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The corrosion behaviour of low alloy steel type AISI 4130 (before and after nitriding) and austenitic stainless steel type AISI 304L were studied in tap water +3.5 per cent NaCl. A liquid nitriding process had been applied on the low alloy steel.

The tests that were carried out in this study were anodic polarization, rotating bending fatigue and axial fatigue using compact tension (CT). For determining the corrosion potential and pitting potential (breakdown potential) for the alloys, anodic polarization curves were established using the potentiodynamic technique. Rotating bending fatigue tests were used to calculate the fatigue strength and damage ratio. Using linear elastic fracture mechanics, the CT specimens were prepared for determining the threshold stress intensity factor, fatigue crack growth rate and fracture toughness in air and in the solution.

The results showed that nitrided specimens showed higher fatigue strength in air compared to stainless steel. However, the corrosion fatigue limit for both these samples were approximately equal, while this limit for non‐nitrided sample was less. Moreover, the non‐nitrided steel had lower corrosion and pitting potentials than did the stainless steel. In addition, the CT tests showed that the nitrided specimens had a lower resistance to crack initiation in air and the solution compared to the non‐nitrided sample and the stainless steel.

These results can be attributed to the chemical and mechanical behaviour of the nitrided layer constituents, mainly FeN and CrN, which were recognized by X‐ray diffraction. Since, these components consist of very hard particles, they act to increase the hardness and fatigue limit. Moreover, due to the low conductivity of these nitrides, the corrosion and pitting potential of the nitrided steel becomes very high. However, the high breakdown potential does not help to increase the corrosion fatigue or damage ratio values due to the porous nature of the nitrided layer.

Although the nitrided steel had very high fatigue strength and pitting potential, this did not reflect in its corrosion fatigue and/or damage ratio improvement because of its surface roughness and the porous nature of the nitrided layer.

The purpose of this paper is to present the results of a study on friction characteristics of plasma, salt‐bath and gas nitrided layers produced in AISI 304 type austenitic and AISI 420 type martensitic stainless steels.

Plasma nitriding processes were carried out with DC‐pulsed plasma in 80% N₂+20% H₂ atmosphere at 450°C and 520°C for 8 h at a pressure of 2 mbar. Salt‐bath nitriding was performed in a cyanide‐cyanate salt‐bath at 570°C for 1.5 h. Gas nitriding was also conducted in NH₃ and CO₂ atmosphere at 570°C for 13 h. Characterization of all nitrided samples has been carried out by means of microstructure, microhardness, surface roughness measurement and friction coefficient. The morphologies of the worn surfaces of the nitrided samples were also observed using a scanning electron microscope. Friction characteristics of the nitrided samples have been investigated using a ball‐on‐disc friction and wear tester with a WC‐Co ball as the counterface under dry sliding conditions.

The plasma nitrided and salt‐bath nitrided layers on the 420 steel surfaces were much thicker than on the 304 steel surfaces. However, there was no obvious and homogeneous nitrided layer on the gas nitrided samples' surface. The plasma and salt‐bath nitriding techniques significantly increased the surface hardness of the 304 and 420 samples. The highest surface hardness of the 304 nitrided samples was obtained by the plasma nitrided technique at 520°C. On the other hand, the highest surface hardness of the 420 nitrided layers was observed in the 450°C plasma nitrided layer. Experimental friction test results showed that the salt‐bath and 450°C plasma nitrided layers were more effective in reducing the friction coefficient of the 304 and 420 stainless steels, respectively.

The relatively poor hardness and hence wear resistance of austenitic and martensitic stainless steels needs to be improved. Friction characteristic is a key property of performance for various applications of austenitic and martensitic stainless steels. This work has reported a comparison of friction characteristics of austenitic 304 and martensitic 420 stainless steels, modified using plasma, salt‐bath and gas nitriding processes. The paper is of significances for improving friction characteristics, indirectly wear performances, of austenitic and martensitic stainless steels.

The kinetics of nitriding in titanium bearing austenitic stainless steels in cylindrical coordination has been investigated. Nitriding at nitrogen partial pressure of 0.5 atm and temperature from 980°C up to 1160oC resulted in the formation of titanium and chromium nitride and above the Cr2N solvus temperature (1100°C), no chromium nitride was formed. The nitrided case may consist of up to three zones: nitrogen in solid solution, precipitation of TiN and finally mixed TiN+Cr2N precipitation. These are in consistent with the affinity of titanium and chromium towards nitrogen which has been thermodynamically justified. To assess the kinetics of nitriding, a mathematical model for nitrogen diffusion in cylindrical system has been developed via solving Fick’s equation for cylindrical coordinate by numerical method. For this purpose the use has been made of the austenite stabilizing effect of nitrogen to correlate the movement of the boundary of the nitrogen stabilized austenite and plastic deformation induced martensite. Since the crystal structure of the material used in this study is of fcc type and it is nitrided in a fully annealed and unstrained state, therefore the effect of excess nitrogen on the kinetics of nitride fronts growth has been assumed as negligible. The results are in good agreement with the previous investigations. Unlike previous works, the present model takes into account the change of nitrogen diffusion coefficient due to nitrogen concentration profile and

The aim is to provide detailed mechanical and metallurgical examinations of ion‐nitrided austenitic‐stainless steels.

Austenitic‐stainless steel was the material chosen for the present study. Ion nitriding process was applied to fatigue and tensile samples prepared by machining. Process temperature was 550°C and treatment time period 24 and 60 h. Then, tensile, fatigue, notch‐impact, hardness tests were applied and metallographic examinations were performed.

High temperature and longer treatment by ion nitriding decreased fatigue and tensile strengths together with notch‐impact toughness. Scanning electron microscopy and energy dispersive X‐ray spectroscopy analysis revealed formation of nitrides on the sample surfaces. Surface hardness increased with an increase in process time due to diffusion of nitrogen during ion nitriding.

It would be interesting to search the different temperature and time intervals of the ion nitriding. It could be a good idea if future work could be concentrated on ion nitriding on welded stainless steels.

Surfaces of mechanical parts are exposed to higher stress and abrasive forces compared to inside mechanical parts during the time period that mechanical components carry out their expected functions. When stresses and forces exceed the surface strength limit of the material, cracks begin to form at the material surface leading to abrasion and corrosion. Therefore, surface strength of materials needs to be increased to provide a longer service life. Ion (plasma) nitriding is a possible remedy for surface wear.

The main value of this paper is to contribute and fulfil the detailed mechanical and metallurgical examinations of ion‐nitrided austenitic‐stainless steels that are being studied so far in the literature.

This paper aims to clarify the friction properties of 304 steel surface modification. The surface modification includes laser texturing processing and nitriding treatment on 304 steel surface, and then the friction properties’ test was conducted on different friction directions and different upper test samples by using microfriction and wear testing machine.

The diameter and spacing of 100-, 150-, 200-, 300-μm pit array on the surface of 304 steel were calculated using a M-DPSS-50 semiconductor laser device. Then, the textured surface was nitriding-treated using a nitriding salt bath device. The chemical composition, surface morphology and surface microhardness of the composite-modified surface were measured by X-ray diffraction and by using an optical microscope and a microhardness tester. The tribological characteristics of the composite-modified surface were tested by MRTR microcomputer-controlled multifunctional friction and wear testing machine.

The result showed that a rule pit texture surface was obtained by the texture processing. The microhardness of nitriding treatment surface reached 574.27HV0.1, which significantly higher than 222.58HV0.1 of 304 steel. The composite-modified surface has excellent anti-friction and wear resistance properties when the upper specimen was GCr15 steel and ZrO2, respectively. The composite-modified surface has excellent anti-friction and anti-wear properties after long time friction under different angles. However, the friction coefficient and wear morphology of the friction pairs are not affected by the friction angle.

Because of the chosen research approach, the research results may lack generalizability. Therefore, researchers are encouraged to test the proposed propositions further.

The paper conducted a systematic study of the tribological characteristics of 304 steel composite modification surface and provided a good basis for the extensive application of 304 steel.

The study provides a good basis for the extensive application of 304 steel.

This paper fulfils an identified need to study the extensive application of 304 steel.

This study aims to assess the performance of SAF 2205 duplex stainless steel against pure wear, tribo-corrosion, corrosion and the synergism between wear and corrosion. The effect of plasma nitriding conducted at low temperature (380°C) on SAF 2205 steel was analyzed.

Three systems were used for assessing the synergism between wear and corrosion: tribo-corrosion – wear tests conducted using the micro-scale abrasion test, performed under a slurry of alumina particles containing 3.5% NaCl; pure wear – tests conducted using the previous system but isolated in a glovebox with a 99% N2 atmosphere; and cyclic polarization under 3.5% NaCl solution. A hard nitrided layer of 3 µm thickness was characterized using X-ray diffraction, presenting expanded austenite.

The wear mode after micro-scale abrasion tests changed in the absence of an oxygen atmosphere. During pure wear, a mixed mode was identified (rolling + grooving), with the grooving mode more intense for the untreated steel. For tribo-corrosion tests, only rolling wear was identified. For all cases, the nitrided samples presented less wear. The corrosion results indicated a higher repassivation potential for the nitrided condition.

The synergism was more positive for the nitrided sample than for the untreated one, which can be considered for surface treatments of duplex stainless steels in practical applications.

A detailed description of wear mechanisms showed a significant change in the presence of oxygen atmosphere, a new approach for isolating pure wear.

The purpose of this study is to select a proper surface treatment to enhance wear resistance of engine camshafts. The camshaft is a relevant part of a diesel engine which works under torsion, fatigue and wear efforts. They are usually manufactured by casting, forging or machining from forged bar of low alloy steels, and in most cases, the machined surfaces are quenched and tempered by induction heating. After that, in many cases, to withstand the efforts imposed on the active surfaces and improve tribology and fatigue properties, the industry used for decades, thermochemical technologies such as salt bath or gaseous nitriding and nitrocarburizing processes.

This paper studied the effects of plasma nitriding and plasma nitrocarburizing, on the tribological behaviour of the steel SAE 1045HM3 proposed to produce camshafts. After the plasma treatments, the change in surface roughness was measured; the modified layers were studied by X-ray techniques and its thickness by optical microscopy. The diffusion zone was evaluated by Vickers microhardness determinations. Tribology tests were performed by pin-on-disc configuration using WC ball as a counterpart.

Results show that plasma nitrided samples present the best tribological behaviour compared with the nitrocarburized ones; also, the influence of the roughness produced by the thermochemical processes appears to be important.

Although both the plasma treatments have been applied for many years, and also reported separately in the scientific literature, there was no information comparing these two treatments for carbon steels, and also, there is not much about tribology in lubricated conditions of nitrided and nitrocarburized carbon steels. In fact, it is not proved that the porosity of the nitrocarburized layer is beneficial for wear resistance in lubricated conditions. In this paper, it was proved that at least in the tested conditions, it is not.

Gas or plasma nitrocarburizing is usually recommended for this kind of applications, although the modified layer is porous. This paper attempts to prove that nitriding could be better than nitrocarburizing, even with a thinner white layer.

This work aims to investigate the wear behavior of manganese phosphate coating on plasma nitrided AISI 5140 steel.

Prior to manganese phosphate coating, plasma nitriding of substrates was performed at gas mixture of 50 percent H₂ and 50 percent N₂, for the different treatment parameters. The structural, mechanical and tribological properties of the substrates were determined using hardness test, optical microscope, scanning electron microscopy , X‐ray diffraction and pin‐on‐disk tribotester. The wear behavior of untreated, nitrided and duplex treated substrates was evaluated under dry sliding conditions.

The results indicated that the duplex treatment improved the wear behavior. It was also observed that manganese phosphating of the nitrided substrates at low temperature (450°C‐2h‐N) resulted in a decrease of the wear rate and yielded a reduction in the friction coefficient by forming a transfer film at the counter face.

This study can be a practical reference and offers insight into the effects of duplex treating on the increase of wear resistance.

Fretting wear exists widely in the field of matching mechanical parts whereas previous research studies mostly focus on the point contact through a ball-plate tribometer. This paper aims to study the influence of wear debris on the fretting wear characteristics of the nitrided medium carbon steel under line contact condition at elevated temperature.

Fretting wear behavior of the nitrided medium carbon steel was experimentally investigated under line contact condition at elevated temperature and different normal loads without lubrication. Wear loss, worn surface and wear debris were studied to analyze the wear mechanism of nitrided steel.

The results showed that surface hardness of the medium carbon steel was notably improved because of the generation of a 230 µm nitrided case. Wear loss increased with the normal load, which was associated with the damage of a thin solid film formed by the wear debris, consisting of iron oxides and chromium oxide rather than only iron or iron oxides. The wear debris became partially amorphous and spherical because it was trapped within the contact interface and was ground, rolled, oxidized under line contact conditions. The spherical wear debris acted as a third body and formed a lubricating film between the contact faces. This lubricating film helped to stabilize the friction coefficient and reduced the wear rate, which further caused the acceleration of wear volume to gradually decrease. The wear mechanisms of the nitrided steel were oxidation wear, abrasive wear and fatigue spalling of the oxide layer.

The findings are helpful to understand the fretting wear behavior of the friction pair under line contact and enrich the fretting tribology theory.

The purpose of this paper is to enhance the corrosion resistance of Cr-Mn austenitic stainless steel (ASS) via low temperature salt bath nitriding and to replace the convectional Cr-Ni ASS with newly developed enhanced corrosion resistive Cr-Mn ASS.

The low temperature salt bath nitriding was performed on Cr-Mn ASS at 450°C for 3 h in potassium nitrate salt bath.

The present paper compares the corrosion resistance of salt bath nitrided Cr-Mn ASS with convectional Cr-Ni ASSs (316 L and 304 L ASSs) in 3.5 per cent NaCl by electrochemical techniques. The electrochemical impedance spectroscopy result shows the increase in film resistance and potentiodynamic polarization results show the enhanced corrosion resistance of nitrided Cr-Mn ASS, which is almost equivalent to that of 316 L and 304 L ASSs. This is attributed to the formation of nitrogen supersaturated dense nitride layer. The present results therefore suggest that the nitrided Cr-Mn ASS may replace costly convectional Cr-Ni ASSs for commercial and industrial applications.

Ever-increasing price of nickel (Ni) is driving the industries to use Ni-free or low-Ni austenitic stainless steels (ASSs). But its corrosion resistance is relatively poor as compared to conventional Cr-Ni ASSs. However, its corrosion resistance can be improved by nitriding. The low temperature salt bath nitriding of Cr-Mn ASS and its electrochemical behavior in 3.5 per cent NaCl has not been studied. The present research paper is beneficial for industries to use low cost Cr-Mn, enhance its corrosion resistance and replace the use of costly conventional Cr-Ni ASSs.