Influence of Thermal Treatment on SCC and HE Susceptibility of Supermartensitic Stainless Steel 16Cr5NiMo (original) (raw)
Related papers
2016
Within this work, the influence of the microstructure of a 16Cr-4Ni low-carbon supermartensitic stainless steel (SMSS) on its SCC resistance was studied. The work was first focused on the determination of the fraction of retained austenite (austenite stable at room temperature) after tempering heat treatments or after plastic deformation. Indeed, this steel exhibits Strain Induced Martensitic Transformation (SIMT) phenomenon which influences the amount of retained austenite. Different microstructures have been prepared and their resistance to SCC has been studied using Slow Strain Rate Tensile (SSRT) tests in an environement containing Na2S. This compound has been chosen in order to reproduce the effect of sulfur/sulphur present in H2S-containing environments. These tests have shown that the decrease in initial retained austenite content leads to a diminution of the SSC resistance.
International Journal of Pressure Vessels and Piping, 2019
The influence of tempering treatments on mechanical properties and hydrogen embrittlement (HE) of 13 wt% Cr martensitic stainless steel (MSS) have been investigated by Charpy impact tests and slow strain rate tensile (SSRT) tests followed by fracture surface examination. The austenitized and quenched specimens were tempered at 300, 550 and 700°C for 2.5 h. The MSS tempered at 550°C showed brittle intergranular (IG) fracture after impact tests indicating its susceptibility to temper embrittlement. The experimental results showed that the 13 wt% Cr MSS is sensitive to HE. The as-quenched condition showed cracking during hydrogen pre-charging itself. Hydrogen pre-charging duration increased the susceptibility to HE of tempered MSS. The maximum HE susceptibility was observed for specimen tempered at 550°C with a drastic reduction in strength and strain to failure. Tempering at 300 and 550°C showed brittle IG fracture with hydrogen pre-charging in SSRT tests whereas increased IG region with ductile dimples was observed for specimen tempered at 700°C with increase of pre-charging duration. The reason for maximum susceptibility to HE of specimen tempered at 550°C is due to synergistic interaction of hydrogen and impurities segregated at prior austenitic grain boundaries.
Super martensitic stainless steels are the most useful steels in the oil gas industries and automobile industries due to their excellent mechanical properties and corrosion resistance. This paper focuses on the microstructure and mechanical & metallurgical properties of super martensitic stainless steels. The main objective has been to review the affect of alloy additions and also different heat treatment processes on microstructure and mechanical properties of super martensitic stainless steels. Additionally, difference in properties and microstructure of martensitic stainless steels and super martensitic stainless steels has been discussed.
Journal of Materials Science
Supermartensitic steels are a new class of martensitic stainless steels developed to obtain higher corrosion resistance and better toughness through the reduction of carbon content, and addition of Ni and Mo. They were developed to more critical applications or to improve the performance obtained with conventional grades AISI 410, 420, and 431. In this study, the influences of the tempering parameters on the microstructure, mechanical properties (hardness and toughness), and sensitization of a Ti-alloyed supermartensitc stainless steel were investigated. The material showed temper embrittlement in the 400–600 °C range, as detected by low temperature (−46 °C) impact tests. The degree of sensitization measured by double loop reactivation potentiodynamic tests increased continuously with the increase of tempering temperature above 400 °C. Healing due to Cr diffusion at high tempering temperatures was not observed. Double tempered specimens showed high amounts (>20%) of reverse austenite but their toughness were similar to specimens single tempered at 625 and 650 °C.
Metals and Materials International, 2019
In the present work the microstructural characterization of the powder-metallurgy X190CrVMo20-4-1 has been performed and correlated with its corrosion properties. The martensitic stainless steel was hardened at different austenitizing and tempering temperatures. Microstructural analyses were carried out using Scanning Electron Microscopy (SEM-EDS) to define the carbide distribution in the steel matrix. Carbides morphology and retained austenite content were evaluated and correlated to the corrosion behaviour of the different heat-treated steels, investigated by means of electrochemical tests. The results show the presence of M 23 C 6 and M 7 C 3 Cr-V based carbides homogenously dispersed in the matrix in annealed and quenching-and-tempering conditions. The carbides dissolution was evaluated by image analysis in every different heat treatment condition. When low tempering temperature was applied, an increasing in retained austenite content was defined by high austenitizing temperature and elevated carbides solubilization. At high tempering temperature, retained austenite content was not up to 5% nor affected by austenitizing temperature. Contrary to the expectations, HRC hardness was not influenced by the heat treatment conditions and retained austenite content. Corrosion resistance of the different heat-treated samples was found to be mainly influenced by retained austenite volume fraction and the tempering temperature. In particular, high austenitizing temperature and low tempering temperatures allowed the best corrosion resistance among the different heat treatment parameters investigated. The results obtained in the experimentation can provide support to the heat treatment optimization of the steel, widely used in tool and mould applications.
Materials Research
Super-austenitic stainless steels (SASS) are alloys with better performance in industrial applications in comparison with standard degrees of austenitic stainless steels (ASS), mainly because of elevated Ni and Mo contents and residual control of certain elements because the improvement of refine techniques. These facts, promotes an improvement of mechanical properties and minimize detrimental effects of intergranular corrosion. Besides, some industrial applications involve high temperatures services, because these alloys families have an excellent creep and oxidation resistances performances. In this work, the objective is evaluate the microstructural and mechanical properties in high Mo SASS exposed at 600˚C in specimens aged until 2000 hours. Thus, hardness and toughness values and Double Loop Electrochemical Potentiodynamic Reactivation (DL-EPR) measurements were analyzed in several thermal aging in comparison to solution treatment condition. Complementary, analysis by Light Optical (LOM), of specimens tested by DL-EPR, and Scanning Electron Microscopies (SEM) in fractured surface from Charpy specimens were also analysed by SEM by backscattered electron mode (BSE). The results show that the aging provokes intergranular embrittlement by inhomogeneous distribution in grain boundaries of Mo rich phase precipitation.
Tribology in Industry
Wear behavior of 13Cr5Ni2Mo supermartensitic stainless steel (SMSS) were investigated in air and in argillaceous paste at room temperature. Prior to wear testing, the samples were subjected to two thermal treatments, namely; quenching followed by double tempering. A pin-ondisc test rig was used to conduct the wear test with a tribo-pair consisting of supermartensitic stainless steel sliding against itself. It was observed that the microstructure of the thermally treated samples mainly consisted of tempered martensite and carbides. Wear results showed that oxidative and abrasive wear dominated the wear process of the treated samples in both dry conditions and in argillaceous paste. Additionally corrosion tests were performed in 5.0% NaCl solution via potentiodynamic polarization tests. It was found that the passive film formation provides a good corrosion resistance to the samples.
Supermartensitic Stainless Steel Deposits: Effects of Shielding Gas and Postweld Heat Treatment
Welding Journal, 2013
Welding supermartensitic stainless steel plays a crucial role in structural components, influencing their toughness and resistance to sulfide stress cracking. Postweld heat treatment (PWHT) adjusts the final properties of the weldments, bearing on microstructural evolution. The objective of this work was to study the effects of different shielding gas mixtures and PWHT on supermartensitic stainless steel all-weld-metal properties. Three all-weld-metal test coupons were prepared according to standard ANSI/AWS A5.22:95, Specification for Stainless Steel Electrodes for Flux Cored Arc Welding and Stainless Steel Flux Cored Rods for Gas Tungsten Arc Welding, using a 1.2-mm-diameter tubular, metal-cored wire under Ar-5% He, Ar-2% CO 2 , and Ar-18% CO 2 gas shielding mixtures in the flat position with a nominal heat input of 1 kJ mm ―1 . The PWHT used was 650°C for 15 min. All-weld metal chemical composition analysis, metallurgical characterization, hardness and tensile property measuremen...