Nanosized precipitates in H13 tool steel low temperature plasma nitriding (original) (raw)
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In this paper we report the influence of temperature (260 to 510 °C) on the AISI H13 steel microstructure and hardness in pulsed plasma nitriding processes. The experimental results show that bulk nitrogen penetration is well represented by a temperature-activated law. Even at the lowest studied temperatures, grain boundary diffusion causes nitrogen to move relatively deep in the bulk sample. The microstructure was studied by X-ray diffraction analysis at grazing angle and in the Bragg–Brentano configuration. Scanning Electron Microscopy with spatially resolved Xray energy disperse spectroscopy was also employed to map nitrogen influence on the morphology of the material. Also, surface (frontal) and profiling nano-indentation was utilized to elucidate the effect of the temperature on the nitrited material hardness.
FORMATION OF LAYERS BY PLASMA NITRIDING IMPOSED TO 32CrMoV13 LOW ALLOY STEEL
The aim of the study is to optimise the application of heat treatments by modifying the nitriding conditions in high temperature process. The influence of gas mixture (composed of N2, H2 and CH4) and time of nitriding on the mechanical and structural properties of 32CrMoV13 low alloy steel samples was studied. The composition and structure of the nitrided layers was determined by EDS and XRD respectively. Vickers micro hardness profiles were also performed to study the influence of the gas mixture and time of nitriding. The morphology of the nitrided layers was observed by optical microscopy. EDS analyses permitted to verify the composition of the layers while their structure was determined by XRD. The time of nitriding was influent on the diffusion layer's thickness and properties. Furthermore, it was obvious that increasing the nitrogen contents from 20 to 80 % in the nitriding gas mixture N2+H2 or adding 5% of methane permits to increase the nitrided layer's thickness a...
Near-surface composition and microhardness profile of plasma nitrided H-12 tool steel
Materials Science and Engineering: A, 1998
Samples of AISI H-12 tool steel were plasma nitrided at 500°C in a mixture of H 2-20% N 2 under a total pressure of 6 mbar, by using DC and pulsed glow discharges. The treatment time varied from 1 to 6 h. X-ray diffraction (glancing angle and q-2q geometry), conversion electron Mö ssbauer spectroscopy, conversion X-ray Mö ssbauer spectroscopy, electron probe microanalysis, optical micrograph and Vickers microhardness were used as analytical techniques. The obtained results suggest that, under the present experimental conditions: (i) The near-surface compound layer consists of a mixture of k%-Fe 4 N and m-Fe x (N, C); (ii) the near-diffusion zone compound layer consists of a mixture of k%-Fe 4 N, m-Fe x (N, C), h¦-Fe 16 N 2 and k-austenite; (iii) the dependence of compound layer thickness on nitriding time violates the parabolic behavior and emphasizes effects from cathode sputtering and radiation-enhanced diffusion.
Influence of the microstructure on steel hardening in pulsed plasma nitriding
The plasma technologies are widely used in metal surface engineering processes. Basically, these treatments improve the mechanical, tribological, and chemical properties of the material such as wear resistance, hardness, fatigue resistance, friction, and corrosion resistance. In this work, a comprehensive study of the influence of the microstructure on hardness of AISI P20 steel treated at different temperatures and times by pulsed plasma nitriding is reported. The processes were done by using a pulsed plasma industrial system. The samples were characterized by nano-indentation hardness, x-ray diffraction XRD, scanning electron microscopy SEM, and x-ray dispersion spectroscopy EDS. At lower treatment temperatures 360 ° C, a high density of small lamellar precipitates, constituted by more-Fe 2–3 N phase than-Fe 4 N phase, is formed. At intermediate treatment temperatures 480 ° C, big lamellar precipitates, constituted by more-Fe 4 N phase than-Fe 2−3 N phase, are formed at grain boundary. At higher treatment temperatures 520 ° C, the nitrided layer does not contain lamellar precipitates and it is only constituted by-Fe phase saturated in nitrogen. Hardness depends on size, shape, and distribution of precipitates and crystalline phases microstructure. The higher hardness values are obtained when more and smaller lamellar precipitates are presented and constituted by more-Fe 2−3 N phase.
Microstructure of tool steel after low temperature ion nitriding
The microstructural development in H13 tool steel upon nitriding by an ion beam process was investigated. The nitriding experiments were performed at a relatively low temperature of ,400uC and at constant ion beam energy (400 eV) of different doses in a high vacuum preparation chamber; the ion source was fed with high purity nitrogen gas. The specimens were characterised by X-ray photoelectron spectroscopy, electron probe microanalysis, scanning and transmission electron microscopy, and grazing incidence and Bragg-Brentano X-ray diffractometry. In particular, the influence of the nitrogen surface concentration on the development of the nitrogen concentration depth profile and the possible precipitation of alloying element nitrides were discussed.
The modification of steel (AISI 316L and AISI 4140) surface morphology and underlying inter-crystalline grains strain due to Xeþ ion bombardment are reported to affect nitrogen diffusion after a pulsed plasma nitriding process. The ion bombardment induces regular nanometric patterns and increases the roughness of the material surface. The strain induced by the noble gas bombardment is observed in depths which are orders of magnitude larger than the projectiles' stopping distance. The pre-bombarded samples show peculiar microstructures formed in the nitrided layers, modifying the in-depth hardness profile. Unlike the double nitrided layer normally obtained in austenitic stainless steel by pulsed plasma nitriding process, the Xeþ pre-bombardment treatment leads to a single thick compact layer. In nitrided pre-bombarded AISI 4140 steel, the diffusion zone shows long iron nitride needle-shaped precipitates, while in non-pre-bombarded samples finer precipitates are distributed in the material.
Small-scale structural and mechanical characterization of the nitrided layer in martensitic steel
Tribology International, 2013
ABSTRACT Pulsed Plasma Nitriding (PPN) of high-strength low-alloy steels used for offshore applications is a promising approach for controlling erosion, corrosion and hydrogen embrittlement under service conditions. In this work, the microstructure, composition and hardness of the nitride layer produced by an optimized PPN process on 2.25Cr–1Mo steel were examined. The nanomechanical properties of the nitride layer were investigated via nanoindentation along the depth of the nitride layer to understand the interconnected effect of the existing microstructure with the one developed after the nitriding process and the nitrogen concentration. The results showed that the nitride layer is composed of a compound layer and diffusion layer with hardness four times higher than the untreated material, which gradually decreases across the diffusion layer.
Surface and bulk modifications in steels after Xe þ ion bombardment are studied. The influence of Xe þ pre-bombardment in steels on pulsed plasma nitriding is examed. Xe þ bombardment induces morphological and structural modifications in steel surface. Modifications by Xe þ bombardment affect nitrides cases microstructure and hardness. a b s t r a c t The modification of steel (AISI 316L and AISI 4140) surface morphology and underlying inter-crystalline grains strain due to Xe þ ion bombardment are reported to affect nitrogen diffusion after a pulsed plasma nitriding process. The ion bombardment induces regular nanometric patterns and increases the roughness of the material surface. The strain induced by the noble gas bombardment is observed in depths which are orders of magnitude larger than the projectiles' stopping distance. The pre-bombarded samples show peculiar microstructures formed in the nitrided layers, modifying the in-depth hardness profile. Unlike the double nitrided layer normally obtained in austenitic stainless steel by pulsed plasma nitriding process, the Xe þ pre-bombardment treatment leads to a single thick compact layer. In nitrided pre-bombarded AISI 4140 steel, the diffusion zone shows long iron nitride needle-shaped precipitates, while in non-pre-bombarded samples finer precipitates are distributed in the material.
SSRG International Journal of Mechanical Engineering, 2022
This study investigated the hardness and wear on DIN 1.2367 hot work tool steel after applying plasma and gas nitriding processes under different conditions. The effect of the plasma nitriding process temperature and the N2:H2 gas mixture ratio was examined in the first group of specimens, whereas the impact of the gas nitriding nitrogen potential and retention time was investigated in the second group of specimens. In the plasma nitriding process applied to the first group, the increase in the N2 ratio in the gas mixture significantly increased the hardness and wear properties of the material. In addition, the wear resistance of the specimen with the highest hardness value was increased. Although the nitriding time and potential nitrogen values in the second group had changed, the diffusion depth and hardness distribution were found to be close.
Metallurgical response of an AISI 4140 steel to different plasma nitriding gas mixtures
Materials Research, 2013
Plasma nitriding is a surface modification process that uses glow discharge to diffuse nitrogen atoms into the metallic matrix of different materials. Among the many possible parameters of the process, the gas mixture composition plays an important role, as it impacts directly the formed layer's microstructure. In this work an AISI 4140 steel was plasma nitrided under five different gas compositions. The plasma nitriding samples were characterized using optical and scanning electron microscopy, microhardness test, X-ray diffraction and GDOES. The results showed that there are significant microstructural and morphological differences on the formed layers depending on the quantity of nitrogen and methane added to the plasma nitriding atmosphere. Thicknesses of 10, 5 and 2.5 µm were obtained when the nitrogen content of the gas mixtures were varied. The possibility to obtain a compound layer formed mainly by γ '-Fe 4 N nitrides was also shown. For all studied plasma nitriding conditions, the presence of a compound layer was recognized as being the responsible to hinder the decarburization on the steel surface. The highest value of surface hardness-1277HV-were measured in the sample which were nitrided with 3vol.% of CH 4 .