Cr Steel Research Articles

Resource-saving technology of heat treatment of parts that quickly wear out in mining equipment

The service life of mining equipment is determined by the durability of only a few, the most responsible parts. Ladles, which are operated in severe conditions of hydroabrasive wear combined with shock loads, are the most fast-wearing element of ball grinding mills. Interrepair cycles of this equipment are determined by the durability of the ladles. It is shown that heat treatment is the most important factor affecting the size and distribution of structural components of steel, which largely depend on its mechanical and operational properties.On the basis of the constructed diagram of the isothermal decomposition of supercooled austenite for modified 40Cr(casting) (Standard of Ukraine) steel, the possibility of obtaining, during continuous cooling in various sections, castings of "ladles" of bainitic structure, in which, after high tempering, a ferrite-cementite mixture with a spherical shape of cementite is formed, providing a high complex of physical and mechanical properties and wear resistance. The developed resource-saving technology of thermal treatment of ladles, which consists in intermittent quenching followed by tempering, made it possible to increase their operational durability by approximately 2 times compared to ordinary 40Cr(casting) steel and increase the maintenance intervals of ball grinding mills.

Machine learning-assisted creep life prediction and empirical formula generation for 9-12% Cr steel

The creep behavior of steels is influenced by factors such as lattice structure, defects, and stress conditions. Given the high cost and time required for creep tests, accurately predicting creep life and minimum creep rate is essential. This study analyzed 9–12% chromium (Cr) steel using a dataset of 1496 entries covering material composition, mechanical properties, minimum creep rate, and creep life. Nine machine learning (ML) models were developed, with the artificial neural network (ANN) achieving the highest prediction accuracy, evidenced by a coefficient of determination (R2) of 0.9973 and a root mean square error (RMSE) of 0.045. A dual-target neural network model provided R2 values of 0.9853 for creep life and 0.9838 for minimum creep rate. Additionally, an empirical equation based on gene expression programming (GEP) achieved an R2 exceeding 0.9741. This study offers novel insights into the design of 9–12% Cr steel with enhanced creep life.

Investigation of corrosion behavior of 5Cr steel in CO₂-silty sand environment: Effects of hydrodynamic impact angles

This study investigates the influence of impact angles on the corrosion behavior of 5Cr steel in a CO2-silty sand environment through hydrodynamics analysis. The primary cause of degradation in 5Cr steel is the combined effect of the mechanical damage to the corrosion product film by silty sand particles and corrosive environment. The severity of damage to the corrosion product film on the 5Cr steel surface caused by silty sand particles at different impact angles, from highest to lowest, is 45°, 90°, and 0°. At an impact angle of 45°, the silty sand exerts equal tangential and normal stresses on the corrosion product film, compromising its integrity and requiring more Cr(OH)3 for repair and stabilization, resulting in the most severe localized pitting corrosion. At impact angles of 0° and 90°, the silty sand exerts only tangential stress and normal stress on the corrosion product film, respectively. The imbalance between normal and tangential stresses at these angles results in shallower and more limited removal of corrosion products, making the destructive effect less significant than at a 45° impact angle.

Formation Mechanism and Influence of Heating Temperature and Holding Time on Surface Decarburization of 40Cr Steel during Hot Forging Process

During hot forging and heat treatment of 40Cr steel, a decarburized layer emerges on the surface, affecting fatigue life. However, the decarbonization of 40Cr steel has not been reported so far. The experiment mainly studies the effect of holding temperature and time on decarbonization. The 40Cr steel undergoes complete decarburization at 700 and 750 °C while experiencing a combination of complete and partial decarburization at 800 °C, transitioning solely to partial decarburization above 850 °C. The decarburized layer thickness measured at 750 and 800 °C is 140 and 200 μm respectively; the total decarburization layer thickness exhibits an exponential increase with the temperature. The thickness of the completely decarburized layer, influenced by varying factors across temperature ranges, initially rises and subsequently declines with the escalation of temperature, reaching its maximum at ≈750 °C. The maximum value of complete decarburization is 146 μm. Simultaneously, the total depth of decarburization is found to be proportional to the square root of time, adhering to Fick's second law. The fitting result is expressed as x = 165.47t1/2 at 750 °C. Notably, the existence of the decarburized layer results in a decrement in both the tensile strength and yield strength of the component, albeit accompanied by a marginal improvement in ductility.

Experimental Investigation of Cr12 Steel Under Electrostatic Minimum Quantity Lubrication During Grinding

In this work, electrostatic minimum quantity lubrication (EMQL) has been applied in grinding. When the droplets were charged, it could promote penetrability in the processing area. The electric field formed between the charged droplets and the surface of Cr12 die steel could affect the hardness of the workpiece surface. The grinding mechanism of EMQL has been revealed under different charging voltage by analyzing the wetting angle of droplets and the hardness of Cr12 surface. The reduction of grinding force (11.5% to 49%), surface roughness (10% to 22.1%), and the increase in grinding ratio (1.9% to 27.3%) and surface quality of EMQL under various charging voltages were studied. The results showed that the wetting angle decreased when the droplets were charged. Compared to MQL, the charged lubricant droplets with better penetrability are easier to penetrate and spread on the contact surface between the grinding wheel and the workpiece, thereby improving the lubrication of the friction interface and obtaining better grinding performance. Moreover, we also found that the positively charged EMQL not only effectively improves the penetrability of droplets but reduces the hardness of the Cr12 surface. Thus, the grinding performances under positively charged EMQL are always better than these under negatively charged when grinding Cr12.

Influence of Deep Cryogenic Treatment on Fatigue Strength of 100Cr6 Bearing Steel

The objective of the study was to assess the impact of cryogenic treatment on the augmentation of fatigue strength in 100Cr6 steel bearings. The chilling process of a material to -185°C is known as cryogenic treatment, and it improves the material's mechanical as well as physical characteristics. This study aimed to investigate the impact of cryogenic treatment on the dimensional stability enhancement of 100Cr6 bearing steel utilizing DCT (deep cryogenic treatment) at -185°C. The dimensional stability has improved by 13.77 percent as a result of DTC in comparison to conventional heat treatment (CHT). The microstructural investigation reveals that the improvement in dimensional stability is because of the conversion of residual austenite into martensite, as well as the precipitation and dispersion of carbides resulting from the cryogenic treatment. The results of the DSC (Differential Scanning Calorimetry) research performed on the bearing steel samples indicate that the DCT mostly promotes martensite instability by triggering carbon clustering as well as transition carbide precipitation. The DTC showed a higher enhancement in dimensional stability than standard heat treatment because of the more homogenized distribution of carbide and the remaining austenite removal.

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.

Influence of different introduction methods of graphene on the mechanical properties and cutting performance of Al2O3/TiB2 ceramic tool materials

This study investigated the effects of incorporating graphene-coated alumina (Al2O3@G) nanoparticles and graphene oxide (GO) on the microstructure, mechanical properties, and cutting performance of Al2O3/TiB2 matrix ceramic tool materials. Compared to the addition of GO, the inclusion of Al2O3@G enhanced the dispersion of graphene in the ceramic tool materials and alleviated defects such as pores caused by graphene agglomeration. Additionally, during sintering, uniformly distributed graphene interwove to form a three-dimensional grid structure owing to grain growth and pore disappearance, increasing the contact area and interface bonding strength between the graphene and the matrix. Based on the results of the microstructure observation and analysis, the favorable interfacial strength not only facilitated load transfer from the ceramic matrix to graphene but also triggered the fracture mechanism of graphene, consuming more fracture energy than the traditional toughening mechanism. The hardness, flexural strength, and fracture toughness of the obtained ATB-G@3.0 ceramic tool material with 3.0 vol% Al2O3@G were measured at 19.52 GPa, 1063.52 MPa, and 9.16 MPa m1/2, respectively, which were 16.82 %, 27.92 %, and 26.87 % higher than those of the ATB-G3.0 ceramic tool material with 3.0 vol% GO. Compared with the ATB-G3.0 ceramic tool, the ATB-G@3.0 ceramic tool displayed superior cutting performance and longer service life when machining hardened steel 40Cr. Furthermore, the addition of Al2O3@G effectively reduced the cutting force, friction coefficient, and cutting temperature of the ceramic tools and enabled the workpiece to achieve better surface processing quality after cutting.

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

The 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

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.