Cr Martensitic Stainless Steel Research Articles

The Growth Behavior and Mechanisms of Pitting Corrosion on Super 13Cr Martensitic Stainless Steel Surfaces at Different Diameter-to-Depth Ratios

This study employs finite element analysis and simulated environmental immersion experiments to methodically investigate the growth behavior of pitting corrosion in stainless steel. It particularly examines how the diameter-to-depth ratio of the pit influences its growth dynamics. The findings underscore substantial variations in growth patterns and corrosion rates corresponding to different diameter-to-depth ratios. Key parameters, including electrolyte current density, potential, Fe2+ and Cl− ion concentrations, and pH values, play a crucial role in the corrosion mechanism. Remarkably, a pronounced increase in the corrosion rate at the pit bottom was observed with the increase in the diameter-to-depth ratio to 1:5. The results of this work provide insight into stainless steel pitting mechanisms, enabling the development of more effective prevention strategies.

Corrosion Analysis and Prevention of Tubing Nipples in Four Wells

A high-temperature and high-pressure gas field in an oil field requires the use of super 13 chromium material due to corrosive environments. In the recent production process, there have been four consecutive cases of corrosion, fracture, and perforation of tubing nipples, which have brought enormous economic losses to the oilfield. This article analyzes the failure causes of these four tubing nipples and proposes preventive measures. In this paper, the macroscopic morphology, chemical composition, mechanical properties, metallography, and microscopic morphology of four failed tubing nipples have been analyzed. Combined with the field service conditions and string structure of the tubing nipples, it is believed that the failure of the tubing nipples is mainly due to the connection of carbon steel and stainless steel materials, forming a typical galvanic corrosion galvanic cell. The geometric and environmental factors of the materials exacerbate this corrosion. Eventually, severe galvanic corrosion occurred on the inner surface of the tubing nipple, resulting in severe wall thinning or partial perforation, and four tubing nipples failed. The failed tubing nipples in Wells A, B, and C have erosion marks, which are caused by the action of high pressure and high flow rate fluids in the well; The inner surface of the tubing nipple in Well D is rusty yellow, mainly due to the corrosion of its inner wall caused by the acid fracturing fluid injected earlier. At the same time, the string structure of four wells shows that the tubing nipple is located at the variable diameter node of the string. When the fluid in the well flows from the large hole into the smaller hole, the fluid in the well will change there, and its flow rate and pressure will also increase, further exacerbating the erosion in this area. With the development of deep wells containing carbon dioxide in oil fields and the application of carbon dioxide injection secondary oil recovery technology, the use of 13Cr martensitic stainless steel is also increasing. In order to avoid the occurrence of similar accidents that will bring huge economic losses to the oil field, it is recommended that the material of the pipe string (including accessories) of such wells be confirmed using a portable direct reading spectrometer before entering the well.

New White Etch Cracking resistant martensitic stainless steel for bearing applications by high temperature solution nitriding

White Etch Cracking (WEC) is a severe and unpredictable failure mode that has been frequently observed in, among others, bearings for wind energy applications. In this work a novel, patented, WEC resistant bearing steel solution is developed through high temperature solution nitriding, followed by a custom heat treatment. Conventional medium carbon, 13 wt% Cr martensitic stainless steels were subjected to the novel process to obtain a nitrogen-rich case. A series of soft annealing, austenitization, cryogenic and tempering treatments converted the nitrogen-rich region into a fine-grained case containing nano-sized precipitates. Test bearings and tribometer specimens were treated with the same sequence of treatments. These specimens were tested under two different accelerated WEC failure promoting conditions. In contrast to standard through-hardened bearing steel the nitrided specimens showed no WEC formation, not even after prolonged testing.

Effect of 12% Mn Addition on Hydrogen Embrittlement Resistance and Corrosion Behavior of Super 13Cr Martensitic Stainless Steel

In article number 2200582, Yu Yan, Yanjing Su, and co-workers design a novel Mn-added 13Cr austenitic stainless steel with high strength through a partial-recrystallization technique and test with in-situ hydrogen-charging incremental step loading technique, which increases hydrogen-induced cracking threshold stress by more than 30% while retains good general corrosion performance.

Effect of Mo Addition on Passive Film of Martensitic Stainless Steels by Semiconductor Analysis in H2S-CO2 Environment

13Cr martensitic stainless steel is widely used in the oil and gas industry. It is well known that the addition of molybdenum (Mo) enhances the passivity of steel. However, the role of Mo in the passive film has not been clarified completely. The subjects of the present research were to reveall the role of Mo in terms of semiconductivity. The Mott-Schottky plot, obtained by impedance spectroscopy, revealed the effect of Mo addition on the semiconducting property of a passive film under an H2S environment in a pH 4.0 solution at 25°C. The results revealed that Cr-O of the inner film and sulfide of the outer film exhibited semiconductor p-type and n-type characteristics, respectively. The number of defects in the film on 2.5 mass% Mo-added steel was approximately half of that in the film on Mo-free steel. The role of Mo was discussed through investigation using x-ray photoelectron spectrometric analysis based on the state of the passive films.

Clarify the effect of reversed austenite on the pitting corrosion resistance of super 13Cr martensitic stainless steel

The effect of reversed austenite on the pitting behavior of super 13Cr martensitic stainless steel (S13Cr MSS) was investigated. The results revealed that reversed austenite was a FCC structure with Ni enrichment after tempering process, and there were no Ni-depleted regions adjacent to it. The reversed austenite content increased with increasing tempering temperature, and the pit depth decreased, as well as the dispersion degree of the Kelvin potential distribution. The reversed austenite reduced the risk of pitting corrosion through increasing the passive film compactness, and inhibiting Cl- penetration. Accordingly, the pitting corrosion resistance was enhanced as the tempering temperature increased.

Prominent role of reversed austenite on corrosion property of super 13Cr martensitic stainless steel

The microstructure and corrosion property of super 13Cr martensitic stainless steel (S13CrMSS) processed by quenching, one-step tempering and two-step tempering were investigated by XRD, SEM, EBSD and TEM-EDS analysis. It has been found that volume fraction of the reversed austenite in the sample treated by two-step tempering treatment was 13.5 vol. % up to the maximum. The reversed austenite almost always nucleated and distributed in martensite laths boundary during tempering and the diffusion of Ni, Mn and C promoted its growth. Enrichment of such elements as Ni, Mn, C and the ultrafine size of the reversed austenite were considered to be the main factor that accounted for the stability of the reversed austenite. At the same time, martensite and reversed austenite satisfy the (1 1¯ 1)γ // (011)α' and [011]γ // [1¯1¯ 1]α' Kurdjumov-Sachs (K–S) orientation relationship. Potentiodynamic polarization curves and electrochemical impedance spectroscopy indicated that two-step tempered specimen exhibited a higher pitting potential, lower corrosion current density, thicker passivation film and superior pitting resistance than the quenching specimen (without reversed austenite) as well as one-step tempering specimen (3.6 vol.%). It has been confirmed that the reversed austenite has a beneficial effect on the corrosion property of S13CrMSS.

Effect of 12% Mn Addition on Hydrogen Embrittlement Resistance and Corrosion Behavior of Super 13Cr Martensitic Stainless Steel

A novel metastable austenitic stainless steel denoted as 13Cr12Mn is obtained by adding 12 wt% Mn to 13Cr–5Ni–2Mo super‐martensitic stainless steel. The designed 13Cr12Mn exhibits a yield strength of 899 MPa, a tensile strength of 1068 MPa, and an elongation of 21.2%. The in situ hydrogen‐charging incremental step loading technique experiments are conducted to evaluate hydrogen embrittlement. The hydrogen‐induced cracking threshold stress of 13Cr12Mn is determined to be 961 MPa, which exceeds that of tempered S13Cr with a similar yield strength by 400 MPa. In addition, 13Cr12Mn also shows good resistance to general corrosion and pitting corrosion in alkaline solutions.

Advantageous Implications of Reversed Austenite for the Tensile Properties of Super 13Cr Martensitic Stainless Steel.

The advantageous implications of the microstructure and volume fraction of reversed austenite for the tensile properties of super 13Cr martensitic stainless steel (13Cr SMSS) in an experiment with quenching and double-step tempering treatment in the temperature range of 550-750 °C were investigated. The results show that, with increases in one-step tempering temperature, the content of reversed austenite was enhanced considerably from 0.9% to 13.3%. The reversed austenite distributed in the martensitic lath boundary conformed to the (11¯1)γ//(011)α' and [011]γ//[1¯1¯1]α' Kurdjumov-Sachs orientation relationship with the matrix. When tempered at 675 °C for 3 h for the first stage and 600 °C for 2 h for the second stage, the maximum volume fraction of reversed austenite was approximately 13.3%, achieving uniform elongation of 10.4% and total elongation of 27.2%. Moreover, the product of strength and elongation (PSE) was 23.5 GPa·% higher than other samples. The outstanding combination of high strength and commendable plasticity was due to the phase transformation of the reversed austenite into secondary martensite during tensile straining. The reversed austenite consumed the plastic energy at the tip of the microcrack and made the crack tip blunt, which hindered the further propagation of the crack, consequently increasing the total elongation and improving toughness.

Dynamical In Situ Study of Morphological Variations on Stainless Steel in a Sour Corrosive Environment

It is still unclear how environmentally assisted cracking, especially sulfide stress cracking (SSC), is caused by corrosion and fracture behavior. In this study, a new in situ technique for an SSC visualization challenge was established and applied for the visualization of microcrack propagation resulting from a single pitting on the steel surface of 13% Cr martensitic stainless steel during four-point bending SSC tests and discussed by combining ex situ x-ray computed tomography (XCT) and electron backscatter diffraction (EBSD). The dynamic behavior of microcracks was visualized successfully, and the microbubbles behavior with the corrosion reaction was also captured. Regarding the relationship between internal structure and microstructure for cracking, it was found that a cavity was formed in the interior of prior to the cracks seen on the surface by XCT, and cracks by EBSD were propagated along prior austenite grain boundaries. On the basis of in situ observations and complementary ex situ analyses, the actual situation of crack on the steel surface was revealed and discussed with both corrosion and fracture over time. This approach provides an opportunity to clarify the SSC occurrence process based on actual SSC tests and contributes to the determination of phenomenological criteria. Furthermore, by combining this in situ technique with commonly known electrochemical measurements such as polarization curves, open-circuit potentials, and electrochemical impedance spectroscopy, it is possible to directly discuss various electrochemical data corresponding to corrosion and fracture behavior, including dissolution and gas evolution.

Tribological study on tempered 13Cr martensitic stainless steel susceptible to interlath/intergranular corrosion under nitric acid sliding conditions

The influence of pre-IGC damage and IGC damage during sliding on the tribology behavior of tempered 13Cr martensitic stainless steel was studied systematically in dry, DM water and nitric acid sliding conditions using a ball on plate configuration with an aim to elucidate the mutual dependence on tribology performance. The coefficient of friction decreased in the order COF Dry sliding (Case A) > COF IGC+ Dry sliding (Case C) > COF Under DM water sliding (Case B) > COF Under nitric acid sliding (Case D) > COF IGC+ Under nitric acid sliding (Case E). The COF values for IGC attacked conditions (0.49 in Case C, 0.3 in Case D) are lower than that of unattacked conditions (0.72 in Case A, 0.4 in case B) irrespective of lubrication. The specific wear rate (k) decreased in the order kCase C > kCase A > kCase B > kCase D > kCase E. The k value for the Case E (3.3 × 10−6 mm3/Nm) is almost 120 times lower than that of Case C (408 × 10−6 mm3/Nm). Such variations were explained based on the combined lubrication effects of nitric acid and thicker oxides formation in the wear track region as confirmed by scanning electron microscopy/energy dispersive spectroscopy and Raman spectroscopy analysis. 3D profilometry and scanning electron microscopy examination of wear tracks revealed mechanical polishing type wear mechanism in nitric acid sliding conditions whereas severe abrasive and severe adhesion plus oxidational wear mechanism in dry sliding conditions of unattacked and IGC attacked conditions, respectively. The mechanical polishing is the synergistic effect of wear and corrosion, ascribed to the colloidal action of the eluted nano-sized carbides from tempered MSS matrix into the sliding nitric acid solution. Despite lower k and COF in nitric acid sliding conditions, accelerated IGC damage occurred in the subsurface of wear track and possibly due to the accelerated dissolution at the acid trapped locations. This study also suggests the importance of considering the subsurface characterization while studying the tribocorrosion behavior of stainless steels in IGC prone conditions.

The Influence of Pickling Treatment Parameters on the Surface State and Pre-Passivation Behavior of Super 13Cr Martensitic Stainless Steel

As a pre-treatment process in the pre-passivation of stainless steel, pickling treatment has a significant effect on the formation of the pre-passivation film. Thus, the surface composition and defects of Super 13Cr martensitic stainless steel (Super 13Cr) were evaluated under different pickling parameters to further improve the corrosion resistance of the pre-passivation film. The samples were prepared using the acid immersion method and by changing the immersion duration and the acid concentration. The inclusion and chemical composition on the Super 13Cr surface were characterized via a scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy (EDS). The pickling treatment contributes little to the morphology, dimension, and other characteristic parameters of the inclusions. With the increasing duration and acidification concentration, the Cr content on the surface of Super 13Cr increases initially and then decreases. By contrast, the Fe content decreases initially and then increases. The pickling parameters corresponding to the lowest Fe content and the highest Cr content are identical, i.e., the exposure duration is 50 s and the acid concentration is 48 g/L. The pickling treatment in this case could be divided into two stages: outer film dissolution and inner film dissolution. The pickling parameters basically contribute little to the defects of martensitic stainless steel but can significantly affect the surface Cr and Fe content. Retaining the Cr-enriched inner layer could improve the content of Cr in the pre-passivation film and then improve the corrosion resistance of the film. Thus, compared with the original sample with native film, the corrosion resistance of the sample with a Cr-enriched inner layer improved by a factor of about 40.

Effect of 12% Mn Addition on Hydrogen Embrittlement Resistance and Corrosion Behavior of Super 13cr Martensitic Stainless Steel

Effect of 12% Mn Addition on Hydrogen Embrittlement Resistance and Corrosion Behavior of Super 13cr Martensitic Stainless Steel

Experimental And Numerical Modelling of Cyclic Softening and Damage Behaviors for a Turbine Rotor Material at Elevated Temperature

In order to better understand the physical process of deformation and cyclic softening a 12% Cr martensitic stainless steel FV566 has been cyclically tested at high temperature in strain control. Increase in temperature was found to increase the cyclic life, softening rate and viscous stress magnitude. An increase in the dwell time led to the acceleration of the material degradation. The microstructure changes and dominating deformation mechanisms were investigated by means of scanning electron microscopy, electron backscatter diffraction and transmission electron microscopy. The results have revealed a gradual sub-grain coarsening, transformation of lath structure into fine equiaxed sub-grains, and misorientation angle development in blocks and packets until material failure. Further, a unified viscoplastic constitutive model coupled with a physically-based damage variable, is proposed to capture the cyclic mechanical behavior and microstructural evolution of the material at elevated temperature. The mechanical strength can be reduced by the decrease in the dislocation density, the coarsening of the martensitic lath and the loss of the martensitic structure under cyclic loading. The proposed physically-based damage variable is driven by the evolutions of dislocation density and martensitic lath width. The good comparisons with test results mean that the proposed model can reasonably model the cyclic elastic-viscoplastic constitutive behavior of the material at high temperature.

Examination of toughness and solidification cracking on 12% Cr martensitic stainless steel weld metal with Ni added

Toughness and weld solidification cracking in the weld metal of martensitic stainless steel containing Ni were investigated. The weld metal of martensitic stainless steel with low C and proper Ni can be applied without PWHT (Post weld heat treatment) due to the microstructure mainly consisting of soft martensite including retained austenite resulting in enough toughness though PWHT is necessary in conventional one because of high hardness as weld condition. However by the addition of Ni the susceptibility to weld solidification cracking can be higher. As the experimental evaluation was conducted in terms of solidification cracking test and Charpy impact test using the weld metal of 12/16%Cr-3/14%Ni steels. As the results the slight amount of ferrite phase caused the lowering of notch toughness within the weld metal including the same level of retained austenite. The excess Ni addition to decrease ferrite phase in solidification process increased the susceptibility to solidification cracking in during solidification process by austenite phase. In conclusion optimum Cr and Ni content to achieve the both of low susceptibility to solidification cracking and high toughness was clarified.

Stress corrosion cracking behavior and mechanism of super 13Cr stainless steel in simulated O2/CO2 containing 3.5 wt% NaCl solution

Good CO2 corrosion resistance has made super 13Cr martensitic stainless steel become widely used in oil industry. However, the corrosion of OCTG (Oil CountryTubular Goods) changes from pure CO2 to O2/CO2/Cl- and other multi-component containing complex environment. To clarify the stress corrosion cracking (SCC) behavior and fracture mechanism of the super 13Cr stainless steel in the corrosive environment containing O2, CO2 and Cl-, the effect of applied potential on the SCC susceptibility of super 13Cr stainless steel in a 10% O2 and 90% CO2 containing 3.5 wt% NaCl solution was investigated by means of potentiodynamic polarization, slow strain rate tensile (SSRT) test and combined with scanning electron microscopy (SEM). The results show that the polarization potential has an influence on the SCC susceptibility of super 13Cr stainless steel in O2/CO2/Cl- containing medium. The SCC susceptibility is high with the anode and cathode polarization applied, and increases with the rise of theabsolute potential values. The SCC mechanism has the following relationships with the applied potentials: a) anodic dissolution happens at 50 mV and 250 mV, b) anodic dissolution and hydrogen embrittlement were observed at −300 mV, and c) hydrogen embrittlement was obtained at −800 mV and −1000 mV.

Structure and Property Modulations of 13Cr Stainless Steel Through Microgravity Solidification and Minor Ce Addition

Solidification controlling and RE doping are effective ways to manipulate the microstructures and performances of 13Cr martensitic stainless steel. In this work by Ying Ruan and co-workers, article number 2100062, the influences of microgravity solidification and Ce addition on microstructure refinement, inclusion spheroidization and mechanical properties of 13Cr steels were explored comparatively.

Effect of Nitrogen on the Hot Deformation Behavior of 0.4C–13Cr Martensitic Stainless Steel

The hot deformation behaviors of 0.4C–13Cr martensitic stainless steel at the nitrogen contents of 0.13% and 0.03%, respectively, are investigated at the deformation condition featuring the temperature range of 1223–1523 K and the strain rate range of 0.01–10 s−1. The variation of flow stress curves of experimental steels with different nitrogen contents is systematically analyzed. According to the flow stress curves, the activation energies determined by regression analysis are 472.77 and 411.58 kJ mol−1 for 0.4C–13Cr steel with N contents of 0.13% and 0.03%, respectively. It demonstrates that the deformation resistance of 0.4C–13Cr steel improves with the increase in nitrogen content. The reason is related to the pinning effect of solid solution nitrogen atoms, and Cr2N particles on dislocations and grain boundaries. The dynamic recrystallization (DRX) kinetics models of experimental steels are established. Furthermore, the microstructures of experimental steels are also analyzed. The result shows that the pinning effect caused by nitrogen also plays an important role in the development of DRX and microstructure evolution. The more nitrogen addition in 0.4C–13Cr steel, the earlier achievement of DRX onset, the slower the DRX kinetics and the finer the microstructure.

Effect of Tempering on Tribological Properties of 13Cr Martensitic Stainless Steel and Alumina Material Pair in Dry Sliding

This present study seeks to understand tribological properties of 13Cr martensitic stainless steel (MSS) in austenitizing and tempering conditions (300, 550, and 700 °C). A ball-on-plate configuration with an alumina ball as the counterface was employed for dry sliding experiments. Complementary analytical techniques such as 3D optical profilometry, optical microscopy, scanning electron microscopy/energy-dispersive spectroscopy, and microhardness measurements were used to elucidate the operating wear mechanism. The results showed that the coefficient of friction (COF), wear rate, and wear mechanism changed significantly with tempering temperature. Austenitized and 300 °C tempering condition exhibited stable COF variations with time, whereas fluctuating and increasing COFs with time were observed in 550 and 700 °C tempering conditions, respectively. Wear resistance for the tempering condition was lower than that for the austenitizing condition, with the least wear resistance for the 550 °C tempering condition. The wear resistance of the alumina ball also followed the same trend as for 13Cr MSS. The least wear resistance of the counterface material was observed against the 550 °C tempering condition. These observations were attributed to the (a) formation of large amount of nanosized carbides and (b) embedment of the counterface material during sliding. The austenitizing and 300 °C tempering conditions showed abrasive plus mild oxidation wear mechanism, whereas tempering at 550 and 700 °C showed delamination plus the presence of adhesion traces and a compacted tribolayer plus severe oxidational wear mechanism, respectively. The present results clearly highlight the changes in wear mechanism of 13Cr MSS against the counterface alumina ball with the developed microstructural changes during tempering treatments.

Structure and Property Modulations of 13Cr Stainless Steel Through Microgravity Solidification and Minor Ce Addition

Both rare‐earth doping and microgravity solidification processing bring significant influences upon the structure formation and mechanical properties of various alloys. Herein, the microstructure and performance of 13Cr martensitic stainless steel are modulated by adding minor Ce content and microgravity solidification by means of drop tube technique. The lattice structure of constituent phase α(Fe) is deformed evidently by microgravity solidification, and the lattice parameter variation is 1.8 times of that caused by Ce addition. The microstructures of this steel processed by arc melting consist of lath‐shaped martensites and a few feather‐shaped bainites whose volume fraction increases with the Ce content. The bainite is replaced by ferrite in the rapidly solidified microstructure of 13Cr steel under microgravity condition. Although both microgravity solidification and Ce addition induce the microstructure refinement and inclusion spheroidization, the former effect plays the dominant role. The compressive properties and microhardness decrease moderately with Ce addition due to the slight increase in bainite, however, the microgravity solidification brought the hardening effect and thus the microhardness of the steel droplets increases with undercooling.