Phase Transformations and Microstructural Evolution: Ferrous Alloys I
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Phase Transformations Committee
Program Organizers: Ashley Paz y Puente, University of Cincinnati; Mark Aindow, University of Connecticut; Sriswaroop Dasari, Idaho National Laboratory; Ramasis Goswami, Naval Research Laboratory; Megumi Kawasaki, Oregon State University; Eric Lass, University of Tennessee-Knoxville; Joshua Mueller, Michigan Technological University; Eric Payton, University of Cincinnati; Le Zhou, Marquette University
Monday 8:30 AM
March 20, 2023
Room: 25C
Location: SDCC
Session Chair: Eric Lass, University of Tennessee-Knoxville
8:30 AM
Microstructural Evolution of Pressure Vessel Carbon Steel Plate during Hydrogen Creep Testing: Jenna Krynicki1; Brandon Rollins2; Kenneth Bagnoli3; Timothy Weihs1; 1Johns Hopkins University; 2DNV GL USA, Inc.; 3Engineering Mechanics Corporation
High temperature hydrogen attack (HTHA) has long been a concern for the petrochemical industry, as failure due to HTHA has had devastating consequences, including loss of human life. Accordingly, the American Petroleum Institute (API) established recommended practice guidelines for “safe” operating conditions for pressure vessels, based upon prior failures and experiences in-service, but without the benefit of vast experimental data. Consequently, with this API-funded project, we generated creep data for pressure vessel steel in hydrogen, at various temperatures, hydrogen pressures, and stresses to better understand HTHA mechanisms. We found that under some conditions, the tertiary creep rate plateaued, which was unexpected and suggests current models may under predict some lifetimes. Using microscopy to show the evolution of microstructures and creep data, we hope to elucidate HTHA mechanisms, improve predictions of creep behavior, and ultimately enhance recommended practices of operation for petrochemical equipment and equipment associated with the future hydrogen economy.
8:50 AM
A Comprehensive Investigation on the Sintering Behavior of CaO-SiO2-CaF2-Al2O3 Slags System: Liang Yu1; Shaopeng Gu2; Guanghua Wen1; Chunhua Ran3; Funian Han1; Zhe Wang1; 1Chongqing University; 2North China University of Science and Technology; 3Teacher's College for Vocational Studies of JiuLongPo District
Sintering behavior were vital significant for the lubrication and transfer heat performance of mold fluxes during the casting process. In this paper, the sintering behavior of CaO-SiO2 slags with different Al2O3 and CaF2 were systematically investigated combining with TG-DSC, XRD, DIL, hemispherical point and SEM techniques. The mineral phase transformation process of slags was understood during the heating process. The results showed that Ca2SiO4 was formed at 1370 °C in CaO-SiO2 slags with 12.63% volume shrinkage. Ca4Si2O7F2 was occurred at 1173 °C with 64.06% volume shrinkage of slags when CaF2 was added to CaO-SiO2 slags. In CaO-SiO2-Al2O3 slags, Ca3Al2O6 was first formed and then transformed into Ca2Al2SiO7 at 1342 °C with 53.63% volume shrinkage. At 1148 °C, the Ca2Al2SiO7 and Ca4Si2O7F2 were coexisted in CaO-SiO2-Al2O3-CaF2 slags with the volume shrinkage of 60.13%. Besides, the solid phase reaction temperatures of slags were decreased by adding CaF2 and Al2O3.
9:10 AM
Can We Make an Electron Beam Weld ‘Disappear’?: Kirstie Bruce1; Mark Taylor1; Jonathan Fellowes1; Luke Burling2; John Francis1; Ed Pickering1; 1University of Manchester; 2Rolls-Royce plc
A novel post-weld heat treatment (PWHT) for electron beam welded pressure vessel steel, SA508 Grade 4N, was developed with the aim of fully homogenising microstructure and properties across the material, essentially making the weld disappear. A number of conventional and novel PWHT schedules were applied, including full re-austenitisation, quench and temper. Hardness was successfully homogenised across the parent and weld in all heat treatments involving re-austenitisation (860°C), but compositional microsegregation in the fusion zone was only removed by applying a homogenisation step at 1200°C. Nevertheless, even after the most severe PWHT, the weld area remained visible optically after etching. Austenite grain growth kinetics and continuous cooling transformation behaviour in the fusion zone and parent material was also studied to determine whether these regions are fundamentally different.
9:30 AM
Chemical Heterogeneity and Quench Rate Considerations for Quench and Partition Processing: Douglas Smith1; Kester Clarke1; Amy Clarke1; 1Colorado School of Mines
Design of quench and partition (Q&P) treatments often assumes chemical homogeneity after the annealing step and quench rates rapid enough to suppress non-martensitic transformations. While these assumptions simplify calculations, the presence of chemical banding and polygonal ferrite suggests that prior microstructure and cooling rate influence Q&P outcomes. Optimum quench temperatures were determined with consideration of chemical banding in the prior microstructure and solute redistribution after different annealing treatments, while the effect of quench rate to these temperatures was investigated through dilatometry and advanced characterization following Q&P. Combined, these investigations suggest differences in local austenite content and chemical stability as a function of prior microstructure and annealing conditions, while also highlighting the effects of polygonal ferrite formation on C partitioning during the quench.
9:50 AM Break
10:10 AM
Surrogate Model to Predict Microstructure and Mechanical Properties in Stainless Steel Cladding under Reactor Operating Conditions: William Frazier1; Yucheng Fu1; Lei Li1; Ram Devanathan1; 1Pacific Northwest National Laboratory
A machine-learning surrogate model was developed to provide rapid predictions of microstructural evolution and service lifetime for reactor materials under conditions of varying temperature and irradiation dose rate. To acquire high-fidelity training data, a Kinetic Monte Carlo (KMC) model was developed to simulate M23C6, γ’, and G phase precipitation kinetics in a 316 series stainless steel cladding. Experimentally reported behaviors of 316 SS in literature were linked to the kinetic parameters of the simulated precipitation in our model. Temperature and irradiation dose rate histories were generated synthetically for periods of up to 10,000 hours for the simulations. Precipitation progress parameters, including volume fraction, number density, and particle size were correlated using statistical methods to develop the surrogate model. Simultaneously, the mechanical properties of the simulated microstructures were evaluated using microstructure-based Finite Element Method (FEM) analysis. The fidelity of our surrogate modeling to the predictions of these simulations is discussed.
10:30 AM
In-situ SEM Study of Hydrogen-dislocation Interactions in Ferritic Stainless-steel: Kyung-Shik Kim1; Cem Tasan1; 1Massachusetts Institute of Technology
Although hydrogen has been reported to have detrimental effects in BCC metals, post-mortem experimental investigations of hydrogen effects has been challenging due to the high diffusivity of hydrogen in this crystal structure. In this research, to overcome this challenge, an in-situ SEM / ECCI based methodology has been employed to study dislocation motion due to hydrogen charging. To this end, an initial density of dislocations was formed by tensile pre-straining a 430 ferritic stainless steel sample to 1%, and then, hydrogen was introduced from the back side using an SEM hydrogen charging setup. As hydrogen was charged, dislocation activity was detected around grain boundaries and inclusions. Further dislocation characterization experiments, and stress calculations were conducted to explain the observed trends.