Microstructure and corrosion behaviour of pulsed plasma-nitrided AISI H13 tool steel (original) (raw)
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Surface & Coatings Technology, 2009
The influence of microstructure on the corrosion behavior of pulsed plasma nitrocarburized AISI H13 tool steel in NaCl 0.9 wt/V % solution is reported. The samples were prepared with different nitrocarburizing treatment times using a constant [CH 4 /H 2 +N 2 ] gaseous mixture by a DC pulsed plasma system. The microstructure of the nitrocarburized layers was analyzed by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction. The corrosion behavior was evaluated by potentiodynamic polarization experiments. The nitrocarburizing process considerably improves the corrosion resistance of the material in a NaCl environment as compared to the untreated H13 steel. The modified surface layer mainly consisting of ε-Fe 2-3 (C,N) and γ′-Fe 4 N phases confers this outstanding behavior. The corrosion resistance dependence on specific nitrocarburizing processes is reported and the role of the surface porosity is discussed.
Influence of alloyin elements on the corrosion properties of steels during plasma nitriding process
Plasma nitriding has potential as an industrial process to improve the wear, fatigue and corrosion resistance of steels. It is well known that the corrosion properties of stainless steel deteriorate when treated with temperatures above 450 0 C. This is because the chromium-alloying element, which is responsible for protection against corrosion, gets converted to chromium nitrides at these temperatures. Whereas low alloy steels and high alloy steels exhibit better corrosion resistance. This is due to the presence of iron nitrides and few chromium nitride phases. In this study an attempt is made to study the effect of alloying elements on the corrosion properties of EN 8 (AISI 1045), En 24 (AISI 4340), AISI H13 and AISI 304 steels during plasma nitriding.
Effects of low and high temperature plasma nitriding on electrochemical corrosion of steel
Materials Today: Proceedings, 2020
This study concerns plasma nitriding of tool steel at different temperatures and its effects on corrosion resistance. Inside the nitriding reactor steel samples were placed on the sample holder after metallographic polishing and then the vacuum chamber was evacuated to a pressure of $0.5 Pa. At a lower temperature of 450°C and the higher temperature of 550°C nitriding was performed for a fixed duration of 10 h. All the nitrided and the bare steel samples studied under X-ray diffraction (XRD) and scanning electron microscopic analysis/energy dispersive X-ray spectroscopy (EDS). Iron nitride (Fe x N, x = 2-3, 4) peaks were revealed in the nitrided steels after XRD analyses. EDS revealed the increased amount of nitrogen in the nitrided sample treated at 550 °C. For the assessment of corrosion resistance of these steel samples potentiodynamic polarization tests were performed in 3.5% NaCl. On comparison, it was found that the steel nitrided at higher temperature is more effective in enhancing the corrosion resistance.
Surface and Coatings Technology, 2004
AISI 410 martensitic stainless steel samples with different metallurgical structures were DC-pulsed plasma nitrided at 623, 723 and 773 K. The samples were ion nitrided in an industrial equipment using a gas mixture consisting of 25% N 2 +75% H 2 under a pulsed DC glow discharge. Optical and scanning electron microscopy, as well as glancing angle X-ray diffraction and microhardness measurements have been used to study the ion nitrided surfaces. All plasma nitrided samples showed surface hardness values higher than 1000 HV; the highest value was obtained at 673 K. The case depth was approximately 30 Am for samples nitrided at 673 and 773 K, while the sample nitrided at 623 K showed an 'expanded ferrite' phase (a N ) and an incipient precipitation of Fe 4 N. Depending on the treatment temperature and time, two fronts were formed, termed diffusion front and transformation front; the latter produces a softening of the nitrided case. Electrochemical measurements showed a decrease of corrosion resistance in the samples nitrided during 20 h at 673 and 773 K. Conversely, the sample nitrided at 623 K presented a low corrosion current and more noble corrosion potential. D
On the wear and corrosion of plasma nitrided AISI H13
Surface and Coatings Technology, 2019
Tool steels are applied in a variety of industrial operations providing a good balance of properties. Surface engineering has the potential to improve productivity and further extend the lifetime of metallic components. In the present work plasma nitriding is applied to the hot work AISI H13 tool steel to improve wear and corrosion characteristics. The steel was nitrided in the tempered condition at three different temperatures and pressures for 5 h of duration. At 450°C of nitriding temperature mainly a diffusion zone is observed while a compound layer is produced at 550 and 650°C. Both surface and bulk hardness decrease as nitriding temperature is increased. Xray diffraction indicates that a mixture of both ε and γ′ iron nitrides is produced in all cases. The content of εnitride appears to decrease with temperature while γ′-nitride and CrN increase. Working pressure does not lead to significant alterations in phase proportion, hardness and wear resistance after plasma nitriding at a given temperature. However, increasing processing temperature, from 450 to 650°C, reduces the wear coefficient from 1.19 • 10 −7 to 7.06 • 10 −8 mm 3 /N•m, respectively, while from the base steel such coefficients are in the order of 10 −5 mm 3 /N•m. Regarding the corrosion behavior, plasma nitriding at 450 and 550°C yields higher corrosion potentials, lower current densities and an extensive passivation range, while the tempered substrate, irrespective the condition, exhibits no passivation. From the wear and corrosion perspective it is concluded that plasma nitriding at 450 or 550°C leads to better corrosion properties while nitriding at 650°C yields a better wear performance.
Plasma nitriding of 90CrMoV8 tool steel for the enhancement of hardness and corrosion resistance
Surface and Coatings Technology, 2011
The aim of the study is to apply a plasma nitriding process to the 90CrMoV8 steel commonly employed in wood machining, and to determine its efficiency to improve both mechanical and electrochemical properties of the surface. Treatments were performed at a constant N 2 :H 2 gas mixture and by varying the temperature and process duration. The structural and morphological properties of nitrided layers were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) coupled with EDS microanalyses. Surface hardening and hardness profiles were evaluated by micro hardness measurements. To simulate the wood machining conditions, electrochemical tests were carried out with an oak wood electrolyte with the purpose of understanding the effects of the nitriding treatment on the corrosion resistance of the tool in operation. X-ray diffraction analyses revealed the presence of both γ′ (Fe 4 N) and ε (Fe 2-3 N) nitrides with a predominance of the ε phase. Moreover, α-Fe (110), γ′ and ε diffraction peaks were shifted to lower angles suggesting the development of compressive stresses in the post nitrided steel. As a result, it was shown that nitriding allowed a significant hardening of steel with hardness values higher than 1200 HV. The diffusion layers were always composed of an outer compound layer and a hardened bulk layer which thickness was half of the total diffusion layer one. No white layer was observed. Similarly, no traces of chromium nitrides were detected. The temperature seemed to be a parameter more influent than the process duration on the morphological properties of the nitrided layer, while it had no real influence on their crystallinity. Finally, the optimal nitriding conditions to obtain a thick and hard diffusion layer are 500°C for 10 h. On the other hand, to verify the effect of these parameters on the corrosion resistance, potentiodynamic polarization tests were carried out in an original "wood juice" electrolyte. After corrosion, surface was then observed at the SEM scale. Electrochemical study indicated that the untreated steel behaved as a passive material. Although the very noble character of steel was somewhat mitigated and the corrosion propensity increased for nitrided steels, the passive-like nature of the modified surface was preserved. For the same optimized parameters as those deduced from the mechanical characterization (500°C, 10 h), surface presented, in addition to a huge surface hardening, a high corrosion resistance.
Plasma Nitriding and Its Effect on the Corrosion Resistance of Stainless Steel 1.4006
Acta Mechanica Slovaca
The plasma nitriding (PN) technology was applied on the martensitic stainless steel 1.4006. The influence of PN on the corrosion resistance of selected material was investigated. The chemical composition of selected steel was verified using the Q4 TASMAN device. The PN process was performed using two stage nitriding procedure. After plasma cleaning procedure at 515 °C for 45 min in a nitriding atmosphere ratio 20H2:2N2 (l/h) was the first stage nitriding procedure performed at 520°C for 16 hours in a nitriding atmosphere ratio 25H2:5N2 (l/h) and followed by the second stage of nitriding procedure performed at 525°C for 4 hours in a nitriding atmosphere ratio 28H2:4N2 (l/h). The microstructure and mechanical properties of the nitride layers were studied using OES spectrometry, optical microscopy, and hardness testing. The depths of plasma nitride layers were also estimated using a cross-sectional microhardness profiles measurement. The corrosion resistance testing of PN stainless steel 1.4006 samples were carried out in a 5 % neutral sodium chloride solution (NSS) in accordance with ISO 9227 standard in the VLM GmbH SAL 400-FL corrosion chamber and visually evaluated. Microhardness and surface hardness of experimental samples were significantly increased, but the corrosion resistance remarkably decreased.
Elevated temperature plasma nitriding and effects on electrochemical properties of steel
Materials Today: Proceedings, 2019
Surface modification of tool steel had been performed by utilizing plasma nitriding at elevated temperature by varying the exposure time. The nitrided steel had shown significantly enhanced corrosion resistance properties. X-ray diffraction (XRD) had revealed the presence of Fe x N (x = 2-3, 4) in the surface modified microstructure after nitriding. In an environment of NaCl potentiodynamic polarization and impedance (EIS) tests of steel with and without nitriding had been performed. Both these tests had shown the improved resistance to corrosion of the steel after nitriding.
2010
This paper compares the ferritic and austenitic plasma nitriding and nitrocarburizing behavior of AISI 4140 low alloy steel carried out to improve the surface corrosion resistance. The gas composition for plasma nitriding was 85% N 2 -15% H 2 and that for plasma nitrocarburizing was 85% N 2 -12% H 2 -3% CO 2 . Both treatments were performed for 5 h, for different process temperatures of 570 and 620°C for ferritic and austenitic plasma treatment, respectively. Optical microscopy, X-ray diffraction and potentiodynamic polarization technique in 3.5% NaCl solution, were used to study the treated surfaces. The results of X-ray analysis revealed that with increasing the treatment temperature from 570 to 620°C for both treatments, the amount of e phase decreased and c 0 phase increased. Nitrocarburizing treatment resulted in formation of a more amount of e phase with respect to nitriding treatment. However, the highest amount of e phase was observed in the ferritic nitrocarburized sample at 570°C. The sample nitrided at 620°C exhibited the thickest layer. The potentiodynamic polarization results revealed that after plasma nitriding and nitrocarburizing at 570°C, corrosion potential increased with respect to the untreated sample due to the noble nitride and carbonitride phases formed on the surface. After increasing the treatment temperature from 570 to 620°C, corrosion potential decreased due to the less e phase development in the compound layer and more porous compound layer formed at 620°C with respect to the treated samples at 570°C.