Tempering Treatment Research Articles

The Evolution of a Microstructure during Tempering and Its Influence on the Mechanical Properties of AerMet 100 Steel

In order to provide guidance for furthering the balance of strength and toughness of AerMet 100 steel through tempering treatment, the effects of the tempering time on microstructure and mechanical properties are investigated. The microstructure evolution, especially M2C precipitates and austenite in AerMet 100 tempered at 482 °C for 1~20 h, was characterized, and its influences on the mechanical properties were studied. The tensile strength decreases gradually, the yield strength increases first and then decreases, and the fracture toughness KIC increases gradually with an increasing tempering time. The strength and toughness matching of AerMet 100 steel is achieved by tempering at 482 °C for 5~7 h. Without considering the martensitic size effect, the influence of the dislocation density on the tensile strength is more significant during tempering at 482 °C. The precipitation strengthening mechanism plays a dominant role in the yield strength when tempering for 5 h or less, and the combined influence of carbide coarsening and a sharp decrease in the dislocation density resulted in a significant decrease in tensile strength when tempering for 8 h or more. The fracture toughness KIC is primarily influenced by the reverted austenite, so that KIC increases gradually with the prolongation of the tempering time. However, a significant decrease in the dislocation density resulting from long-term tempering has a certain impact on KIC, giving rise to a decrease in the rising amplitude in KIC after tempering for 8 h or more.

Effects of tempering temperature on the precipitation behaviors of nanoparticles and their influences on the susceptibility to hydrogen embrittlement of a Cr–Mo–V steel

This paper presents an experimental study of tempering treatment to optimize the precipitation behavior of nano-sized particles for improving the resistance to hydrogen embrittlement (HE) of an AISI 4330-type low-alloy high-strength steel. The precipitates and dislocations in the microstructure, which serve as irreversible and reversible hydrogen traps, were quantitatively investigated using TEM, X-ray diffraction and hydrogen permeation techniques. It was found that V-rich M2C precipitates of less than 2 nm size appeared when tempered at 610 °C, a tempering temperature associated with the lowest HE susceptibility of the tempered steel. Furthermore, the hydrogen could promote movement of the multiple dislocation at the low-temperature tempering process but pin the separated dislocation at higher temperature tempering process. The interaction of the dislocations (i.e., multiple dislocation or separated dislocation) with nanoprecipitates and hydrogen atoms produced the hydrogen-induced hardening/softening behavior in a hydrogen-charging environment.

2 GPa H13 steels fabricated by laser powder bed fusion and tempering: Microstructure, tensile property and strengthening mechanism

The successful manufacture of crack-free and highly dense H13 tool steel using laser powder bed fusion (LPBF) has been widely reported. Although the phases contain only martensite and some (<20 %) of residual austenite (RA), the differences in tensile properties are very large in previous studies. Here, the microstructure and tensile properties of the LPBF-fabricated H13 steels with different heat treatments were comparatively studied. Tensile strengths ranged ∼2.0–2.2 GPa for the optimal as-built and direct-tempered samples. By increasing the heat input, the RA content was reduced to 0.1 % and the microstructure contained only hierarchically fine martensite with improved tensile properties and anisotropy. Based on the full-martensitic microstructure in the optimal as-built samples, secondary hardening was achieved by direct tempering at 530–590 °C with tensile strengths of ∼2.1–2.2 GPa and improved elongations (4.93–6.43 %). The optimal direct-tempered samples yielded higher tensile strengths compared to the standard heat-treated counterparts. For the direct-tempered samples, the substantial retaining of the fine martensitic structure and high density of dislocations introduced by LPBF was the key to the excellent properties rather than the precipitates. This work elucidated the effect of the LPBF process, direct tempering, and standard heat treatment on the tensile property of H13 steel. It is concluded that process optimization for LPBF fabrication of H13 steel requires not only defect avoidance but also fine martensite and low-content RA. On this base, the LPBF-prepared H13 steel can be directly tempered to further obtain components with excellent tensile properties, which are superior to the standard heat-treated counterparts.

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 heat treatment on microstructure and properties of 10B21 cold-heading steel for fasteners

Fasteners are widely used in automobile, electronic and other fields, and the demand for high performance fastener materials is increasingly urgent. 10B21 mild steel has the advantages of good plasticity, obvious heat treatment effect and so on. It is used to produce fasteners below grade 9.8. In this paper, the domestic 10B21 boron steel as the research object, through quenching, tempering and other heat treatment, change its structure from ferrite to tempered martensite, in order to improve the strength and hardness.

Changes in water status and microstructure reveal the mechanisms by which tempering affects drying characteristics and quality attributes of medicinal chrysanthemums

To elucidate the mechanism behind the heterogeneity in the water distribution during the drying process of medicinal chrysanthemum (Imperial chrysanthemum), and thereby optimize the drying process, this study introduced an innovative approach by incorporating tempering into the drying process and evaluated the effects of hot air drying (HAD), infrared-assisted hot air drying (IR-HAD), and tempering-incorporated IR-HAD (TD+IR-HAD) on the water status, microstructure, and phytochemicals of dried chrysanthemums. Results showed a significant difference in the rate of dehydration between the central and marginal parts of chrysanthemums. The highest difference in moisture content value (1.34 g water/g dry matter) was observed between these two parts for samples subjected to 2.5 h of IR-HAD drying. Consequently, the sample subjected to 2.5 h of IR-HAD drying was selected for tempering. After the optimal tempering treatment (12 h), the samples were subjected to an additional 0.5 h of IR-HAD drying. This incorporated drying method (TD+IR-HAD) effectively reduced the drying time and energy consumption. Transverse relaxation curves and microstructural observations further confirmed that these reductions were related to the enhancement of water mobility and the formation of microchannels during tempering. As a result, chrysanthemums dried using TD+IR-HAD showed increased contents of chlorogenic acid, luteolin, total phenolic, total flavonoid, antioxidant capacity, and the number of volatile compounds compared to HAD and IR-HAD. Overall, these results highlight the potential of TD+IR-HAD as a promising drying technique for enhancing the value and applications of medicinal chrysanthemums in industrial settings.

Influence of thermomechanical processing and tempering temperature on tensile flow and work hardening behaviour of India specific reduced activation ferritic martensitic steel

In the present work, an indetailed investigation has been carried out on the effect of thermomechanical treatment (TMT) and tempering temperature on microstructural features, tensile flow characteristics and work hardening behaviour of the India specific reduced activation ferritic martensitic (INRAFM) steel. The flow and work hardening characteristics of the studied steel are described by using the Voce constitutive equation and Kocks- Mecking (K-M) approach respectively in the temperature range of 300–873 K. The steel subjected to TMT and tempering for 90 min at 1033 K shows a refined martensitic lath width, finer size (Cr/W/Fe)23C6 and (V/Ta) (C/N) precipitates with an increment in number density. Furthermore, increase in tempering temperature coarsened the refined structural features. Voce equation closely fits the flow curves at 823 K and 873 K, but shows a slight deviation at temperatures below 773 K. The parameters derived from Voce equation are fairly in good correaltion with the experimental values. The strain hardening rate (θ) vs. true stress (σ) plots portrayed stage-I and stage-III work hardening stages and their corresponding phenomena were discussed. In addition, the effect of TMT and tempering treatment on the work hardening parameters obtained from K-M approach and inter-barrier spacing of the steel were also presented in this study. The work hardening characteristics of the steel signifcantly improved upon TMT due to refinement in microstructural features. The flow stress and work hardening parameters decreases with raise in test temperature due to the dominant effect of dynamic recovery.

EBSD-data analysis of an additive manufactured maraging 300 steel submitted to different tempering and aging treatments

Maraging is a high alloy steel sensitive to the precipitation of intermetallics from a supersaturated solid solution during aging heat treatments. The precipitation phenomenon is well described in the literature, which gave rise to the alloy name regarding a martensite matrix with precipitates formed by aging treatment. Many studies have been performed to characterize this material, usually subjected to many sample preparations for transmission microscopy, which is very laborious, and few EBSD analyses. Therefore, in this work, a large study was conducted using electron backscatter diffraction (EBSD) to analyze maraging microstructures through band-contrast, kernel average misorientation (KAM), grain orientation spread (GOS), and misorientation distribution. Our results show that solubilization of the additive manufactured maraging steel resulted in a more homogeneous microstructure with new angle grain boundaries. Furthermore, tempering heat treatments relieve martensite strain, increasing band contrast values. Posterior aging presented a low impact on the results of EBSD analysis.

Improvement in low-temperature toughness of Fe-6.5Mn-0.08C Medium-Mn steel by multi-step heat treatment

In this study, a novel multi-step heat treatment method, including intercritical annealing and tempering, is proposed to improve the low-temperature toughness of Fe-6.5Mn-0.08C medium-manganese (Mn) steel. The effects of the subsequent tempering treatment on the microstructural evolution and low-temperature toughness of medium-Mn steel were investigated and compared with those of a single intercritical annealing treatment. Medium-Mn steel subjected to intercritical annealing exhibited a duplex microstructure composed of martensite and nanolaminate-retained austenite. The subsequent tempering treatment after intercritical annealing generated a more homogenous distribution of retained austenite, together with an increase in the volume fraction of the retained austenite. The uniformly distributed retained austenite prevented Mn segregation at prior austenite grain boundaries, and the high fraction of retained austenite effectively inhibited crack propagation, leading to an improvement in the low-temperature toughness. In addition, the subsequent tempered medium-Mn steel contained a considerable amount of retained austenite, which could transform into martensite during the impact test, resulting in an impact fracture morphology that changed from cleavage facets to dimples at low temperatures.

Boosting Mechanical Properties of W6Mo5Cr4V2 Alloy Fabricated by Directed Energy Deposition Through Tempering Heat Treatment

The utilization of laser‐directed energy deposition (DED) for fabricating alloys offers the potential to customize their mechanical and physical properties, surpassing traditional casting limitations. Herein, a DED‐adopted flat‐top laser is applied in producing W6Mo5Cr4V2 alloy, a material widely used in mold making, double‐screw production, and crushing roller manufacturing. To minimize its residual stress and potential defects, and enhance the performance of the deposited sample, it undergoes tempering heat treatment at 560 °C for 1 h. According to the analysis results, the deposited W6Mo5Cr4V2 alloy is predominantly composed of martensite, carbide, and a minor amount of retained austenite. Upon tempering, the retained austenite transforms into martensite, effectively reinforcing the properties of the W6Mo5Cr4V2 alloy by precipitating secondary carbides. Furthermore, the microhardness value of the alloy increases by 12% after tempering heat treatment. Both adhesive and abrasive wear are observed during the friction and wear process, resulting in a 10% reduction in friction coefficient, thereby significantly improving the wear resistance of the W6Mo5Cr4V2 alloy. The average tensile strength of the heat‐treated W6Mo5Cr4V2 sample is 762.34 MPa, which is higher than the deposited sample's 646.6 MPa. Notably, the tensile fracture displays typical brittle characteristics.

Evaluation of post weld heat treatments and susceptibility to sulfide stress corrosion cracking of simulated HAZ in forged supermartensitic stainless steel UNS S41427

Supermartensitic stainless steels (SSMSs) with 12–13%Cr, 5%Ni, 2%Mo and microadditions were developed to casings, tubullars and mandrels used in the oil and gas off-shore production. These materials have great resistance to aqueous medium containing large amounts of CO2 and can withstand high temperatures and large amounts of chloride as well. However, SMSSs have a limited resistance to H2S containing solutions, and may fail due to sulfide stress cracking (SSC). This limit is even lower for forged and welded components that used in mandrels. Recent studies have been developed to find an operational envelope for safe use of SMSSs in sour production systems. The present study shows the results of slow strain rate testing (SSRT) of a forged V-alloyed SMSS submited to thermal simulation in Gleeble machine to produce a coarse grain heat affected zone (HAZ). The microstructure of the HAZ is characterized by fresh martensite, intergranular delta ferrite and fine precipitates which increase the hardness to a level above the maximum limit for sulfide stress corrosion cracking. The effects of two post weld heat treatments (PWHT) on the mechanical properties and susceptibility SSC were evaluated. Single and double tempering treatments provoked the decrease of hardness and the increase of ductility parameters. However, specimens representative of the HAZ, base metal, and HAZ with single and double tempering presented high SSC susceptibility parameters in SSRT in saline solution (200,000 ppm NaCl) with 1.0 psia of H2S partial pressure, and pH 4.5.

Improving toughness and strain-hardening of a silicon-enriched ferritic/martensitic (F/M) steel via an austenite isothermal hot-rolling (AIHR) process

Si-enriched ferritic/martensitic (F/M) heat resistance steels are emerged as structural materials in advanced thermal and nuclear power stations attributed to their satisfactory corrosion resistance to coolants. However, the low toughness from high Si content over 0.5 wt% due to the formation of weaking δ-ferrite phase and the weak bonding between ferrite and martensite has been a tough trouble for application. Long time annealing at austenitizing temperature could alleviate ferrite phase but at the sacrifice of coarsening carbides and grains. Here we present an austenite isothermal hot-rolling (AIHR) strategy in which multi-pass rolling and limited annealing time are conducted at isothermal states above the austenitizing temperature. This increased toughness by almost 700% (from 7 to 56 J/cm2) meanwhile the same yield strength (787 MPa) compared to the normal quenching + tempering treatment (NT, 757 MPa). The control of element diffusion and dynamic recrystallization (DRX) by AIHR accelerated the dissolution of ferrite within short process time, coupled with the reduced {100} cleavage plane & texture and the reduction of grain size and M23C6 phases, which are responsible for the improved toughness. Besides, higher strain hardening exponent accompanying refined microstructure and primary dislocation density implies deformation stability of the steel via AIHR process. These results provided a possible way of tailoring both the strength/toughness trade-off and the hardening ability on a Si-enriched F/M steel.

Effect of Heat Treatment on Microstructure and Properties Evolution of Stainless Steel Cladding Plate.

Heat treatments are necessary sometimes in order to improve comprehensive properties of stainless steel cladding plate (SSCP). However, carbon atoms in carbon steel diffuse into stainless cladding during the heat treatment process, thus decreasing its corrosion resistance. In this paper, optical microscopy, scanning electron microscopy, and microhardness and shear testing were employed to characterize the microstructure and mechanical properties of the bonding interface in SSCP. Then, the corrosion resistance of the stainless steel cladding surface was evaluated by electrochemical tests. The results showed that the diffusion of carbon atoms played an important role in enhancing the bonding strength of SSCP, but might lead to intergranular sensitization of the cladding surface because of chromium carbide precipitation. Notably, this precipitation could be induced by quenching and tempering treatment, and hindered by solution treatment. Hence, the cladding surface on SSCP after single solution treatment possessed the superior corrosion resistance, and SSCP with continuous solution and tempering treatment exhibited the highest bonding strength.

Characterization of microstructural evolution with pre-strain in BG801 bearing steel: Grain, carbides, retained austenite and martensite

The method of multiple cryogenic and tempering treatments significantly limits the microstructure regulation of BG801 bearing steel. In this work, the pre-strain was introduced in the vacuum-melted BG801 steel combing with heat treatment (HT) to adjust the microstructures. The samples were subjected to uniaxial tensile at room temperature with different strains (engineering strain of 0, 0.15, 0.175, 0.2), then heating to 1323 K and water-cooling. The results showed that higher pre-strain was beneficial to obtain finer prior austenite grain (PAG) and martensite grains, and a low fraction of retained austenite (RA) in BG801 steel. With increasing pre-strain, the PAG was elongated along the RD direction (rolling direction) without a change in size. The recrystallized grains with a size of about 5–6 μm nucleated inside the PAG during HT. Meanwhile, the high-density dislocations were introduced in the tensile samples by pre-strain, promoting the growth of micron-M6C by accelerating the diffusion of alloy elements during HT. And the evolution of RA and martensite indicated that the pre-strain accelerates transformation from austenite to martensite by transferring elements from the matrix to M6C and introducing shear bands into the matrix to promote the nucleation of martensite.

Investigation on microstructure and mechanical properties of electron-beam-welded joint of reduced activation ferritic/martensitic steel fabricated by selective laser melting

The microstructure and mechanical properties of the complex low-activation ferritic–martensitic components of the China Fusion Engineering Test Reactor (CFETR) were examined in this study. The quenching–tempering treatment of CLF-1 steel formed by selective laser melting (SLM) (referred to as the QTed material) was carried out to analyze the effects of heat treatment on the microstructural and mechanical properties. Meanwhile, the microstructural and mechanical characteristics of CLF-1 steel electron beam welding (EBW) joints after quenching–tempering (referred to as the EBWed material) were investigated. Compared with the untreated sample (referred to as the SLMed material, with an ultimate tensile strength (UTS) = 979.8 ± 12.7 MPa and elongation (EL) = 3.7% ± 0.4%), the quenching–tempering treatment improved the EL of CLF-1 steel effectively (QTed material, 22.3% ± 0.1%), while it decreased the UTS correspondingly (505.6 ± 11.8 MPa), which mainly was due to the change in the grain size and structure during the heat treatment. The special microstructural distribution characteristics of the CLF-1 fabricated via SLM determined that the fracture mechanism was transgranular ductile/intergranular brittle mixed fracture. After electron beam welding of the QTed material, the tensile properties of the joint (UTS = 710.6 ± 21.4 MPa, EL = 9.7% ± 0.1%) were between those of the SLMed and QTed materials. The fracture appeared in the heat-affected zone (HAZ), proving that the strength of the weld was higher than that of the base metal. The microstructure of the weld was almost completely composed of coarse lath martensite, and the accumulation of dislocation clusters, precipitated M23C6-type carbides, and precipitated MX-type carbides contributed to the improvement of the yield strength (YS). The HAZ could be divided into three regions based on the different heating temperatures, and every region had different grain structures composed of mainly martensite and ferrite. The contributions of four strengthening mechanisms to the YS of CLF-1 steel were analyzed quantitatively, which lays a foundation for further improving the performance of CLF-1 steel and improving its application feasibility on the first wall of a fusion reactor.

Investigation of the Effect of Tempering and Cryogenic Treatment on Mechanical Properties of Boron Steels

Boron steels are a group of steels that stand out with their high wear resistance and hardenability. In this study, 33MnCrB5-2 boron steel was shaped by applying hot forging process. After the hot forging process, the microstructure examinations and mechanical tests of the materials were carried out. A group of materials was cryogenically treated at -80 °C for 2 hours. Then, a different group of materials was austenitized at 890 °C and quenched, and then tempered at 400 °C for 90 minutes. In the last group of materials, after tempering heat treatment, cryogenic treatment was applied at -80 °C for 2 hours. Hardness and abrasion tests were carried out on the samples that were subjected to cryogenic treatment and tempering heat treatment. Microstructure analyzes were examined with the help of scanning electron microscope (SEM) and optical microscope. Element distributions from different regions in the microstructure were analyzed with energy-dispersive X-ray spectrometry (EDS). The crystallite size of the materials were calculated by X-ray diffraction. The results showed that the hardness value and wear resistance of the samples that were cryogenically treated after tempering gave higher values compared to the other samples.

Rapid tempering of a medium-carbon martensitic steel: In-depth exploration of the microstructure – mechanical property evolution

Rapid tempering is a remarkable sustainable and energy-efficient way to modify properties of as-quenched martensite, particularly its toughness and ductility. In this work, tensile and fracture toughness properties, and microstructural evolution of a medium-carbon (0.4 wt%), low-alloy steel under different rapid tempering circumstances are discussed. The hot-rolled and direct-quenched specimens were subjected to rapid tempering treatments (heating rate of about 90 °C/s) to the different tempering temperatures (320–720 °C). As a reference material, one sample was subjected to conventional tempering at 420 °C for one hour. The results indicated that the mechanical properties and microstructural features are influenced considerably by tempering temperature rather than the holding time. Despite the short tempering duration, the strength of tempered martensite dropped (from a max. tensile strength of ∼ 2100 MPa to a min. of ∼ 1100 MPa) while ductility increased with increasing tempering temperature (from a tensile elongation of 4% to ∼ 15%). However, the rapidly tempered sample at 420 °C experienced a loss of fracture toughness as a result of coarse stick-like cementite precipitation. Microstructural observations revealed that, even with a short time frame, tempering temperature plays a significant role in the resulting cementite morphology. At lower tempering temperatures, the cementite precipitates have a stick-like structure, while at higher temperatures, they become more globular/spheroid-like. This change in cementite morphology led to an enhancement in fracture toughness. Overall, the results indicated that, by a proper design of the rapid tempering process, an excellent combination of tensile properties and fracture toughness can be obtained compared to conventional tempering while significantly saving time and energy.

Microstructure and mechanical properties of 631 Stainless Steel: Study of Yield Slip and Strain Rate Mechanism with Austempering and Martempering

The microstructure and mechanical properties of 631 stainless steel, including tensile fracture and impact toughness, were compared in this study between austempering and martempering processes. The experimental results showed that the mechanical properties of 631 stainless steel increased as the temperature of martempering process increased from 520 °C to 720 °C, in contrast to previous literature, which suggested that the optimal tempering temperature was around 500 °C. Furthermore, 631 stainless steel treated with 720 °C austempering has superior tensile strength and impact toughness to traditional martempered 631 stainless steel. This suggests that the austempering process not only conserves energy but also improves the mechanical properties of 631 stainless steel. Furthermore, the precipitation mechanism during the tempering process can reduce the slip of secondary yield in 631 stainless steel. Additionally, the precipitation mechanism during tempering process can alleviate the secondary yield of 631 stainless steel. In both tensile strain rate tests and high-speed impact tests, it was confirmed that austempered 631 stainless steel had potential application in springs due to low strain-induced embrittlement susceptibility. Furthermore, long-term (24 hr) high-temperature tempering treatment showed that 631 stainless steel still maintained reliability and stability in high-temperature environment.

Evaluation of hole expansion ratio of ultra-high strength martensitic steels produced with various processing routes

Hole expansion ratio of hot rolled ultra-high strength martensitic steels with tensile strength around 1000 MPa was evaluated. Steels were produced with direct quenching and traditional reheat and quenching processes with final thickness of 3 mm. Achieved yield strength values (Rp0.2) varied between 918 – 1068 MPa depending on the processing route. Mean hole expansion ratios (HER) in direct-quenched (DQ) and direct-quenched and tempered (DQT) conditions were between 22 – 36 %, and no clear improvement was seen after tempering treatment compared to quenched variant. HER values for reheat and quenched (RQ) and reheat, quenched and tempered (RQT) variants were between 31 – 49 %, and the highest values were achieved with RQT steels, which were tempered at 600 °C. Based on the field emission scanning electron microscope with electron backscatter scanning diffraction (FESEM-EBSD) analysis/characterization of martensite grain size, more uniform grain structure was discovered in RQ steels, which could be the reason for improved HER properties. HER values were also compared to tensile test results (uniform elongation, true thickness strain), and formability maps were constructed. However, only minor correlation was found between HER and true thickness strain values.

Effect of Heat Treatment on Crevice Corrosion Behavior of 304 Stainless Steel Clad Plate in Seawater Environment.

With the application of stainless steel clad plate (SSCP)-enlarging in the marine engineering field, awareness of the consequences of heat treatment on ameliorating microstructure and mechanical properties in stainless steel (SS)/carbon steel (CS) joints is being raised. However, carbide diffusion from a CS substrate to SS cladding may damage the corrosion resistance during inappropriate heating. In this paper, the corrosion behavior of a hot rolling-produced stainless steel clad plate (SSCP) after quenching and tempering (Q-T) treatment, especially crevice corrosion, was studied by electrochemical and morphological methods, such as cyclic potentiodynamic polarization (CPP), confocal laser scanning microscope (CLSM) and scanning electron microscopy (SEM). Q-T treatment led to more significance in carbon atoms diffusion and carbide precipitation, which made the passive film of the SS cladding surface on the SSCP unstable. Subsequently, a device for measuring the crevice corrosion performance of SS cladding was designed; the Q-T-treated cladding showed lower re-passivation potential (-585 mV) during CPP when compared to as-rolled (-522 mV), with the maximum corrosion depth ranging from 70.1 μm to 150.2 μm. In addition, the processing of crevice corrosion on SS cladding could be divided into three parts, including the initiation, propagation and development stages, which were driven by the interactions between corrosive media and carbides. The generation and growth mechanism of corrosive pits in crevices were revealed.