Effect of High Strain-Rate Deformation and Aging Temperature on the Evolution of Structure,Microhardness, and Wear Resistance of Low-Alloyed Cu–Cr–Zr Alloy

The effect of the preliminary high strain-rate deformation, performed via the method of dynamic channel-angular pressing (DCAP), and subsequent annealings on the tribological properties of a dispersionhardened Cu–0.092 wt % Cr–0.086 wt % Zr alloy has been investigated. It has been shown that the surfacelayer material of the alloy with a submicrocrystalline (SMC) structure obtained by the DCAP method can be strengthened using severe plastic deformation by sliding friction at the expense of creating a nanocrystalline structure with crystallites of 15–60 nm in size. It has been shown that the SMC structure obtained by the high strain-rate DCAP deformation decreases the wear rate of the samples upon sliding friction by a factor of 1.4 compared to the initial coarse-grained state. The maximum values of the microhardness and minimum values of the coefficient of friction and shear strength have been obtained in the samples preliminarily subjected to DCAP and aging at 400°С. The attained level of microhardness is 3350 MPa, which exceeds the microhardness of the alloy in the initial coarse-grained state by five times.     

Effect of Cold Deformation on the Friction–Wear Property of a Biomedical Nickel-Free High-Nitrogen Stainless Steel

The microstructural,mechanical and corrosion properties of different cold-rolled biomedical nickel-free highnitrogen stainless steels(NFHNSSs) were investigated to study the effect of cold deformation on its dry wear resistance as well as corrosion–wear behaviors in distilled water and Hank's solution. The results indicated that NFHNSS was characterized by stable austenite and possessed excellent work-hardening capacity; due to increasing cold deformation,the corrosion resistance just decreased very slightly and the dry wear rate decreased initially but subsequently increased,while the corrosion–wear resistance was improved monotonically in both distilled water and Hank's solution in spite of the presence of corrosive ions. The friction coefficients for different cold-rolled NFHNSSs were very close under the same lubricating condition,but they were the largest in distilled water compared to that in dry wear tests and Hank's solution.     

Al, Si, and Al�CSi Coatings to Improve the High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

Oxidation resistance of chromium steels is due to the formation of Cr₂O₃ on the surface. However, this surface layer destabilizes above 1,000 °C and does not protect the metal. In this study, three types of coatings were applied to AISI 304 stainless steel (SS), and the microstructure and oxidation resistance of the coatings were investigated. Aluminum coating, silicon coating, and the codeposition of Al and Si were deposited on an SS substrate by the pack cementation method. The microstructure of the samples was then examined by SEM and EDS, and phases were identified by XRD. The oxidation resistance of these samples was studied in air at 1,050 °C. The results showed that the best resistance to oxidation was obtained, in order, from the codeposition of Al?CSi, Al coating, and Si coating.     

Improved Oxidation Resistance of a New Aluminum-Containing Austenitic Stainless Steel at 800 °C in Air

The oxidation resistance of austenitic stainless steels modified with various aluminum contents was investigated. The weight gain per unit area is in parabolic relation to oxidation time, and the oxidation rate significantly decreases with increased aluminum content. Outer layer oxides of austenitic stainless steel transform from Cr₂O₃ to a composite oxide layer comprising Cr and Al, and more dense Al-containing oxides formed with increasing the added Al contents. Since the diffusion of element Al is enhanced and the diffusion of element Cr is inhibited, the oxides enriched in Al dramatically contribute to the improved oxidation resistance of austenitic stainless steels at high temperature. The possible oxidation mechanisms are also proposed based on microstructural observations.     

The Effect of NiAl Coatings on Oxidation Behavior of AISI 403 Stainless Steel

STAINLESS STEEL TYPE AISI403possess a highdegree of resistance to atmospheric corrosion becauseof its ability to form a dense adherent oxide film,whichprotects the material from further attack[1].Thiscomposition was developed to meet the requirementsfor some gas turbine components.The alloy is notparticularly recommended for use in hot corrosion andoxidation environments.Therefore,a protective coatinglayer is essential for such applications as hot sectioncomponents in gas turbine[2].A…     

The Effect of NiAI Coatings on Oxidation Behavior of AISI 403 Stainless Steel

This paper reports the oxidation behavior of stainless steel type 403 as a substrate material with and without NiAl coating. Evaluation of oxidation resistance was performed on uncoated and coated specimens at 850 and 1050℃. Acommercial diffusion process was used for the formation of NiA1 intermetallic coatings on the specimens. Before aluminizing, a layer of nickel, about 40μm, was deposited on specimens by electroplating. Various techniques including SEM, EDAX, optical microscopy and micro-hardness testing were employed to investigate the coatings before and after oxidation tests. Nickel-aluminides produced by two stage; plating-aluminizing, treatment with NiA1 on the surface increased the performance of stainless steel samples significantly.     

Effect of Intergranular Precipitation on the Internal Oxidation Behavior of Cr–Mn–N Austenitic Stainless Steels

The effect of intergranular precipitation on the internal oxidation behavior of Cr–Mn–N austenitic steels at 1000 °C in dry air atmosphere was investigated using scanning electron microscope, transmission electron microscope, and X-ray diffraction analysis. The results show that intergranular M23C6 carbide morphologies play an important role on the internal oxidation behavior of Cr–Mn–N steels. During the period of the oxidation, both discontinuous chain-shaped and continuous film-shaped intergranular M23C6 carbides precipitated along the grain boundaries. Internal oxides of silica preferentially intruded into the matrix along grain boundaries with discontinuous M23C6 carbide particles, while silica was obviously restricted at the interfaces between the external scale and matrix on the occasion of continuous film-shaped M23C6 carbides. It is seemed that reasonable microstructure could improve the oxidation resistance of Cr–Mn–N steels.     

Investigations on the Corrosion Behaviour and Structural Characteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. However, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel.The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fcc lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in H2SO4) and pitting corrosion (in NaCl).     

The Effect of Intensity Pulsed Ion Beam Irradiation on Wear Resistance of High-speed Steel

INTENSITY pulsed ion beam(IPIB)technology hasbeen developed over the last two decades primarily fornuclear fusion and high-energy density physicsresearch,which is also named as high-intensity pulsedion beam technology(HPIB)and becomes a newmodification technique of materials surface such as inthe fields of metal materials modification,functionalfilms and nano-powder synthesis[1-5].Directdeposition of a beam into a solid surface results in arapid melt and resolidification with heating and…     

Effect of Pre-Oxidation at 800?��C on the Pitting Corrosion Resistance of the AISI 316L Stainless Steel

In situ X-ray diffraction was used to identify the oxides formed on the AISI 316L (containing 2% Mo) stainless steel during isothermal oxidation at 800 °C, in air. Good oxidation behavior was observed on this steel when considering kinetics, structural characteristics and scale adherence. It was demonstrated that molybdenum plays a protective role in that it hinders the outward iron diffusion and leads to the lower growth rate and the better scale adherence. The oxide scale was then composed of Cr₂O₃ with a small amount of Mn_1,5Cr_1,5O₄ at the external interface. Pre-oxidation of the AISI 316L also improved its aqueous corrosion resistance. No pitting corrosion occured during the corrosion test. Aqueous corrosion testing also showed that the oxide scale formed at 800 °C is crack-free and still adherent after cooling to room temperature.     

Effect of Pyrrole and N-Methylpyrrole Coatings on Corrosion Resistance of Mild Steel

COATING ON THE SURFACE of metals bypolymeric materials have been widely used inindustries for the protection of this materials against ofcorrosion[1-4].Electropolymerization is an effective technique forthe surface coating of various conductive materialswith wide variety of polymers with various thick nesses[5].Recently,electropolymerization of pyrrole on steelsubstrates has been investigated with the aim ofproducing uniform and strongly adherent coatings[6-9].It was found that only lim…     

Adsorption of the IFKhAN-92 Inhibitor on Chromium–Nickel Steel from Mineral Acid Solutions

Protection of Metals and Physical Chemistry of Surfaces - Impedance spectroscopy was used to study the adsorption of the IFKhAN-92 inhibitor, a triazole derivative, on cathodically polarized...     

Effect of Plastic Deformation on the Structure and Properties of High-Nitrogen Alloys of the Fe – Cr System

The structure, strength, and ductility of alloys of the Fe – Cr – N system bearing from 15 to 24% chromium and from 0.4 to 1.3% nitrogen are studied after rolling at 20, 450, 800, 900, 1000, 1100, and 1200°C. It is shown that the highest hardening due to cold plastic deformation is provided in alloys with metastable -solid solution that undergoes transformation into strain martensite ( ). In hot plastic deformation the alloys are hardened due to the formation of a fragmented structure. The data of electron microscopic studies are used to determine the role of the phase composition in the hardening of the alloys.     

The Effect of Silicon on the Electronic Structure and Corrosion–Electrochemical Behavior of Austenitic Steels1

The regularities of the effect produced by alloying with silicon (up to 6% Si) on the corrosion–electrochemical behavior of austenitic stainless steels of various structure types (single-phase or with the precipitation of second phases) in a solution of 1 mol/l HClO₄ + 0.25 mol/l NaCl at 22°C and in 27 and 65% HNO₃ at 70°C and at the boiling point are clarified. Nuclear -resonance (Mössbauer) spectroscopic studies enabled us to develop a mechanism of enhancing the passivability of the steels studied at potentials corresponding to their active–passive transition and accelerating the transpassivation process by silicon. The hypothesis proposed is based on the change in the electron density distribution around iron nuclei induced by silicon and accordingly the change in the chemisorption interactions between the surface iron atoms and the polar molecular and ionic components of the solution.     

The Effect of Water Vapor on the Transition from Internal to External Oxidation of Austenitic Steels at 1,073 K

The effect of water vapor on the transition from internal to external oxidation of austenitic alloys has been conducted at 1,073 K under the equilibrium oxygen partial pressure for the coexistence of Fe and FeO. Critical Cr concentrations in the Fe–Cr–30Ni (at.%) austenitic alloys were determined to be 30 at.% in dry atmosphere and 37 at.% in humid atmosphere. Thus, water vapor significantly affected the transition from internal to external oxidation of austenitic alloys. Two oxides of Cr₂O₃ and FeCr₂O₄ precipitated in the Fe–5Cr–30Ni (at.%) alloy and solid state reaction for the formation of FeCr₂O₄ may be influenced by water vapor. Oxygen permeability, which was estimated by considering the effective stoichiometric ratio, was also enhanced by water vapor.     

Study of the Adsorption of the IFKhAN-92 Inhibitor on the Surface of Chromium–Nickel Steel from Hydrochloric and Sulfuric Acid Solutions by Ellipsometry

Protection of Metals and Physical Chemistry of Surfaces - The method of reflective ellipsometry has been used to study the adsorption of the IFKhAN-92 inhibitor that is a triazole derivative on...     

Lanthanum Effect on the Isothermal High Temperature Oxidation Behavior at 1,000 °C of a Phosphoric Acid-Treated AISI 304 Stainless Steel

Many studies have shown that a phosphoric-acid treatment improves the high temperature oxidation resistance in air of some alloys. Interestingly, though, the phosphoric-acid treatment generates a structural modification of the steel surface which is catastrophic for the high-temperature oxidation behavior at 1,000 °C. The aim of our work was to test the effect of a reactive element sol–gel coating on high-temperature oxidation resistance of phosphoric acid-treated AISI 304 steel. The oxide scale growth mechanisms were studied by exposing La-coated and uncoated phosphoric acid-treated 304 steel samples to high-temperature conditions in air. A phosphoric-acid treatment modified the structural composition and the surface morphology of the AISI 304 steel by the formation of a FeH₂P₃O₁₀ structure, leading to hematite formation and to a breakaway phenomenon. Lanthanum coating, after initial phosphoric-acid treatment, led to the formation of LaCrO₃ which limited through-scale cracking and reduced the growth of iron oxides.     

Effect of Cold-Rolling on Precipitation Phenomena in Sensitized Type 316L and 304L Austenitic Stainless Steels

Precipitation phenomena in Type 316L and 304L stainless steels were studied mainly by transmission electron microscopic (TEM) observations after cold-rolling ranging from 0% (as solution annealed) to 80% reduction in thickness,and then by sensitization treatment. Precipitates were identified by electron diffraction analysis and EDS analysis.Precipitates observed in sensitized 316L stainless steel were sigma and chi phases, whereas carbide and sigma were observed in sensitized 304L stainless steel. Recrystallized grains were formed in 30% cold-rolled and sensitized 304L.However, the tendency toward recrystallization in sensitized 316L was much lower than in 304L. Precipitation of sigma and chi phases was accelerated by cold-rolling and they were observed at grain boundaries in lower cold-rolling; they were also seen, in grain interiors in higher cold-rolling. Higher deformation induced partially recrystallization combined with precipitation, resulting in the formation of heterogeneous microstructures.     

Wear Resistance of Austenitic Steel Fe–17Mn–6Si–0.3C with High Silicon and High Manganese

To solve the problem of poor wear resistance in conventional Hadfield steels under medium and low stress,a new kind of steel with high silicon and high manganese Fe–17Mn–6Si–0.3C was designed and its wear resistance was studied.The results showed that it exhibited better wear resistance than conventional Hadfield steel in both dry friction and abrasive friction.The better wear resistance of the new steel with high silicon and high manganese resulted from the stressinduced γ→ε martensitic transformation.     

Investigation on Microstructure,Wear Behavior and Microhardness of Al−Si/SiC Nanocomposite

Aluminum matrix nano-composites have been widely used in various fields such as aerospace, automobile, and packing industries. In this study, the effect of nano-SiC content on the microst-ructure, wear resistance and micro-hardness of Al–Si/SiC nano-composite was investigated. In this regard, Al–Si matrix was reinforced by different amounts of nano-SiC: 0, 0.5, 1, 1.5, 3, 5, 10 wt %. The results showed that with increasing the nano-SiC weight ratio, nano-particles are agglomerated and unsuitable sintering increases the porosity, as pores and cavities. For more than 1.5% weight ratio of nano-SiC in the matrix, the wear resistance and the micro-hardness decreased. The results of the wear test, scanning electron microscopy, energy dispersive X-ray spectroscopy and worn surfaces showed that the dominant wear mechanism is controlled by nano-SiC contents. This study indicated that with adding nano-SiC particles more than the optimal content, wear resistance and micro-hardness of Al–Si/SiC nano-composite increased more than twice.