EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

For a long time it was well accepted, that steel structures can be exposed to service load spectra involving very high numbers of cycles (up to one billion of cycles and more) based on fatigue strength data limited to not more than 10 millions of cycles. Since several severe accidents and more recent experiments had shown that fatigue failure may occur at very high numbers of cycles exceeding...

Current and future developments in lightweight design of cyclically loaded components require the use of high-strength materials. Additionally, longer and longer operating times are demanded, hence a safe service life is of outstanding importance. It is widely known that certain alloys can still fail after exceeding 1e7 cycles and a change in the failure mechanism from surface induced to...

Fatigue properties of hard metals are a concern in many of its applications. However, due to its low ductility and limitations in physical design fatigue testing may be difficult to carry out. Long life endurance, as in the Very High Cycle Fatigue (VHCF) range, is also of relevance in many hard metal applications as for metal cutting tools used in milling or intermittent cutting processes....

The development of rail transportation results in more and more passage of trains on the railtracks, which implies service conditions more conducive to the appearance of defects due to wear or cyclic fatigue. One of these defects is the ‘White Etching Layers’. These latter owe their name to the fact that it appears white on Optical Microscopy (OM) after Nital Etching, and consists of...

Cementite decomposition is crucial in microstructural degradation in steels subjected to fatigue/wear loading conditions. Examples include the deformation and decomposition of cementite in pearlitic rail steels and in the formation of white etching areas (WEAs), which cause premature failures of wind turbine gearbox bearings (WTGBs). Therefore, it is worthwhile to study the fundamentals of...

Ultra-high-strength steel (UHSS) fasteners, like screws, bolts or clamps, are characterized by a good combination of strength and toughness. The utilization of UHSS opens up new possibilities for reducing the weight of cars and, therefore, for reducing greenhouse gas emissions. However, the distinctive susceptibility of UHSS to hydrogen embrittlement has been limiting the use of fasteners with...

Advanced high-strength steels (AHSS) possess great combination of mechanical properties such as ductility, strength, toughness and good crash behavior. The utilization of AHSS in the automotive industry opens up new possibilities for reducing the weight of cars and, therefore, for reducing greenhouse gas emissions. However, the proneness of AHSS to hydrogen embrittlement counteracts the...

The degrading effect hydrogen has on the mechanical properties of metals has been frequently observed in the past. Yet, the exact mechanics are not fully understood. These mechanisms do not only depend on environmental and mechanical conditions, like atmospheric composition or applied stresses, but also highly on the microstructure of the materials. Because hydrogen is not homogeneously...

Deterioration in mechanical properties of metals and alloys due to hydrogen is known as hydrogen embrittlement, which leads to the catastrophic failure of structural components. The phenomenon of hydrogen embrittlement has been known for decades [1] and several mechanisms have been proposed to cause the hydrogen embrittlement such as hydrogen enhanced localized plasticity (HELP), hydrogen...

Technological enhancements created new demands on the material properties of aerospace materials. One of the most common materials used in the aerospace industry is titanium alloys because of their high strength to volume ratio. To meet these needs, titanium alloys with higher operating temperatures and with better mechanical properties are developed. Titanium alloys consist of alpha and beta...

Electrically conducting metal layers play a crucial role in flexible and form adjusting electronic devices and components. Conductive metal coatings on polymer substrates are often combined with thin metal interlayers to improve adhesion to the substrate. These adhesion promoting interlayers are mostly brittle in nature, greatly affecting a device’s susceptibility to damage under mechanical...

Cold rolling followed by heat treatment was performed on commercially pure titanium with a bimodal harmonic structure, which is defined as a coarse-grained region (Core) surrounded by a network structure of fine grains (Shell), and fatigue crack propagation tests were conducted to clarify the effects of the rolling reduction, rolling direction, and force ratio. From the relationship between...

During the operation of turbines in jet engines or in power plants, high thermal and intermittent mechanical loads appear, which can lead to high-temperature fatigue failure. Since Fatigue is a complex and time-consuming process, it is important to develop realistic numerical models to predict fatigue behaviour and to extrapolate the limited experimental results into a wider range of...

Thread rolling processes are most used to manufacture external threaded screws, as plastic deformation for external threading significantly increases productivity, saves materials, and enhances the reliability and durability of the products. Except for the premature in-service failure, fatigue failure is the most considerable factor which limits the lifetime of the rolling dies. Often changing...

Thermal oxidation is a method of surface treatment to improve the wear characteristics of titanium alloys, a material group frequently exposed to wear, e.g. in orthopedic implants or engine valves. Different process designs of thermal oxidation have been shown in the past. Single-step oxidation at elevated temperature in an oxidizing environment, such as air, leads to a protective TiO2 layer...

In order to prevent the activation of 60Co cobalt particles in the primary circuit of nuclear reactors, it is necessary to replace cobalt-based alloys of the Stellite type, used as abrasion-resistant coatings, with cobalt-free alloys. Several materials, including commercially iron- or nickel-based alloys, have been tested in the past, but none of them has equivalent characteristics to those of...

Fe-based hardfacing alloys with high carbon and chromium content possess good wear resistance properties in severe environmental conditions [1]. In the present study, the wear behaviour of Norem02, a duplex stainless steel containing 1.3 wt.% carbon and 24 wt.% chromium and elaborated by Hot Isostatic Pressing (HIP), was investigated. HIP represents an attractive pressure-assisted sintering...

Over the last decades, the strong regulations about pollution and environmental impact have favoured the introduction of eco-friendly lubricants as a good alternative to the classic mineral oils. This work concerns the tribological characterization in lubricated conditions of an EN AW-4006 aluminum alloy superficially treated with three different hard anodizing processes. In particular, a...

The use of Cr(VI) is restricted by regulations such as REACH, and its use will be forbidden in 2024. This is valid not only for surface treatments but also for repair and maintenance, when the removal of oxide layers needs to be done with Cr free solutions. The solutions currently in use are Cr(VI) based ones and NaOH as Cr free alternative. A suitable stripping process will assure a uniform...

Inconel625 is a nickel-based alloy characterized by high strength at high temperature and corrosion resistance in harmful environments. Unfortunately, high hardness, poor machinability and low thermal conductivity make it difficult to fabricate components with a complex shape. These problems can be solved using additive manufacturing (AM). Application of AM Inconel625 in an aggressive...

Aluminum is an important metal because of its physical and mechanical properties, high strength-to-density ratio, and very good resistance to atmospheric corrosion. In atmospheric conditions, a passive layer of aluminum oxide forms on aluminum, which provides atmospheric corrosion resistance. However, this protective layer fails in harsh conditions, e.g. in presence of highly concentrated...

Inorganic inhibitors (mainly nitrites) have been traditionally used to control the corrosion of steel reinforcements without significantly changing the concrete properties. Their negative effects on the environment have led to the search of alternatives, such as nature-based green inhibitors extracted from plants. The successful use of some natural substances, such as ginger, orange peel and...

The most common of the shape memory alloys are those based on TiNi (titanium nickelide). They have a unique set of properties – high values of recoverable deformation and developed forces, high corrosion resistance, which is why they are often used in many industries and medicine.
Shape-memory alloys have a unique ability to restore shape when heated, and it is known that repeated heat...

The concept of Preventive Conservation of cultural artefacts in museums and collections (e.g. statues, weapons, coins, etc.) is based on mitigation of the deterioration or damage due to material ageing as well as biological, mechanical and chemical degradation processes on-going over time. These changes of the materials have to be described in models and validated by experimental data [1]. For...

Throughout the years, there has been a great interest in developing performant alloys having good corrosion and good wear resistance. The challenge that arises is related to designing and developing cost-effective corrosion-wear resistant alloys. Within this framework, our study is a preliminary investigation to develop a competitive low-cost stainless steel having good corrosion-abrasion...

In the present approach the corrosion performance of electrospun core-shell nanofibers designed using electrospinning techniques was evaluated. Electrospinning is a well-established and flexible process which already demonstrated the manufacturing up-scale mass production capability with relatively low costs. It is the most promising and rapid process to generate continuous, ultrafine fibres...

The corrosion resistance and the mechanical behaviour assessment of structural alloys is crucial for the durability and the safety of the lead cooled Fast Reactor and accelerated driven systems. Moreover, it is well-known that the presence of a liquid metal may compromise the good performances of a metallic alloy due to liquid metal corrosion or liquid metal assisted mechanical damage. To...

Constant tendency toward the materials properties improvement nowadays creates the opportunities for the scientists, and furthermore the manufacturers all over the world to design, form and produce new alloys almost every day. Considering the fact that companies all over the world look for alloys with the highest values of mechanical properties coexisting with a reasonable electrical...

In this work, we present a method to produce fatigue samples with controlled internal defects which are used to induce internal crack initiation. Diffusion bonding of metal sheets containing defects created by femto laser machining is used to produce sharp notches in the bulk of samples whose geometry and size enable to perform synchrotron tomography in situ fatigue tests (sample diameter...

The Gas metal arc welding (GMAW) creates strong microstructure gradients generating residual stress fields that influence the mechanical response and service life of welded structures. Under mechanical loadings, the welding residual stresses can be relaxed or redistributed. This work attempts to study the relaxation of welding residual stress generated by GMAW. Three types of lap joints...

As long as the samples are large compared to the atomistic scale, the material behavior can be described as a continuum, especially in fatigue applications. The disolacation arrangements that form during the fatigue of face-centered cubic materials are well-known and typically have structural dimensions ranging from a few hundred nanometers to a few micrometers. So what happens when the sample...

Fatigue crack propagation in near-threshold regime was studied in the 304L austenitic stainless steel in two microstructural states: as-received (AR) with finer microstructure and low susceptibility to the TRIP effect, and solution-annealed (SA) with coarser microstructure and higher susceptibility to TRIP. At the load ratio R = 0.1 the threshold was higher in the SA state than in the AR state...

To strengthen materials and therefore improve the mechanical properties of parts, some of the most widely used techniques are the mechanical surface treatments. Among them, SMAT (Surface Mechanical Attrition Treatment) has great potential for strengthening mechanical components subjected to cyclic loads. This treatment is based on multidirectional impacts of spherical balls set in motion using...

The mechanical properties, such as low cycle fatigue resistance, are tightly connected to the character of microstructure. Various processing techniques result in distinctively different microstructures which directly affect cyclic behaviour and fatigue life. This study presents a comparison of conventionally processed metastable austenitic stainless steel 304L with its SLM-processed...

Nanofluids are solid-liquid mixtures composed of solid nanofibers or nanoparticles with size in the range of 1 to 100 nm that are suspended in a fluid. Their applications span in cooling of engines and electronics, heat exchange in solar collectors, heat storage systems and as coolants in manufacturing. The use of nanofluids has been proved in some cases to offer a positive effect on the...

For the design of cyclically loaded components, influence of defects, i.e., non-metallic inclusions, and thus, defect tolerance of material have to be considered. Preliminary work on bearing steel 100Cr6 has shown, that the cyclic hardening potential and associated defect tolerance increase with higher contents of retained austenite, whereby deformation-induced...