The paper presents the results of examinations of materials and tribological properties of chromized carbide layers produced on tool steel by means the powder method, modified by the use of low pressure during the process, for the avoidance of the oxidation of the batch. Investigations of the structure of the layers, the topography of the surface of chromized steel samples, their hardness, Young′s modulus, layers adhesion to steel core and tribological properties were conducted. It was proved that the structure and proprieties of chromized carbide layers produced by means of both methods are similar. However, layers produced with the novel vacuum method have greater thicknesses than layers received with the powder method, at the same process parameters (the time and the temperature). This means that, with the novel vacuum method, one could produce layers at lower temperatures than is possible by means of the traditional pack powder method, which has an essential meaning from the point of view of mechanical proprieties of the steel core.
The technological properties of the hot-work tool steels depend on their microstructural quality induced by the production process and the heat treatment. One of the frequently applied methods to improve microstructure is preheat treatment. The treatment of carbonitriding X37CrMoV5-1 steel has been investigated in fluidized bed furnaces. Thickness and phase composition have been conducted using optical microscopy Neophot 32 and scanning microscopy, JEOL 5400, after etching in nital.
The paper presents the results of examinations of the structure and properties of duplex layers of the CrC+(Co-W) type, produced in a vacuum chromizing process on a tool steel surface covered with Co-W electrolytic alloy. A comparison of the CrC+(Co-W) type duplex layers with the CrC type single carbide layers, produced in vacuum chromizing process, were performed. Studies of layers thickness, their hardness, structure, and concentration depth profiles of elements in the diffusion zone of these layers were carried out. Tribological properties of the layers and corrosion resistance were determined. It has been proven that the wear resistance by friction of the CrC+(Co-W) type duplex layers, produced by means vacuum chromizing of tool steel covered with Co-W alloy electrolytic coating, is as good as single carbide layers of the CrC type, but their corrosion resistance is higher.
The structures and properties of the CrC-TiC type duplex layers with an intermediate chromium carbide sublayer and an outer one of titanium carbide, as well as of the TiC-CrC type layers with an intermediate titanium carbide sublayer and an outer one of chromium carbide, produced on steels, were investigated. The structure of the duplex layers produced on plain carbon and alloy steel was compared with the single layers. The microstructure and chemical composition of these layers was determined by means of optical and transmission electron microscopy and X-ray phase analysis. A spectral linear analysis of the Cr, Fe, and Ti concentration in the diffusion zone was performed by means of an X-ray microanalyzer. Proof was presented that the thickness of the outer TiC layer depends on the thickness of the intermediate chromium carbide sublayer. This sublayer slows down the formation of the outer TiC layer. The structure of the chromium carbide sublayer undergoes changes during the process formation of the titanium carbide layer. The hardness and tribological properties of the layers have been determined. A comparison of CrC-TiC and TiC-CrC duplex layers with the CrC and TiC single carbide layers was performed. It was shown that the tribological properties of the CrC-TiC duplex layers are better than those of the TiC-CrC duplex layers, and those of the CrC and TiC type single carbide layers.
The paper discusses the results of research on the structure and tribological properties of hybrid layers produced on the surface of medium-carbon steel in hybrid treatment, combining gas carburizing process with the next treatment, i.e. diffusion chromizing and PVD treatment. A comparison was made of the structure and tribological properties of the layers obtained as a result of hybrid treatment with the layers produced in a single diffusion chromizing process. The studies of the layers concerned their structure, chemical composition, thickness, and hardness. Linear wear of the layers were performed by means of three-cylinder-cone method. It has been shown that the linear wear of samples with hybrid layers, produced on medium carbon steel, is less than 50% of samples with single carbide layers. This indicates very good anti-wear properties of hybrid layers.
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