Influence Of Chromium Content Research Articles

Influence of Chromium Content and Stabilization on Tribocorrosion of Ferritic Stainless Steel

In recent years, the ferritic stainless steels have been proposed as a competitive alternative option for the bio-fuel and concrete mixer industries. The goal of the present work is to evaluate, using a recently proposed new methodology, the effect of chromium content with and without stabilization (Ti and Nb) on the tribocorrosion of ferritic stainless steels. For comparative purposes, a carbon steel (0.15 wt% C) was also studied. A reciprocating motion tribometer associated with a potentiostat assured that the potential scan during the tests was used under a constant load and sliding velocity. To this end, a recently introduced approach was applied. It consisted of performing sliding tribological tests to strictly evaluate the mechanical wear, potentiodynamic corrosion tests to determine the corrosion resistance in the absence of mechanical wear, and tribocorrosion tests, which combine both mechanical wear and corrosion degradation from chemical/electrochemical effects. Concerning the tribological performance, the 16% Cr steel showed a higher friction coefficient and lower wear rate than the 11% Cr steel. Carbon steel, in turn, presented the lowest friction coefficient and the highest wear rate among all materials. The corrosion tests showed that a higher chromium content was associated with a greater corrosion resistance. The similarities of the wear mechanism between the tribocorrosion and the tribological tests were verified and it can possibly explain the obtained synergy (S), which was slightly positive (11% Cr (S = 0.009 mg/min), 11% CrTi steel (S = 0.031 mg/min) and 16 % Cr steels (S = 0.005 mg/min)), as the tribocorrosion worsened the wear resistance of the materials, although insignificantly. The exception is the carbon steel, whose synergy effect was drastically higher than all other materials with chromium content (S = 2.674 mg/min).

The influence of chromium content on wear and corrosion behavior of surface alloyed steel with Fe(16−x)Crx(B,C)4 electrode

In this study, the electrodes containing Fe(16−X)CrX(B,C)4 (X = 3,4,5) were used for surface alloying on an AISI 1010 steel substrate. The alloy structure of the coating exhibits in-situ composite structure with a large amount of reinforcing carbides and borides phases as to be hypoeutectic and hypereutectic structure in the surface alloyed layer. The obtained composition of the alloy shows that it contains much more interstitial hard phases in the alloyed layer than the conventional hardfacing alloys used in the industrial applications for the hardfacing of the steels. The morphological and microstructural properties showed that layer microstructure changed from hypoeutectic to hypereutectic structure with an increase in chromium content. The results of these studies revealed that the microstructure of hardfacing layers consists of interstitial phases of α(Fe-Cr) and (Fe,Cr)23(C,B)6 as major phases, (Fe,Cr)2(C,B) and (Fe,Cr)7(C,B)3 as minor phases in the in-situ composite structure. The composite hardness’ in the alloyed surface layers of the Fe(16−X)CrX(B,C)4 alloys ranged from 711 HV to 1164.3 HV. Wear test against alumina ball shows that the friction coefficients of the surface alloyed layers decreased with increase in applied loads and decrease in chromium content in the Fe(16−X)CrX(B,C)4 alloy composition. Coefficient of friction ranged from 0.55 to 0.79 in the present study. Wear rates of the surface alloyed steels caused to increase with decrease in chromium content and increase in applied loads. The wear rates of the alloyed layer changed between 3.07 × 10 and 5 mm3/m and 6.95 × 10−5 mm3/m. The corrosion resistance of the alloyed layers was measured by a potentiostatic polarization test. Icorr and Ecorr of the coated layers changed from 1.813 to 9.965 µA/cm2 and −704.786 to −745.792 mV, depending on alloyed layer compositions. With increasing chromium content, the corrosion resistance of the coating layer has changed in a nobler side.

Influence of Chromium Content and Prior Deformation on the Continuous Cooling Transformation Diagram of Low-Carbon Bainitic Steels

The effect of chromium content and prior hot deformation of the austenite on the continuous cooling transformation (CCT) diagram of a newly developed low-carbon bainitic steel has been studied using dilatometer measurements conducted on a Gleeble 3800 simulator with cooling rates ranging from 2-80 °C/s. After austenitization at 1100 °C, specimens were either cooled without strain or given 0.6 strain at 880 °C prior to dilatometer measurements. The resultant microstructures have been studied using laser scanning confocal microscopy, scanning electron microscopy and macrohardness measurements. CCT and deformation continuous cooling transformation (DCCT) diagrams were constructed based on the dilatation curves, final microstructures and hardness values. Depending on the cooling rate, the microstructures of the investigated steels after cooling from the austenite region consist of one or more of the following microstructural components: lath-like upper bainite, i.e. bainitic ferrite (BF), granular bainite (GB), polygonal ferrite (PF) and pearlite (P). The proportion of BF to GB as well as the hardness of the transformation products decreased with decreasing cooling rate. The cooling rate at which PF starts to appear depends on the steel composition. With both undeformed and deformed austenite, increasing the chromium content led to higher hardenability and refinement of the microstructure, promoting the formation of BF and shifting the ferrite start curve to lower cooling rates. Prior hot deformation shifted the transformation curves to shorter times and higher temperatures and led to a reduction in hardness at the low cooling rates through the promotion of ferrite formation.

Influence of Chromium Content on the Microstructure and Mechanical Properties of Thermomechanically Hot-Rolled Low-Carbon Bainitic Steels Containing Niobium

The effect of chromium content in the range of 1 wt.%–4 wt.% on the microstructure and mechanical properties of controlled-rolled and direct-quenched 12 mm thick low-carbon (0.04 wt.%) steel plates containing 0.06 wt.% Nb has been studied. In these microalloyed 700 MPa grade steels, the aim was to achieve a robust bainitic microstructure with a yield strength of 700 MPa combined with good tensile ductility and impact toughness. Continuous cooling transformation diagrams of deformed and non-deformed austenite were recorded to study the effect of Cr and hot deformation on the transformation behavior of the investigated steels. Depending on the cooling rate, the microstructures consist of one or more of the following microstructural constituents: bainitic ferrite, granular bainite, polygonal ferrite, and pearlite. The fraction of bainitic ferrite decreases with decreasing cooling rate, giving an increasing fraction of granular bainite and polygonal ferrite and a reduction in the hardness of the transformation products. Polygonal ferrite formation depends mainly on the Cr content and the cooling rate. In both deformed and non-deformed austenite, increasing the Cr content enhances the hardenability and refines the final microstructure, shifting the ferrite start curve to lower cooling rates. Preceding austenite deformation promotes the formation of polygonal ferrite at lower cooling rates, which leads to a decrease in hardness. In hot-rolled and direct-quenched plates, decreasing the Cr content promotes the formation of polygonal ferrite leading to an increase in the impact toughness and elongation but also a loss of yield strength.

Influence of chromium content on microstructural and electrochemical supercapacitive properties of vanadium nitride thin films developed by reactive magnetron co-sputtering process

Abstract Two-dimensional nanostructured transition metal nitride-based thin film electrodes have been gaining importance in the electrochemical supercapacitor applications. In this work, Cr doped vanadium nitride (VN) thin films as an electrode material for high-performance supercapacitors have been demonstrated. In this study, reactive magnetron co-sputtering technique was adopted to fabricate phase pure VN as well as VN films doped with different Cr contents. These films were directly investigated as electrodes without using any additional binders. The phase purity and the surface chemistry of the Cr doped VN thin films were investigated using XRD and XPS techniques. Furthermore, EDS and X-ray elemental mappings were used to confirm the content of Cr and its distribution in these electrode films. The Cr −5.7 at. % doped VN thin film electrodes exhibited an extraordinary supercapacitor performance with the maximum areal capacitance of 190 mF/cm2 compared to the areal capacitance of 27 mF/cm2 for the un-doped VN at a scan rate of 10 mV/s. Moreover, the Cr-5.7 at. % doped VN thin film electrodes showed excellent electrochemical cycling stability and excellent reversibility with the capacitance retention of 92.4 %. It could be noticed that the incorporation of metal such as Cr could be a viable method to improve the electronic or ionic conductivity of the metal nitrides for supercapacitor applications.

Influence of material properties of stainless steel on the ignition probability of flammable gas mixtures due to mechanical impacts

Grazing impact experiments of various types of stainless steels were performed in explosive atmospheres of hydrogen, acetylene, ethylene or propane with air. Depending on the gas mixture, kinetic energy of the impact, and applied stainless steel, the dominant ignition sources are either separated particles or hot friction surfaces. An influence of chromium content on the ignition probability was not found, although an increase in chromium content results in a reduction of the oxidizability of separated particles. Additionally, the influence of the material properties thermal conductivity, specific heat, density and hardness on the ignition probability of the hydrogen–air mixture was investigated. With increasing thermal conductivity a decreasing rate of ignitions was observed. In contrast, an influence of the physical properties specific heat, density and hardness on the ignitability was not found.

CO2[sbnd]Oxidative Dehydrogenation of Ethane to Ethylene over Cr/MCM-41 Nanocatalyst Synthesized via Hydrothermal/Impregnation Methods: Influence of Chromium Content on Catalytic Properties and Performance

A series of mesoporous Cr(x)/MCM-41 nanocatalysts with 0, 2, 5, 8 and 11wt.% content of chromium were synthesized by hydrothermal/impregnation method. The effect of chromium loading on the structure and catalytic performance of Cr/MCM-41 nanocatalysts in the oxidative dehydrogenation of ethane with CO2 was investigated. The catalysts were characterized by XRD, FESEM, EDX, DRS, BET and FTIR analysis. Various chromium species including Cr6+, Cr3+ and crystalline Cr2O3 were found in the calcined Cr(x)/MCM-41 samples. Particles of crystalline α-Cr2O3 were detected in the catalyst with Cr total content above 2wt.%. The variation of Cr content indicates that the Cr6+/Cr3+ ratio of samples increased with the Cr loading up to 8wt.%. However, a decreasing trend was observed with further increase of Cr content. This can be justified by Cr surface density. It was found that there is an optimum Cr content in Cr(8%)/MCM-41 for the best catalytic activity, attributable to higher active Cr6+ species, and more uniform dispersion of chromium species with monolayer coverage on MCM-41 and also, homogeneous surface morphology with smallest particle size. It was found that this catalyst effectively dehydrogenated ethane to ethylene in the presence of CO2 at 700°C, giving 53% ethylene yield.

Effect of Chromium Content on the Oxidation Behavior of Ni-Cr Model Alloys in Superheated Steam

The present study investigated the oxidation behavior of Ni-xCr model alloys (14 ≤ x ≤ 30 wt pct) in steam at 973 K (700 °C), with particular emphasis on the influence of chromium content. Mirror polishing was employed to reduce the hardened layer, thereby avoiding the synergetic effect with dislocations in the subsurface. To elucidate the oxidation behavior, weight gain measurements and the meticulous characterization of the oxide scale were performed. The optimal Cr content (24 wt pct) corresponded to an oxidation rate slower than the parabolic rate due to the growth of a protective Cr oxide layer. Increasing the Cr content above the optimal amount led to the degradation of oxidation resistance.

Influence of chromium content on microstructure and grain boundary serration formation in a ternary Ni-xCr-0.1C model alloy

The influence of chromium content on microstructure and grain boundary serration formation in a ternary Ni-xCr-0.1C model alloy was investigated. First, the cast alloys were hot-compressed and then solution treated to obtain a recrystallized structure. Second, a proprietary heat treatment was employed to all of the compressed alloys to produce the serrated grain boundaries. The recrystallization retardation of the alloys increased with increasing chromium content after the first step. This may be attributed to the change in lattice distortion due to the addition of chromium into the solid solution of the nickel matrix, and it was also affected by Zener drag pressure exerted by the formation of carbides suppressing the grain growth during solution treatment. Furthermore, the grain boundary serrations were found in all of the alloys after the second step. It was determined that the serrated grain boundary was initially formed without carbide formation during slow cooling. The formation of grain boundary serration is thought to be promoted by lattice distortional strain near grain boundaries due to discontinuous chromium segregation. The higher chromium content promoted a substantial increase in the lattice distortion energy, which resulted in a higher amplitude of the serrated grain boundary.

Matrix effect in atomic emission determination of impurities in Cr2O3

We have studied the influence of chromium content on calibration curves for atomic emission analysis of chromium oxide using graphite powder. The results demonstrate that the intensity of impurity lines in the system varies nonlinearly. The effect is interpreted in terms of possible underlying processes.

The morphology of nitrided iron–chromium alloys; influence of chromium content and nitrogen supersaturation

Abstract Different iron–chromium alloys (4, 8, 13 and 20 wt.% Cr) were nitrided in NH3/H2 gas mixtures at 580°C. The nitrided microstructure was investigated by X-ray diffraction, light microscopy, hardness measurements and scanning electron microscopy. Composition depth-profiles of the nitrided zone were determined by electron probe microanalysis. Various microstructures develop, depending on the nitriding conditions and the alloy composition (chromium content). The initial development of coherent, sub-microscopical CrN nitrides leads to a state of hydrostatic stress allowing the uptake of excess nitrogen dissolved in the ferrite matrix. It is shown that the outcome of the subsequent discontinuous coarsening process, which leads to a lamellar microstructure, has a close relation to the nitrogen supersaturation. As a result, the occurrence of a distinct gradient in hardness across the nitrided zone can be understood.

Pitting Corrosion of Steam Turbine Blading Steels: The Influence of Chromium Content, Temperature, and Chloride Ion Concentration

Abstract Two industry-standard steam turbine blading steels, FV566 containing 11% Cr and FV520B containing 13.5% Cr by weight, are characterized with respect to chloride-induced pitting corrosion u...

Influence of chromium content on the dry machining performance of cathodic arc evaporated TiAlN coatings

Physical vapour deposition (PVD) titanium aluminium nitride coated cutting tools are used extensively in global manufacturing for reducing production costs and improving productivity in a number of aggressive metal-cutting operations, namely, dry and high-speed machining. In this investigation, the performance of Ti 1− x Al x N and Ti 1− x− y Al x Cr y N coatings was assessed on Co-HSS twist drills used to machine grey cast iron. The failure criterion for drills was defined as a critical sized flank wear land at the outer corners of the drills. Using this criterion, the average tool life of uncoated twist drills was increased by factors of 2.5, 3.0 and 3.0 by Ti 0.59Al 0.41N, Ti 0.27Al 0.19Cr 0.54N and Ti 0.21Al 0.14Cr 0.65N coatings, respectively. Notwithstanding the similar increase in average tool life, the Ti 1− x− y Al x Cr y N coatings produced more consistent results than the Ti 1− x Al x N coated drills with standard deviations of 67, 3 and 19 holes, respectively. This result has significant practical implications in manufacturing, since drills are not replaced on an individual basis, but rather on a preset tool change frequency. The present paper discusses the performance of Ti 1− x Al x N and Ti 1− x− y Al x Cr y N coated drills in terms of average and practical drill life and concludes with remarks on the characterisation of PVD coatings and their significance on the performance of Co-HSS twist drills when dry machining grey cast iron.

Influence of microstructure and chromium content on oxidation behaviour of spin cast high speed steels

The influence of the chromium content and of the volume fraction of primary carbides on the thermal oxidation behaviour of spin cast high speed steels and semi-high speed steels used for the production of hot mill rolls was studied at 700°C. Oxidation nucleates at the carbide–matrix interface and carbides have a higher oxidation resistance than the matrix. Moreover carbides dissolve a higher amount of chromium than the matrix. As a consequence of these effects, the oxidation rate of these steels decreases by increasing the chromium content of the matrix and by decreasing the carbide volume fraction.

Chromium effect on some properties of melt-spun amorphous and nanostructured alloys

The influence of chromium content on the structure, thermal properties and Curie temperature of (Fe xCr 1 − x 73.5Cu 1Nb 3Si 13.5B 9 (x = 0.85–1.0) alloys in the form of rapidly quenchedribbons is described. The structure of the samples in the amorphous and nanocrystalline state has been studied by transmission electron microscopy (TEM). Chromium alloying results in the refinement of the nanocrystalline grains. From differential thermal analysis (DTA) it is evident that the Cr addition leads to the shift of the first DTA crystallization peak (crystallization of α-FeSi phase embedded in amorphous matrix) to the higher temperatures and to the narrowing of the interval between the first and the second exothermic peak (formation of Fe, Nb borides). Perhaps the formation of Cr borides (thermodynamically more stable than FeNbB) within the temperature range 1180–1260 K is observed on DTA curves. In the case of alloy without Cr the third exothermic peak was not present. Curie temperature decreases with increasing Cr content.

The Influence of Chromium Content on the Precipitation of γ′ (Ordered Ni3Ti) in Some Austenitic Steels

A series of four austenitic steels containing 2% Ti and 25% Ni, with chromium contents ranging from 4% to 17%, have been solution-treated at 1150 °C and aged at 750 °C for periods up to 2200 hours. Precipitation processes were followed by electron microscopy.In every case the γ′ phase precipitated initially coherently and in parallel orientation with the matrix, there being no tendency for the formation of randomly oriented γ′, as reported by Pitler and Ansell [Trans. Am. Soc. Metals, 57 (1964) 727]. The stacking-fault energy of these alloys appeared to be consistently lower than that estimated by Pitler and Ansell, and serious doubts are cast on their proposal.In alloys of lower chromium content, there was a tendency for the γ′ phase to nucleate preferentially in the region adjacent to the grain boundaries. One factor contributing to this effect is considered to be the change in relative density of matrix and precipitate as the chromium content of the matrix is reduced, lending to a vacancy-emitting rather than a vacancy-absorbing situation.

Influence of chromium content on magnetic and corrosion properties of stainless steels

Influence of chromium content on magnetic and corrosion properties of stainless steels

Influence of chromium content on magnetic and corrosion properties of stainless steels

Influence of chromium content on magnetic and corrosion properties of stainless steels

Influence of Chromium Content on Corrosion of Plasma-Nitrided Steels

Abstract Commercial steels with varying chromium contents were plasma nitrided for 25 h in a 70% nitrogen (N2) + 30% hydrogen (H2) gas atmosphere at 520°C under a pressure of 670 Pa. Steels tested included AISI types 4140, with 1% Cr (UNS G41400); H-13, with 5% Cr (UNS T20813); D-2, with 12% Cr (UNS T30402); and 431, with 16% Cr (UNS S43100). Surface layers obtained were characterized using optical microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and scanning electron microscopy with energy dispersive x-ray spectroscopy. Potentiodynamic polarization curves were obtained at room temperature (RT) on samples immersed in an aerated 0.05 M sodium sulfate (Na2SO4) solution of pH 3.0. Polarization tests were repeated at various depths beneath the surface after grinding successively with abrasives and finishing with 3-μm diamond paste. Potential-vs-time graphs were recorded. Nitrided steels with up to and including 12% Cr showed an increase in corrosion resistance, whereas a decrease was observed ...

Influence of chromium content in a low alloy steel on its tensile properties

Influence of chromium content in a low alloy steel on its tensile properties