Heat Treatment Conditions Research Articles

Vacuum processing temperature effect on highly coercive recycled NdFeB permanent magnets with Pr-based alloy addition

This study presents a modified method for recycling NdFeB scrap magnets, producing up to 100 kg of recycled sintered NdFeB magnets per batch. By adding a Pr-based alloy to N40H-grade NdFeB scrap and optimizing vacuum sintering and heat treatment conditions, we enhanced the magnetic properties and corrosion resistance of the recycled magnets. Various analyses, including BH Tracer measurements, FE-EPMA, accelerated corrosion tests, and C/N/O content analysis, evaluated differences in magnetic properties, microstructure, corrosion resistance, and impurity content. Optimal recycling involved vacuum sintering at 1085 °C, followed by heat treatments at 900 °C and 470 °C. Recycled magnets with PrCoGa alloy showed superior properties, such as an intrinsic coercivity (iHc) of 1414 kA/m, remanence (Br) of 1.290 T, and a maximum magnetic energy product ((BH)max) of 315.4 kJ/m, meeting N40H standards. Accelerated corrosion tests also indicated enhanced corrosion resistance in recycled magnets with Pr90Co8Ga2 alloy. This research offers a commercially viable approach for NdFeB magnet and rare earth element recycling.

Innovative Implementation of Computational Fluid Dynamics in Proteins Denaturation Process Prediction in Goose Breast Meat and Heat Treatment Processes Optimization

This study aimed to calculate the optimal thermal processing parameters for goose meat using CFD simulation. CFD provides a precise determination of heat treatment conditions by predicting protein denaturation and mass loss, leading to higher quality and improved sensory experience and, thus, acceptance of products. Accurate calculation of these conditions reduces energy losses and enhances process efficiency in the food industry. This study focused on the prediction of protein denaturation and cooking loss in goose breast meat during roasting. Specific CFD techniques, including conjugate heat transfer and phase change models, were utilized to ensure accuracy in protein denaturation prediction. These models accounted for variations in meat composition, such as fat and water content across different samples, which improved the accuracy of the predictions. Optimal conditions were determined using a mathematical model. These conditions were 164.65 °C, 63.58% humidity, and a fan rotation of 16.59 rpm for 2000 s. The myosin, collagen, and actin denaturation levels, as well as cooking loss, closely matched predicted values. The findings show that CFD is a valuable method for evaluating protein denaturation and cooking loss in goose breast meat, potentially improving product quality and consistency in gastronomy and the meat industry. This innovative optimization method enhances food production efficiency and elevates sensory characteristics, physicochemical properties, and nutritional value, contributing to consumer satisfaction and market competitiveness. The model proposed in this paper can be adapted to predict denaturation in other types of meat or food products with necessary modifications, offering broad applicability. Potential limitations of using CFD in protein denaturation prediction in complex food matrices include the need for detailed compositional data and computational resources, which can be addressed in future research.

Effects of post-deposition annealing on structure and mechanical properties of multilayer Ti/DLC films

The multilayer (Ti/DLC) × 3 films were deposited using a DC arc evaporator with a titanium cathode and a pulsed cathode-spark evaporator with a graphite cathode. Following the deposition of the films, a heat treatment process was performed in air and Ar atmosphere at temperatures of 200 °C and 400 °C. The investigation of the films involved the examination of their structure, surface morphology, and chemical composition using AFM, SEM, XPS and Raman. Additionally, the mechanical properties of the films were assessed by nanoindentation, sclerometry and wear test. Changes in the structure, RMS roughness, С-sp2/С-sp3 ratio of carbon atoms in the film and the formation of Ti-C carbide were determined in relation to the heat treatment conditions. Studies have demonstrated that subjecting materials to heat treatment at temperatures of 400 °C results in a decrease in friction coefficient and an increase in hardness. The deposition of films on the working surfaces of microdrills with subsequent heat treatment leads to a reduction in wear, an extension of their service life, and an improvement in drilling accuracy as compared to microdrills without films. Furthermore, microdrills with (Ti/DLC) × 3 films annealed in air at 400 °C exhibit negligible size reduction and better drilling accuracy.

Manipulation of strength and ductility of AA5182-O through cyclic bending under tension and annealing processing

Aluminum alloy (AA) 5182-O sheets are processed by continuous bending under tension (CBT) followed by heat treatment to investigate microstructural changes for optimizing strength and ductility of the alloy. Bending depth and pull speed parameters of the CBT process are optimized to enhance the achievable strain beyond a conventional uniaxial tension, by inducing significant microstructural changes in the sheets. CBT processed samples are subsequently heat treated at various time-temperature regimes to determine the best recovery condition. The combination of CBT and heat treatment effect on the mechanical properties is examined by the subsequent uniaxial tension experiment. Measured microstructural changes in terms of grain structure and texture by electron backscattered diffraction (EBSD) show that it is possible to change a 〈001〉 cube texture typically present in rolled and annealed AA sheets into a 〈111〉 fiber texture by combining CBT and annealing processing. Moreover, measured mechanical responses reveal that a particular combination of CBT and heat treatment at 270 °C for 2 h can increase strength by over 75 % at the expense of 37 % reduction of uniform ductility. Interestingly, only a complete recrystallization after CBT restores the r-value of as-received material, while the intermediate heat treatment conditions lower the r-value.

Failure analysis of fatigue crack propagation in specimens of AlSi10Mg aluminum alloy produced by L-PBF: Effect of different heat treatments

Fatigue crack growth behavior of AlSi10Mg aluminum alloy processed by laser powder bed fusion (L-PBF) was studied for three material conditions: as-built, stress relieved and hot isostatic pressed. An improvement in the fatigue crack growth resistance was found for the heat-treated conditions which was attributed to the residual stress relief induced by the heat treatments. The stress ratio did not affect the fatigue crack growth in regime II which was explained by the absence of crack closure. Fatigue crack growth rates were predicted using a model based on the cyclic plasticity of the tested aluminum alloy. The proposed model agreed well with the experimental results.

Synthesis of Molybdenum Oxide Nanofibers with Multiple Surface Facets Via Electropsinning Followed by Rapid Thermal Treatment

A MoO3 nanofiber prepared by electrospinning and subsequent heat treatment is attracting significant attention due to its structural advantages. Vibrant studies are being conducted to control its morphology and diameter to improve its properties. In this study, we demonstrated the synthesis of α-MoO3 nanofibers with multiple surface facets by controlling the heating rate and temperature in the heat treatment step for removing polymer and crystallizing MoO3 from the electrospun polymer/precursor nanofibers. The analysis results show that the faster heating rate and higher heat treatment temperature in the thermal treatment process are more favorable for forming a shape in which particles with facet planes are connected. Finally, we observed the morphological change according to the heat treatment time to confirm the effect of the heat treatment conditions on the shape of MoO3 and interpreted the results in terms of nucleation and crystal growth.

Nanostructured TiO2 synthesized by different methods: Relationship between TiO2 porosity and crystalline-amorphous structure

The present manuscript focuses on important aspects regarding TiO2, which is typically used in many applications. On one hand, a thorough review of methods for synthesizing nanostructured TiO2 is presented. Using these methods, and different post-synthesis heat-treatment conditions, close to thirty TiO2 materials have been prepared, and their porous texture and crystalline and amorphous structure have been characterized. In this large number of samples, the porous texture characterization has revealed a high contribution of mesoporosity in a large number of the synthesized materials, being in many materials around 60–70 %. Moreover, different percentages of crystalline phases, anatase, brookite, rutile, and amorphous titania are developed depending on the TiO2 preparation conditions. These fractions have been determined from X-ray diffraction data using the “simple” characterization method reported by Cano-Casanova et al., inspired by Jensen et al., and Bellardita et al., also exploring its limitations. This analysis has allowed assessing a linear relationship between porosity, particularly between the surface area, and the amorphous phase content in titanium dioxide. A relationship had been previously suggested in the literature, but never correlated in such a way. In summary, the present study constitutes a tool to help other researchers select the most suitable method for synthesizing nanostructured TiO2 materials with target properties and, also, to characterize them, and have a very easy and straightforward estimation of TiO2 amorphous phase content after the determination of their surface areas.

Comprehensive study on scale-induced heterogeneity of (Ni2CrCo)94Nb3V3 high-entropy alloy variable-width thin-walled structure fabricated by additive manufacturing

Laser additive manufacturing (AM) shows excellent advantages in near-net shape of complex parts. In this work, the (Ni2CrCo)94Nb3V3 high-entropy alloy variable-width thin-walled structures were fabricated by directed energy deposition, and its microstructure and mechanical properties at the narrow and wide ends were systematically studied in the printed and different heat treatment states. In the printed state, the 〈001〉 crystallographic orientation along the building direction and the 〈111〉 crystallographic orientation along the scanning direction are formed at the narrow and wide ends of the sample, respectively. The preferred crystallographic orientation is eliminated and numerous annealed twins are occurred at high-temperature annealing, while the original grain morphology and crystallographic orientation is not changed significantly after direct aging. In the printed state, the yield strength and ultimate tensile strength of the wide end are increased by 10.69 % and 11.60 % compared with that of the narrow end, and the elongation is decreased by 18.74 %. The differences in tensile properties at the narrow and wide ends of the sample are mainly related to the crystallographic orientation and dislocation density, without taking the statistically stored dislocations into account. The strength of both narrow and wide ends is significantly increased, but the difference in tensile performance between them is not changed through direct aging. In addition, the strength is slightly decreased and the difference in tensile properties between the narrow and wide ends is eliminated by high-temperature annealing. The results present in the current study provide new insights for the LAM optimizing design of thin-walled parts with complex structures.

Optimization of electrophoretic deposition and thermal treatment of Cu–Mn spinel matrix for spinel/perovskite composite coating used as SOC metallic interconnect

The electrophoretic deposition of a mixture of copper-manganese spinel oxide matrix with perovskite oxide dispersion phase and subsequent two-step sintering was investigated as a means of obtaining a new spinel/perovskite composite coating for application in metallic interconnects for solid oxide cell (SOC) technologies. The effect of a number of factors was examined, including electrophoretic deposition parameters such as solvent type, time, voltage, and dispersant content as well as different heat treatment conditions on the quality of the matrix of the coating material. A solution of ethanol-acetone (25/75 v/v) and 2.0 g L−1 of iodine dispersant with a deposition time of 60 s and a voltage of 60 V provided the thickest, most uniform coating as deposited. SEM observations showed that a dense coating of Cu–Mn spinel was obtained after 8 h of reduction at 1000 °C followed by 6 h of oxidation at 850 °C. Selected preparation parameters were applied to deposit composite coatings with a Cu–Mn spinel matrix and the addition of LNF, LSC and LSCF perovskites.

Effect of B4C and graphene on the microstructural and mechanical properties of Al6061 matrix composites

Materials that are lightweight with superior strength and improved structural properties have consistently been highly sought after in the aircraft and automobile industries for their superior performance. This study investigates the effect of graphene and boron carbide (B4C) additions on the microstructural & mechanical properties of Al6061 MMCs in fabricated and T6 heat-treated conditions. The powder metallurgy technique is used to fabricate the Al6061 hybrid composites reinforced with different volume fractions. i.e 0.5,1 wt% of graphene and 3,6 wt% of B4C. XRD, Optical microscope, FE-SEM with EDAX mapping, Hardness, and Compression tests were employed to evaluate and characterize the Al6061/Gr/B4C hybrid composites. After the T6 ageing treatment, both hardness and compressive strength were increased to 61.08% and 68.51% compared to base Al6061 matrix alloy. The sample Al6061/0.5% Gr/6%B4C-T6 exhibits the highest hardness value of 91HV and sample Al6061/1%Gr/6%B4C-T6 gives the value of higher compressive strength of 298 MPa. The higher tensile strength was observed in the sample Al6061/0.5%Gr/6%B4C-T6 which is 209.53 MPa with 8.907% elongation. The T6 heat treatment has a significant role in the strength improvement. Whereas increment in graphene has no impact on the tensile strength. The tensile strength of Al6061/0.5%Gr/6%B4C-T6 was improved by 43.56% compared to the base Al6061 alloy.

Optimizing a canola-gelatine-urea bio-adhesive: effects of crosslinker and incubation time on the bonding performance

The importance of creating eco-friendly and health-conscious materials has become paramount in striving to attain long-term development goals. For the past decades, constant efforts have been made to tackle the issue of formaldehyde release from wood-based panels which, to date, are still mainly produced from unsustainable synthetic adhesives. In the pursuit of sustainable and environmentally responsible adhesive solutions for the wood industry, sodium bisulfate, sodium bisulfite, and sodium nitrite were used under different heat treatment conditions as crosslinkers for canola protein-based bio-adhesive formulations. The developed adhesive formulations showed outstanding mechanical properties, with a viscosity below 4000 mPa/s despite the relatively high solid content, as well as excellent bonding performances. The one-layer particleboards bonded with the canola-based adhesive demonstrated outstanding mechanical properties, with the internal bonding and the bending strength values surpassing 0.60 N/mm2 and 10 N/mm2, respectively. Notably, the sodium nitrite-crosslinked variants exhibited significantly superior performance compared to the UF-bonded control boards. Longer incubation times generally improve bonding strength, with sodium nitrite showing the most pronounced effects. The results of this research showcase not only the possibility of developing a plant protein-based wood adhesive with high solid content, but also the potential superiority of canola protein-based wood adhesives when compared to conventional, synthetic counterparts. These findings offer valuable insights for optimizing bio-based adhesives in wood composite manufacturing, highlighting sodium nitrite as a promising crosslinker for enhancing the adhesive’s performance.

Production of lactulose from lactose using a novel cellobiose 2-epimerase from Clostridium disporicum

Lactulose is a semisynthetic nondigestive sugar derived from lactose, with wide applications in the food and pharmaceutical industries. Its biological production routes which use cellobiose 2-epimerase (C2E) as the key enzyme have attracted widespread attention. In this study, a set of C2Es from different sources were overexpressed in Escherichia coli to produce lactulose. We obtained a novel and highly efficient C2E from Clostridium disporicum (CDC2E) to synthesize lactulose from lactose. The effects of different heat treatment conditions, reaction pH, reaction temperature, and substrate concentrations were investigated. Under the optimum biotransformation conditions, the final concentration of lactulose was up to 1.45 M (496.3 g/L), with a lactose conversion rate of 72.5 %. This study provides a novel C2E for the biosynthesis of lactulose from low-cost lactose.

Role of heat treatment conditions in the high-temperature deformation behavior of laser-powder bed fused Fe–Cr–Ni–Al maraging stainless steel

The present research investigates the high-temperature behavior of laser powder bed fused (LPBF) Fe–Cr–Ni–Al maraging stainless steel (equivalent to PH13–8Mo). Fully dense PH13–8Mo samples are printed using an EOS M290 printer, and the effect of different heat treatments on high-temperature behavior and microstructure development is investigated. The material is studied under as-printed (AP), austenitized aged (AA, austenitized at 900 °C for 1 h followed by aging at 530 °C for 3 h), and direct-aged (DA, aged at 530 °C for 3 h) conditions. Uniaxial compression tests are conducted using a Gleeble® 3500 thermal-mechanical simulator at 400 °C and 500 °C at a quasi-static strain rate of 0.0001 s−1 to a final true strain of 0.2, while the microstructure characterization is performed using Electron Backscatter Diffraction and Transmission Electron Microscopy. At room temperature, the AA sample shows the highest hardness (strength), but at temperatures of 400 °C and 500 °C, the DA sample possesses the highest strength. Interestingly, the AP sample exhibits comparable strength to the DA sample at 500 °C, which could indicate for applications at these high temperatures, LPBF-PH13-8 Mo does not require any heat treatment.

Effect of Li+ on luminescence properties and thermal stability of glass ceramics containing SrMoO4

Dy3+, Eu3+ co-doped glass ceramics (GCs) containing SrMoO4 crystalline phase were prepared by melt-curing-crystallization method. The most favorable heat treatment conditions for the glass ceramics were found to be 610 °C/2 h by differential scanning calorimetry (DSC), ultraviolet spectrophotometer (UV–Vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The best doping concentrations of Dy3+ and Eu3+ in this glass ceramic were 0.8 % and 0.6 %, concentration quenching caused by dipole-dipole interactions occurs when the content of rare earth ions in GCs continues to increase. The chromaticity coordinates of the Dy3+- Eu3+ co-doped glass ceramics changed from cool white light to warm white light with the addition of Eu3+ concentration. At the optimal doping concentration (0.8 % Dy3+-0.6 % Eu3+), the chromaticity coordinate of glass ceramics is (0.3972, 0.3331), and the related color temperature is 3047 K. The luminescence intensity can still reach about 80 % of room temperature at 180 °C, and its thermal quenching activation energy is 0.233 eV. This suggests that glass ceramics have excellent thermal stability. After adding an appropriate amount of Li+, the crystalline phase of the glass ceramics remained unchanged and the luminous intensity of the glass ceramics increased by a factor of about 1.4 in the same environment. The thermal quenching activation energy of the glass ceramic doped with 0.2 % Li+-0.8 % Dy3+-0.6 % Eu3+ was 0.344 eV. The experimental results indicate that GCs has potential application prospects in the field of solid-state lighting.

Experimental research and optimization based on response surface methodology on machining characteristics of cast Al-7Si-0.6 Mg alloy: Effects of cutting parameters and heat treatment

In this study, structural, mechanical and machining features of Al-7Si-0.6 Mg alloy manufactured by permanent mold casting (PMC) in both as-cast (AC) and T6 heat-treated (HT) conditions were investigated. Structural and mechanical properties were determined using conventional methods. Milling experiments were conducted with titanium aluminum nitride (TiAlN) coated carbide end mills in CNC milling machine under conditions of three different cutting speeds (V: 50, 80 and 110 m/min), feed rate (f: 0.08; 0.16 and 0.24 mm/rev) and constant depth of cut (DoC) (1.5 mm). It was seen that structure of AC Al-7Si-0.6 Mg comprised of aluminum-rich α-Al, coral-like eutectic Al-Si, primary Si, Mg2Si, Fe-rich plate, acicular β-Fe (β-Al5FeSi) and script-like π-Fe (π-AlSiMgFe) intermetallic phases. Eutectic Al-Si, primary Si, β-Fe and π-Fe phases in the structure of the alloy in the HT condition were partially dissolved and turned into an agglomerated and spherical state. While the hardness (HB), yield (YS) and tensile strength (TS) of the alloy raised with HT, the elongation to fracture (EF) reduced. While cutting force (CF), surface roughness (SR), built-up layer (BUL) and built-up edge (BUE) decreased with increasing V, they increased with increasing f in the milling of both cast and HT alloys. Adhered layers and feed marks were consisted of the cutted surfaces of the alloys. While the most adhered layer was observed in AC alloys at a low V (50 m/min) and high f (0.24 mm/rev) combination, the least adhered layer formation was observed at the highest V and the lowest f value in HT alloys. Optimum parameters with Response Surface Methodology (RSM) were determined as V: 125 m/min and f: 0.04 mm/rev in AC and HT cases. The statistical significance of V and f on CF and SR was revealed by analysis of variance (ANOVA), while mathematical models were improved to predict CF and SR.

Structural and magnetic transformations in the system YBaCo4O7+X (x = 0, 0.1, 0.2)

The modification of magnetic and elastic properties of YBaCo4O7+x (x = 0, 0.1) cobaltite series at a small controlled deviation x = 0, 0.1, 0.2 from stoichiometry has been investigated. The non-stoichiometric cobaltites with x > 0.1 are found to be separated into two structural phases with different values of x under certain synthesis and heat-treatment conditions of the YBaCo4O7+x system (x = 0, 0.1, 0.2). A non-trivial magnetic behavior is observed in stoichiometric YBaCo4O7. Magnetic moment ΔM = MFC–MZFC induced by an external magnetic field (an analog of thermo-residual magnetization) exhibits anomalies at magnetic phase transition temperatures TN1 and TN2 that coincide with Young’s modulus anomalies. Conversely, in the magnetic susceptibility curves taken in the FC and ZFC modes, phase transitions are not discerned. When x deviates from stoichiometry, the ratio between two magnetic ions Co3+/Co2+ changes, the induced moment ΔM increases, and a residual ferromagnetic moment of ∼ 10-2μB appears in the magnetization curves at low temperatures. At a slight deviation from the oxygen stoichiometry in the samples, the structural distortion disappears, and the anomalies in the elastic characteristics near the TN region rapidly diffuse and vanish. It has been found that when YBaCo4O7+x cobaltites deviate from stoichiometry, the evolution of their magnetic properties is similar to that observed at the transition from Y-based to Ca-based cobaltite. Two scenarios of the cobalt subsystem magnetic behavior with an increasing fraction of cobalt Co3+ ions have been discussed.

Effect of heat treatment on AlSi10Mg composite 3D printed energy absorption structures

To enhance the energy absorption characteristics of the energy-absorbing structure in metal alloy 3D printing, various heat treatment conditions were studied on the 3D printed hourglass multi-cellular energy-absorbing structure (HTMEAS). The results reveal that as the annealing temperature rises, the structural morphology of the α-Al+Si phase in AlSi10Mg alloy undergoes alterations, particularly when the annealing temperature remains below 300°C. After heat treatment, the HTMEAS can contract layer by layer along the gradient and undergo controllable and orderly deformation. The maximum energy absorption, displacement, and peak force reached 758 J, 30 mm, and 30 kN, respectively.These values represent a significant enhancement of 146.8 %, 157.8 %, and 50 % compared to those without heat treatment, showcasing commendable mechanical properties. This advancement establishes a solid theoretical framework and assurance for the future development and refinement of 3D printing energy-absorbing structures.

Complete-joint-penetration vacuum laser beam welding of nickel-based superalloy 718Plus

Deep-penetration welding of nickel-based superalloys is an indispensable manufacturing technique for aircraft engines, aerospace engines, and nuclear containers. In this study, a newly developed vacuum laser beam welding method was used to weld a 9 mm thick superalloy 718Plus. A defect-free complete joint penetration weld with a high depth-to-width ratio was fabricated. The macro/microstructures, microhardness, tensile properties, and fatigue properties of weld joints under both as-welded and heat-treated conditions were systematically examined. The weld joint showed a microstructure of planar, cellular, columnar, and equiaxed crystals from the fusion line to the center line. The post-weld heat treatment had an insignificant effect on the grain structure but changed the precipitated phase in the weld. The newly formed γ′ and η phases were observed in the heat-treated sample. The mechanical properties showed microhardness, tensile strength, elongation, and fatigue strength of 488.6 HV, 1347.0 MPa, 13.7%, and 399 MPa, respectively, which were 104.6%, 93.2%, 77.8%, and 74.2% of those of the base metal, respectively. Both as-welded and heat-treated samples exhibited ductile ruptures. The excellent mechanical properties of the heat-treated joints were attributed to the formation of precipitated phases.

Magnetic and acoustic sensors in the age of digitalization for industrial production

The challenges of digitalization are giving rise to new generations of measurement technology. This does not necessarily involve the use of new physical principles; rather, the importance of handling and generating valuable data has increased. We present a new measuring system that samples and digitizes analogue signals at 50 MHz with 24-bit conversion. Every 43 µs, a Fourier step is generated for 1,024 data points via an FPGA-based measurement card. The resulting spectral data diagram can then be electronically filtered to improve the signal-to-noise ratio. With this procedure, further possibilities have been created to improve data analysis and data handling, one of which is a parametric pattern recognition, which transfers selectable signals to a library based on the spectral data diagram and searches for them in future data using a similarity algorithm. The use of Python is another building block. With Python, machine learning methods can be transferred from training directly to the measurement system and can run there directly using the extensive library standards. Sensor-fusion is a module that allows analog data to be analyzed via the measurement card, but at the same time also links digital data with analog data by connecting DAQ modules from a third source as virtual ports and transmitting values to shared databases. This article shows the application of the described measurement concept using magneto-inductive sensors and piezoelectric sensors. Magnetic sensors react sensitively to material changes and can reliably determine mechanical parameters such as hardness, residual stresses and grain size. The mentioned software functions enable non-contact measurement of ferromagnetic materials at high throughput speeds. So far limited to laboratory applications, magnetic sensors can also be used safely in harsh industrial conditions. Applications include rapid differentiation of heat treatment conditions, detection of grinding burn and hardness measurements. Acoustic sensors are used in areas that are difficult to access or whose environmental conditions make the use of optical systems in particular difficult. The sensors can mainly detect cracks, frictional behaviour and wear quantities. Applications are in particular straightening processes of hardened steel components, wire drawing, welding, deep drawing and machining. In general, this method can also be used to monitor other sensors and thus raise them to a new level of evaluation technology and data analysis.

Relating rolling contact fatigue (RCF) life to the microstructure evolution in aerospace grade bearing steels: A comparison of Cronidur-30 with AISI 440C

This article presents an extensive analysis of the microstructural evolution under various heat treatment conditions, mechanical properties (hardness), and rolling contact fatigue (RCF) life assessment and sub-surface crack analysis are studied on high nitrogen bearing steel Cronidur-30(Cr-30). An optimum solutionising temperature range has been identified which ensures desirable hardness as well as low retained austenite content. The microstructure consists of primary M2 (C, N) and secondary M23C6 carbides. Sizes of carbides in Cr-30 are significantly smaller than in AISI 440C and this plays a critical role in enhancing the RCF life of Cr-30. A larger area fraction of fine carbides results in branches and subsequent sub-branches of cracks in Cr-30 steel. However, the AISI 440C sample exhibits extensively interconnected cracks due to the presence of larger carbides. The tempering response of Cronidur-30 exhibited a peak hardness of 61 HRC at both lower (150 °C) and higher (475 °C) temperatures. Higher temperature tempering showed L1 life improvement of over 0.5 fold compared to lower temperature tempering.