Chromium Martensitic Stainless Steel Research Articles

Susceptibility of X17CrNi16-2 martensitic stainless steel to hydrogen embrittlement after conventional and deep cryogenic heat treatment

A low carbon/ high chromium martensitic stainless steel, X17CrNi16-2, was heat treated using two different hardening and tempering regimes (1050 °C/480 °C or 980 °C/600 °C) — promoting either a high strength or high toughness state, respectively − and further combined with deep cryogenic treatment (DCT) at −196 °C for 24 h. Over recent years DCT has been recognized as a promising technique to improve the properties of steel, predominantly with respect to its tensile strength, toughness and wear resistance. The influence of DCT on the hydrogen embrittlement resistance of martensitic stainless steel has not yet, however, been reported.A slow strain rate tensile test (SSRT) with simultaneous cathodic hydrogen charging was selected as the method to assess potential susceptibility to hydrogen embrittlement (HE). Relatively low-intensity hydrogen charging, utilizing a constant current density of 0.1 mA/cm2, in a non-corrosive, slightly alkaline buffer solution, led to a clear reduction in the ultimate tensile stress. This reduction, and therefore the HE susceptibility, was more pronounced in the steel with a higher strength (i.e. that subject to the 1050 °C/ 480 °C heat treatment condition). Furthermore, DCT did not appear to have any impact on the steel’s mechanical properties in the presence of hydrogen. Fractographic analysis showed clear evidence of HE in the hydrogen-charged specimens.This paper presents results of the SSRT tests and further fractography results, and discusses the impact of conventional and deep cryogenic treatment on HE susceptibility.

Analysis of the Behavior of Different Steel Alloys Subjected to Uniaxial Mechanical Fully Reversed Fatigue Tests

The favorable choice of material for structural elements for a specific purpose of use depends on the properties of the material that define its behavior in given conditions. Considering the possibility of the appearance of different types of mechanical failures during work under defined conditions, this paper deals with research on the behavior of materials subjected to uniaxial mechanical fully reversed fatigue tests at room temperature in an air atmosphere. The research refers to structural steel (S235JRC+C /1.0122), alloyed carbon steel (18CrNi8/1.5920) and chromium martensitic stainless steel (X46Cr13/1.4034). The tests were performed in an air atmosphere at room temperature, and the test results are presented in the form of a stress-life (S-N) diagrams. The fatigue (endurance) limit (/MPa) obtained for each of the tested materials subjected to a mechanical fully reversed fatigue test, (R = - 1), at room temperature, is as follows (material / fatigue limit): 1.0122/202; 1.5920/285; 1.4034/325. In addition, at room temperature, the parameters such as ultimate tensile strength and yield strength, as well as the level of Charpy impact energy, were determined.

Understanding the Anomalous Corrosion Behaviour of 17% Chromium Martensitic Stainless Steel in Laboratory CCS-Environment—A Descriptive Approach

To mitigate carbon dioxide emissions CO2 is compressed and sequestrated into deep geological layers (Carbon Capture and Storage CCS). The corrosion of injection pipe steels is induced when the metal is in contact with CO2 and at the same time the geological saline formation water. Stainless steels X35CrMo17 and X5CrNiCuNb16-4 with approximately 17% Cr show potential as injection pipes to engineer the Northern German Basin geological onshore CCS-site. Static laboratory experiments (T = 60 °C, p = 100 bar, 700–8000 h exposure time, aquifer water, CO2-flow rate of 9 L/h) were conducted to evaluate corrosion kinetics. The anomalous surface corrosion phenomena were found to be independent of heat treatment prior to exposure. The corrosion process is described as a function of the atmosphere and diffusion process of ionic species to explain the precipitation mechanism and better estimate the reliability of these particular steels in a downhole CCS environment.

The Role of Observation-Measurement Methods in the Surface Characterization of X39Cr13 Stainless-Steel Cutting Blades Used in the Fish Processing Industry.

In the modern fish processing industry, flat fishes play an important role. They are processed into a final product in the form of a fillet during the skinning operation, which is carried out on machines operating in automated production lines. These machines are usually equipped with a single planar cutting blade or a few of such blades. The high-efficiency skinning and industrial conditions cause rapid wear of the cutting edge of the blade, which is detrimental to the quality of the final product. One of the forms of renewing the cutting ability of these types of tools is the regeneration carried out with the use of precise traverse surface grinding. The results of this process must be carefully verified for determining its correctness and possible optimization of its parameters. The main goal of this article was to characterize the usefulness of a number of observational and measuring methods to evaluate the results of the technical blade regeneration process. In this work, a number of contemporary observation–measurement methods such as optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), optical profilometry (OP), and angle-resolved scattering (ARS), supported by image processing and analysis techniques, were analyzed. The authors focused on presenting the role of the abovementioned methods in the surface characterization of planar cutting blades made of X39Cr13 chromium martensitic stainless steel before and after the technological operation of flat-fish skinning. Additionally, the surface condition after the regeneration process carried out using the five-axis CNC (computerized numerical control) grinding machine was also assessed. Numerous results of surface observations, elemental composition microanalysis, high-accuracy surface microgeometry measurements, and quantitative and qualitative analysis confirming the possibility of using the proposed methods in the presented applications are presented.

SANDMEYER ALLOY 410 (UNS S41000)

Abstract Sandmeyer Alloy 410 (UNS S41000) is a general purpose 12% chromium martensitic stainless steel that can be heat treated to obtain a wide range of mechanical properties. This alloy possesses good corrosion resistance along with high strength and hardness. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, machining, and joining. Filing Code: SS-1316. Producer or source: Sandmeyer Steel Company.

Frictional characteristics of impregnated graphite with different graphitization degree versus chromium stainless steel under varying PV values

An experimental study was performed by employing a seal pair of phenolic resin impregnated graphite and high chromium martensitic stainless steel 9Cr18. A purpose-built test rig was designed and fabricated to study the effect of face temperature on the surface morphology of a seal ring made of phenolic resin impregnated graphite with different graphitization degrees for varying PV values (pressure × velocity). As revealed by the results, the effect of rotational speed on heat generation between the two mating surfaces was more significant than that of fluid pressure. The effects of surface frictional temperature between the two faces were found different when the phenolic resin impregnated graphite ring with different graphitization degrees. The worn surfaces of the phenolic resin impregnated graphite rings were examined with the assistance of scanning electron microscopy and 3D measuring laser microscopy to investigate the wear mechanism for these different mating rings. Both adhesive and abrasive wear mechanisms were discovered under the working conditions. It was found out that the phenolic resin impregnated graphite ring with a high degree of graphitization was worn more severely at high PV values. Under the conditions of high speeds or high PV values, the phenolic resin impregnated graphite with fine and compact graphite matrix particles, medium degree of graphitization, high thermal conductivity and hardness is the top choice.

Corrosion-Electrochemical behavior of 13% chromium (Cr) martensitic stainless steel in hydrochloric acid (HCl) solutions

Corrosion-Electrochemical behavior of a commercial API5CT grade L80 type 13Cr tubing enriched with microalloying elements is studied in 6, 7.5, 9, 12 and 15% HCl solutions by electrochemical methods. The objective is to contribute to the comprehension of corrosion phenomena caused by HCl of similar concentrations, generally used in acidizing job. The corrosion morphology is examined by scanning electron microscopy (SEM) coupled with EDAX. The soluble corrosion products are analyzed by atomic absorption spectroscopy and colorimetric methods. General, as well as localized, corrosion is present. The severest general corrosion with a maximum rate of 26 mm/year is obtained at 15% HCl. The localized corrosion which morphologically differs as function of HCl concentrations is revealed by SEM investigation. In all the above HCl solutions, the commercial 13% Cr martensitic stainless steel tubing shows no passive state. Above 6% HCl, the microalloying elements promote forming a discontinuous film of the corrosion products. The corrosion rate slightly decreases in 15% HCl compared to the published data on a conventional 13% Cr martensitic stainless steel tubing. This is due to both the chemical composition (silicon, manganese and vanadium) and microstructural properties. Copper seems to additionally accelerate the corrosion of the alloy.

Failure analysis of turbo-blower blades

Twelve percent chromium martensitic stainless steel blades of the medium-pressure stage of a thermoelectric centre turbo-blower broke during use. The present work will investigate the possible causes for the premature failure of these blades and the condition of the high-pressure blades. The results indicated that at least one of the blades of the medium-pressure stage failed by a corrosion-fatigue mechanism, whose nucleation was associated with the presence of corrosion pits on its suction side. The high-pressure blades presented hardness bellow the specification and presence of corrosion pits and cracks. The softening of the microstructure (from 250 to 220 HV) could not be explained by microstructural instability during the intermittent use of the blade, indicating that either the material was initially tempered at a higher temperature or that the working temperature is higher than the predicted. A rough and conservative estimation of the residual life of the high-pressure blades indicated that the high-pressure blades should also replaced. The quality of the feed water (from the sea) used for the production of the vapour should be optimised and any action taken to improve the cleanliness and dryness of the equipment during its intermittent use may improve the life of the blades.

高温純水中のＺｒ‐２．５ｗｔ％Ｎｂ合金とＳＵＳ４０３Ｍｏｄのすき間腐食

Crevice corrosion characteristics of 13% chromium martensitic stainless steel bearing 3.5% nickel and zirconium alloy containing 2.5% niobium (Zr-2.5wt%Nb) were investigated in high temperature pure water. Corrosion of the stainless steel occurred in the crevice, while corrosion of the Zr-2.5wt%Nb was inhibited. Corrosion pits were formed on the stainless steel in the early period of the corrosion test. However, these pits were repassivated in the subsequent corrosion test and the pits did not propagate. The Zr-2.5wt%Nb allo absorbs the subsequent corrosion test and the pits did not propagate. The Zr-2.5wt%Nb allo absorbs the correlated with the corrosion of the stainless steel.

The effect of prior mechanical deformation on hydrogen transport through 13% chromium martensitic stainless steel

Hydrogen permeation measurements have been made on a 13% chromium martensitic stainless steel which had been previously mechanically deformed. Tensile deformation was applied up to strains of 8%, corresponding to the UTS, and cold rolling was used to generate higher levels of deformation up to 50%. Analysis of the permeation transients for strains below UTS has shown a small but significant increase in the number of reversible trap sites, which is consistent with their association with dislocations. There was little change in the number of irreversible trap sites by virtue of maintaining the strain below the level at which significant interfacial separation could occur. The results of this study confirm that the major reversible trap sites in this steel are associated with dislocations.

The effect of temperature and H2S content on the cracking resistance of a 13% chromium martensitic stainless steel in acidified NaCl

The cracking resistance of a 13% chromium martensitic stainless steel has been determined, using the slow strain rate technique, as a function of the temperature (23−80°C) and H2S content of acidified NaCl. A clear correlation between relative time-to-failure and sub-surface hydrogen content (Co) has been established at each temperature. However, it is shown that the predominant factor determining cracking is the fractional occupancy of reversible trap sites. A broad correlation has been identified between relative time-to-failure and fractional occupancy of traps irrespective of whether the latter is obtained by varying temperature, H2S content or pH (≤3.6).

The effect of temperature and H2S concentration on hydrogen diffusion and trapping in a 13% chromium martensitic stainless steel in acidified NaCl

The hydrogen uptake and trapping characteristics of a 13% Cr martensitic stainless steel have been determined as a function of the temperature (23–77°C) and H2S content of acidified solutions of NaCl. The sub-surface hydrogen content, evaluated from the steady-state permeation flux, increases with increasing temperature for constant solution composition. Analysis of the permeation transients has been undertaken using a diffusion-trapping model which incorporates both reversible and irreversible trapping with varying degrees of occupancy. The density of reversible trap sites is independent of temperature and is approximately 2.3 × 1019 sites cm−3. The binding energy is −(40–46) kJ mol−1. The higher values in this range are associated with the elevated temperatures. The density of irreversible trap sites shows a decrease in value above 23°C. These temperature effects may reflect uncertainty in characterizing the lattice diffusion coefficient.

Analysis of hydrogen diffusion and trapping in a 13% chromium martensitic stainless steel

A theoretical analysis has been made of the combined effects of reversible and irreversible trapping, with varying degrees of occupancy, on hydrogen transport in steels. The analysis has been coupled with repetitive electrochemical permeation measurements to characterise the diffusion and trapping parameters associated with a 13% Cr martensitic stainless steel commonly used for oil production tubing. The density of reversible and irreversible traps was (3.0 ± 1.0) × 10 19 sites cm −3 and about 1.5 × 10 19 sites cm −3 respectively. The binding energy of the reversible traps was (− 38.7 ± 1.0) kJmol −1. The capture rate constant for the irreversible traps was (4.8 ± 1.3) × 10 −19 cm −3 s −1. Assuming the same value for the reversible traps a release rate constant for the reversible traps of about (3.4 ± 1.6) × 10 −2 s −1. Knowledge of these parameters enables improved calculation of hydrogen charging times, which is essential for establishing reliable test methodology. It is recommended that the use of an effective diffusion coefficient, as a quantitative parameter for characterising hydrogen transport, be abandoned in systems for which irreversible trapping is dominant.

UHB STAVAX ESR

Abstract UHB STAVAX ESR is a chromium martensitic stainless tool steel which is Electro-Slag Refined (ESR) to provide the best polishability. It is characterized by (1) excellent polishability, (2) high hardness, (3) good hardenability and (4) fair corrosion resistance. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties as well as fracture toughness. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: SS-299. Producer or source: Uddeholm Aktiebolag. See also Alloy Digest SS-331, August 1976.

Mechanism of Cracking of High Strength Martensltic Stainless Steels in Sodium Chloride Solutions

Abstract This paper reviews previously proposed mechanisms for the environmentally induced cracking of high strength steels in sodium chloride. The electrochemical basis for the differentiation between hydrogen embrittlement and active path corrosion is examined along with the consequences of the recently demonstrated acidification that occurs in areas of localized geometry such as precracks, pits, and crevices. From electrochemical studies on a modified 12% chromium martensitic stainless steel, data are presented which indicate that hydrogen absorption occurs under conditions of exposure previously thought to preclude this possibility; that is, at applied bulk potentials noble to the reversible hydrogen potential. Data are also presented to show that the activation energy for crack growth at the corrosion potential and at cathodic and anodic applied potential is 9.5 Kcal/mole (±1); a value close to that reported previously for the cracking of cathodically embrittled steel. The experimental data are explained on the basis that an embrittlement process associated with hydrogen absorption is responsible for crack growth under all conditions of applied potential. With polarization at potentials active to the hydrogen reversible potential, hydrogen absorption results directly from the bulk cathodic discharge of protons. At the corrosion potential and more noble potentials, hydrogen absorption takes place from the cathodic discharge of protons occurring in the low pH conditions resulting from the hydrolysis of anodic dissolution products in pits. In the noble potential region, although active path anodic dissolution appears not to be the mechanism of crack growth, anodic dissolution is a prerequisite to crack growth by a hydrogen embrittlement mechanism. It is suggested that a similar mechanism can explain the cracking behavior of other high strength steels in sodium chloride solutions where conditions suitable for hydrolysis arise either by pitting or by crevice corrosion occurring in the presence of a mechanical precrack.

マルテンサイト型13%クロムステンレス鋼の熔接組織および急熱急冷による組織の挙動

Metallographic studies have been performed on the structures of weld metal and the heat-affected zone of 13% chromium martensitic stainless steel. The heat-affected zone was obtained by single bead welding, in which a single bead 10∼12 cm in length was placed on a 13% chromium stainless steel plate of 200×75×20 mm3. The isothermal austenitization diagrams (T-T-A diagram, Time-Temperature-Austenitization diagram) were determined for two specimens differently pre-heat treated. The specimen was heated in a salt bath, followed by rapid quenching in water, and then the T-T-A diagram was obtained from changes in hardness (Hv) and in matrix structure.The results may be summarized as follows: (1) In the specimen heated at 1050°C for 30 min and then oil quenched, the heat-affected zone is shaply divided into two parts; one is heated over the Ac1 point and the other is tempered at a lower temperature than the Ac1 point. This is characterized by hardness. (2) The hardness of the heat-affected zone approaches that of base metal by a short-time annealing at 700°C, but the chromium carbide is aggregated in the heat-affected zone. (3) By rapid heating and cooling, the 13% chromium stainless steels with varying carbon contents show a different hardness and an almost identical Ac1 point. The hardness curve exhibits a peak at a maximum heating temperature. (4) From the T-T-A diagrams of the specimens differently treated, it is clear that, in the rapid heating and quenching, a very short holding time is sufficient for hardening when the specimen is heated up to a specified temperature. (5) As to the different pre-heat treatment of the 13% chromium martensitic stainless steel, the austenitization time of the specimen that received only solid solution treatment is shorter than that of the annealed specimen.