Abstract
The paper presents study results focused on the microstructural, mechanical, and physicochemical properties of B-Cr coatings obtained by means of modification of diffusion borochromized layers by diode laser beam. The studies were conducted on 145Cr6 tool steel. Diffusion borochromized layers were produced at 950 °C in powder mixture containing boron carbides as a source of boron and ferrochrome as a source of chromium. In the next step these layers were remelted using laser beam. Powers: 600, 900, and 1200 W were used during these processes. The microstructure, microhardness, chemical composition, as well as wear and corrosion resistance of newly-formed B-Cr coatings were determined. As a result of laser beam interaction, the diffusion borochromized layer was mixed with the steel substrate. The study showed that too low laser beam power causes cracks in the newly formed B-Cr coating, and on the other hand, too higher laser beam power causes deep remelting resulting in the loss of microhardness. The reduced corrosion resistance in comparison with diffusion borochromized layers was caused by occurrence cracks or deep remelting. For B-Cr coatings produced using laser beam power 600 W, a small decrease in wear resistance was observed, but note that this coating was much thicker than diffusion borochromized layers. On the other hand, laser beam power of 1200 W caused a significant decrease in wear resistance. Newly formed B-Cr coatings had an advantageous microhardness gradient between the layer and the substrate.
Highlights
In recent times, material science has been developing very strongly
This paper presents the results of tests of microstructure, phase and chemical composition, microhardness, corrosion resistance, and wear resistance of borochromized layers modified with a diode laser beam
The study analyzed changes in microstructure, chemical composition, microhardness, corrosion resistance, and wear resistance by friction of B-Cr surface layers obtained as a result of remelting the borochromized layer with a laser beam on 145Cr6 steel
Summary
Material science has been developing very strongly. Researchers very often take up problems related to the analysis of new materials produced by powder metallurgy [1], additive manufacturing [2], or foundry technologies [3]. One of major technologies of material processing is heat treatment It enables improvement of properties by changing the microstructure both within the core of the material and in the subsurface zone [5]. When assessing diffusion-boronized layers and assigning them to a specific application, particular attention should be paid to their brittleness at the subsurface zone. Information can be found in the literature on the use of processes involving simultaneous introduction of boron and additional chemical elements These can be, for example, carbon [9], copper [10], aluminium [11], or chromium [10,12,13,14,15,16]. The application of the process consisting of diffusive saturation with boron and chromium contributes to reduction of brittleness; the produced layer has a hardness similar to the boronized layer
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