ProgramMaster Logo
Conference Tools for 2020 AWS Professional Program
Login
Register as a New User
Help
Submit An Abstract
Propose A Symposium
Presenter/Author Tools
Organizer/Editor Tools
About this Abstract
Meeting 2020 AWS Professional Program
Symposium 2020 AWS Professional Program
Presentation Title Microstructure and Mechanical Properties of Intercritical-Treated Grade 91 Steel
Author(s) Yiyu Wang, Wei Zhang, Yong Chae Lim, Yanli Wang, Zhili Feng
On-Site Speaker (Planned) Yiyu Wang
Abstract Scope * Introduction Intercritical heat affected zone (ICHAZ) exposed to an intercritical peak temperature between AC1 and AC3 has been reported as one of the most susceptible regions to premature creep failures, for example, Type IV cracking, in creep resistant steel weldments. However, cracking mechanisms within the ICHAZ itself are not fully clear and needs further clarifications. Partial austenization and precipitate dissolution in intercritical heat treatment result with highly localized microstructure heterogeneity, which leads to large variations in creep deformation behaviors. Microstructure evolutions promoted by post weld heat treatment could make the situation even worse by accelerating creep strength degradation. Building a close correlation between these complex microstructures generated by the intercritical thermal cycles and mechanical properties, especially creep resistance at elevated temperature is challenging but essential. * Experimental Procedures In this study, Grade 91 steel (plate) was used as the base metal (BM). Three heat-treated specimens, designated as BM, IT, and ITT, were analyzed in comparison. The "BM" was normalized at 1100 C for 30 min and tempered at 760 C for 60 min. The "IT" specimen was exposed to an intercritical treatment at 860 C for 5 min. Following the intercritical treatment, an additional tempering at 760 C for 120 min was applied to the "ITT" specimen. Mechanical properties, including hardness, room-temperature tensile strength, and high-temperature creep strength, were evaluated for the three heat-treated specimens. Microstructure of the BM and heat-treated specimens before and after creep testing was characterized with a Zeiss AXIO optical microscope, a Hitachi S4800 field-emission scanning electron microscopy (FESEM), and a JEOL 6500F FESEM equipped with an EDAX electron backscatter diffraction (EBSD) system. * Results and discussion The BM shows a typical structure of tempered martensite. Fine precipitates (mainly M23C6 carbides) distribute along the prior austenite grain boundaries (PAGBs) and martensitic packets/blocks after tempering. The complex structures in the intercritical-treated specimen (IT) consist of 68.9% newly-transformed martensite (NTM) grains from partial austenization and 31.1% over-tempered martensite (OTM) grains. These OTMs are nearly free of internal sub-boundaries and coarse precipitates inside or along grain boundaries. Dissolution of precipitates led to a much lower precipitate density, comparing with that in the BM. Undissolved but coarsened precipitates are also observed inside those NTMs. Fine equiaxed grains are observed as the major structure in the ITT specimen after an additional tempering. The BM has a moderate hardness of about 247 HV0.5. The IT specimen exhibits the highest hardness of 332 HV0.5, which is contributed from those NTM grains. The additional tempering led to the ITT specimen's lowest hardness of 178 HV0.5. The yield strength and ultimate tensile strength (UTS) of the BM are 611 MPa and 739 MPa, respectively. The elongation of the BM is 20 %. The IT specimen exhibits the largest strength with a yield strength of 690 MPa, an UTS of 1054 MPa, and the lowest elongation of 17 %. These high strength and low ductility are believed to be contributed from those new-transformed martensite grains. After additional tempering, the yield strength and UTS of the ITT specimen decreased significantly to 419 MPa and 596 MPa, respectively. Accordingly, the elongation of the ITT specimen increased to 30 %. Creep strengths of the three specimens tested at 650 C and 100 MPa are compared. The BM shows the highest creep resistance with a minimum creep strain rate of 0.0013%/h. Creep curves of the IT and ITT specimens are not typical three-stage creep curve. The specimens quickly went into the tertiary creep stage with a very short secondary creep. The IT and ITT specimens fractured with a total life of 31.8 h and 19.2 h, respectively. The minimum creep strain rate of the ITT specimen is 0.49 %/h, which is twice of the 0.24 %/h of the IT specimen. * Conclusion In this study, microstructure and mechanical properties of intercritical-treated structure in Grade 91 steel were characterized and tested. The partial austenization during an intercritical treatment led to transformation of new martensite (69.9%) in the treated specimen. 31.1% tempered martensite were over-tempered close to ferrite. Undissolved precipitates coarsened and remained in those newly-transformed martensite grains. The significantly increased hardness (332 HV0.5) and tensile strength (1054 MPa) were contributed from those transformed martensite grains. After an additional tempering at 760 C, an obvious grain growth of those over-tempered martensite occurred. The fine newly-transformed martensite laths became fine equiaxed grains. Continuous grain growth pushed the coarsened precipitates together. These structural evolutions led to a lowered hardness of 178 HV0.5 and a reduced tensile strength of 596 MPa in The ITT specimen. The IT specimen shows a higher creep strength at 650 C than that of the ITT specimen. But both the IT and ITT specimens exhibit extremely low creep resistance, comparing with the BM. Severe creep deformation was observed on the creep fractured specimens. Grain growth is still noticeable in the crept specimens even with this short-term creep test. Elongation of coarsened grains from the over-tempered martensite contributed to plastic fracture of the specimens. Inclusions have assisted nucleation and growth of cavities and micro-cracks.
Proceedings Inclusion? Definite: Other (describe below)

OTHER PAPERS PLANNED FOR THIS SYMPOSIUM

101st Year of the American Welding Society: Changes in Welding & Outlook
Additive Manufacture of the First Concentric Reduction Sleeve Used in the Brazilian Oil and Gas Industry
Additive Manufacturing Using Semi-Solids
Advances in Robotic Arc DED AM for Shipbuilding
An Efficient Part-Scale Model to Predict Distortion on Overhang Structure in Laser Powder Bed Fusion Additive Manufacturing
An Overview of LME Cracking in Advanced High Strength Automotive Steels
Analysis and Control of Humping Defect in Laser Wire Direct Deposition Process
Analysis of Dynamic Evolution of Weld Pool for the Real-Time Monitoring of Penetration Using Deep Learning
Avoiding Tool Failure and Defects in Friction Stir Welding Using Machine Learning
Bondline Properties in High Frequency Welding of Steels
Building a Digital Twin for Welding Process Monitoring, Visualization and Control Based on Deep Learning
Characterization of the Fourth Generation of Nickel-Chromium Welding Products for Nuclear Service
Chipping Study of Friction Element Welding
Computational Modeling on Defect Formation during Self-Reacting Friction Stir Welding
Copper Foil Welding for Battery Manufacturing
Correlating Laser Power and Microstructural Properties of Additively Manufactured Ti-6Al-4V Fabricated by Directed Energy Deposition
Creep Strength Variation in Simulated ICHAZs of Grade 91 Steel
Design of an Austenitic Steel Weldment System Using ICME
Development of Industry 4.0 Software for Arc-Welding Energy Monitoring and Traceability
Development of Interlayer Technology to Join Advanced Materials for the Transportation Industry
Development, Optimization, and Mechanical Testing of ER80S-G Girth Welds on Internally Clad API 5L Grade X65 Pipes
Dissimilar Joining of Carbon Fiber Reinforced Composite to Magnesium Alloy by Friction Self-Piercing Riveting Process
Effect of Aluminum on Primary Carbides in Chromium Carbide Overlays
Effect of Chemical Composition of Welding Consumable on Slag Formation and Weld Corrosion Resistance
Effect of Heating Rate on Austenite Formation in a Low Carbon Microalloyed Steel
Effect of Phase Transformations on Mechanical Properties of Ti Free Grade 300 Maraging Steel Manufactured by Laser Powder Bed Fusion (LPBF)
Electron Beam Brazing of Stainless Steel using NIORO Filler Metal
Evaluation of Braze Joints for Hydrogen Purification Diffuser
Experimental Studies of Wire Feeding Electron Beam Welding-Brazing of Aluminum to Stainless Steel and Titanium
Failure Analysis: Evaluating a Low Strength Solder Joint
Fundamentals and Techniques for High-Speed Imaging of Welding
GMA Weldability Between AISI 316L Pipes Manufactured by Conventional and Additive Manufacturing Processes
High Deposition Gas Metal Arc Variants for Directed Energy Deposition Additive Manufacturing
High Efficient Modification of Arc Welding Processes via Modeling and Sensing Weld Pool Behaviors
High Penetration Buried Arc Gas Metal Arc Welding for Shipyard Steel Plate Fabrication
Hybrid Laser Welding on API 5L Pipeline Steels
Hyper-Duplex Stainless Steel Intermetallic Precipitation Behavior during Cladding
Improper Weld Field Fabrication Caused Premature Failure
In-situ Measurement and Numerical Simulation for Linear Friction Welding of Complex Titanium Structures
In-situ Synchrotron Diffraction Measurement of Solidification Behavior during Laser Welding of Multi-Principal-Component Alloy
Induction Heating-Assisted Friction Stir Welding in Low Carbon Steel Plates
Influence of Composition on the Solidification and Mechanical Properties of HP-Modified Heat-Resistant Austenitic Stainless Steels
Influence of Cooling Rate on Microstructure Formation in Rapid Solidification of Ni2MnGa Alloy
Influence of Hydrogen on the Softened HAZ in Various Carbon Steel Welds
Integrated Computational Materials Engineering (ICME) Techniques to Enable a Material-Informed Digital Twin Prototype for Marine Structures
Integrated Modeling of Multi-Process Automotive Lap Joining – Part 3: Microstructure and Mechanical Properties
Investigation of a Curly Toolpath in Friction Stir Welding
Investigation of Laves Phase Formation in Inconel 718 Fabricated by Laser Powder Bed Fusion
Investigation of Thermally Assisted Friction Element Welding
Joining Dissimilar Metals of DP590 Steel and AZ31B Magnesium Sheets by Ultrasonic Spot Welding
Low-cycle Fatigue Evaluations of Ni-Steel Dissimilar Joints for Coke Drum Welding Repairs
Machine Learning for Automatic Recognition of Microstructures
Material Characteristics of Wire Arc Additive Manufactured Inconel 718
Mechanical Properties Assessment of Carbon and Low-Alloy Steel Parts Built by GMA-DED
Mechanics of the Solid-State Bonding and Prediction of Thermomechanical Responses in Friction Stir Welding
Mechanistic Models and Machine Learning to Mitigate Common Defects in Metal Printing
Metallic Powder Core Tubular Wire Development for Additive Manufacturing
Microstructural and Mechanical Property Characterization of Reaction Synthesis Aluminum Metal Matrix Composites Produced by Additive Manufacturing
Microstructural Characterization and Mechanical Property Evaluation of Fusion Zones in a 10 wt% Ni Steel Weld Metal
Microstructure and Mechanical Properties of 410 Stainless Steel Using Different Shielding Gases in the Wire-Arc Additive Process
Microstructure and Mechanical Properties of Intercritical-Treated Grade 91 Steel
Microstructures and Microhardness of LENS DED Deposits of Ti/TiC MMCs
Mitigation of Liquid Metal Embrittlement in Galvannealed AHSS Welds Using High Entropy Alloy Filler
Modal Analysis of Ultrasonic Welding to Enable Multi-Spot Dissimilar Material Joining
Modeling and Comparing Human Welder’s Operation Between Stereo Camera and Virtual Reality
Modeling of In-Situ Tempering of a Creep Resistant Ferritic Martensitic Steel during Multi-Layer Additive Manufacturing
Modeling of Mash Seam Welding Using Improved Electro-Thermo-Mechanical Simulation
Modelling of Laser Cladding Using Gaussian Heat Source Profile and Verification with Experimental Results
Multi-Scale and Multi-Physics Modeling of Process-Microstructure-Property Relationship in Metal Additive Manufacturing
New Approaches in Friction Welding Advanced PM Nickel Base Superalloys
Novel Thermal Spray Alloy for Corrosive Applications
Numerical Study on Heat Transfer Mechanisms in Electric Arc Columns
Optimization of Tool Path and Microstructure in Large Scale Metal Additive Manufacturing with Multi-Heat Sources
Phase Transformation Analysis and Microstructural Characterization of the Heat Affected Zone in Grade 92 Steel Welds
Procedure Qualification Schemes and Build Results for Directed Energy Deposition Additive Manufacturing
Process Control Using Predictive Equations for Zero Programming Laser Cladding Facility
Process, Microstructure and Fracture Mode of Magnesium to Steel Dissimilar Metal Spot Joints
Pulsed-Arc Welding of Battery Tabs for Vehicle Electrification
PWHT of 347SS Weldments for Thermal Energy Storage Concentrating Solar Power Applications
Real-Time Prediction of Weld Penetration from Dynamic Weld Pool-Arc Images Deep Learning Based
Recent Developments in Metal Additive Manufacturing
Research and Development of a Novel TIG Welding Technology for Joining Thin Sheets Applying in Metal Forming Field
Residual Stress Measurement on High-Strength Steel Panels for Shipbuilding Application
Resistance Spot Welding Challenges, Root Causes, and Suggested Welding Practices When Welding 3rd Generation AHSS
Role of Retained Austenite in Mechanical Response of Additively Manufactured 17-4 PH Stainless Steel
Simulation of Laser Brazing of Sheet Panels and Parametric Studies on Thermally-Induced Distortion Reduction
SMART Camera in the Welding Torch for Manual Welding Quality and Productivity
State-of-the-Art of Underwater Wet Welding Practice
Strain Ageing of Inconel 740H and 347H
Suitability of Using Thin Wire in Wire Arc Additive Manufacturing (GMA-DED)
Sulfur Implantation in Alloy 690 for the Study of Ductility-Dip Cracking
Surface Modification via Metal Deposition and Selective Alteration
Surface Treatment of 3-D Printing Parts
Temper Bead Welding
The Correlation of Hardness to Toughness and the Superior Low Temperature Impact Properties of Martensite in RPV Steels Applied to Temper Bead Qualification
The Role of Inclusions in Duplex Stainless Steels Produced Using Laser-Based Directed Energy Deposition Additive Manufacturing
Ultrasonic Vibration Assisted Electron Beam Additive Manufacturing
Unit Block-Based Process Planning Strategy of WAAM for Complex Shell-Shaped Component
Universal Representation of Arc Shape and Arc Column Characteristics for DC Electric Arcs Burning in Argon and Helium
Variation in Microstructure and Properties in the Heat Affected and Fusion Zones of Low-Density Fe-Mn-Al-C Steel Welds
Variations in Microstructure and Mechanical Properties with Solidification Mode in L-PBF 316L
Weld Metal Cooling Rate-Mechanical Property Response of Fe-10Ni Steel Gas Metal Arc Weld Deposits and Other Experimental Observations
Weldability and Microstructural Evolution of Fusion Welds in a γ’ Strengthened TRIP Steel
Welding and Joining Challenges in the Astrospace Industry
Welding of FeMnAl High-Manganese Lightweight Steel
Wetting and Low Temperature Bonding of Zirconia Metallized with Ti-Containing Active Solders

Questions about ProgramMaster? Contact programming@programmaster.org