This study forms part of the current research on modern steel groups with higher resistance to abrasive wear. In order to reduce the intensity of wear processes, and also to minimize their impact, the immediate priority seems to be a search for a correlation between the chemical composition and structure of these materials and their properties. In this paper, the correlation between prior austenite grain size, martensite packets and the mechanical properties were researched. The growth of austenite grains is an important factor in the analysis of the microstructure, as the grain size has an effect on the kinetics of phase transformation. The microstructure, however, is closely related to the mechanical properties of the material such as yield strength, tensile strength, elongation and impact strength, as well as morphology of occurred fracture. During the study, the mechanical properties were tested and a tendency to brittle fracture was analysed. The studies show big differences of the analysed parameters depending on the applied heat treatment, which should provide guidance to users to specific applications of this type of steel.

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Abstract:In the article, the structure and selected mechanical properties of welded Hardox 600 steel are presented. It is shown that, after welding of this material in as-delivered condition (i.e., with post-martensitic structure), structures of lower wear resistance are created within heat-affected zones. These zones are over 80 mm wide, which makes them susceptible to uneven and fast wear in their intended applications. On the grounds of microscopic tests and hardness measurements, a thermal treatment of welded joints is suggested, consisting of quenching and low-temperature tempering of heat-affected zones. As a result of this treatment, the material structure in these areas becomes similar to the base material structure. Under laboratory conditions, the performed heat treatment does not cause any incompatibilities (cracks) in the welds.

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This paper presents the forecasting of the wear of working elements in an abrasive soil mass using the theoretical wear model. One of the widely used models providing a basis for the relationships describing wear is the Holm-Archard model. This relationship describes abrasive wear because of the contact between two bodies. The model assumes that the wear of an operating part is directly proportional to the sliding force and distance and inversely proportional to the hardness of the material of the part. To date, the model has not been verified in the wear of a soil mass, which is a discrete friction surface. Four grades of steel resistant to abrasive wear, intended for the manufacturing of operating parts exposed to wear within a soil mass, Hardox 500, XAR 600, TBL Plus and B27, were subjected to testing. TBL Plus steel was characterised by the smallest wear irrespective of the soil type. In turn, the highest values of the wear were noted in the light soil for Hardox 500, in the medium soil for XAR 600, while in the heavy soil for B27. Based on the obtained results, a high correlation coefficient was noted, with the highest values obtained for light and heavy soils.

The paper presents structure and mechanical properties of welded joints of the high-strength, abrasive-wear resistant steel Hardox Extreme. It was shown that, as a result of welding this steel, structures conducive to lowering its abrasion-wear resistance are created in the heat-affected zone. Width of the zone exceeds 60 mm, which results in accelerated wear in the planned applications. On the grounds of the carried-out examinations of structures and selected mechanical properties, a welding technology followed by heat treatment of heat-affected zones was suggested, leading to reconstruction of HAZ structures that is morphologically close to the base material structure. In spite of high carbon equivalent (CEV) of Hardox Extreme, the executed welding processes and heat treatment did not result in the appearance, in laboratory conditions, of welding imperfections in the welded joints.

One of the most important problems encountered during operation of machine parts exposed to abrasive action is their wear. In addition, these parts often work under dynamic loads, so their satisfactory ductility is also required. A combination of these apparently opposing properties is to a large degree possible in low-alloy martensitic steels containing boron. These steels are manufactured by numerous metallurgical concerns, but their nomenclature is not standardised and they appear under names given by the manufacturers, and their specifications are available in commercial information materials only. Till now, Hardox steels have been objects of great interest but, with regard to the continuous development of materials engineering, the created material database requires regular supplementation. To that end, two grades of steels from this group, Brinar 400 and Brinar 500, were subjected to comparative analysis of their abrasive-wear resistance in relation to properties of competitive grades Hardox 400 and Hardox 500. Abrasive-wear resistance tests were carriedout in laboratory conditions using a tribotester T-07. In addition, to identify the main wear mechanisms, worn surfaces of the specimens were examined with use of a scanning electron microscope.