Surface Hardness Of Stainless Steel Research Articles

The “Expanded” Phases in the Low-Temperature Treated Stainless Steels: A Review

Low-temperature treatments have become a valuable method for improving the surface hardness of stainless steels, and thus their tribological properties, without impairing their corrosion resistance. By using treatment temperatures lower than those usually employed for nitriding or carburizing of low alloy steels or tool steels, it is possible to obtain a fairly fast (interstitial) diffusion of nitrogen and/or carbon atoms; on the contrary, the diffusion of substitutional atoms, as chromium atoms, has significantly slowed down, therefore the formation of chromium compounds is hindered, and corrosion resistance can be maintained. As a consequence, nitrogen and carbon atoms can be retained in solid solutions in an iron lattice well beyond their maximum solubility, and supersaturated solid solutions are produced. Depending on the iron lattice structure present in the stainless steel, the so-called “expanded austenite” or “S-phase”, “expanded ferrite”, and “expanded martensite” have been reported to be formed. This review summarizes the main studies on the characteristics and properties of these “expanded” phases and of the modified surface layers in which these phases form by using low-temperature treatments. A particular focus is on expanded martensite and expanded ferrite. Expanded austenite–S-phase is also discussed, with particular reference to the most recent studies.

Increase in surface hardness of stainless steel through graphene growth on stainless steel surface by chemical vapor deposition using waste vegetable oil as a carbon source

Stainless steel has been widely utilized due to it high resistance of corrosion, rust, and stain more than ordinary steel. However, a hardness of stainless-steel surface is not high resulting in engineering applications of stainless steel are limited. Graphene is an extremely hard material therefore the growth of graphene on stainless steel can increase the surface hardness of stainless steel. Vegetable oil consists of triglyceride which has abundant carbon in the constituent. Vegetable oil has been widely used for cooking. After the cooking, a huge amount of the waste vegetable oil is flushed down the drain resulting in water pollution. However, the waste vegetable oil still contains abundant carbon which can be used as a carbon source for graphene growth on stainless steel by chemical vapor deposition (CVD). In this study, the surface hardening of stainless steel through graphene growth on stainless steel by CVD using waste palm oil as a carbon source is demonstrated. The results show that the fourth-used palm oil can be utilized as a carbon source for the growth of graphene on stainless steel by CVD. Moreover, the graphene growth on stainless steel by CVD using the fourth-used palm oil can increase the surface hardness of stainless steel by 175%.

Increasing Surface Hardness of S304 Stainless Steel by High Quality Graphene Grown by Chemical Vapor Deposition

Stainless steel is widely utilized due to its higher corrosion resistance and gloss than ordinary steels. However, the applications of stainless steel are still limited because of its low surface hardness. Graphene is a superb material, which has an intrinsic strength of 130 GPa. In this report, the growth of high quality graphene on S304 stainless steel by chemical vapor deposition using acetylene gas as a carbon source is demonstrated. The surface hardness of stainless steel after growing high quality graphene is investigated by nanoindentation technique. High quality graphene can increase the surface hardness of stainless steel from 1.54 GPa to 10.08 GPa. Moreover, the effect of graphene quality on the surface hardness of S304 stainless steel is studied. High quality graphene grown by CVD using acetylene gas as a carbon source can increase the surface hardness of stainless steel about two times more than low quality graphene grown by using methane gas.

Surface Hardening of Stainless Steel by Coating Graphene Using Thermal Chemical Vapor Deposition

Stainless steel is widely used due to its high resistance to corrosion, rust and stains. However, the surface hardness of stainless steel is not high. This limits its engineering applications. Graphene is a material with a very high intrinsic strength. In order to broaden the range of applications of stainless steel, coating it with graphene is a good choice to enhance its surface hardness. In this report, we have improved the surface hardness of stainless steel by growing graphene on stainless steel surface using thermal chemical vapor deposition. The growth of graphene was also studied. The results show that the growth of graphene on stainless steel can harden the surface of stainless steel.

The improvement of the surface hardness of stainless steel and aluminium alloy by ultrasonic cavitation peening

This article presents first results of the experimental investigation of the influence of the cavitation shot less peening process on the properties of stainless steel and aluminium alloy specimens. The cavitation field was generated by an ultrasonic horn submerged in water and operated by an ultrasonic generator. The temperature of the water was controlled by thermometer and adjusted by separate water cooling system. The mass loss, the mass loss rate and the modification of the surface hardness are evaluated for different cavitation exposure intervals. The mass loss was measured by micro weighing scale and the surface hardness by the micro-hardness meter. The presented results indicates the significant improvement in the surface hardness for both tested materials.

Improving by postoxidation of corrosion resistance of plasma nitrocarburized AISI 316 stainless steels

Austenitic stainless steels are widely used in several industries such as chemistry, food, health and space due to their perfect corrosion resistance. However, in addition to corrosion resistance, the mechanic and tribological features such as wear resistance and friction are required to be good in the production and engineering of this type of machines, equipment and mechanic parts. In this study, ferritic (FNC) and austenitic (ANC) nitrocarburizing were applied on AISI 316 stainless steel specimens with perfect corrosion resistance in the plasma environment at the definite time (4 h) and constant gas mixture atmosphere. In order to recover corrosion resistance which was deteriorated after nitrocarburizing again, plasma postoxidation process (45 min) was applied. After the duplex treatment, the specimens’ structural analyses with XRD and SEM methods, corrosion analysis with polarization method and surface hardness with microhardness method were examined. At the end of the studies, AISI 316 surface hardness of stainless steel increased with nitrocarburizing process, but the corrosion resistance was deteriorated with FNC (570 °C) and ANC (670 °C) nitrocarburizing. With the following of the postoxidation treatment, it was detected that the corrosion resistance became better and it approached its value before the process.

Corrosion and mechanical properties of duplex-treated 301 stainless steel

Plasma nitriding is a widely used technique for increasing the surface hardness of stainless steels, and consequently, for improving their tribological properties. It is also used to create an interface between soft stainless steel substrates and hard coatings to improve adhesion. This paper reports on the mechanical and corrosion properties of AISI301 stainless steel (SS) after a duplex treatment consisting of plasma nitriding followed by deposition of Cr bond coat and CrSiN top layer by magnetron sputtering. Mechanical properties of the deposited films, such as hardness ( H) and reduced Young's modulus ( E r), were measured using depth-sensing indentation. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) were carried out to evaluate resistance to localized and to general corrosion, respectively. The corrosion behavior has been correlated with the microstructure and composition of the surface layers, determined by complementary characterization techniques, including XRD, SEM, and EDS. The CrSiN layers exhibited an H value of 24 GPa, whereas the nitrided layer was shown to present a gradual increase of H from 5 GPa (in the nitrogen-free SS matrix) to almost 14 GPa at the surface. The electrochemical measurements showed that the nitriding temperature is a critical parameter for defining the corrosion properties of the duplex-treated SS. At a relatively high temperature (723 K), the nitrided layer exhibited poor corrosion resistance due to the precipitation of chromium nitride compounds and the depletion of Cr in the iron matrix. This, in turn, leads to poor corrosion performance of the duplex-treated SS since pores and defects in the CrSiN film were potential sites for pitting. At relatively low nitriding temperature (573 K), the nitrided interface exhibited excellent corrosion resistance due to the formation of a compound-free diffusion layer. This is found to favor passivation of the material at the electrode/electrolyte interface of the duplex-treated SS.

Femtosecond and Nanosecond Laser Peening of Stainless Steel

We have compared the results of laser shock peening obtained by using a femtosecond laser with those obtained by using a nanosecond laser. Commercial SUS304 stainless steel was used as the test sample. The sample was subject to femtosecond or nanosecond laser-shock loading in a plasma confined by water. The Vickers microhardness test was used to evaluate the work hardening in the sample due to the plastic deformation induced by the laser peening. The surface hardness of stainless steel increased linearly with laser energy. The results of this study indicate that the extent of work hardening is similar for both femtosecond and nanosecond laser peening.

Avaliação da resistência ao desgaste de aços inoxidáveis endurecíveis por precipitação nitretados

A nitretação por plasma consiste num tratamento efetivo para o aumento das durezas superficiais dos aços inoxidáveis, podendo ser realizada em temperaturas inferiores às usadas nos processos convencionais, evitando-se assim, a formação de nitretos de cromo, que prejudicariam a resistência à corrosão do material. Os aços inoxidáveis endurecíveis por precipitação foram desenvolvidos após a Segunda Guerra Mundial em decorrência das necessidades da indústria aeroespacial, que necessitava de materiais resistentes à corrosão em temperaturas mais elevadas. Nesse trabalho, foi produzido um aço inoxidável endurecível por precipitação com uso de Nb e um aço comercial PH 13-8Mo endurecível por precipitados à base de Cu, para fins de comparação em termos de produção de camadas nitretadas e de resistências ao desgaste abrasivo. O Nb mostrou-se um eficiente formador de precipitados endurecedores do aço, com o pico de dureza ocorrendo em poucos minutos de tratamento. Nos dois aços, obtiveram-se camadas nitretadas com boa uniformidade. A resistência ao desgaste do aço com Nb nitretado foi muito superior à do aço PH 13-8Mo também nitretado.

Solutions to improve surface hardness of stainless steels without loss of corrosion resistance

Ion nitriding is an extensively industrialised process enabling steel surfaces to be hardened by nitrogen diffusion, with a resulting increase in wear, seizure and fatigue resistance. Unfortunately, its direct application to stainless steels, while enhancing their mechanical properties, also causes a marked degradation in their corrosion resistance. By adapting the plasma process however, it is possible to reconcile improvement of tribological properties with maintenance of corrosion resistance. This may be obtained by working with base nitrogen and/or base carbon plasmas. The material properties obtained with a nitrogen plasma are discussed, using, as an example, the application of this process to the control rod clusters of pressurised water nuclear reactors (PWR). This nitriding process is then compared with low temperature nitriding and/or carburising thermionically enhanced low pressure plasma processes which have been recently developed. Following this type of treatment it is possible to increase the wear rate resistance of austenitic stainless steels by 60 to 700 times, while fully conserving the corrosion resistance of the untreated alloy.

Electronic structures and nitride formation on ion-implanted AISI 304L austenitic stainless steel

Abstract A N + 2 implantation technique was employed to improve the surface hardness of stainless steel, and the electronic structures and nitride formation of the ion-implanted layer were investigated and compared with those produced using other techniques, including plasma nitriding. AISI 304L austenite stainless steel was irradiated by 80 keV N + 2 with a dosage ranging from 1.0×10 16 to 1.0×10 18 ions cm −2 at room temperature. The formation of various nitrides was confirmed by X-ray diffraction. The quantitative hardness of the samples was measured by using a Knoop microhardness tester. X-ray photoelectron spectroscopy was also carried out to elucidate the chemical states and electronic structures of the ion-implanted layers. The measurements were repeated after post-annealing at 400 °C for 1 h in a high vacuum. Changes in phase, chemical state and electronic structures were observed according to the ion dose and heat treatment.

Enhanced surface hardness by boron implantation in nitinol alloy

Boron implantation into Nitinol alloy has a potential for developing improved Nitinol root canal instruments with excellent cutting properties, without affecting their superelastic bulk-mechanical properties. The surface hardness of nickel-titanium (NiTi) alloy, also known as "Nitinol" (50 atm% nickel+50 atm% titanium), has been improved by ion-beam surface modification. With an implantation dose of 4.8 x 10(17) boron/cm2, a high concentration of boron (30 atm%) is incorporated into NiTi alloy by 110 keV boron ions at room temperature (25 degrees C). Boron-implanted and unimplanted (pure) Nitinol alloys show surface hardness of 7.6 +/- 0.2 and 3.2 +/- 0.2 GPa, respectively, at the nanoindentation depth of 0.05 micron. The ion-beam-modified NiTi alloy exceeds the surface hardness of stainless steel.