Advanced Materials and Simulation

Prof Zbigniew Pater: h–index 16 (according to Scopus), number of citations 933, number of publications 466, number of patents 117 (6 European) – Head of the Computer Modelling and Metal Forming Technologies at Lublin University of Technology, since 2012 the Dean of the Faculty of Mechanical Engineering at Lublin University of Technology, 2008-2012 Vice-Rector for Science at Lublin University of Technology, 1996-99 chief design engineer in SIPMA SA - the leader in the production of agricultural machines; specialist in numerical modelling, virtual prototyping and optimisation of forming processes as well as designing innovative machines used in plastic forming of metals.

One of the major problems of metal forming is material cracking during the process. This phenomenon can be simulated with the so-called damage function, which depends on the stress and strain state. Cracking occurs when this function reaches the critical value, determined experimentally in the calibrating test [1,2]. The currently applied tests are based on compression, tension and torsion. It is also known that the more similar the stress state during the test is to the stress state of the analysed process, the more accurate the material cracking prognostication. Due to this fact, new calibrating tests, dedicated to a chosen metal forming method are constantly sought after. Such a new method is rotational compression of a sample in a channel created by two cooperating tools [3]. At a sufficiently long compression path the strain, with its value changing in the axial area of the sample (compressive to tensile and the other way round), is causing the material to crack as a result of the Mannesmann effect [4-7]. For this reason, the critical values determined in this test are particularly important in the utilitarian manner. Upon conducting a numerical simulation of the test one obtains the damage values for the axial area of the sample, which are then assumed to be the critical damage values. A significant advantage of this calibrating test is the fact that it can be applied in the hot working conditions based on machines (rolling mills) used in the industrial conditions.

David Hradil has completed his engineer’s degree Ing. at the age of 26 years. He graduated at Brno University of Technology as a Material Engineer. He work like a R&D engineer in research company COMTES FHT a.s., Dobrany, Czech Republic. His area of interest is heat treament and material engineering. Last 3 years he is active attendent of Heat treatment conferences over the world. His main topis of interest in cryogenic treament, thermochemical treatment, tribology and technology of material production and treatment.

Low alloy steel used for the production of excavator teeth is a very advantageous option in terms of price. However, the wear resistance of these teeth is insufficient. Excavator teeth have a very short service life, which leads to their constant replacement and interruption in extraction itself. The solution offered is to replace the existing steel with more alloyed steel, with higher abrasion resistance (e.g. Hadfield steel). However, this solution significantly increases the price of entire mining. The number of teeth produces is in the order of several thousand per year. Service life enhancement is also possible by adjusting the heat treatment process (HT) or by using thermo-chemical treatment (TCT). This work discusses the use of cryogenic treatment and the boridation process while preserving existing material. The effect of HT and TCT used procedure was observed by wear resistance method the pin-on-disc and by abrasion resistance test. Due to the boridation, a very significant increase in resistance was achieved, as confirmed by the results of the tests carried out. For the testing were used method Pin-on-Disk and abrasive resistance test performed using abrasive cloth.

Jakub Kotous has completed his engineer’s degree Ing. at the age of 24 years. He graduated at University of West Bohemia in Pilsen as a Material Engineer. He works like a R&D engineer in research company COMTES FHT a.s., Dobřany, Czech Republic and he continues in doctoral studies. His dissertation is aimed on advanced methods for heat treatments of precipitation strengthened steel. His area of interest is in heat treament and technology of steel processing. He is aimed on induction heat treatment, carbide spheroidization and treatment of spring steel.

Generally, the underlying motivation for shortening the manufacturing process is cost saving. Sometimes, this proves unfeasible. Final quality is often directly proportionate to the time expended. This is the case with soft annealing. The effects of spheroidisation annealing are diffusion-controlled, which means the process is time-consuming. When the annealing times are reduced, the proportion of spheroidised carbides decreases. Development and optimisation of soft annealing processes in furnaces led to a progress which cut the process times by several hours thanks to steps involving partial or full austenitizing. Still, the treatment requires several hours to complete. Recently, research into and development of the ASR (Accelerated Spheroidisation and Refinement) at COMTES FHT led to a spheroidising process with durations on the order of minutes. The ASR relies on rapid induction heating and cycling around Ac1. Alternatively, the process can be induced by thermomechanical treatment. In the absence of long holding times, grains and carbides cannot coarsen, leading to much finer microstructures than soft annealing. This is manifested in the subsequent quenching process and the final mechanical properties. The present experiment focused on comparing mechanical properties of heat-treated ASR-spheroidised material and conventionally soft annealed material. The effects on fracture toughness and fatigue behaviour were closely monitored. The experimental material was 51CrV4 spring steel.

Tomas Gregor finished his PhD. in Experimental investigation of polymeric materials where he focused on computer tomography of polymers which is very challenging due to extremely low absorption in Xray wavelengths. After the research career he moved his focus to automotive industry as a leader of his own laboratory. Since 2018 he returns to material research with specialization to material enhancement with surface layer that can improve the key properties of each application.

The coating is a common way to improve the properties of any product surface. The added material can have higher toughness, lower friction or even higher corrosion resistance compared to the substrate. The additive technology is also used where the original surface is worn out and the new part is much more expensive to manufacture compared to material addition and machining back to the original size. This contribution deals with a comparison of three different coating technologies: high-velocity oxygen fuel (HVOF), wire flame spray (WFS) and arc spray (AS). Literature offers comparisons of the above-mentioned methods based on the surface properties and wear/shear load resistance. However usually, there occurs also some stress/strain induced by temperature or mechanical interaction. The coating hardness is higher compared to the substrate and the delamination is accompanied with acoustic emissions. Authors used this information to detect the first signal of the de-adhesion of coating from substrate or coating rupture during the tensile test. The acoustic signal from the coating comes before any rupture is visible which can be used for failure identification way ahead any failure. The acoustic emission method was proved to be eligible for the detection of the behaviour of all tested coatings.