High Chromium Research Articles

Hardness increases due to (Fe, Cr)2C carbide precipitated during natural aging in high chromium cast iron

The effect of natural aging on the microstructure of carbides and martensite in high chromium cast iron subjected to a destabilizing heat treatment was investigated by correlative experimental and theoretical methods. It was observed for the first time that fine η-(Fe, Cr)2C carbides precipitated from the martensite matrix in water-quenched high chromium cast iron during natural room temperature aging, which led to a remarkable hardness increase (by 3.4 HRC). On one hand, the obvious hardness increase was attributed to the fine precipitation of M2C carbides which was observed by transmission electron microscopy. On the other hand, it is also caused by high Cr content in the η-(Fe, Cr)2C carbides, which was confirmed by first-principles calculations.

Optimization of friction stir welding process parameters using MCDM method

Friction Stir Welding (FSW) is categorized into a solid-state welding process which is preferred to join aluminum-based materials effectively. Generally, aluminum-based materials are welded using solid state welding than fusion-based welding due to the chance of hot cracking, loss of elements and porosity. Process parameters and its selection in FSW process are important and it leads to efficient of weld quality. Taguchi concept is a standard optimization procedure but it has a limitation of not capable to solve multi objective problems simultaneously. Multi Criteria Decision Making (MCDM) method can be used for solving multiple objectives simultaneous effectively. Al-6061 T6 alloy is used as workpiece and carbon steel, H13 tool steel and high carbon high chromium steel is used as tool materials. The important process parameters considered are rotational speed of tool and welding speed. Response parameters selected are tensile strength and microhardness of welded joints. Process parameters are optimized using MCDM method and the optimum values obtained are rotational speed of 700 rpm and welding speed of 35 mm/min. It is understood that better tensile strength and microhardness of FSW joints at optimized condition due to adequate material flow, fine grain size and pulsating action. MCDM method has simple calculation procedure and easier solving methodology for machining parameters optimization.

Growth Kinetics, Microstructure Evolution, and Some Mechanical Properties of Boride Layers Produced on X165CrV12 Tool Steel

The powder-pack boriding technique with an open retort was used to form borided layers on X165CrV12 tool steel. The process was carried out at 1123, 1173, and 1223 K for 3, 6, and 9 h. As a result of boriding the high-chromium substrate, the produced layers consisted of three zones: an outer FeB layer, an inner Fe2B layer, and a transition zone, below which the substrate material was present. Depending on the applied parameters of boriding, the total thickness of the borided layers ranged from 12.45 to 78.76 µm. The increased temperature, as well as longer duration, was accompanied by an increase in the thickness of the FeB zone and the total layer thickness. The integral diffusion model was utilized to kinetically describe the time evolution of the thickness of the FeB and (FeB + Fe2B) layers grown on the surface of powder-pack borided X165CrV12 steel. The activation energy of boron for the FeB phase was lower than that for the Fe2B phase. This suggested that the FeB phase could be formed before the Fe2B phase appeared in the microstructure. The high chromium concentration in X165CrV12 steel led to the formation of chromium borides in the borided layer, which increased the hardness (21.88 ± 1.35 GPa for FeB zone, 17.45 ± 1.20 GPa for Fe2B zone) and Young's modulus (386.27 ± 27.04 GPa for FeB zone, 339.75 ± 17.44 GPa for Fe2B zone). The presence of the transition zone resulted from the accumulation of chromium and carbon atoms at the interface between the tips of Fe2B needles and the substrate material. The presence of hard iron and chromium borides provided significant improvement in the wear resistance of X165CrV12 steel. The powder-pack borided steel was characterized by a four times lower mass wear intensity factor and nine times lower ratio of mass loss to the length or wear path compared to the non-borided material.

Ferrite in the HAZ of Dissimilar Temperature Probe Welds

Abstract Protector tubes for temperature sensors were welded onto experimental gas turbine compressor blades. While the blades were made of a high alloy hard-martensitic stainless chromium steel, a high alloy metastable austenitic stainless steel was used for the tiny protector tubes. The dissimilar weld joint was applied using manual GTAW. A large amount of blocky delta ferrite formed in the HAZ immediately adjacent to the fusion line, on the side of the martensitic steel. Delta ferrite in such dissimilar welds might detrimentally affect the mechanical properties of the weld joint. It was therefore recommended not to use the affected experimental blades in test engine service. Even though no failure occurred in this case, one was prevented by declaring the subject instrumented parts unfit for test engine service.

Reusable carbon dot/chitin nanocrystal hybrid sorbent for the selective detection and removal of Cr(VI) and Co(II) ions from wastewater

The last few decades have seen a dramatic increase in heavy metal ions in industrial wastewater, especially Cr6+ and Co2+ ions, which have been shown to adversely affect human health; thus, there is a great need for their removal. Existing removal methods are time-consuming, expensive, and require high technical skills; therefore, there exists a need for a quick, simple, and cost-effective method. Chitin was selected from natural materials (shrimp waste), and an inexpensive, biodegradable, fluorescent carbon dot/chitin nanocrystal (C-dot/ChNC) sorbent for the simultaneous detection and removal of heavy metal ions from wastewater was synthesized from it. C-dot/ChNC shows high selectivity and sensitivity to Cr6+ and Co2+ ions and has high chromium(VI) and cobalt(II) adsorption capacities. These ions are weakly adsorbed on the C-dot/ChNC surface and are easily removed during regeneration, showing high cyclability. Thus, C-dot/ChNC is a viable sorbent for the removal of heavy metal ions during wastewater treatment.

Metagenomic Analysis of Garden Soil-Derived Microbial Consortia and Unveiling Their Metabolic Potential in Mitigating Toxic Hexavalent Chromium.

Soil microbial communities connect to the functional environment and play an important role in the biogeochemical cycle and waste degradation. The current study evaluated the distribution of the core microbial population of garden soil in the Varanasi region of Uttar Pradesh, India and their metabolic potential for mitigating toxic hexavalent chromium from wastewater. Metagenomes contain 0.2 million reads and 56.5% GC content. The metagenomic analysis provided insight into the relative abundance of soil microbial communities and revealed the domination of around 200 bacterial species belonging to different phyla and four archaeal phyla. The top 10 abundant genera in garden soil were Gemmata, Planctomyces, Steroidobacter, Pirellula, Pedomicrobium, Rhodoplanes, Nitrospira Mycobacterium, Pseudonocardia, and Acinetobacter. In this study, Gemmata was dominating bacterial genera. Euryarchaeota, Parvarchaeota, and Crenarchaeota archaeal species were present with low abundance in soil samples. X-ray photoelectric spectroscopy (XPS) analysis indicates the presence of carbon, nitrogen-oxygen, calcium, phosphorous, and silica in the soil. Soil-derived bacterial consortia showed high hexavalent chromium [Cr (VI)] removal efficiency (99.37%). The bacterial consortia isolated from garden soil had an important role in the hexavalent chromium bioremediation, and thus, this study could be beneficial for the design of a heavy-metal treatment system.

Effect of quenching temperature on microstructure and properties of low silicon hypereutectic high chromium cast iron

In this paper, the effects of different quenching temperatures on the microstructure and properties of Fe–4.0C–35.0Cr–0.5Si (wt.%) low-silicon hypereutectic high-chromium cast iron (LS-HHCCI) was investigated. The effect of quenching temperature on the microstructure of LS-HHCCI was analyzed by optical microscope, scanning electron microscope, and X-ray diffractometer. After quenching at different temperatures, the hardness and wear resistance of LS-HHCCI were tested by Rockwell hardness tester, microhardness tester, and wear testing machine. The results show that the microstructure of as-cast LS-HHCCI is mainly composed of austenite matrix and M7C3 carbides. After quenching, the austenite matrix is transformed into martensite, and M23C6 type secondary carbides are precipitated in the matrix. As the quenching temperature increased from 950 °C to 1100 °C, the eutectic carbides first appeared as fine needles, and then they gather and grow up, showing elongated or lumpy. The hardness and abrasion resistance first increase and then decrease, it reached peak values of 67.2 HRC at the temperature of 1050 °C, while the wear resistance is the best.

Use of potential bacterial strains to remove Hexavalent Chromium from an aqueous medium and the Periyar River sediments

Chromium is one of the most abundant metals in the earth's crust mined as chromites. Industries that widely use compounds containing chromium as Cr(III) in the tanning process generally release effluents with high chromium levels into natural water resources, frequently without appropriate effluent treatment. Though physical and chemical methods of chromium removal are adopted, the processes are expensive, use a lot of energy and generate secondary toxic waste. The removal of chromium by biological resources on the other hand is more environmentally friendly, less expensive, and lacks the release of secondary pollutants. The present study is aimed towards the assessment of the Cr(VI) reduction capability of two bacterial strains, Alcaligenes sp. (S11) and Listeria sp. (S18) used as a consortium. These bacterial strains were isolated from the Periyar river of Kerala, India. Batch mode studies were carried out by live bacterial cells and an integrated study was carried out to test the bacterial strains on chromium-contaminated water and sediments through bioreactor and column study respectively under optimized conditions. The phytotoxicity of the treated water was studied on black gram. In the bioreactor study, the maximum Cr(VI) reduction capacity of bacterial consortium (S11 and S18) was found to be 97%. The successive experiment for the toxicity of treated water on the black gram indicated that there was no toxicity in the growth parameters of the plant.

Development of a hardbanding material for drill pipes based on high-manganese steel reinforced with complex carbides

In the present study the new “casing-friendly” hardbanding alloy based on high-manganese steel reinforced with complex carbide particles was developed by combining thermodynamic modelling within the CALPHAD approach and first-principles calculations. The alloy, deposited by flux cored arc welding on a steel substrate, has a composite structure consisting of manganese-austenite with the ability to work hardening, fine (up to 5 µm) inclusions of the multicomponent carbide (Nb, Ti, Mo, V) and C the thin layers of (Mo,V)C at the austenite grain boundaries. The comparative wear tests carried out with commercially available hardfacing materials of the Fe-W-C and Fe-Cr-C systems showed that the proposed alloy has the best combination of properties preventing the wear of the drill casing, while its abrasion resistance as well as wear resistance in sliding friction conditions by steel counterbody is close to hypereutectic high chromium alloys. The microhardness tests performed on deformed specimen areas after the friction tests show the presence of a significant hardness gradient in the range of 800-450 HV at a distance of about 300 µm when moving perpendicularly away from the zone of friction contact. During the microscopic observation of the layer deposited with the developed alloy and the interfaces between the deposit and the base steel no cracks, pores delamination were detected indicating a strong metallurgical bonding. The hardbanding process was performed for drill pipe joints with the worn Fe-based high chromium alloy hardbanding after exploitation, which allows the drill pipe to be reused with the same durability.

Effect of in-situ (Ti&W)C multiphase particles on three-body abrasive wear of high chromium cast iron

In this paper, the effect of in-situ (Ti&W)C multiphase particles on the microstructure and the three-body abrasive wear behavior of high chromium cast iron was investigated. The results reveal that the different W/Ti ratios in the preforms can lead to significant differences in the microstructure and properties of the composites. The best microstructure and wear resistance of the composite (M3) is achieved when the W/Ti ratio is 4/6. Under the same wear conditions, the wear resistance of the M3 composite is more than twice as high as that of the matrix material. Furthermore, the presence of (Ti&W)C multiphase particles in the microstructure improves the hardness of high chromium cast iron, promoting its transition from cutting, fatigue, and the M7C3 fracture-exfoliation wear mechanism in the abrasive wear to micro-cutting and fatigue wear.

Three-Body Abrasive Wear Performance of High Chromium White Cast Iron with Different Ti and C Content

The need for better wear-resistant materials to reduce cost and save the environment is noteworthy. The striking wear resistance of high chromium white cast iron (HCCI) has made it industry’s predominant choice. The three-body abrasive wear resistance performance of HCCI was investigated based on combined Ti and C. The Ti and C content varied in different percentages. The addition of Ti resulted in refined M7C3 carbides and TiC crystallization. The hardness was significantly affected by the addition of Ti. The increment in Ti content resulted in a decrease in the hardness, leading to a higher wear rate. However, the individual contribution of C led to higher hardness and, hence, better wear resistance, which is contrary to Ti. Out of the three specimens with 3, 3.5, and 4 wt.% C content, the 4 wt.% C series showed the highest hardness but the lowest wear rate and depth. This study found that the combination of a lower percentage of Ti with a higher percentage of C in HCCI can have a worthwhile result in abrasive wear.

Study on Potential Causes of Defects Following Heat and Thermochemical (Carburising) Treatments of Linear Bearings

Abstract Guide rings and rolling bodies are mainly made of alloy steel with a high chromium content, heat treated, as well as of carburising steel. The efforts to improve the standard of quality of bearing steels are determined by the interest of continuously increasing the adhesion of constructive types. These steels are recommended for large bearings which operate under shock and vibration conditions. Thermochemical treatments are followed by quenching and tempering heat treatments. However, undesirable defects occur sometimes on the surface of the carburised layer and solutions are constantly being sought to identify the causes thereof.

First-principles study on corrosion resistance of copper-bearing hypereutectic high chromium cast iron

Based on the Tafel formula, Butler-Volmer equation, and first-principles calculations, the bulk model, surface model, and polarization prediction curve of the Hypereutectic High Chromium Cast Iron (HHCCI) matrix were constructed. The results show that the predicted corrosion current density (2.19×10 -5 A·cm 2 ) of the copper-bearing HHCCI matrix is lower than the measured corrosion current density of the copper-bearing HHCCI (4.41×10 -5 A·cm 2 ) under the acidic condition of pH=1. In the neutral environment of pH=7, the corrosion resistance of HHCCI is better than that of HHCCI under acidic conditions. The predicted corrosion current density of the copper-bearing HHCCI matrix (4.39×10 -10 A·cm 2 ) is also smaller than that of copper-free HHCCI (7.98×10 -10 A·cm 2 ), which shows that the corrosion resistance of copper-containing HHCCI matrix is better than that without copper from the perspective of first-principles calculation. Combined with the electrochemical experimental results, it can be seen that the corrosion potential (-409.76 mV) of 1.5 wt.% Cu HHCCI is significantly higher than that of 0 wt.% Cu HHCCI (-450.34 mV). The trend of the electrochemical test results is consistent with the predicted trend of the calculated polarization curve, which indicates that copper alloying can improve the corrosion resistance of HHCCI. Predicted polarization curves on γ-Fe (100) surfaces (PH=1): (a) γ-Fe (Cu-Free); (b) γ-Fe (Cu-Bearing) • Predicting corrosion resistance using equations and first-principles. • Copper improves the predicted current density of HHCCI matrix at pH=1. • Copper improves the current density of HHCCI at electrochemical experiments. • Copper alloying improves HHCCI corrosion resistance.

Tribology in mining: Highlights in iron ore abrasiveness

This article aims to present results on research, recently developed, and related to wear of equipment to meet the challenges of the mining industry. Emphasis is done to iron ore mining in Brazil due to the relevance of the sector for its economy and the relevance of tribology for assets and productivity. Results and considerations cover wear of equipment (conveyor belts, ore pipelines) and development of high chromium cast iron (HCCI) microstructures to face the wear. Under wet erosive wear caused by pumped slurries with different compositions of solid particles the wear of samples tested follows a trend in which those with higher silica contents provided greater mass losses of high chromium cast iron (HCCI) samples. On the other hand, when surface protection against wear of components is the objective, the presence of niobium in a hardfacing coating contributed to increase resistance to abrasion, due to the presence of niobium carbides (NbC). It was also demonstrated that there is a positive correlation between the degree of metamorphism of iron ore throughout its genesis and evolution in relation to the abrasiveness.

Effect of ultra-high boron additions on microstructure and mechanical properties on high chromium steel

Abstract In this work, the change on the microstructure and mechanical properties of high chromium steel investigated by adding ultra-high boron contents. Specimens produced by casting method. A total of 430 type martensitic stainless steel scraps melted in an induction furnace where the chemical composition of melt controlled (by adding ferro alloys, de-oxidation, removing nitrogen, etc.). At 1550 °C, melt was poured into sand molds with the shape of Y blocks. Wet chemical analysis was used for boron analysis. The change on the microstructure and mechanical properties (hardness test, Charpy impact test and pin on disc abrasive wear test) determined. Experimental results revealed that, martensitic matrix obtained in both boron free steel and ultra-high boron steels. Chromium carbides and borides were embedded each other (M2B and M7(C, B)5 type of carbide/borides) according to X-ray diffraction results. With the change of boron content, carbide/boride volume fraction, distribution and shapes were changed as well. Hardness and abrasion resistance improved for the steels having higher boron contents however impact toughness deteriorated significantly.

Dislocation nucleation mechanisms during nanoindentation of concentrated FeNiCr alloys: unveiling the effects of Cr through molecular simulations

Fe-based alloys with high chromium and nickel concentrations are very attractive for efficient energy production in extreme operating conditions. We perform molecular dynamics (MD) simulations of nanoindentation on fcc FeNiCr multicomponent materials. Equiatomic FeNi, Fe55Ni19Cr26, and Fe74Ni8Cr18 are tested by using established interatomic potentials and similar conditions, for the elucidation of key dislocation nucleation mechanisms and interactions. Generally, we find that the presence of Cr in these alloys reduces the mobility of prismatic dislocation loops, and increases their area, regardless of crystallographic orientation. Dislocation nucleation and evolution is tracked during mechanical testing as a function of nanoindentation strain and Kocks–Mecking continuum modeling displays good agreement with MD findings. Furthermore, the analysis of geometrically necessary dislocations (GNDs) is consistent with the Ma–Clarke’s model at depths lower than 1.5 nm. The presence of Cr leads to a decrease of the GND density with respect to Cr-less FeNi samples, thus we find that Cr is critically responsible of increasing these alloys’ hardness. Post-indentation impression maps indicate that Ni–Fe–Cr compositions display strain localization and hardening due to high Cr concentration.

Microstructural effect and wear performance of high chromium white cast iron alloyed with V, W, and different Cr contents

Microstructural effect and wear performance of high chromium white cast iron alloyed with V, W, and different Cr contents

Parametric analysis through ANFIS modelling and optimization of micro-hole machining in super duplex stainless steel by die-sinking EDM

ABSTRACT Super duplex stainless steel (SDSS) contains ferrite and austenite in equal proportions. The high chromium imparts good corrosion resistance and high-temperature workability but the low thermal conductivity and high work hardening reduces its machinability by traditional methods. In this study, the feasibility of using electric discharge machining (EDM) to create geometrically accurate microholes with high productivity has been explored. Individual effect of input process parameters like pulse-on-Time (Ton), pulse-off time (Toff) and current (I) on material removal rate (MRR), overcut (OC) and taper angle (TA) has been investigated through adaptive neuro fuzzy inference system (ANFIS). Furthermore, hybrid multiobjective optimisation technique of grey relational analysis (GRA) combined with principal component analysis (PCA) was used to determine the optimal process input parameters. During hole sinking µ-EDM, increase of pulse on time increases the MRR, whereas the OC and taper decrease. GRA-PCA optimisation technique yields optimal input parameters which enhances MRR by 5.92% and rescues the OC and TA by 27.1% and 75%, respectively.

Resistance against Abrasive Wear and Corrosion of Laser Powder Bed Alloyed High Chromium Tool Steels

Additive manufacturing by laser-based powder bed fusion of metals (PBF-LB/M) enables the production of complex shaped components. High-carbon tool steels tend to cracking during PBF-LB/M due to internal stresses caused by the rapid solidification. Expensive atomization and long lead times for powder generate high costs in this processing route. In situ alloying during PBF-LB/M of powder blends from conventionally available powders enables a more flexible approach of alloy design. For industrial use, the mechanical properties of in situ alloyed parts must be comparable to those of conventionally manufactured parts. In some cutting and forming applications, high wear resistance and corrosion resistance are required simultaneously. High alloyed cold work tool steels with sufficient chromium solved in the metal matrix fulfill these demands. Herein, AISI H13 has been modified by Cr3C2 and elemental Cr to suit these requirements. Two novel alloys are modeled thermodynamically and processed by PBF-LB/M. In-depth microstructural investigations by backscatter electron imaging and diffraction in combination with abrasive wear tests and potentiodynamic polarization curves allow microstructure property correlations for different heat-treated conditions. Partial crack-free processing, hardenability, formation of Cr-rich carbides, and residual Cr-rich inclusions are observed and their influence on the wear and corrosion resistance is discussed.

On the Prediction of the Damage of High Chromium White Cast Iron Under the Impact of Barite Rocks: Modeling and Experiments

On the Prediction of the Damage of High Chromium White Cast Iron Under the Impact of Barite Rocks: Modeling and Experiments