Carbon Martensitic Stainless Steel Research Articles

Effect of Spheroidizing Annealing Process on Microstructure and Properties of Quenching and Tempering 60Cr16MoMA Martensitic Stainless Steel

The effect of spheroidizing annealing on carbide characteristic parameters, mechanical properties and wear resistance of the quenching and tempering (Q&T) high carbon martensitic stainless steel is investigated. The microstructure of the steel is characterized and analyzed through various techniques, including scanning electron microscope (SEM), X‐ray diffraction (XRD), electron backscattering diffraction (EBSD), and transmission electron microscope (TEM). Results show that the microstructure of the annealing steel is mainly composed of ferrite and M23C6 carbide. With the rise of austenitizing temperature, the average diameter of carbide of the annealed steel increases. The average diameter of carbides in the Q&T steel changes in the same way as that observed in the annealed steel. The steel has the lowest annealing hardness, highest Q&T toughness, and wear resistance at an annealed soaking temperature of 860 °C. The influence factor of the toughness and wear resistance can be identified that small‐sized carbides and low angle grain boundaries exhibit strong interface adhesive strength. This reduces the probability of cracking in the particle or at the interface.

Advancement of strength and toughness in ultra-low carbon martensitic stainless steel by reversed austenite

It has been proven that martensite matrix accompanied by fine reversed austenite is beneficial to improve the strength and toughness in martensitic steels to a certain extent. In order to achieve this unique microstructure, the existing methods, like quenching at high temperatures, multiple heat treatment processes, increasing Ni content, raise the economic cost and operation difficulty. In this work, fine reversed austenite was formed in Fe13Cr4NiMo steel with relatively low nickel content (4 wt%) by one-time relatively low temperature quenching (860 °C) and tempering process. Then the formation mechanism and effect on mechanical properties of reversed austenite were discussed. The 0.55 vol% reversed austenite with the size of 260 nm can be formed in Fe13Cr4NiMo steel under quenching at 860 °C for 40 min and tempering at 650 °C for 2 h. The reversed austenite maintained a deviation of ∼2° from K-S relationship with the martensite matrix. In addition, the formation of reversed austenite was caused by short circuit diffusion of element-free redistribution, which caused the reversed austenite to be more inclined to nucleate at subgrain boundaries and grow up restrictedly. Furthermore, the Fe13Cr4NiMo steel that contained reversed austenite hindering dislocation movement and coordinating deformation possessed excellent plasticity of 18.4 % and Charpy impact energy of 289 J while maintaining high strength of 872 MPa at room temperature.

Influences of partial substitution of C by N on the microstructure and mechanical properties of 9Cr18Mo martensitic stainless steel

Large eutectic carbides presenting in the matrix deteriorate the mechanical properties of high carbon martensitic stainless steel. In the present work, nitrogen-alloyed martensitic stainless steel with different C/N ratios were designed by partial substitution of C by N of 9Cr18Mo, and their microstructure and mechanical properties were investigated. The results show that, with increasing the content of N up to 0.15 wt% in the experimental steel, the quantity and the size of eutectic carbides decrease； and the net-work eutectic carbides are gradually eliminated. The microstructure of all the steels is composed of lath martensite, twin martensite and M23C6 carbides. With partial substitution of C by N, the morphology of martensite blocks evolves from a lath shape to a blocky one, the quantity of twin martensite increases, and the nano-scaled Cr2N nitrides precipitate in the martensite matrix. The steel containing 0.15 wt% N exhibits the hardness of 60.5 HRC, a fracture strength of 1900 MPa and an elongation rate of 1.6 % due to hot rolling and heat treatment, which is attributed to the refinement of carbides and grains, solid solution of C and N, as well as the dense dislocation.

Evolution of M7C3 carbides near the solidus and the influence of Mn element on the formation of M23C6 carbides in a high carbon martensitic stainless steel 90Cr18MoV

The evolution behavior of M7C3 carbides in a 90Cr18MoV martensite stainless steel during high temperature diffusion annealing treatments at temperatures near the solidus was investigated. Results showed that only M7C3 carbides dissolved, and the dissolution of large-sized M7C3 carbides was limited when the temperature was below the solidus. However, when the temperature was above the solidus, a certain amount of liquid phase appeared around the grain boundaries. Meanwhile, two different types of precipitates appeared within the grains. And these two types of precipitates were eutectic products that mainly consisted of M7C3 carbides and bcc phase, and divorced eutectic products that mainly consisted of M23C6 carbides, respectively. Thermodynamic calculations indicated that with the increase of Mn content, the Gibbs free energy of M23C6 carbides would be lower than that of M7C3 carbides. Thus, the difference in Mn content was the main reason for the formation of those two types of precipitates, i.e., M7C3 carbides were formed in regions with low Mn content and M23C6 carbides were observed in areas with high Mn content.

The Reliability of Single-Step and Double-Step Quench and Partitioning Heat Treatments on an AISI 420A Low Carbon Martensitic Stainless Steel

The microstructural and mechanical effects of various single-step (SS) and double-step (DS) quench and partition (Q&P) heat treatments applied to an AISI 420A low carbon martensitic stainless steel (MSS) has been studied. The goal with this work is to reach a total elongation (E pct) of 12 pct and an ultimate tensile strength (UTS) above 1200/1300 MPa, but ultimately to achieve a superior strength-ductility balance in comparison to its traditional Quench and Temper (Q&T) counterpart. This is being done by retaining austenite within the steel’s martensitic matrix at room temperature (RT) using novel SS and conventional DS Q&P heat treatments. Considerable work has been done to optimize DS Q&P heat treatments, but little has been done to understand the effects of removing a subsequent heating cycle through SS Q&P heat treatments has on MSSs. With that being said, partitioning is performed at the same quench interruption temperature for the SS Q&P heat treatments, and reheated to a higher temperature for the DS Q&P heat treatments. Experimental investigations were carried out on 1 mm thick, sheet samples to increase the number of potential applications for this steel and heat treatment. The microstructure of different SS and DS Q&P heat treatments was investigated through X-ray diffraction (XRD) and transmission electron microscopy (TEM) while mechanical property investigations were carried out using tensile and fracture toughness testing. DS Q&P heat treated samples quenched to 130 °C and partitioned for industrially relevant times of 10 and 30 minutes featured the highest values in terms of total elongation, tensile strength and fracture toughness. The SS Q&P heat treatments, on the other hand, were able to achieve improved mechanical properties to its Q&T counterpart. Overall, this work opens up the possibility of increased MSS usage for reliable, thin-walled component production with improved properties through Q&P heat treatment methods. The best results achieved in this study are a UTS of 1585 MPa, E pct of 22 pct, and a fracture toughness of 77 kJ/m2. Their lower total elongation of 9.6 pct is balanced by high tensile strength of 1812 MPa, ensuring higher toughness compared to traditional Q&T samples.

Underlying Mechanism for “Loss of Passivation” Effect of a High-Carbon Martensitic Stainless Steel Coating via Laser Cladding

Recently, laser cladding (LC) technology has become a cost-effective and convenient method to protect metal substrate from corrosion by producing metal coating with high corrosion resistance. In order to fully investigate the pitting mechanism for high carbon martensitic stainless steel (HMSS) coating, the microstructure and pitting performance of high-carbon martensitic stainless steel (HMSS) samples, which were produced via laser cladding (LC) and hot isostatic pressing (HIP) were comparatively investigated via electrochemical measurements and electron microscopies. Dendritic and network connected M23C6 carbides are the main precipitates in the HMSS coating, while the M23C6 carbides in HMSS bulk are spherical or elongated in shape. Pitting resistance of the HMSS coating is dramatically deteriorated. The massive and continuously distributed dendritic M23C6 carbides could form a large-area cathode and cause the micro-galvanic corrosion of the HMSS-LC coating matrix, thus can be considered as underlying factor for the “loss of passivation (LOP)” effect of the HMSS coating.

Pressure effect on the structural, magnetic and thermophysical properties of X12Cr13 martensitic stainless steel prepared by powder metallurgy method

Low carbon (C: 0.03-0.15%) and high Cr contents (Cr: 11-15%) martensitic stainless steel (MSS) is widely used for industrial applications due to its good mechanical properties and corrosion resistance. In this study, we investigated the pressure effect on the structural, magnetic and thermophysical properties of X12Cr13 MSS which was compacted using powder metallurgy method under 400 and 600 MPa pressures and sintered at 1200 °C temperature for an hour under Ar atmosphere. Pressing and sintering processes resulted in increased density of microstructures from 5.84 g/cm 3 to 6.12 g/cm 3 , decreased porosity from 7.58% to 3.39%, increased hardness from 93.24 HB to 110.09 HB (N/ mm 2 ) and decreased carbide particles from 2.65% to 2.13 wt% in the structures. We observed α -Fe, γ -Fe and M 23 C 6 (M: Cr or Fe) phase formations in the structure due to the applied pressure and the sintering process. The magnetic properties of these steels have been investigated as a function of temperature between 300-400 K and applied magnetic field of ±4 T. We observed improved magnetic properties with increasing pressure, and ferromagnetic to paramagnetic phase transition occurred from 300 K to 400 K. While maximum saturation magnetization is found to be 70 emu/g at 300 K for 600 MPa sample, maximum magnetic susceptibility and permeability for 600 MPa sintered sample are recorded as 17.13 and 1.08 m 3 /kg, respectively. Also, the maximum specific heat capacity and enthalpy are recorded as 1.85 J/g °C and 536.05 J/g (at 579 °C temperature) on the sample compacted on the 600 MPa pressure, respectively. • X12Cr13 MSS samples were prepared by P/M method at 400 MPa and 600 MPa. • 600 MPa pressing and 1200 °C sintering enhanced physical and magnetic properties • MSS prepared at 600 MPa exhibits 110.09 HB hardness and 6.12 g/cm 3 density. • The maximum saturation magnetization found to be 70 emu/g at RT for 600 MPa sample. • The 600 MPa sample provided 536.0 J/g heat storage capacity at 579°C.

Wear resistance of an additively manufactured high-carbon martensitic stainless steel

The dry sliding wear behaviour of a high carbon martensitic stainless steel (HCMSS) consisting of ~ 22.5 vol% of chromium (Cr)- and vanadium (V)-rich carbides processed by electron beam melting (EBM) has been captured. The microstructure consisted of martensite and retained austenite phases with a homogeneous distribution of sub-micron-sized V-rich and micron-sized Cr-rich carbides, leading to relatively high hardness. The CoF decreased ~ 14.1% with increasing load in the steady-state, due to the material transferred from the wear track over the counterbody. The wear rate of the HCMSS compared to martensitic tool steel processed in the same manner, and it was nearly identical under low applied load. The dominant wear mechanism was removal of the steel matrix through abrasion, followed by the oxidation of the wear track, while three-body abrasive wear occurred with increasing load. A plastically deformed zone beneath the wear track was revealed through cross-sectional hardness mapping. Specific phenomena occurred with increasingly aggressive wear conditions were described with carbide cracking, pull-out of V-rich carbides and matrix cracking. This study revealed the wear performance of the additively manufactured HCMSS, which could pave the way for producing components for wear-related applications ranging from shafts to plastic injection moulds via EBM.

Pulsed FCAW of Martensitic Stainless Clads onto Mild Steel: Microstructure, Hardness, and Residual Stresses

The low carbon martensitic stainless AWS 410NiMo steel has in its chemical composition 13% chromium, 4% nickel, and 0.4% molybdenum (wt.%) and is used in turbine recovery, rotors, and high-pressure steam pump housings due to its resistance to impact at low temperatures, as well as to corrosion and cavitation. Those applications of the AWS 410NiMo steel frequently demand repair, which is performed by welding or cladding. Arc welding is a well-established technique for joining materials and presents several parameters that influence the mechanical performance of the weld bead. Although numerous welding processes exist, optimizing welding parameters for specific applications and materials is always challenging. The present work deals with a systematic study to verify the correlation between the pulsed fluxed core arc welding (FCAW) parameters, namely pulse current and frequency, welding speed, and contact tip work distance (CTWD), and the bead morphology, microstructure formation, residual stress, and hardness of the martensitic clad. The substrate used was the AISI 1020 steel, and the AWS 410NiMo steel was the filler metal for clad deposition. From the initial nine (9) samples, three (3) were selected for in-depth characterization. Lower heat input resulted in lower dilution, more elevated hardness, and lower compressive residual stresses. Therefore, the results highlight the need for selecting the proper heat input, even when using a pulsed FCAW procedure, to achieve the desired performance of the clad. In the present case, a higher heat input appears to be more advantageous owing to the lower convexity index, smooth hardness transition between fusion and heat-affected zones in addition to more elevated compressive stresses.

A Novel Reticular Retained Austenite on the Weld Fusion Line of Low Carbon Martensitic Stainless Steel 06Cr13Ni4Mo and the Influence on the Mechanical Properties

When performing fluorescent magnetic particle testing in steel welding-repaired zones, as traditional viewpoint usually ascribes magnetic particle indications to discontinuous welding defects such as cracks, incomplete fusion, etc., welding-repaired zones showing indications of these defects are always judged to be unqualified. In this study, a novel reticular phase was identified on the weld fusion line of 06Cr13Ni4Mo. By selected area electron diffraction, it was proved to be an austenite. By roasting test, it was proved to be induced by the thermal effect of welding. Non-ferromagnetic reticular austenite reduces the overall magnetic permeability, leading to the presence of fluorescent magnetic particle indication. Though the mechanical properties of the welding repaired zone are changed by the reticular austenite with the yield strength, tensile strength, and microhardness decreasing to 571 MPa, 752 MPa, and 279, respectively, they still exceed the required values of standard specifications. 06Cr13Ni4Mo welding-repaired zones showing magnetic particle indications induced by reticular austenite are qualified and should be accepted.

Influence of reversed austenite on the properties of a 13Cr4NiMo ultra‐low carbon martensitic stainless steel in different environments

AbstractIn this study, the influence of reversed austenite on the mechanical and corrosion resistance properties of 13Cr4NiMo martensitic stainless steel was investigated. The results reveal that the reversed austenite content in the sample increases with the increase of tempering times. The presence of an appropriate amount of reversed austenite not only improves the comprehensive mechanical properties of martensitic stainless steel but also reduces the susceptibility to pitting corrosion.

Multiscale in-situ studies of strain-induced martensite formation in inter-critically annealed extra-low-carbon martensitic stainless steel

An extra low carbon martensitic stainless steel with 16% ultrafine grained metastable reverted austenite was subjected to uniaxial tensile testing and investigated with in-situ energy-dispersive synchrotron X-ray diffraction (XRD) and in-situ electron backscatter diffraction (EBSD) to reveal the complex interplay between stress, strain and martensitic transformation. In-situ XRD demonstrated that, upon surpassing the yield strength, the fraction of reverted austenite declined linearly with increasing true stress, which was associated with transformation-induced plasticity (TRIP). EBSD and XRD consistently showed that the texture of martensite evolved from an initially weak texture towards a strong 110α′ fiber parallel to the tensile axis. For the first time, stress partitioning between (remaining) reverted austenite and the martensite matrix was determined quantitatively during in-situ XRD by averaging over the stress values obtained from lattice strains for multiple reflections. Martensite accommodates the majority of the applied load while reverted austenite is severely plastically deformed. XRD shows strong plastic anisotropy in austenite. In-situ forward-scatter electron imaging and advanced variant analysis of the EBSD data indicate that plastic deformation and strain-induced austenite-to-martensite transformation is concentrated along boundaries between martensite blocks and packets which are inclined up to ∼55° with respect to the tensile direction. These regions were preferred sites for strain-induced martensite formation.

Effect of heat treatment on the chromium‐depleted zones of a high carbon martensitic stainless steel

AbstractHeat treatments are commonly applied in the martensitic stainless steels to achieve high wear resistance and hardness; however, they can lead to a decrease in corrosion resistance due to the precipitation of chromium‐rich carbides. The present work investigates the effect of austenitizing and tempering parameters on the microstructure, hardness, and passivation and reactivation currents of AISI 440C. A double‐loop electrochemical potentiodynamic reactivation test is performed to evaluate the dissolution and precipitation of chromium‐rich carbides. The volume fraction of phases after heat treatment is estimated by X‐ray diffraction. Results show that an increase in the austenitizing temperature leads to an increase in the carbide dissolution, and also in the amount of retained austenite. As a consequence, low passivation and reactivation currents are obtained. When austenite is the main phase, the increase of austenitizing time contributed to an increase in the degree of sensitization due to austenite grain boundary carbon enrichment. However, the presence of austenite after tempering kept part of the carbon in a solid solution resulting in low passivation and reactivation currents.

Welding and Thermal Spray Processes for Maintenance of Hydraulic Turbine Runners: Case Studies

Abstract: Hydraulic runners are susceptible to failures by cracks or wear by erosion, corrosion, or cavitation. The modern runners are fabricated in carbon steel and martensitic stainless steel. Arc welding processes normally do the repair of eroded areas, or cracked parts. Each material or type of repair needs specific criteria, procedures, and precautions to guarantee their success and prevent future issues, like the recurrence of the cracks or reduction of the useful life of the runner by modifications of the original material. Wear-resistant coatings are applied by welding or by thermal spray processes, considering this last one has no metallurgical interaction with the material of the runner, keeping the original properties of the material. For several years the companies Copel GeT, Lactec, UTFPR, and UFPR collaborate on the study of different techniques, methods, and processes to repair hydraulic runners, this work aims to present a short compilation, and examples of some results obtained applied on real runners.

Rolling Contact Fatigue Resistance of Cryogenically Treated AISI 440C Steel

AISI 440C is a high carbon martensitic stainless steel, primarily used in bearing applications. For this study, one group of AISI 440C steel disks was quenched in oil and tempered. Another group was soaked in liquid nitrogen (− 196 °C) immediately after quenching for 5 h and then tempered. The resulting microstructures were analyzed as well as the rolling contact fatigue (RCF) performance using two methodologies, with and without artificial defects. It was found that the microstructural modifications generated by the cryogenic treatments did not improve significantly the RCF resistance of the material. However, this work supports the use of artificial defects as a valid methodology for conducting accelerated rolling contact fatigue experiments.

Double-step inter-critical tempering of a supermartensitic stainless steel: Evolution of hardness, microstructure and elemental partitioning

The maximum allowed hardness for low carbon martensitic stainless steel components used in the oil and gas industry is 247 HV. Inter-critical tempering is an effective method for hardness control due to the production of stable reverted austenite. By conducting multiple-step tempering cycles, the austenite reversion kinetics can be accelerated and its thermal stability upon cooling can be greatly increased. In this work, supermartensitic stainless steel samples were subjected to two-step inter-critical tempering cycles. First, all samples were heat-treated at 625 °C for 2.5 h to minimize hardness through the maximization of stable austenite. Then, a second stage tempering with temperatures between 560 and 720 °C for 2.5 h was studied. The amount of stable reverted austenite at room temperature increased for second stage temperatures below 625 °C. Between 625 and 670 °C, the amount of reverted austenite notably increased at high temperature but it had limited thermal stability upon cooling. Above 670 °C, all newly reverted austenite was completely unstable during the cooling stage and partial dissolution of the stable austenite obtained after the first tempering cycle also occurred. Interestingly, hardness was mostly insensitive to the stabilization of additional austenite or to the newly formed fresh martensite.

Dry sliding wear research on C45 carbon steel, 41Cr4 alloyed steel and X3CrNi13-4 martensitic stainless steel

In this paper, the experimental research refers to the dry sliding wear behaviour of three type of steels namely carbon steel (C45), alloyed steel (41Cr4) and martensitic stainless steel (X3CrNi13-4). From the X3CrNi13-4 martensitic stainless steel, three different batches with varying percentages of chromium and nickel were analyzed. For all the steels, the research was made using a tribometer (CSM Tribometer) through to the pin-on-disk method (POD), where the friction coefficient and wear rate were determined. All these tests were made according to the ASTM G99 standard, with the same working conditions for all five samples, only for the two batches of the X3CrNi13-4 steel, the motor speed was varied. The obtained results were presented through characteristic graphs for the friction coefficient and through images acquired with a digital and a laser microscope respectively with a specialized software regarding the wear track profiles. It can be concluded that the C45 carbon steel showed the good tribological behaviour with the highest dry sliding wear resistance.

Phase structures and morphologies of tempered CA6NM stainless steel welded by hybrid laser-arc process

The post-weld tempered microstructure of hybrid laser-arc welded CA6NM, a cast low carbon martensitic stainless steel, was investigated. The microstructural evolutions from the fusion zone to the base metal were characterized in detail using optical microscopy, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD) and microhardness techniques. The fusion zone, in its post-weld tempered condition, consisted of tempered lath martensite, residual delta-ferrite with various morphologies, reversed austenite and chromium carbides. The reversed austenite, which can be detected through both EBSD and XRD techniques, was found to be finely dispersed along the martensite lath boundaries, particularly at triple junctions. Based on the EBSD analysis, the orientation relationship between the reversed austenite and the adjacent martensite laths seemed to follow the Kurdjumov-Sachs (K-S) model. The results also revealed the presence of the reversed austenite in the different regions of the heat affected zone after post-weld tempering. The microindentation hardness distribution was measured, and correlated to the evolution of the corresponding microstructure across the welds.

Surface modification of low carbon martensitic stainless steel by current heating technique in graphite

Abstract The tribological and corrosion behaviors of the AISI 420 martensitic stainless steel treated by the current heating technique were studied for tribological and corrosion applications. The steel was treated at the applied electric powers of 100–300W, and characterized by scanning electron microscopy, energy dispersive spectroscopy, hardness test, pin-on-disk tribological test, potentiodynamic polarization test, and electrochemical impedance spectroscopy. The hardness, the coefficient of friction, and the wear rate were improved with the increasing applied electric power, caused by the increase in the formation of M 2 O 3 , M 23 C 6 , and M 7 C 3 . The corrosion behavior of the treated steel tended to improve at the high applied electric power. The steel treated by the current heating technique, in the appropriate condition, is suitable for tribological and corrosion applications.

UGI 4057 AIR

Abstract UGI 4057 Air is a carbon martensitic stainless steel with nickel for aerospace applications. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: SS-1247. Producer or source: Schmolz + Bickenbach USA Inc..