed to understand the grain growth kinetics in austenitic stainless steel. The empirical procedure was developed leading to the obtainment of variables that could define the grain growth kinetics based on different temperature ranges. The heat treatment process was isothermally held using quenching and deformations dilatometer at a temperature ranging from 900 °C to 1200 °C and holding times between 30 s to 240 s. The kinetic rates were estimated using an empirical equation. Based on the observations obtained by using optical microscopy. The result shows that the grain size can be predicted at a lower temperature than 1200 °C. However, the grains show irregular growth at a recrystallization temperature of 1200 °C which leads to a difficult estimation of grain size. It was observed that the variation in values of n and K are associated with the precipitation of the different micro-alloyed elements presented in the stainless steel SS316L. It can be also concluded that the texture plays an important role in the resulting kinetics change.

Wire-arc additive manufacturing (WAAM) complex components can be built-up layer by layer from metallic construction materials. In this investigation two different WAAM processes with high built-up rates (CMT and pulsed GMAW) were compared in terms of geometry formation and component properties. The reference is a rectangular thin-walled geometry made of the austenitic stainless steel 316LSi (1.4430). During the welding process, the temperature development in the weld layer was measured. The experimental comparison of CMT (\({\text{R}}_{\text{m}}=630 {\text{MPa}}\)) and pulsed GMAW (\({\text{R}}_{\text{m}}=605 {\text{MPa}}\)) is completed by the determination of the mechanical properties using micro-tensile tests. Furthermore, the additive-manufactured walls were cold rolled with a subsequent heat treatment or hot rolled to provide proof of formability and forming induced property improvement.

With the increasing demand for sustainable technologies, a lot of focus has been directed towards the development of better lubrication methodologies. The widespread use of automobiles has led to environmental degradation, and to deal with this, sustainable lubrication plays a vital role. The current chapter is focused on various basic concepts involved in lubrication for engine and transmission. The various types of lubricants such as synthetic and vegetable oils are included. A section on the basic concepts related to semisolid lubricants has also been added. The categorization has been presented based on the contacting materials such as aluminium, iron, magnesium and copper alloys. Apart from the state of the art in the aforementioned topics, challenges in each type of lubrication have also been discussed.

Background and Objective: The properties of SS316L stainless steel plate are significant due the wide range of usage of the stated material.It can be governed by the chemical composition and microstructure.This study deals with the investigation of major parameters used for predicting the grain size of austenitic stainless steel SS316L at different temperature range.The major grain growth variables such as; kinetic exponent and grain growth rate constant had been studied to interpret the mechanism in the samples with different heat treatment settings.Materials and Methods: The material investigated was austenitic stainless steel SS316 L. Samples were isothermally held at various temperatures and holding time.Results: Based on the results, the kinetic rates were plotted by using the Arrhenius equation to predict the grain size.Using this method the estimated grain size shows an acceptable error percentage up to 12.5% for temperature at 1100EC and for the temperature of 1200EC or above.Conclusion: it is concluded the grain growth will be abnormal at higher temperature range, the precipitate that occurs at the grain boundary layer can be implemented for a modified Arrhenius equation.

Abstract In this research, FEM simulation was created butt joint with weld filler 3D-solid geometry. The assigned substrate element type is created and modeled on a 9 mm thickness. The three-passes of butt joint was undergoing with using the MSC Marc / Mentat student version simulation and simufact welding simulation. The butt joint designed with three passes which are penetration, filler pass and the capping for both simulations. Thermo-mechanical FEM simulations using MSC Marc / Mentat student version and simufact welding are implemented throughout the analysis. The preferred heat source model is an ellipsoid Goldak normally used for arc welding processes and weld path process in one direction. The temperature distribution caused by the welding process on the specimens must be analyzed with the same clamping conditions and the same load. Both simulations were collecting the temperature distribution to observe the calibration of software. From the results of the temperature distribution, which simulation can be assessed which is more accurate. But to be more accurate in comparing it, the two simulations must be compared directly with the experimental, with the similar material, dimensions, and welding parameters.

The description and modelling of the forming behaviour is essential for the numerical prediction of material flow and the applied forming force. A representative stress state as well as comparable strain rate and temperatures should be considered during material characterization. In the presented investigations, an extruded aluminium alloy (EN AW-6060 T6) was formed for different compression tests with diverse specimen geometries (cylinders, discs, flat rings, cuboids) and compared with the tensile and torsion tests under the same forming conditions and with one and the same initial microstructure with an average grain size of 50 µm. To ensure that no microstructural changes during the deformation process (recrystallization) affect the measurement results due to load-related material anomalies, all tests for the material characterization were started at room temperature. The comparison is based on the cylindrical compression test, because this is standardised for room temperature (DIN 50106) and, due to the compressive stress, is the most suitable material description for bulk forming processes. However, in the stacked compression tests without additional guide elements, a much higher friction between the layers is required than between the workpiece and the tool, so that the deformation is not concentrated on the centre of the specimen (with regard to height) and the middle layers won’t get out due to high tangential stresses. By consideration of these conditions the stacked tests are comparable to the cylindrical compression test. However, the friction between material and die must be taken into account for compression tests as well as the resulting forming heat when calculating the flow curve. Based on this, the forming behaviour can be modelled according to various flow curve approaches for cold forming processes. In general, it was found that all flow curves of the tensile tests, torsion tests and the compression test were in the range of ± 7.5 % based on the cylinder compression test.

This paper describes the sensitive influence of material parameters on the final numerical simulation result of forming process as one of virtual manufacturing applications. Although existing commercial software system provide predefined material properties, these can nevertheless differ with the actual material which might result in inaccuracies. Hence, material data needs to be enhanced to gain better simulation results. This investigation begins with development of flow curve of steel DC04 (1.0338) based on compressive test with various effective plastic strains under consideration of rolling direction. Further, Forming Limit Diagram (FLD) is to be defined by using Nakajima test to determine the strains up to the fracture for deep drawing process. In this research, the enhanced application on sheet forming process is modelled and simulated as well as verified under laboratory condition using an oil-hydraulic press. It can be demonstrated that the numerical simulation results are very sensitive due to the essential differences in material properties. However, this procedure will lead to time and cost intensive measurements of the material behaviour, which is mandatory for an accurate forecast of real forming process.