The Tribology of Amorphous Surfaces Formed by Wear of Thermal Spray Coatings

1998 ◽  
Author(s):  
D.M. Scruggs
Keyword(s):  
High Energy ◽  
X Ray Diffraction ◽  
Coating Structure ◽  
Flow Process ◽  
Wear Process ◽  
Spray Coatings ◽  
Fundamental Properties ◽  
Coating Characteristics ◽  
Equipment Wear ◽  
Temperature Crystallization

Abstract This paper describes the wear induced transformation of crystaline metal surfaces into amorphous and/or microcrystalline surfaces that exhibit gross changes in the fundamental properties of friction, wear, hardness and toughness. The coatings are applied using wire and powder feed to TWAS and HVOF equipment. Wear processes investigated include adhesive wear, low stress abrasion, grinding wear and galling. The effects of chemical makeup of the surfaces and the alloy structure are examined using microscopy and x-ray diffraction. The surface & underlying coating characteristics including roughness, microstructure, hardness and friction coefficient are determined. Results show that the surface structure is dependent on the wear vector. The structural transformation is a function of the chemical makeup and intrinsic wear resistance of the crystalline alloy coupled with the energy input of the wear process. High energy wear such as grinding wear can overcome the transformation. The results also suggest that the micro-welding that occurs between asperities in crystalline alloys is replaced by a flow process on the transformed surface. Coating structure, glass transition temperature, crystallization temperature and critical cooling rate of the transformed surface are much more significant than the chemistry of the alloy once the transformation takes place.

scholarly journals Toward Elusive Iodoplumbic Acid HPbI3: High-Energy Isochoric Synthesis of Hydronium Forms of the PbI3- Anion at Elevated Temperature and Pressure

2021 ◽  
Author(s):  
Szymon Sobczak ◽  
Athena M. Fidelli ◽  
Jean-Louis Do ◽  
George P. Demopoulos ◽  
Audrey Moores ◽  
...  
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Hydriodic Acid ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
High Pressure And Temperature ◽  
One Dimensional ◽  
Diamond Anvil ◽  
Temperature And Pressure ◽  
Temperature Crystallization

High-pressure and -temperature crystallization and X-ray diffraction crystallography have revealed hydronium forms of the proposed but never demonstrated iodoplumbic acid HPbI<sub>3</sub>. Depending on the pressure range, the reaction of PbI2 and aqueous concentrated hydriodic acid under isochoric conditions in a diamond anvil cell (DAC) held between 0.11 and 1.20 GPa produces two hydrated hydronium salts with compositions [H<sub>3</sub>O][PbI<sub>3</sub>].<i>n</i>H<sub>2</sub>O (<i>n</i>=3,4). Comprised of polymeric one-dimensional PbI<sub>3</sub><sup>-</sup> anions, these hydronium salts represent the so far best match for the elusive HPbI<sub>3</sub> progenitor of hybrid lead perovskites. We also reveal a new three-dimensional polymorph of lead iodide (PbI<sub>2</sub>), so far known only as a layered structure.<br>

scholarly journals Toward Elusive Iodoplumbic Acid HPbI3: High-Energy Isochoric Synthesis of Hydronium Forms of the PbI3- Anion at Elevated Temperature and Pressure

2021 ◽  
Author(s):  
Szymon Sobczak ◽  
Athena M. Fidelli ◽  
Jean-Louis Do ◽  
George P. Demopoulos ◽  
Audrey Moores ◽  
...  
Keyword(s):  
Three Dimensional ◽  
High Energy ◽  
Hydriodic Acid ◽  
X Ray Diffraction ◽  
Lead Iodide ◽  
High Pressure And Temperature ◽  
One Dimensional ◽  
Diamond Anvil ◽  
Temperature And Pressure ◽  
Temperature Crystallization

High-pressure and -temperature crystallization and X-ray diffraction crystallography have revealed hydronium forms of the proposed but never demonstrated iodoplumbic acid HPbI<sub>3</sub>. Depending on the pressure range, the reaction of PbI2 and aqueous concentrated hydriodic acid under isochoric conditions in a diamond anvil cell (DAC) held between 0.11 and 1.20 GPa produces two hydrated hydronium salts with compositions [H<sub>3</sub>O][PbI<sub>3</sub>].<i>n</i>H<sub>2</sub>O (<i>n</i>=3,4). Comprised of polymeric one-dimensional PbI<sub>3</sub><sup>-</sup> anions, these hydronium salts represent the so far best match for the elusive HPbI<sub>3</sub> progenitor of hybrid lead perovskites. We also reveal a new three-dimensional polymorph of lead iodide (PbI<sub>2</sub>), so far known only as a layered structure.<br>

Characterizations of Synthetic 8mol% YSZ with Comparison to 3mol %YSZ for HT-SOFC

2020 ◽  
Vol 38 (4A) ◽  
pp. 491-500
Author(s):  
Abeer F. Al-Attar ◽  
Saad B. H. Farid ◽  
Fadhil A. Hashim
Keyword(s):  
Ionic Conductivity ◽  
Electrochemical Impedance ◽  
Structural Information ◽  
Impedance Analysis ◽  
High Energy ◽  
Yttria Stabilized Zirconia ◽  
X Ray Diffraction ◽  
Stabilized Zirconia ◽  
Powder Morphology ◽  
X Ray

In this work, Yttria (Y2O3) was successfully doped into tetragonal 3mol% yttria stabilized Zirconia (3YSZ) by high energy-mechanical milling to synthesize 8mol% yttria stabilized Zirconia (8YSZ) used as an electrolyte for high temperature solid oxide fuel cells (HT-SOFC). This work aims to evaluate the densification and ionic conductivity of the sintered electrolytes at 1650°C. The bulk density was measured according to ASTM C373-17. The powder morphology and the microstructure of the sintered electrolytes were analyzed via Field Emission Scanning Electron Microscopy (FESEM). The chemical analysis was obtained with Energy-dispersive X-ray spectroscopy (EDS). Also, X-ray diffraction (XRD) was used to obtain structural information of the starting materials and the sintered electrolytes. The ionic conductivity was obtained through electrochemical impedance spectroscopy (EIS) in the air as a function of temperatures at a frequency range of 100(mHz)-100(kHz). It is found that the 3YSZ has a higher density than the 8YSZ. The impedance analysis showed that the ionic conductivity of the prepared 8YSZ at 800°C is0.906 (S.cm) and it was 0.214(S.cm) of the 3YSZ. Besides, 8YSZ has a lower activation energy 0.774(eV) than that of the 3YSZ 0.901(eV). Thus, the prepared 8YSZ can be nominated as an electrolyte for the HT-SOFC.

scholarly journals Effects of Recycled Fe2O3 Nanofiller on the Structural, Thermal, Mechanical, Dielectric, and Magnetic Properties of PTFE Matrix

Polymers ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 2332
Author(s):  
Ahmad Mamoun Khamis ◽  
Zulkifly Abbas ◽  
Raba’ah Syahidah Azis ◽  
Ebenezer Ekow Mensah ◽  
Ibrahim Abubakar Alhaji
Keyword(s):  
Electron Microscopy ◽  
High Energy ◽  
Filler Loading ◽  
Complex Permeability ◽  
X Ray Diffraction ◽  
Thermal Expansion Coefficients ◽  
Transmission Electron ◽  
Energy Ball ◽  
Hematite Fe2o3 ◽  
Ptfe Composites

The purpose of this study was to improve the dielectric, magnetic, and thermal properties of polytetrafluoroethylene (PTFE) composites using recycled Fe2O3 (rFe2O3) nanofiller. Hematite (Fe2O3) was recycled from mill scale waste and the particle size was reduced to 11.3 nm after 6 h of high-energy ball milling. Different compositions (5–25 wt %) of rFe2O3 nanoparticles were incorporated as a filler in the PTFE matrix through a hydraulic pressing and sintering method in order to fabricate rFe2O3–PTFE nanocomposites. The microstructure properties of rFe2O3 nanoparticles and the nanocomposites were characterized through X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM). The thermal expansion coefficients (CTEs) of the PTFE matrix and nanocomposites were determined using a dilatometer apparatus. The complex permittivity and permeability were measured using rectangular waveguide connected to vector network analyzer (VNA) in the frequency range 8.2–12.4 GHz. The CTE of PTFE matrix decreased from 65.28×10−6/°C to 39.84×10−6/°C when the filler loading increased to 25 wt %. The real (ε′) and imaginary (ε″) parts of permittivity increased with the rFe2O3 loading and reached maximum values of 3.1 and 0.23 at 8 GHz when the filler loading was increased from 5 to 25 wt %. A maximum complex permeability of 1.1−j0.07 was also achieved by 25 wt % nanocomposite at 10 GHz.

scholarly journals In-Situ High-Energy X-ray Diffraction Study of Austenite Decomposition During Rapid Cooling and Isothermal Holding in Two HSLA Steels

2021 ◽  
Vol 52 (5) ◽  
pp. 1812-1825
Author(s):  
Sen Lin ◽  
Ulrika Borggren ◽  
Andreas Stark ◽  
Annika Borgenstam ◽  
Wangzhong Mu ◽  
...  
Keyword(s):  
Isothermal Holding ◽  
Weight Percent ◽  
High Energy ◽  
Decomposition Kinetics ◽  
Bainitic Transformation ◽  
Austenite Decomposition ◽  
X Ray Diffraction ◽  
Rapid Cooling ◽  
X Ray

AbstractIn-situ high-energy X-ray diffraction experiments with high temporal resolution during rapid cooling (280 °C s−1) and isothermal heat treatments (at 450 °C, 500 °C, and 550 °C for 30 minutes) were performed to study austenite decomposition in two commercial high-strength low-alloy steels. The rapid phase transformations occurring in these types of steels are investigated for the first time in-situ, aiding a detailed analysis of the austenite decomposition kinetics. For the low hardenability steel with main composition Fe-0.08C-1.7Mn-0.403Si-0.303Cr in weight percent, austenite decomposition to polygonal ferrite and bainite occurs already during the initial cooling. However, for the high hardenability steel with main composition Fe-0.08C-1.79Mn-0.182Si-0.757Cr-0.094Mo in weight percent, the austenite decomposition kinetics is retarded, chiefly by the Mo addition, and therefore mainly bainitic transformation occurs during isothermal holding; the bainitic transformation rate at the isothermal holding is clearly enhanced by lowered temperature from 550 °C to 500 °C and 450 °C. During prolonged isothermal holding, carbide formation leads to decreased austenite carbon content and promotes continued bainitic ferrite formation. Moreover, at prolonged isothermal holding at higher temperatures some degenerate pearlite form.

scholarly journals Spatially Resolved Forming Mechanisms Detection in Single Point Incremental Forming Using Synchrotron Based Texture Analysis

2021 ◽  
Author(s):  
Mateus Dobecki ◽  
Alexander Poeche ◽  
Walter Reimers
Keyword(s):  
Texture Analysis ◽  
Incremental Forming ◽  
Single Point ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Forming Mechanism ◽  
Spatially Resolved ◽  
Step Down ◽  
Stress States

AbstractDespite the ongoing success of understanding the deformation states in sheets manufactured by single-point incremental forming (SPIF), the unawareness of the spatially resolved influence of the forming mechanisms on the residual stress states of incrementally formed sheet metal parts impedes their application-optimized use. In this study, a well-founded experimental proof of the occurring forming mechanisms shear, bending and stretching is presented using spatially resolved, high-energy synchrotron x-ray diffraction-based texture analysis in transmission mode. The measuring method allows even near-surface areas to be examined without any impairment of microstructural influences due to tribological reactions. The depth-resolved texture evolution for different sets of forming parameters offers insights into the forming mechanisms acting in SPIF. Therefore, the forming mechanisms are triggered explicitly by adjusting the vertical step-down increment Δz for groove, plate and truncated cone geometries. The texture analysis reveals that the process parameters and the specimen geometries used lead to characteristic changes in the crystallites’ orientation distribution in the formed parts due to plastic deformation. These forming-induced reorientations of the crystallites could be assigned to the forming mechanisms by means of defined reference states. It was found that for groove, plate and truncated cone geometries, a decreasing magnitude of step-down increments leads to a more pronounced shear deformation, which causes an increasing work hardening especially at the tool contact area of the formed parts. Larger step-down increments, on the other hand, induce a greater bending deformation. The plastic deformation by bending leads to a complex stress field that involves alternating residual tensile stresses on the tool and residual compressive stresses on the tool-averted side incrementally formed sheets. The present study demonstrates the potential of high-energy synchrotron x-ray diffraction for the spatially resolved forming mechanism research in SPIF. Controlling the residual stress states by optimizing the process parameters necessitates knowledge of the fundamental forming mechanism action.

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