Hannu Hänninen - Academia.edu (original) (raw)

Papers by Hannu Hänninen

International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017

An experimental program has been conducted in order to understand how the spinodal decomposition ... more An experimental program has been conducted in order to understand how the spinodal decomposition may affect material properties changes in Type 316L BWR pipe weld metals. The program includeed Charpy-V, tensile, SCC crack growth and in-situ fracture toughness testing as a function of aging time and temperature. In this paper we report results of fracture toughness, SCC crack growth rate and fracture morphology studies of Type 316L stainless steel weld metals under simulated BWR conditions, consisting of 288°C, high purity water containing 300 ppb dissolved oxygen (defined for purposes of this paper as “In-Situ”). SCC crack growth results show an approximately 2X increase in crack growth rate over that of the unaged material. In-situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40% over the corresponding at-temperature air values. Detailed analysis of the results strongly suggest that spinodal decomposition is responsible for the degradation in properties measured ex-environment. Analysis of the results also strongly suggests that the in-situ properties degradation is the result of hydrogen absorbed by the material during exposure to the high temperature aqueous environment.

Social Science Research Network, 2022

Suppressing hydrogen embrittlement in martensitic steels is a longstanding challenge. Here, we st... more Suppressing hydrogen embrittlement in martensitic steels is a longstanding challenge. Here, we studied the effects of prior austenite grain (PAG) shape and size with a 0.25C steel utilising novel in situ H-charging, constant-displacement Tuning-fork testing (TFT) and H-permeation tests. Anisotropic elongated PAG structure has enhanced HE resistance transverse to the rolling direction (RD) with slower crack propagation rate (CPR) and quasi-cleavage fracture. Larger elongated grains are prone to intergranular fracture when crack propagates in RD. Reaustenitised equiaxed PAGs fail with intergranular cracking, which accelerates max CPR up to threefold compared to quasi-cleavage. All the microstructures have similar H-diffusion ~5 × 10 − 7 cm 2 /s and density of reversible H-traps N T ~ 3 × 10 16 , irrespective of PAG surface area, indicating that PAG boundaries are not effective diffusion paths. Deformed PAG boundaries mitigate susceptibility to intergranular cracking.

Corrosion Reviews, May 15, 2023

The main objective of the 'Innovative stainless steel applications in transport vehicles' INSAPTR... more The main objective of the 'Innovative stainless steel applications in transport vehicles' INSAPTRANS project was to disseminate the technical knowledge and application experience from two recently finished ECSC/RFCS-funded research projects, 'Stainless steels in bus constructions' ('Stainless steel bus') and 'Development of lightweight train and metro cars by using ultra high strength stainless steels' (DOLTRAC). The main project task was the preparation of a design handbook from the results data of the underlying projects, demonstrating the full potential of, and giving guidelines for, the application of safe and lightweight stainless steel structures in ground transport applications. The handbook was distributed, and is still available to the public free of charge in both paper and electronic forms. Interested in European research? RTD info is our quarterly magazine keeping you in touch with main developments (results, programmes, events, etc.). It is available in English, French and German. A free sample copy or free subscription can be obtained from:

Steam generators (SG) are key components in pressurized water reactors (PWR). Their task is to co... more Steam generators (SG) are key components in pressurized water reactors (PWR). Their task is to convert heat generated in nuclear reaction into steam for turbines. This is done in a heat exchanger where the primary pressurized water (radioactive) heats and boils secondary water (non-radioactive). The heat exchanger part of SG is a tubular structure consisting of thousands of tubes manufactured from stainless steels or nickel based alloys. For materials selection point of view SG tubes have several aspects that have to be taken into account. They must withstand both chemical and mechanical load but at the same time must have good physical properties in order to conduct heat between water cycles. SGs in PWRs are at the boundary of primary and secondary water cycle loops. Therefore their structural integrity is important for safe NPP operation. This paper reviews and compares alternative materials used in SG-tubes based on their physical and mechanical properties using Cambridge Engineering Selector-software (CES).

The Tekes project Structural integrity of Ni-base alloy welds (SINI) was carried out at Aalto Uni... more The Tekes project Structural integrity of Ni-base alloy welds (SINI) was carried out at Aalto University and VTT during the period from 2010 to 2014. In nuclear industry applications, the degradation of Ni-base alloy dissimilar metal welds (DMWs), both in pressurised water reactor (PWR) and in boiling water reactor (BWR) plants, is an extensive international problem. The project participates with ongoing international cooperation in USA (Electric Power Research Institute EPRI, Alloy 690/52/152 PWSCC Research Collaboration) and in Japan (Tohoku University) for the conduction of new Ni-base alloy research. The research need is actual, especially because indications have been found in the DMWs in the reactor pressure vessel nozzle of BWRs similar to Finnish BWR designs and European pressurised water reactor (EPR PWR)-plant under construction contains a large number of varying and new types of dissimilar metal welds of which no previous experience is available. The main focus of the project was to investigate the weldability of Alloy 690 base metal corresponding filler metal Alloy 52 and the properties of the welded joint. Comparable reactor pressure vessel (RPV) safe-end weld joint was made by narrow-gap tungsten inert gas (TIG) welding with Alloy 52 filler metal for research purposes. Also prototypical BWR reactor pressure vessel (RPV) safe-end weld joint was made with Alloy 82/182 filler metals. Determination of the mechanical properties and characterization of the microstructures of the welded joints were conducted. Crack initiation tests in autoclave were made in different environments. After PINC (Program for the Inspection of Nickel Alloy Components) round-robin program new PARENT (Program to Assess Reliability of Emerging Nondestructive Techniques for Dissimilar Metal Welds) round-robin program was started where VTT participated. Based on the PINC results, new non-destructive testing methods were developed to enhance the reliability of detection and accuracy of sizing of flaws in nickel-based alloy dissimilar metal welds. Separate reports: 1. Holmström, P. (2012), The effect of mismatch on the mechanical properties of a dissimilar metal weld. M.Sc. Thesis, Aalto University, Espoo, Finland, 162 p. + app. 4 p.

Materials Science and Technology, Dec 1, 2004

ABSTRACT

International Hydrogen Conference (IHC 2016): Materials Performance in Hydrogen Environments, 2017

An experimental program has been conducted in order to understand how the spinodal decomposition ... more An experimental program has been conducted in order to understand how the spinodal decomposition may affect material properties changes in Type 316L BWR pipe weld metals. The program includeed Charpy-V, tensile, SCC crack growth and in-situ fracture toughness testing as a function of aging time and temperature. In this paper we report results of fracture toughness, SCC crack growth rate and fracture morphology studies of Type 316L stainless steel weld metals under simulated BWR conditions, consisting of 288°C, high purity water containing 300 ppb dissolved oxygen (defined for purposes of this paper as “In-Situ”). SCC crack growth results show an approximately 2X increase in crack growth rate over that of the unaged material. In-situ fracture toughness measurements indicate that environmental exposure can result in a reduction of toughness by up to 40% over the corresponding at-temperature air values. Detailed analysis of the results strongly suggest that spinodal decomposition is responsible for the degradation in properties measured ex-environment. Analysis of the results also strongly suggests that the in-situ properties degradation is the result of hydrogen absorbed by the material during exposure to the high temperature aqueous environment.

Social Science Research Network, 2022

Suppressing hydrogen embrittlement in martensitic steels is a longstanding challenge. Here, we st... more Suppressing hydrogen embrittlement in martensitic steels is a longstanding challenge. Here, we studied the effects of prior austenite grain (PAG) shape and size with a 0.25C steel utilising novel in situ H-charging, constant-displacement Tuning-fork testing (TFT) and H-permeation tests. Anisotropic elongated PAG structure has enhanced HE resistance transverse to the rolling direction (RD) with slower crack propagation rate (CPR) and quasi-cleavage fracture. Larger elongated grains are prone to intergranular fracture when crack propagates in RD. Reaustenitised equiaxed PAGs fail with intergranular cracking, which accelerates max CPR up to threefold compared to quasi-cleavage. All the microstructures have similar H-diffusion ~5 × 10 − 7 cm 2 /s and density of reversible H-traps N T ~ 3 × 10 16 , irrespective of PAG surface area, indicating that PAG boundaries are not effective diffusion paths. Deformed PAG boundaries mitigate susceptibility to intergranular cracking.

Corrosion Reviews, May 15, 2023

The main objective of the 'Innovative stainless steel applications in transport vehicles' INSAPTR... more The main objective of the 'Innovative stainless steel applications in transport vehicles' INSAPTRANS project was to disseminate the technical knowledge and application experience from two recently finished ECSC/RFCS-funded research projects, 'Stainless steels in bus constructions' ('Stainless steel bus') and 'Development of lightweight train and metro cars by using ultra high strength stainless steels' (DOLTRAC). The main project task was the preparation of a design handbook from the results data of the underlying projects, demonstrating the full potential of, and giving guidelines for, the application of safe and lightweight stainless steel structures in ground transport applications. The handbook was distributed, and is still available to the public free of charge in both paper and electronic forms. Interested in European research? RTD info is our quarterly magazine keeping you in touch with main developments (results, programmes, events, etc.). It is available in English, French and German. A free sample copy or free subscription can be obtained from:

Steam generators (SG) are key components in pressurized water reactors (PWR). Their task is to co... more Steam generators (SG) are key components in pressurized water reactors (PWR). Their task is to convert heat generated in nuclear reaction into steam for turbines. This is done in a heat exchanger where the primary pressurized water (radioactive) heats and boils secondary water (non-radioactive). The heat exchanger part of SG is a tubular structure consisting of thousands of tubes manufactured from stainless steels or nickel based alloys. For materials selection point of view SG tubes have several aspects that have to be taken into account. They must withstand both chemical and mechanical load but at the same time must have good physical properties in order to conduct heat between water cycles. SGs in PWRs are at the boundary of primary and secondary water cycle loops. Therefore their structural integrity is important for safe NPP operation. This paper reviews and compares alternative materials used in SG-tubes based on their physical and mechanical properties using Cambridge Engineering Selector-software (CES).

The Tekes project Structural integrity of Ni-base alloy welds (SINI) was carried out at Aalto Uni... more The Tekes project Structural integrity of Ni-base alloy welds (SINI) was carried out at Aalto University and VTT during the period from 2010 to 2014. In nuclear industry applications, the degradation of Ni-base alloy dissimilar metal welds (DMWs), both in pressurised water reactor (PWR) and in boiling water reactor (BWR) plants, is an extensive international problem. The project participates with ongoing international cooperation in USA (Electric Power Research Institute EPRI, Alloy 690/52/152 PWSCC Research Collaboration) and in Japan (Tohoku University) for the conduction of new Ni-base alloy research. The research need is actual, especially because indications have been found in the DMWs in the reactor pressure vessel nozzle of BWRs similar to Finnish BWR designs and European pressurised water reactor (EPR PWR)-plant under construction contains a large number of varying and new types of dissimilar metal welds of which no previous experience is available. The main focus of the project was to investigate the weldability of Alloy 690 base metal corresponding filler metal Alloy 52 and the properties of the welded joint. Comparable reactor pressure vessel (RPV) safe-end weld joint was made by narrow-gap tungsten inert gas (TIG) welding with Alloy 52 filler metal for research purposes. Also prototypical BWR reactor pressure vessel (RPV) safe-end weld joint was made with Alloy 82/182 filler metals. Determination of the mechanical properties and characterization of the microstructures of the welded joints were conducted. Crack initiation tests in autoclave were made in different environments. After PINC (Program for the Inspection of Nickel Alloy Components) round-robin program new PARENT (Program to Assess Reliability of Emerging Nondestructive Techniques for Dissimilar Metal Welds) round-robin program was started where VTT participated. Based on the PINC results, new non-destructive testing methods were developed to enhance the reliability of detection and accuracy of sizing of flaws in nickel-based alloy dissimilar metal welds. Separate reports: 1. Holmström, P. (2012), The effect of mismatch on the mechanical properties of a dissimilar metal weld. M.Sc. Thesis, Aalto University, Espoo, Finland, 162 p. + app. 4 p.

Materials Science and Technology, Dec 1, 2004

ABSTRACT