Generally, tool steels for cold work are obtained by rolling and forging processes. They are treated to have a structure conferring to the material a high toughness limit in terms of wear resistance and endurance. The objective of this study is the thermochemical heat treatment of industrial steel blades made of AISI 02 types, intended for polymer crushing. The effects of nitrocarburizing (Tenifer) and gaseous carbonitriding processes on surface characteristics are considered. These surface treatments increase the usefulness of properties, that is, fatigue strength, wear and corrosion resistance of this microalloyed steel. The influence of treatment duration and the thickness of the layers on surface properties are investigated. The analysis and characterization are carried out using physical analysis [optical microscopy, scanning electron microscopy, X-ray diffraction and glow discharge optical emission spectroscopy (GDOES) techniques] and mechanical measurements (microhardness, weight loss and residual stresses) of treated material. The results are intended to contribute in defining and optimizing the adequate choice of treatments for this type of steel in industrial conditions.
In the present study, the effect of thermal treatment on the mechanical and structural properties of chromium carbide coatings with different thicknesses is evaluated. The coatings were deposited by cathodic magnetron sputtering on XC100 steel substrates. Samples were annealed in vacuum, at different temperatures ranging from 700 to 1000°C for 1 h, resulting in the formation of chromium carbides. X-ray diffraction (XRD), microanalysis X/energy-dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy analysis were used to characterise the samples. Mechanical properties were evaluated by nano-indentation tests and the residual stress was calculated with the Stoney formula. The XRD analysis suggests the formation of the Cr 7 C 3 , Cr 23 C 6 carbides at 900°C. For thin films, they transformed totally to ternary (Cr, Fe) 7 C 3 carbides and their partial transformation has been observed in the case of thick films at 1000°C, without the formation of Cr 3 C 2. The EDS and XPS showed the diffusion mechanism between the chromium film and the steel substrate for the Cr, Fe, C, O elements during the annealing treatment. The increase of chromium film thickness from 0.5 to 2.64 µm, contributed to the significant enhancement of mechanical properties such as hardness (H) (from 12 to 26.3 GPa) and Young's Modulus (E) (from 250 to 330 GPa), respectively.
Gaseous carbonitriding effects on improvement of surface characteristics of new hot working tool steel close to as either chromium AISI H11 or AISI H13 are investigated. Experimental results are related to three aspects: formed layers, microstructure and obtained precipitates. The formed layers are characterised by their basic properties, which are thickness, depth, formed phases, hardness and wear resistance. Microstructure and the diffusion mechanism suggested that high temperature gas carbonitriding process has the potential of improving the mechanical properties with shorter processing time. The arrangement of carbonitrides, nitrides, chromium oxides and retained austenite and Fe 3 C carbides allowed obtaining tool performance from the moderate low mass. Microstructural characterisations were performed by metallographic techniques, electron dispersive energy, X-ray diffraction techniques, optical and scanning electron microscopy and glow discharge optical electron spectroscopy. The mechanical properties were assessed mainly by standard hardness and wear tests.
is an open access repository that collects the work of Arts et Métiers ParisTech researchers and makes it freely available over the web where possible. Binary Cr-N, Zr-N and Cr-Zr-N films were synthesised using a R.F. reactive magnetron sputtering technique by co-sputtering Cr and Zr. The crystalline structure, morphology, mechanical and tribological properties of the films as a function of Zr content were characterised by X-ray diffraction, microanalysis X (WDS, EDS), X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, nanoindentation, scratch adhesion and pin-on-disc sliding wear tests. The residual stress was calculated with the Stoney formula. The Cr-Zr-N films exhibit a two-phase microstructure, containing a cubic (CrN, ZrN) with hexagonal (Cr 2 N, Zr 2 N) phases, as shown by X-ray diffraction. As the Zr content increased, a columnar and compact structure is developed with a low surface roughness. The results reveal that the mechanical and tribological properties of the films were found to depend on the Zr content and the hardness (maximum 26.3 GPa) is greatly improved in comparison with CrN and ZrN films, especially at 31 at.-% Zr. In the scratch test, the hardest film (Cr 0.18 Zr 0.31 N 0.47 ) exhibited an adhesive failure at Lc 2 = 34.3 N.
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