NTI-WEAR PROPERTIES OF MEDIUM CARBON STEEL AFTER CARBURIZING WITH SUBSEQUENT DIFFUSION CHROMIZING AND PVD TREATMENT

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.

TRIBOLOGICAL PROPERTIES OF BEARING STEEL AFTER HYBRID TREATMENT, COMBINED DIFFUSION CHROMIZING WITH THE PVD METHOD

The objective of the research in this work was the modification of the structure of chromized carbide layers on a bearing steel surface by the combination of diffusion chromizing with subsequent treatment, chromium nitride deposition by the PVD method, carried out to improve their tribological properties. As a result, CrC+CrN type hybrid layers on the surface of bearing steel were obtained. For comparison, the properties of single chromized carbide layers produced on a bearing steel surface in diffusion chromizing by the pack powder method were tested. Investigations of the layers’ microstructures, phase composition, depth profiles of elements in the layer diffusion zone, and hardness were carried out. Tribological properties (linear wear) of the layers were performed by means of taper-three rolls tests. It has been proved, that the resistance to abrasive wear of the CrC+CrN type hybrid layers is almost two times higher than that for single CrC carbide layers.

Effects of laser heat treatment of steel following diffusion chromizing

Purpose: This paper presents the findings of a study of laser heat treatment of C45 steel following diffusion chromizing. The aim of the study was to assess the effect of laser heating of steel subjected on the microstructure of its surface layer. Design/methodology/approach: Diffusion chromizing was conducted at the temperature of 1050°C for 8 hours in a LABOTHERM LH15/14 laboratory furnace. A powder mixture of the following composition was used to produce the layer: Cr2O3 with an addition of Al, kaolin and an activator – ammonium chloride NH4Cl. Diffusion chromizing of C45 steel was followed by laser heat treatment with a dual diode TRUDISK 1000 laser device. The treatment was carried out in four variants with a laser beam of 400 to 900 W. The microstructure of the surface layer was assessed with a scanning electron microscope Tescan Vega 5135. Hardness tests were carried out by the Vickers method on crosswise microsections. The chemical composition of the diffusion layer was assessed by optical emission spectrometry. Findings: The results revealed the presence of a modified surface layer following laser heat treatment in each of the variants. Research limitations/implications: This study focuses on the effect of laser heating of C45 steel subjected to diffusion chromizing on the microstructure of its top layer. Presented research are the first step of the investigation of the surface layer of steel after diffusion chromizing and laser treatment. Next one will be consisted in detailed investigation of microstructure (phases identification) of the achieved surface layer using (among other methods) X-ray diffraction. Practical implications: Laser heat treatment of C45 steel after diffusion chromizing can be applied to parts of machines and devices used in various branches of industry exposed to tribological wear and corrosion. Originality/value: The results of the experiment were affected by the composition of the powder mixture and process parameters of the diffusion chromizing and the laser treatment.