Effect Of Chromium Addition Research Articles

Preparation and high-temperature tribological performance of laser clad MoNi coatings with chromium addition

In order to enhance the wear resistance of MoNi matrix coatings at elevated temperature, high-temperature wear resistant MoNi matrix coatings with different Cr contents (3.0 wt%, 7.0 wt% and 11.0 wt%) were prepared on the 718 alloy substrate by laser cladding. The high-temperature tribological performance was investigated sliding against Si3N4 ceramic ball by using ball-on-disk tribo-tester from room temperature to 1000 °C. The effects of chromium addition on the microstructure and the tribological performance of coatings were systematically studied. The coatings with dendritic structure consisted of Mo, Cr9Mo21Ni20 and Cr1.12Ni2.88 phases. The coatings showed a good metallurgical bonding interface with the substrate. There was a critical value of Cr content which could best reinforce the high-temperature wear resistance of MoNi matrix coating. The coating containing 7 wt% Cr had the best wear resistance over a wide temperature range, which was due to the in-situ formed salt compounds, high hardness and oxide lubricating film. The wear mechanism of three coatings transferred from the fatigue wear and abrasive wear to the oxidative wear with the increase in testing temperature.

Effect of chromium addition on the copper binder structure, properties and adhesion to diamond

The study covers the effect of chromium on the structure, mechanical properties, and adhesion of alloys used as a binder for metal-diamond composites. Cu–Cr powder mixtures were obtained by high-energy ball milling in a planetary centrifugal mill. This process was used to obtain two-phase Cu–Cr powders with uniformly distributed submicron Cr particles. Cu–Х%Cr compact samples (where Х = 10, 30 and 50 %) were obtained by hot pressing. It was found that Cu–30%Cr compact samples showed the best mechanical properties (9 times higher as compared to pure copper). These alloys feature a hardening mechanism based on the Hall–Petch law. The resulting alloys have a homogenous ultrafine structure, which results in high ultimate bending strength (2330 MPa). Chromium addition to the copper binder considerably increases its adhesion to diamond in metal-diamond composites due to chemical interaction between chromium included into the binder and diamond carbon with Cr3C2 carbide formation.

The Influence of Cr Addition and Heat Treatment on Dilatometric Characteristics of Cast Fe-Al-Si Intermetallic Alloys

The cast Fe-Al-Si type intermetallic alloys (with or without chromium content) were investigated with the aim to obtain the values of thermal expansion coefficient and describe the dilatometric behavior of alloys. The effect of chromium addition, as well as the influence of heat treatment on the structure and dilatometric characteristics (thermal expansion coefficient, CTE), were described. It has been shown that the presence of chromium does not significantly influence the values of thermal expansion coefficient of as-cast alloys so that chromium addition can be substituted by higher silicon content. The annealing used for phase stabilization slightly decreases the CTE values for chromium doped alloys, nevertheless only in the higher temperature range. In comparison, CTE values of the alloy without chromium are slightly increased by the annealing used in the whole temperature interval. But, the differences are not significant from the point of view of technical practice.

Effect of chromium additions on the structure and physical properties of manganese-based films

The formation of metastable structures of manganese films with chromium additions obtained by the method of modernized three-electrode ion-plasma sputtering is studied. It is shown that the deposition of pure manganese leads to the formation of nanocrystalline β-Mn and MnO oxide. Heating in vacuum above 700 K leads to the film oxidation. The addition of Cr to the composition of the films prevents the formation of MnO oxide. It is shown that the activation energy of structural changes decreases with an increase in the energy of deposited atoms for pure manganese and MnCr films. Magnetization hysteresis is observed only in freshly sprayed Mn and MnCr films.

Effect of Chromium Addition and Regimes during Electrospark Alloying with Aluminum Matrix Anode Material of Steel 45

Introduction. Electrospark alloying is used to produce hardening coatings. Anodic materials with unique properties include metal matrix composites based on aluminum. The aim of the work is to develop new aluminum matrix anode composite materials with high efficiency indicators during electrospark alloying of carbon steel 45. Materials and Methods. Structural carbon steel 45 was used as the substrate (cathode). Aluminum matrix materials are chosen as the anode materials. The value of the cathode weight increment and the anode erosion were determined by the gravimetric method on the Shinko Denshi HTR-220 CE electronic scale with an accuracy of ±∙10–4 g. To study the microstructure and metallography of the surface of the anode materials, the microscopes EVO-50 XVP and Altami MET 3 APO from S. ZEISS were used. The device CALOTEST CSM Instruments was used to study coatings for microabrasive wear. Results. There is developed a methodological scheme for achieving the efficiency of the electric spark alloying parameters and the properties of the doped layer depending on the composition of the anodic metal matrix composite material based on aluminum with the addition of chromium and processing modes. The mode of Institute of Materials Science electrospark installation with pulse energy of 14.4 J was set for anode material application during electrospark alloying. It is established that after electric spark alloying of steel 45, the hardness and wear resistance of the surface increase by 2-3 times, and the heat resistance ‒ by 5–18 times. Discussion and Conclusion. The series of increasing the cathode mass, the erosion resistance of the electrode materials, mass transfer coefficient, heat resistance, hardness and wear resistance of the alloyed layer are obtained. The obtained series are a convenient tool for achieving various efficiency parameters in electric spark alloying depending on the selected anode material and processing modes.

Effect of chromium addition on the reactivation of the titanium-iron-manganese (TiFe0.85Mn0.15) alloy

Titanium-iron (TiFe) is known to be highly sensitive to oxidation, and this impacts its use in hydrogen storage applications. To investigate the ability to control the surface oxidation of TiFe-based alloys, TiFe0.85Mn0.15 was used as a base alloy due to its ease of activation and the addition of Cr investigated to facilitate its re-activation upon oxidation. Upon the formation of TiFe0.85Mn0.15Crx (x = 0.15 and 0.30) an improvement in reactivation was observed. After exposure of TiFe0.85Mn0.15Cr0.30 to air for 2 h, the alloy could be re-activated at 150 °C under a 3 MPa hydrogen pressure. In comparison, a temperature of 300 °C under the same hydrogen pressure was needed to re-activate TiFe0.85Mn0.15. This indicates that Cr addition provided to some extent resistance against deactivation. This is also reflected in the HP-DSC measurements where a partial oxide reduction was observed at 100 °C for the oxidised TiFe0.85Mn0.15Cr0.30 alloy as opposed to the 220 °C of TiFe0.85Mn0.15. The partially reduced species acted as catalytic sites for hydrogen activation.

Effect of Chromium Addition on Microstructure and Corrosion Resistance of A356-5vol.%TiB <sub>2</sub> Composites

Effect of Chromium Addition on Microstructure and Corrosion Resistance of A356-5vol.%TiB <sub>2</sub> Composites

The Effect of Chromium Additions on the Microstructure and Some Mechanical Properties of Delta Steel Company Nodular Cast Iron

The Effect of Chromium Additions on the Microstructure and Some Mechanical Properties of Delta Steel Company Nodular Cast Iron

Improvement in varistor properties of CaCu3Ti4O12 ceramics by chromium addition

The effect of chromium addition on the structure and electrical properties of CaCu3Ti4O12 is studied. Compositions based on the formula CaCu3Ti4-xCrxO12-δ (x = 0, 0.025, 0.050 and 0.075 mol%) are prepared by solid-state reaction. Pellets sintered at 1070 °C for 12 h are characterised by X-ray diffraction, scanning electron microscopy/energy dispersive spectroscopy and impedance spectroscopy. Current density-electric field, dielectric loss and permittivity measurements are also carried out. Rietveld refinement showed the substitution of Cr(III) on the Ti(IV) site, with the maximum substitution for x = 0.025 mol%. The generation of electrical defects in the grain boundary region by chromium doping is responsible for increasing the electric breakdown field strength and nonlinearity coefficient at room temperature from 1723 V/cm and 5.29 for x = 0 mol% to 3431 V/cm and 8.16 for x = 0.025 mol%. This composition shows the greatest improvement in ceramic varistor parameters.

The Effect of Chromium Addition and Heat Treatment on Phase Composition of Cast FeAlSi Alloys

A structural studies have been performed on Fe-Al-Si iron aluminides with or without addition of chromium prepared by standard cast process. The effect of chromium addition and subsequent annealing on the phase composition was studied. Very fine precipitates were observed on the grain boundaries in the alloy without chromium addition. On the other hand, complex chromium carbides formed in the structure of chromium doped alloy. The annealing of alloy without Cr addition leads to partial dissolution of secondary phase particles. Unlike the chromium-doped alloy, where the secondary phase coarsed during the annealing process.The phase composition of the alloys was studied by means of scanning electron microscopy (SEM) equipped by energy dispersive X-ray spectrometer (EDX). The electron backscattered diffraction (EBSD) was used for phase verification.

Effect of Chromium Addition on the Cyclic Oxidation Resistance of Pseudo-Binary (Mo,Cr)3 Si Silicide Alloy

AbstractThis paper describes the performance under cyclic oxidation of (Mo,Cr)3 Si compound with different Cr additions for possible coating application. Cyclic oxidation was carried out at 1,000 °C at different intervals during 250 h. Oxidized surface samples were analysed by scanning electron microscope where epitaxial oxide scales were observed mainly in samples with higher Cr content which may provide protection against surface oxidation. X-ray diffraction studies have shown the Cr2O3 and SiO2 formation as the main oxide scale; after analyses, it was found that these oxides are responsible for the best oxidation protection, with 36 at.% Cr being the optimal chromium concentration. At lower chromium concentrations, pest reaction occurred in the oxidized samples at times less than 25 h as a result of the formation of the unstable molybdenum oxide.

The Effect of Chromium Addition on Physical Properties of Cu-Al Based High Temperature Shape Memory Alloy

The Effect of Chromium Addition on Physical Properties of Cu-Al Based High Temperature Shape Memory Alloy

Effect of chromium addition on properties of sinter-forged Fe–Cu–C alloy steel

The present work deals with sinter-forged powder metallurgical (P/M) steels alloyed with chromium by addition of ferrochrome powder, which allows a close control over the chromium contents of alloy steels. Chromium contents can be varied by adjusting appropriately weighed ferrochrome powder in the P/M mixtures. Fe–Cu (2%) and C (0.7%) is the base composition for this P/M alloy steel. Study with the addition of 0.5% and 3% chromium by weight in the form of ferrochrome powder is carried out. The P/M alloy steel of base composition with no chromium content is also prepared for comparative study. The paper deals with these three alloy steels formed by the sinter-forging technique of powder metallurgy. The results of hardness and wear in hardened and tempered condition are reported in the present work.

Effects of Chromium Additions upon Microstructure and Mechanical Properties of Cold Drawn Pearlitic Steel Wires

Cr-containing pearlitic steel wires were prepared through cold drawing and simulated galvanization process. Effect of chromium microalloying on microstructural and mechanical properties of the steel wires was investigated. Experimental results show that size of pearlitic colonies of the steel rods decreased as Cr content increased from 0.2 to 0.6 wt.%; meanwhile, interlamellar spacing was little affected because of isothermal phase transition in salt bath. The tensile strength of the pearlitic steel rods was increased from 1480 to 1550 MPa. The tensile strength of the Cr-containing cold drawn wires (e = 1.58) was increased about 33%, and the torsion circle of the wires were about 15 with cleavage fracture. After annealing at 450 °C for 2 min, tensile strength of the wires increased, but torsion circle was decreased to less than 5. As the annealing time increased, the torsion circle of the steel wires with 0.2 wt.% Cr was improved to about 10 with cleavage fracture, while the torsion performance of the wires having high Cr contents remained low because of delamination fracture. The cementite platelets in Cr-containing wires turned into cementite crystal particles during cold drawing. Microstructure observation and thermal analysis have confirmed that thermal stability of cementite was enhanced with the increase of Cr content.

The Effect of Chromium Addition on Fluidity, Microstructure and Mechanical Properties of Aluminium LM6 Cast Alloy

The Effect of Chromium Addition on Fluidity, Microstructure and Mechanical Properties of Aluminium LM6 Cast Alloy

Effects of chromium on the morphology and mechanical properties of Fe2B intermetallic in Fe-3.0B alloy

In this work, the effects of chromium addition on the morphology and mechanical properties of Fe2B in Fe-3.0B alloy have been systematically investigated by a combination of experimental observations and the first-principles calculations. The results indicate that, with chromium addition in Fe-3.0B alloy ranging from 0 to 2.5 wt%, the average grain size of the boride firstly decreases and then increases slightly, mainly attributed to the volume fraction of coarse block boride. The nanoindentation hardness H of the boride remains almost constant while the elastic modulus E r firstly drops and then rises. Accordingly, the H/E r of the boride achieves a peak value at the chromium addition of 2.0 wt%, where the highest toughness is obtained. High-resolution transmission electron microscopy (HRTEM) observation demonstrates that the lattice of borides evolves from tetragonal to orthorhombic ((Fe, Cr)2B) after chromium addition, in good accordance with the calculation results. During the lattice evolution, a shrinkage of B–B bond along [002] direction is simultaneously revealed. The inherently weak B–B bond can be strengthened, which improves fracture toughness of Fe2B.

Effects of Cr on anodising and microstructure of cast aluminium alloys

Aluminium has been widely used in several applications due to its outstanding properties such as light weight and high corrosion resistance. However, development of surface mechanical properties and corrosion resistance is necessary for many applications especially in severe environment. The improvement of surface properties of commercial 6063 aluminium alloy by aluminium anodizing process was studied in this research. Chemical compositions of aluminium are important factor on aluminium matrix and properties of anodized layer. The addition of chromium in commercial 6063 aluminium alloy with different chromium amounts were prepared by ingot metallurgy. The effects of chromium addition on the microstructure, and corrosion properties were investigated. The minimum surface roughness of ingot obtained is 2.44 μm (Rq) can be seen inspecimen of 100-g chromium addition. The chromium amount also plays important role on corrosion resistance. Passive film was found in chromium-added anodized samples. Owing to the microstructure, addition of chromium leads to formation of intermetallic compounds in the aluminium matrix. These compounds are responsible for changes in microstructure and corrosion properties of bulk aluminium and anodized layer.

Effect of Chromium Addition on the Coarsening of Cu-particle in Ferritic Stainless Steels

Effect of Chromium Addition on the Coarsening of Cu-particle in Ferritic Stainless Steels

Effect of ChromiumAdditions on the Thermal Conductivity of Diamond Particle Dispersed Cu Matrix Composites Fabricated by SPS

Effect of ChromiumAdditions on the Thermal Conductivity of Diamond Particle Dispersed Cu Matrix Composites Fabricated by SPS

Effects of chromium additions on the three-body abrasive wear behavior of Fe-3.0 wt% B alloy

The effects of chromium additions on three-body abrasive wear behavior of Fe-3.0wt% B alloy have been systematically investigated using a moving wedge type of apparatus and two types of abrasives (SiC and SiO2 grains). Features of both the worn surface and subsurface have been discussed with regard to the respective wear rates. As chromium increased, the wear rate of Fe-3.0wt% B alloy first decreases to a minimum and then increases slightly for both abrasives. That behavior exactly reflects an opposite trend to the fracture toughness of the boride. The wear rate against SiC is evidently higher than that against SiO2. Mixed layers comprised of boride fragments and fatigued metallic matrix can be observed on the worn surfaces of the sample without Cr. Furthermore, the surface roughness resulting from wear first decreases and then increases using SiC; however, no obvious change takes place in the case of wear by SiO2. In the worn subsurface, serious fracture of the boride phase appears in 0wt% Cr sample while nearly no such cracks can be found in the 2wt% Cr sample. It is concluded that during three-body abrasive wear process involving both impact and indentation, the fracture toughness of the boride phases, apart from the bulk material hardness, plays a key role in the wear behavior of Fe-3.0wt% B alloy.