Cr Steel Research Articles

Influence of Al content on the microstructure and corrosion resistance in high manganese Fe–Mn–Al–C–Cr steels

Influence of Al content on the microstructure and corrosion resistance in high manganese Fe–Mn–Al–C–Cr steels

Wear and Friction Characteristics of In Situ TiC-Reinforced Ti3SiC2-Ti5Si3 Composites Against 100Cr6 Steel Counterpart

In this study, the dry sliding characteristics of a Ti3SiC2/Ti5Si3 matrix reinforced with different TiC contents against a 100Cr6 steel ball were investigated. The composites were fabricated using the spark plasma sintering method with Ti, SiC, and C powders. SEM revealed that the composites possessed damage tolerance behavior, where grain pull-out, buckling, delamination, and diffuse microcracking were observed. In comparison, the unreinforced composite showed severe adhesive wear and tribo-oxidative wear mechanisms. The integration of the TiC phase in the Ti3SiC2/Ti5Si3 matrix enhanced the wear resistance by at least one order of magnitude. A new wear regime was observed in the TiC-reinforced composites, classified as mild wear, where tribo-oxidation and third-body abrasion were dominant, with ferrous deposits on the sliding surfaces.

Effect of Al content on mechanical properties and corrosion performance of novel Fe-Cr-Al alloy steels in a CO2-O2 coexistence environment

The present study involved preparing five novel Fe-Cr-Al alloy steels with varying Al content based on commercially available 3Cr steel. The effect of Al content on the mechanical properties and corrosion performance in a CO2-O2 coexistence environment was investigated in novel Fe-3Cr-(0–2.5)Al alloy steels, and the microhardness, impact, and tensile properties were measured and compared. The corrosion rate, corrosion product film, and corrosion mechanism were studied using a weight-loss method, microscopic characterization, and electrochemical tests. The results showed that the tensile and impact properties of Fe-Cr-Al alloy steels exhibited a decreasing trend with increasing Al content. No localized corrosion was observed at an Al content of 2 wt%, attributed to the formation of a dense amorphous corrosion product film on the material surface and pre-passivation. Among the alloy steels examined in this study, the 3Cr2Al alloy steel exhibited the most optimal balance between mechanical properties and corrosion resistance.

Elimination of surface spottiness defects and characterisation of the nitrocarburised surface for 40Cr steel

Elimination of surface spottiness defects and characterisation of the nitrocarburised surface for 40Cr steel

Influence of Immersion Orientation on Microstructural Evolution and Deformation Behavior of 40Cr Steel Automobile Front Axle during Oil Quenching.

This study employs the finite element method to investigate the microstructural evolution and deformation behavior of a 40Cr steel automobile front axle during the quenching process. By establishing a multi-physics field coupling model, the study elucidates the variation patterns of the microstructure field in the quenching process of the front axle under different immersion orientations. It is found that along the length direction, the bainite and martensite structures decrease from the center to the edge region, while the ferrite structure shows an increasing trend. Additionally, the influence of immersion orientation on the hardness of the front axle's microstructure and deformation behavior is thoroughly discussed. The results indicate that, firstly, when quenched horizontally, the hardness difference among different regions of the front axle is approximately 8.2 HRC, whereas it reaches 10.3 HRC when quenched vertically. Considering the uniformity of the microstructure, the horizontal immersion method is preferable. Secondly, due to the different immersion sequences in different regions of the front axle leading to varying heat transfer rates, as well as the different amounts of martensite structures obtained in different regions, the deformation decreases along the length direction from the center to the edge region. Horizontal immersion quenching, compared to vertical immersion, results in a reduction of approximately 56.2% and 48.9% in deformation on the representative central cross-section (A-A) and the total length of the front axle, respectively. Therefore, considering aspects such as microstructure uniformity and deformation, the horizontal immersion quenching orientation is more favorable.

Dry sliding behavior of transparent yttrium aluminum garnet against 100Cr6 steel balls

Dry sliding behavior of transparent yttrium aluminum garnet against 100Cr6 steel balls

Microstructural and mechanical characterization of chromium carbide layers obtained on 100Cr6 and X200Cr12 steels by conversion

Carbides and Nitrides of transition metals are widely used due to their interesting properties. Several deposition methods and techniques can be used to produce carbide and nitride coatings. The choice of how to make the deposit depends on several parameters such as, the conditions of use of these deposits, the thickness to be produced, the adhesion between the substrate the deposit, and the cost. In this work, hard coatings of chromium carbide were produced by a conversion treatment on 100Cr6 and X200Cr12 steels. The conversion treatment consists of electrode position of chromium on the surface of 100Cr6 and X200Cr12 steels followed by diffusion annealing treatment at 1000 and 1100 °C for holding times of 1 and 2 hours. The obtained results show that, for all the conversion treatments carried out in this work, there was formation of chromium carbides layer on the surface of steel. However, it should be noted that the nature of the constituting phases of the formed layer depends on the temperature of the diffusion annealing treatment and the duration at this temperature. It should also be noted that the X-ray diffraction analysis has allowed us to show the existence of chromium oxide in addition to chromium carbides. The microhardness profile and the scratch test show that the X200Cr12 steel sample shows better results.These properties are usually obtained by expensive methods such as PVD, CVD, while we can obtain them by easy and inexpensive methods.

Comparative analysis of microstructure and corrosion resistance in laser-clad austenitic and martensitic stainless-steel coatings

Post-casting austenite often possesses better corrosion resistance than martensite. In order to compare the difference of corrosion resistance between austenitic stainless steel coating (ASSC) and martensitic stainless steel coating (MSSC) in the powder metallurgical state, two stainless steel Fe-based alloy coatings of the same process parameter were prepared on the surface of 40Cr steel by using laser cladding technology. Through SEM, EBSD, XRD and electrochemical tests, the microstructure, phase and cross-section metallurgical bonding condition of the coating were studied, and the difference in corrosion resistance between the two was comprehensively analyzed. The results showed that the main phase structure of ASSC was the FCC phase, and the main phase structure of MSSC was the BCC phase. The average self-corrosion current (9.92 × 10−8 A/cm2) and average self-corrosion rate (1.04 × 10−3 g/m2·h) of MSSC were 4.77 % and 5.62 % of ASSC, respectively. In addition, the polarization resistance, impedance value, and passivation film density of MSSC are higher than ASSC, MSSC has less damage from corrosion. The combination of factors, such as fabric refinement and passivation film density, makes the corrosion resistance of MSSC better than ASSC.

The Process of Steam Oxidation Degradation of High Cr Steel after 125 000 Hours at 568 °C under 16.5 MPa

AbstractThe aim of this work was to analyze the effect of steam oxidation when TP347HFG grade steel was exposed to industrial conditions for 125 000 hrs at 568 °C under 16.5 MPa pressure. The testing material was acquired from one of the coal power plants operating in Poland. Comprehensive investigations were carried out on the outer surface and cross section of the exposed sample using XRD, SEM/EDS and TEM. The analysis revealed the development of a fine grain oxide scale thickness spanning from 20 to 200 µm, consisting Fe2NiO4 (78 %), Cr1.3Fe0.7O3, Fe2O3 (0.8 %) and Fe3Co (0.8 %). Cross-sectional observations showed the formation of grains rich in Nb precipitates type MX carbonitrides surrounded by M23C6 carbides developed as a continuous net at the grain boundaries. The extent of material degradation under the influence of temperature, pressure and exposure time has been meticulously discussed. Graphical Abstract

Effect of air pressure and flow on steels materials in simulated wet fire drives

The corrosion behaviour of N80, 3Cr, and 5Cr steels were investigated under wet fire drive conditions using a high-temperature and high-pressure autoclave, weight-loss method, and scanning electron microscopy analysis. The findings indicated that elevated air pressure (4–6 MPa) and flow rates (0.5–1.5 m/s) significantly exacerbated corrosion, leading to both localised pitting and general corrosion on the steel samples. Predominant components of the corrosion product scales were identified as FeCO3 and Cr2O3. Notably, N80 steel exhibited higher pitting sensitivity compared to 3Cr and 5Cr steel, whereas 5Cr steel demonstrated superior corrosion resistance under the experimental conditions. Consequently, it is recommended to use cost-effective pipes with adequate corrosion resistance, such as various low-alloy pipes with differing chromium (Cr) contents, in oilfield applications. This study underscores the importance of selecting corrosion-resistant pipes as a primary means of corrosion prevention in oil and gas operations. Furthermore, it provides valuable insights into the corrosion performance of diverse steel materials in wet fire drive environments, offering pertinent implications for corrosion mitigation strategies within the industry.

Influence of Part Size on Microstructure during Austempering of Medium Carbon Low‐Alloy Steels

In this work, the influence of part dimensions on the microstructure of low‐alloy steel during its austempering has been studied. 0.41C‐0.24Si‐0.63Mn‐0.93Cr steel of different diameters ranging from 5 to 16 mm has been austempered at 350 °C for 10 min. Despite similar austempering conditions, an increase in the size and fraction of acicular/polygonal ferrite has been noted with an increase in the diameter of the samples. From the experimental observations and analytical calculations based on multi‐dimensional transient heat transfer analysis, the cooling rate during austempering has been observed to increase with a decrease in the sample diameter. Variation in ferrite grain size and fraction is due to different cooling rates encountered by different sized specimens during austempering. Close agreement between the experimental and theoretically estimated ferrite grain size due to variation in cooling rate during austempering has been noted.

The formation control and microstructure evolution of macrosegregation in laser offset welding on steel-nickel dissimilar alloy

To precisely control the melting of two base metals, laser offset welding is an effective method for managing the interfacial microstructure in dissimilar metal welds. Macrosegregation exhibits a markedly different morphology near the steel-nickel fusion line, which plays an important role in premature creep failure. In this study, it was found that an offset of the laser beam towards the nickel correlated with an increase in macrosegregation. When the laser beam was biased towards the steel, the partially mixed zone (PMZ) and transition zone (TZ) of 9Cr steel were identifiable within the macrosegregation, displaying a distinct solidification mode. Lath martensite and fine austenite formed in the PMZ, with alternating distributions of martensite and austenite observed in the TZ. Conversely, when the laser beam was biased towards the nickel, the unmixed zone (UMZ) of 9Cr steel was observed within the macrosegregation. Nanoindentation tests revealed that the maximum nanohardness in macrosegregation reached 5.90 GPa in the PMZ due to the formation of lath martensite, while the minimum nanohardness was 1.30 GPa in the TZ due to reduced martensite formation. Additionally, the TZ exhibited a significant reduction in resistance to plastic deformation. The various microstructures of macrosegregation were attributed to the solidification process and the dilution rate of 9Cr steel. When the liquidus temperature of WM exceeded 1455℃, a wide TZ formed in the macrosegregation due to adequate mixing. In contrast, when the WM had a significantly lower liquidus temperature than the 9Cr steel, only UMZ and PMZ formed in the macrosegregation due to preferential solidification and insufficient mixing. To minimize macrosegregation and eliminate the softening TZ, a laser beam offset towards the steel between 0.1 mm and 0.2 mm is recommended.

Effect of cobalt on Microstructure and toughness properties of 9Cr-1.8W-0.4Ni-xCo weld metal

In this research, microstructural characterization and mechanical properties of 9%Cr, 0.4%Ni (including W and Mo) steel weld metal with alloyed cobalt were investigated. Due to their strong creep resistance, oxidation resistance, and low thermal expansion, 9%Cr steels are used in nuclear power plants, petrochemical industries, and fossil fuel-powered power plants that operate in high temperature conditions. In this context, weld metals comprising 0.5 %, 1 % and 1.5 % cobalt and cobalt-free weld metal were produced by SMAW (shielded metal arc welding) technique. Microstructure of the weld metals were characterized with optical microscope (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Also, XRD analysis was performed on the bulk samples and precipitated carbide/nitride phases extracted from the weld metals. In addition, differential scanning calorimetry (DSC) was used to determine the phase transformations. Thermo-Calc modeling study was also performed. Hardness, tensile and Charpy-V impact tests were carried out to determine the mechanical properties. The hardness did not change significantly when cobalt up to 1.5 % in the weld metal. However, with the increase of cobalt, the yield and tensile strength increased without affecting the elongation value too much. In the Charpy impact tests performed at different temperatures (−40 °C, −20 °C, +20 °C, +40 °C, +60 °C), the amount of cobalt increased toughness, especially at +40 and + 60oC temperatures. Ductile brittle transformation temperature (DBTT) of the weld metal with 1.5 % Co decreased from 29 °C to 15 °C compared to cobalt free weld metal. It is thought that this may be caused by the further separation of C, Cr and W from the matrix through forming precipitate by the cobalt effect. Besides the mechanical properties, microstructure was also affected by adding Co with inhibition of delta ferrite formation which decrease the toughness. Curie temperature increased with increasing cobalt content detected by DSC.

Preliminary investigations of microbiologically influenced corrosion of 304 stainless steel by anaerobic Clostridioides difficile biofilm

Clostridioides difficile is a pathogenic anaerobe that potentially causes microbiologically influenced corrosion (MIC). Coupons of 304 stainless steel (SS) were incubated with C. difficile in deoxygenated brain heart infusion supplement medium. After a 7-d incubation, C. difficile biofilms were observed on the 304 SS coupon surfaces. The sessile cell count on 304 SS coupons were (1.9 ± 0.5) × 107 cells/cm2. It was found that this high-grade SS did not suffer measurable corrosion weight loss and pitting. X65 carbon steel was used to verify C. difficile bio-corrosivity. A 7-d weight loss of 0.9 ± 0.2 mg/cm2 was found on X65 coupons with the same incubation condition, which manifested as uniform corrosion. 13%Cr steel, also known as 420 SS which is a low-grade SS that is prone to pitting, was used to verify pitting by C. difficile. A 15.2 μm pit was observed after 26 d of incubation. Electrochemical tests were conducted in a 10 mL biofilm/MIC test kit. The electrochemical analysis of electron mediator injection indicated that MIC of 304 SS by C. difficile belongs to extracellular electron transfer-MIC. A 100 ppm (w/w) tetrakis (hydroxymethyl)phosphonium sulfate (a green biocide) injection test proved that it is a suitable disinfectant for C. difficile.

The transient thermal ageing of Eurofer 97 by mitigated plasma disruptions

Plasma disruptions in a commercial-scale tokamak will impose high magnitude, short-duration thermal loads on its plasma-facing first wall. Despite a plethora of mitigation measures, these severe, off-normal events are likely to briefly expose the structural materials of the first wall to significant temperature excursions. Eurofer 97, the reference structural material for the plasma-facing first wall of the EU DEMO tokamak, is a reduced activation 9Cr steel with a normalised and tempered ferritic/martensitic microstructure. Repeated exposure to the thermal effects of disruptions over the operating lifetime of a reactor may promote a cumulative evolution of Eurofer 97′s microstructure, affecting key material properties crucial to first wall performance. This novel transient thermal degradation mechanism has been explored via a laser-based transient heating experiment, supported by time-dependent finite element thermal analysis studies of DEMO’s water-cooled lithium–lead first wall during a mitigated plasma disruption. Transient-affected samples of Eurofer 97 were characterised via scanning and transmission electron microscopy techniques (SEM/TEM), including electron backscatter diffraction (EBSD), energy-dispersive X-ray spectroscopy (EDX), and selective area electron diffraction (SAED). Microhardness and magnetisation testing data are also presented. A single 700 °C thermal transient was found sufficient to coarsen and partially recrystallise Eurofer 97′s tempered martensite sub-grains at the tungsten-Eurofer 97 interface. Further transient exposure at 700 °C resulted in the significant growth of equiaxed grains, the nucleation of intergranular Cr-rich M7C3 and M23C6 carbides, and the coarsening of V-rich and intra-granular Ta-rich MX precipitates. The microstructural effects of 850 °C transients are also reported. Notably, after 1,000 transients at 850 °C the hardness of Eurofer 97 was found to have decreased by 32 %.

Optimizing the resistance of Cr-advanced steel to CO2 corrosion with the addition of Ni

The findings of this study indicate that Cr-advanced steels exhibit increased corrosion resistance when Ni is incorporated into the alloy. To investigate this phenomenon, the corrosion products and corrosion behavior of Cr-advanced steels with varying Ni contents were evaluated in CO2-saturated NaCl solutions at 90 and 180 °C. The underlying corrosion resistance mechanism can be elucidated from two distinct perspectives. At 90 °C, the addition of Ni into Cr-advanced steels causes the transformation of Fe oxides to NiFe2O4, and it offers superior protection for steel. In addition, the NiFe2O4 phase generated with electronegative properties can enhance the adsorption of Fe2+, thereby promoting the precipitation of FeCO3 crystals. Furthermore, the residual Ni in the inner film continues to serve a pivotal role in the filling of a considerable number of pores and cracks. Upon comprehensive evaluation of the associated costs, the Cr-advanced steel with enhanced corrosion resistance through the incorporation of 1.0 wt% Ni content provides a potential alternative to a conventional 3Cr steel in a CO2 environment. On the other hand, at 180 °C, the concentrations of Fe2+ and CO32− are significantly higher than the solubility of FeCO3 in initial corrosion, which is conducive to generate a denser nanometer-size FeCO3 layer with a better protectiveness, and thus, the effect of Ni is significantly weakened.

High tribological performance of quenched–tempered 40Cr steel treated by plasma oxynitriding

Alloy steel 40Cr was treated by plasma oxynitriding after quenching and tempering. The microstructures, mechanical properties, and tribological performances of plasma oxidized–nitrided layer at tempering temperatures of 500, 520, and 540 °C were investigated. The typical tempered sorbite structure was present when the 40Cr alloy steel was treated by quenching at 900 °C and tempering. A special structure of mixed oxide–nitride layer along with the veinlike nitride phase was formed after plasma oxynitriding. The surface hardness of the quenched–tempered 40Cr alloy steel was significantly improved. The quenched 40Cr alloy steel tempered at 520 °C exhibited the highest hardness of approximately 973 HV0.2 and the lowest wear rate of about 1.72 × 10−14 m3 N−1 m−1 than the samples tempered at 500 and 540 °C. The oxide and nitride phases inside the plasma oxidized–nitrided layer played important roles in the improvement of the surface mechanical properties and the tribological performance of the quenched–tempered alloy steel.

Operando characterization of Cr-containing alloy passivation film by synchrotron radiation

Techniques of electrochemical-spectroscopic ellipsometry, electrochemical-Raman spectroscopy, and electrochemical-grazing incidence X-ray diffraction using the electrochemical synchrotron radiation source were combined to characterize the growth process of chromium-containing passivation film. The operando method can characterize passivation film in detail and monitor the growth process of these films, which can not be done sufficiently using uncombined traditional structural characterization techniques. For example, Fe-18 wt%Cr steel was used to monitor the passivation process, such as adsorbed species that transformed into stable species and the decrease in the dissolution of internal metals. This means that the operando method developed in this work could effectively monitor passivation.

Combined Gleeble physical welding simulation and low-cycle thermo-mechanical fatigue for heat-affected zone material for 9Cr steel: Experimental testing and through-process model

Combined Gleeble physical welding simulation and low-cycle thermo-mechanical fatigue for heat-affected zone material for 9Cr steel: Experimental testing and through-process model

Tribological behaviour of microindented 100Cr6 steel surfaces in dry contact conditions

In the present work, we studied the dry tribological behaviour of a 100Cr6 steel, the spherical surface of which was texturized with microindentation. The purpose of adopting a mechanical indentation technique on a non-planar surface was to simultaneously evaluate the effectiveness of adopting a fast, deformation-based technique for improving the contact tribological properties. Specifically, dimples were created using an automatic microhardness tester equipped with a Vickers indenter, setting a load of 0.5 N. Friction tests were performed at different speeds considering textured surfaces with two different void ratios (VRs). Textured and untextured surfaces were tested using a ball-on-disc tribometer. In addition, the effect of dimple size was evaluated by producing Vickers indented surfaces at a load of 5 N per each indentation, while keeping the VR values unchanged and testing the frictional properties of such surfaces at a fixed speed of 4.18 mm/s. Textured surfaces were deeply investigated to motivate the improvement of tribological properties. Notably, compared to the untextured samples, the microindented samples exhibited a much lower coefficient of friction (COF), with a friction reduction compared to the untextured case ranging from 45 to 65%, depending on the VR values. The adoption of large dimples allowed the reduction of the COF, already at smaller VR value but, in such a case, the presence of bulges at the edge of the dimple worsens the wear resistance of the counter surface. In addition to reducing the contact area and the capability to trap any debris in the dimples, the local measurement of strength allowed to clarify that the friction reduction is also determined by the work hardening effect produced by the microindentation texturing. Considering the significant improvements recorded in terms of COF and the high ability to indent even non-planar surfaces, the proposed approach can be considered very promising and, therefore, industrially applicable (e.g. using a specifically designed multi-indenter tool) to affect the friction behaviour of components, even locally, during both their use and their production.