Wear Mechanisms of PTFE in Humidified Hydrogen Gas

2011 ◽  
Author(s):  
Kazuhiro Nakashima ◽  
Carlos Morillo ◽  
Yoshie Kurono ◽  
Yoshinori Sawae ◽  
Joichi Sugimura
Keyword(s):  
Transfer Film ◽  
Hydrogen Gas ◽  
Aisi 316L ◽  
Hydrogen Environment ◽  
Sealing Material ◽  
Safety And Reliability ◽  
Machine Elements ◽  
Rubbing Pair ◽  
Machine Systems ◽  
Pin On Disk

PTFE is used as sealing material of machine elements in hydrogen utilizing machine systems, such as fuel cell vehicles and related infrastructures. It is necessary to know the tribological property of sealing materials in hydrogen gas to realize safety and reliability of machine elements operated in hydrogen environment. In this study, humidity in gases was focused on and its effects on the friction and wear of rubbing pair of PTFE pin and AISI 316L disk was investigated in pin-on-disk wear apparatus. The result indicated that the humidity in hydrogen gas had little effect on the friction coefficient between PTFE and AISI 316L. However, the specific wear rate of unfilled PTFE was clearly affected by the humidity. The amount of PTFE transfer film formed on the stainless surface gradually decreased with decreasing the humidity in hydrogen gas. The similar results could be obtained in inert argon gas as well. Water molecules remained in gaseous environments would be included in the formation process of PTFE transfer film affect on formation of PTFE transfer film. The humidity in hydrogen gas should be regulated to ensure the tribological behavior of the PTFE/stainless sliding pair being used in the hydrogen environment.

scholarly journals Stacking Fault Energy in Relation to Hydrogen Environment Embrittlement of Metastable Austenitic Stainless CrNi-Steels

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1170
Author(s):  
Robert Fussik ◽  
Gero Egels ◽  
Werner Theisen ◽  
Sebastian Weber
Keyword(s):  
Phase Transformation ◽  
Intermediate Stage ◽  
Tensile Tests ◽  
Stacking Fault ◽  
Hydrogen Gas ◽  
Stacking Fault Energy ◽  
Austenitic Steels ◽  
Aisi 304L ◽  
Hydrogen Environment ◽  
Gas Atmosphere

Metastable austenitic steels react to plastic deformation with a thermally and/or mechanically induced martensitic phase transformation. The martensitic transformation to α’-martensite can take place directly or indirectly via the intermediate stage of ε-martensite from the single-phase austenite. This effect is influenced by the stacking fault energy (SFE) of austenitic steels. An SFE < 20 mJ/m2 is known to promote indirect conversion, while an SFE > 20 mJ/m2 promotes the direct conversion of austenite into α’-martensite. This relationship has thus far not been considered in relation to the hydrogen environment embrittlement (HEE) of metastable austenitic CrNi steels. To gain new insights into HEE under consideration of the SFE and martensite formation of metastable CrNi steels, tensile tests were carried out in this study at room temperature in an air environment and in a hydrogen gas atmosphere with a pressure of p = 10 MPa. These tests were conducted on a conventionally produced alloy AISI 304L and a laboratory-scale modification of this alloy. In terms of metal physics, the steels under consideration differed in the value of the experimentally determined SFE. The SFE of the AISI 304L was 22.7 ± 0.8 mJ/m2 and the SFE of the 304 mod alloy was 18.7 ± 0.4 mJ/m2. The tensile specimens tested in air revealed a direct γàα’ conversion for AISI 304L and an indirect γàεàα’ conversion for 304mod. From the results it could be deduced that the indirect phase transformation is responsible for a significant increase in the content of deformation-induced α’-martensite due to a reduction of the SFE value below 20 mJ/m2 in hydrogen gas atmosphere.

Hydrogen environment assisted cracking in X70 welding heat-affected zone under a high-pressure hydrogen gas

2020 ◽  
Vol 109 ◽  
pp. 102746
Author(s):  
Thanh Tuan Nguyen ◽  
Un Bong Beak ◽  
Jaeyeong Park ◽  
Seung Hoon Nahm ◽  
Naehyung Tak
Keyword(s):  
High Pressure ◽  
Heat Affected Zone ◽  
Hydrogen Gas ◽  
Hydrogen Environment ◽  
Pressure Hydrogen

Substitution of High-Pressure Charge by Electrolysis Charge and Hydrogen Environment Embrittlement Susceptibilities for Inconel 625 and SUS 316L

2006 ◽  
Author(s):  
Kota Murakami ◽  
Nobuaki Yabe ◽  
Hiroshi Suzuki ◽  
Kenichi Takai ◽  
Yukito Hagihara ◽  
...  
Keyword(s):  
High Pressure ◽  
Hydrogen Content ◽  
Hydrogen Diffusion ◽  
Hydrogen Charge ◽  
Hydrogen Desorption ◽  
Hydrogen Gas ◽  
Inconel 625 ◽  
Extension Rate ◽  
Hydrogen Degradation ◽  
Hydrogen Environment

Hydrogen-fuel-cell vehicles have been developed and the gaseous pressure in the current major storage tanks of the vehicles varies from 35 to 70 MPa because of the demand for the increase in running distance. Hydrogen refueling stations are required to be resistant to 100 MPa hydrogen gas and the alloys used for such stations are required to have an excellent resistance to hydrogen environment embrittlement (HEE). The purposes of the present study are to substitute the high-pressure gaseous charge of hydrogen by electrolysis charge and to evaluate hydrogen degradation susceptibilities for Inconel 625 and SUS 316L in the environments substituted by electrolysis charge. Electrolysis hydrogen was charged to Inconel 625 and SUS 316L at various electrolysis fugacities and gaseous hydrogen was charged from 0.3 to 45 MPa hydrogen gas at 90°C. Hydrogen states and contents were compared using thermal desorption analysis (TDA). Hydrogen degradation susceptibilities were evaluated using the slow strain rate technique (SSRT) at a constant extension rate of 8.6×10−6 /s at room temperature. The fundamental properties of thermal hydrogen desorption for Inconel 625 and SUS 316L were first analyzed to compare the hydrogen states after hydrogen charge by electrolysis and high pressure. The peak temperatures and profiles of hydrogen desorption do not change with charging temperature. When hydrogen is charged by electrolysis and high pressure until hydrogen saturation at 90°C, the peak temperatures and profiles are the same in both environments. This means that hydrogen diffusion during and hydrogen states after hydrogen absorption are independent of charging method in spite of the differences in adsorption and dissociation reaction on the specimen surfaces. Using Sieverts law, the fugacity of electrolysis can transform into gaseous pressure. This indicates that high-pressure hydrogen environments in pipes or other components at hydrogen refueling stations can be substituted by electrolysis charge. Fracture strain in Inconel 625 decreases as hydrogen content charged by electrolysis increases, whereas that in SUS 316L does not change regardless of the hydrogen content of 161.5 mass ppm. Grain boundary fracture is observed on the surface of Inconel 625 absorbing a hydrogen content of 27.5 mass ppm, which corresponds to 59.2 MPa hydrogen gas at R.T using Sieverts law. In contrast, the fracture surfaces of SUS 316L hydrogen-charged at extremely high fugacities remain ductile dimples. Thus, hydrogen degradation susceptibility is much lower for SUS 316L than for Inconel 625.

Tribological Characterization of Polymeric Sealing Materials in High Pressure Hydrogen Gas

2010 ◽  
Author(s):  
Yoshinori Sawae ◽  
Kanao Fukuda ◽  
Eiichi Miyakoshi ◽  
Shunichiro Doi ◽  
Hideki Watanabe ◽  
...  
Keyword(s):  
High Pressure ◽  
Stainless Steel ◽  
Wear Behavior ◽  
Hydrogen Gas ◽  
Gaseous Hydrogen ◽  
Surface Oxide Layer ◽  
Chemical Compositions ◽  
Hydrogen Environment ◽  
Sealing Materials ◽  
Pressure Hydrogen

Bearings and seals used in fuel cell vehicles and related hydrogen infrastructures are operating in pressurized gaseous hydrogen. However, there is a paucity of available data about the friction and wear behavior of materials in high pressure hydrogen gas. In this study, authors developed a pin-on-disk type apparatus enclosed in a high pressure vessel and characterized tribological behavior of polymeric sealing materials, such as polytetrafluoroethylene (PTFE) based composites, in gaseous hydrogen pressurized up to 40 MPa. As a result, the friction coefficient between graphite filled PTFE and austenitic stainless steel in 40 MPa hydrogen gas became lower compared with the friction in helium gas at the same pressure. The chemical composition of worn surfaces was analyzed by using X-ray photoelectron spectrometer (XPS) after the wear test. Results of the chemical analysis indicated that there were several differences in chemical compositions of polymer transfer film formed on the stainless disk surface between high pressure hydrogen environment and high pressure helium environment. In addition, the reduction of surface oxide layer of stainless steel was more significant in high pressure hydrogen gas. These particular effects of the pressurized hydrogen gas on the chemical condition of sliding surfaces might be responsible for the tribological characteristics in the high pressure hydrogen environment.

scholarly journals Зависимость механических и трибологических свойств a-C : H : SiO-=SUB=-x-=/SUB=--пленок от амплитуды напряжения смещения подложки

2021 ◽  
Vol 91 (8) ◽  
pp. 1286
Author(s):  
А.С. Гренадеров ◽  
А.А. Соловьёв ◽  
К.В. Оскомов ◽  
М.О. Жульков
Keyword(s):  
Bias Voltage ◽  
Steel Surface ◽  
Chemical Vapor ◽  
Stainless Steel Surface ◽  
Aisi 316L ◽  
Substrate Bias Voltage ◽  
Mechanical And Tribological Properties ◽  
316L Steel ◽  
The Coefficient Of Friction ◽  
Pin On Disk

The paper presents the AISI 316L stainless steel surface modification by plasma-assisted chemical vapor deposition of a-C:H:SiOx film using the pulsed bipolar substrate bias voltage. The mechanical and tribological properties of the a-C:H:SiOx film and the steel surface are examined using the nanoindentation method and the pin-on-disk tribometer, respectively. The optimum value is obtained for the amplitude of the negative pulse of the bipolar bias voltage, when the hardness of the a-C:H:SiOx film is high (19±2 GPa). This hardness value is 3.5 times greater, than the hardness of the AISI 316L steel surface (5.5±0.1 GPa). At the same time, the coefficient of friction of the film is low (0.08), which is 9 times lower than that of the steel (0.72). The wear rate values are found to be 8.5×10-7 and 3.7×10-5 mm3N-1m-1 for the coated and uncoated steel, respectively. The structure and composition of the obtained films are studied by Raman spectroscopy and scanning electron microscopy.

scholarly journals Effect of Relative Humidity on the Tribological Properties of Self-Lubricating H3BO3Films Formed on the Surface of Steel Suitable for Biomedical Applications

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
E. Hernández-Sanchez ◽  
A. Chino-Ulloa ◽  
J. C. Velazquez ◽  
H. Herrera-Hernández ◽  
R. Velázquez-Mancilla ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Boric Acid ◽  
Biomedical Applications ◽  
Surface Film ◽  
The Self ◽  
Aisi 316L ◽  
316L Steel ◽  
Continuous Surface ◽  
Short Annealing ◽  
Pin On Disk

The effect of environmental humidity on the self-lubricating properties of a thin film of boric acid (H3BO3) was evaluated. H3BO4films were successfully formed on the surface of AISI 316L steel. The study was conducted on AISI 316L steel because of its use in biomedical applications. First, the samples were exposed to boriding to generate a continuous surface layer of iron borides. The samples were then exposed to a short annealing process (SAP) at 1023 K for 5 min and cooled to room temperature while controlling the relative humidity (RH). Five different RH conditions were tested. The purpose of SAP was to promote the formation of a surface film of boric acid from the boron atoms present in the iron boride layers. The presence of the boric acid at the surface of the borided layer was confirmed by Raman spectroscopy and X-ray diffraction (XRD). The self-lubricating capability of the films was demonstrated using the pin-on-disk technique. The influence of RH was reflected by the friction coefficient (FC), as the samples cooled with 20% of RH exhibited FC values of 0.16, whereas the samples cooled at 60% RH showed FC values of 0.02.

Evaluation of Hydrogen Environment Embrittlement and Fatigue Properties of Stainless Steels in High Pressure Gaseous Hydrogen: Investigation of Materials Properties in High Pressure Gaseous Hydrogen—2

2007 ◽  
Author(s):  
Tomohiko Omura ◽  
Mitsuo Miyahara ◽  
Hiroyuki Semba ◽  
Masaaki Igarashi ◽  
Hiroyuki Hirata
Keyword(s):  
High Pressure ◽  
Aluminum Alloy ◽  
Fatigue Life ◽  
Stainless Steels ◽  
Austenitic Stainless Steels ◽  
Hydrogen Gas ◽  
Gaseous Hydrogen ◽  
Fatigue Properties ◽  
Chemical Compositions ◽  
Hydrogen Environment

Hydrogen environment embrittlement (HEE) susceptibility in high pressure gaseous hydrogen was investigated on 300 series austenitic stainless steels and A6061-T6 aluminum alloy. Tensile properties of these materials were evaluated by Slow Strain Rate Testing (SSRT) in gaseous hydrogen pressurized up to 90MPa (13053 psig) in the temperature range from −40 to 85 degrees C (−40 to 185 degrees F). HEE susceptibilities of austenitic stainless steels strongly depended upon the chemical compositions and testing temperatures. A6061-T6 aluminum alloy showed no degradation by hydrogen. Fatigue properties in high pressure gaseous hydrogen were evaluated by the external cyclic pressurization test using tubular specimens. The tubular specimen was filled with high pressure hydrogen gas, and the outside of the specimen was cyclically pressurized with water. Type 304 showed a decrease in the fatigue life in hydrogen gas, while as for type 316L and A6061-T6 the difference of the fatigue life between hydrogen and argon environments was small. HEE susceptibility of investigated materials was discussed based on the stability of an austenitic structure.

Effect of Hydrogen Gas Pressure on the Mechanical Properties of Low Alloy Steel for Hydrogen Pressure Vessels

2007 ◽  
Author(s):  
Yoru Wada ◽  
Ryoji Ishigaki ◽  
Yasuhiko Tanaka ◽  
Tadao Iwadate ◽  
Keizo Ohnishi
Keyword(s):  
Crack Growth ◽  
Hydrogen Pressure ◽  
Stable Crack Growth ◽  
Pressure Vessels ◽  
Hydrogen Gas ◽  
Gaseous Hydrogen ◽  
Strength Level ◽  
Crack Growth Behavior ◽  
Test Machine ◽  
Hydrogen Environment

To provide engineering data useful in design, manufacture and operation of hydrogen storage vessels in hydrogen refueling stations, fatigue test machine equipped with high-pressure hydrogen autoclave was introduced. The effect of steel’s strength level, temperature effect, fracture toughness and pressure effect were evaluated in gaseous hydrogen environment. When steel’s strength level exceeds around 930MPa to 1000MPa, the elongation and notch tensile properties deleteriously degraded. The elongation reduction by the effect of hydrogen increased with lowering the temperature. The same sensitivity to temperature on crack growth behavior was observed. However, it was shown that the gaseous hydrogen environment only affect the slow stable crack growth but did not affect the critical flaw growth of the steel at low temperature, i.e. fast fracture. The pressure dependence of notch tensile strength ranging from 0.1MPa to 75MPa hydrogen pressure shows approximately 1/2 power dependence.

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