scholarly journals Tailored Mechanical Properties and Residual Stresses of a-C:H:W Coatings

2014 ◽  
Vol 996 ◽  
pp. 14-21 ◽  
Author(s):  
Christoph Schmid ◽  
Harald Hetzner ◽  
Stephan Tremmel ◽  
Felix Hilpert ◽  
Karsten Durst
Keyword(s):  
Mechanical Properties ◽  
Residual Stresses ◽  
Regression Model ◽  
Bias Voltage ◽  
Ion Beam ◽  
Image Correlation ◽  
Internal Stresses ◽  
Main Process ◽  
Applied Bias ◽  
Applied Bias Voltage

In this study, three different a-C:H:W coatings with predefined hardness values, ranging from 10 up to 16 GPa, were deposited by adjusting bias voltage according to a previously created regression model. For this purpose, the influence of the main process parameters of the used reactive unbalanced magnetron sputtering process on the mechanical properties of the a-C:H:W coating was investigated previously by nanoindentation. For a systematical evaluation of the single effects, parameters were varied according to a central composite design. The three coating variants of this study were investigated in terms of microstructure, mechanical properties and residual stresses. It turned out, that by the use of the regression model, a-C:H:W coatings with tailored mechanical properties can be deposited. Residual stresses were measured by means of focused ion beam milling of a double-slit geometry, which causes the internal stresses to relax, and mapping of the resultant relief strain by digital image correlation. A linear relation between the applied bias voltage and the hardness, the modulus of the coating as well as the determined relief strain was observed. Thus, residual stresses of the coatings increase disproportionately with applied bias voltage. The obtained results can be helpful for tailored coating design and further optimization of a-C:H:W coatings.

scholarly journals Influence of Applied Bias Voltage on the Composition, Structure, and Properties of Ti:Si-Codoped a-C:H Films Prepared by Magnetron Sputtering

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Jinlong Jiang ◽  
Qiong Wang ◽  
Yubao Wang ◽  
Zhang Xia ◽  
Hua Yang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Magnetron Sputtering ◽  
Bias Voltage ◽  
Tribological Properties ◽  
Structure And Properties ◽  
Applied Bias ◽  
Applied Bias Voltage ◽  
Methane Mixture ◽  
Composition Structure

The titanium- and silicon-codoped a-C:H films were prepared at different applied bias voltage by magnetron sputtering TiSi target in argon and methane mixture atmosphere. The influence of the applied bias voltage on the composition, surface morphology, structure, and mechanical properties of the films was investigated by XPS, AFM, Raman, FTIR spectroscopy, and nanoindenter. The tribological properties of the films were characterized on an UMT-2MT tribometer. The results demonstrated that the film became smoother and denser with increasing the applied bias voltage up to −200 V, whereas surface roughness increased due to the enhancement of ion bombardment as the applied bias voltage further increased. The sp3carbon fraction in the films monotonously decreased with increasing the applied bias voltage. The film exhibited moderate hardness and the superior tribological properties at the applied bias voltage of −100 V. The tribological behaviors are correlated to the H/E or H3/E2ratio of the films.

scholarly journals Influence of the Silver Content on Mechanical Properties of Ti-Cu-Ag Thin Films

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 435
Author(s):  
Saqib Rashid ◽  
Marco Sebastiani ◽  
Muhammad Mughal ◽  
Rostislav Daniel ◽  
Edoardo Bemporad
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Residual Stresses ◽  
Physical Vapor Deposition ◽  
Ion Beam ◽  
Antibacterial Properties ◽  
Image Correlation ◽  
Potential Candidate ◽  
Clear Trend ◽  
Control Film

In this work, the ternary titanium, copper, and silver (Ti-Cu-Ag) system is investigated as a potential candidate for the production of mechanically robust biomedical thin films. The coatings are produced by physical vapor deposition—magnetron sputtering (MS-PVD). The composite thin films are deposited on a silicon (100) substrate. The ratio between Ti and Cu was approximately kept one, with the variation of the Ag content between 10 and 35 at.%, while the power on the targets is changed during each deposition to get the desired Ag content. Thin film characterization is performed by X-ray diffraction (XRD), nanoindentation (modulus and hardness), to quantitatively evaluate the scratch adhesion, and atomic force microscopy to determine the surface topography. The residual stresses are measured by focused ion beam and digital image correlation method (FIB-DIC). The produced Ti-Cu-Ag thin films appear to be smooth, uniformly thick, and exhibit amorphous structure for the Ag contents lower than 25 at.%, with a transition to partially crystalline structure for higher Ag concentrations. The Ti-Cu control film shows higher values of 124.5 GPa and 7.85 GPa for modulus and hardness, respectively. There is a clear trend of continuous decrease in the modulus and hardness with the increase of Ag content, as lowest value of 105.5 GPa and 6 GPa for 35 at.% Ag containing thin films. In particular, a transition from the compressive (−36.5 MPa) to tensile residual stresses between 229 MPa and 288 MPa are observed with an increasing Ag content. The obtained results suggest that the Ag concentration should not exceed 25 at.%, in order to avoid an excessive reduction of the modulus and hardness with maintaining (at the same time) the potential for an increase of the antibacterial properties. In summary, Ti-Cu-Ag thin films shows characteristic mechanical properties that can be used to improve the properties of biomedical implants such as Ti-alloys and stainless steel.

scholarly journals Influence of the Silver Content on Mechanical Properties of Ti-Cu-Ag Thin Films

2021 ◽  
Author(s):  
Saqib Rashid ◽  
Marco Sebastiani ◽  
Muhammad Zeeshan Mughal ◽  
Rostislav Daniel ◽  
Edoardo Bemporad
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Residual Stresses ◽  
Physical Vapor Deposition ◽  
Ion Beam ◽  
Antibacterial Properties ◽  
Image Correlation ◽  
Potential Candidate ◽  
Clear Trend ◽  
Control Film

In this work, the ternary titanium, copper and silver (Ti-Cu-Ag) system is investigated as a potential candidate for the production of mechanically robust biomedical thin films. The coatings are produced by physical vapor deposition-magnetron sputtering (MS-PVD). The composite thin films are deposited on a silicon (100) substrate. The ratio between Ti and Cu was approximately kept one, with the variation of the Ag content between 10 and 35 at.%, while the power on the targets is changed during each deposition to get the desired Ag content. Thin film characterization is performed by x-ray diffraction (XRD), nanoindentation (modulus and hardness) and Atomic force microscopy to determine the surface topography. The residual stresses are measured by focused ion beam and digital image correlation method (FIB-DIC). The produced Ti-Cu-Ag thin films appear to be smooth, uniformly thick and exhibit amorphous structure for the Ag contents lower than 25 at.%, with a transition to partially crystalline structure for higher Ag concentrations. The Ti-Cu control film shows higher values of 124.5 GPa and 7.85 GPa for modulus and hardness respectively. There is a clear trend of continuous decrease in the modulus and hardness with the increase of Ag content, as lowest value of 105.5 GPa and 6 GPa for 35 at.% Ag containing thin films. In particular, a transition from the compressive (-36.5 MPa) to tensile residual stresses between 229 MPa and 288 MPa are observed with an increasing Ag content. The obtained results suggest that the Ag concentration should not exceed 25 at.%, in order to avoid an excessive reduction of the modulus and hardness with maintaining (at the same time) the potential for an increase of the antibacterial properties. In summary, Ti-Cu-Ag thin films shows characteristic mechanical properties that can be used to improve the properties of biomedical implants such as Ti-alloys and stainless steel.

scholarly journals Effect of Ion Irradiation on Nanoindentation Fracture and Deformation in Silicon Carbide

JOM ◽  
2021 ◽  
Author(s):  
Alexander J. Leide ◽  
Richard I. Todd ◽  
David E. J. Armstrong
Keyword(s):  
Mechanical Properties ◽  
Silicon Carbide ◽  
Residual Stresses ◽  
Focused Ion Beam ◽  
Electron Backscatter Diffraction ◽  
Ion Irradiation ◽  
Ion Beam ◽  
Resolution Electron ◽  
Radiation Induced ◽  
Compressive Residual Stresses

AbstractSilicon carbide is desirable for many nuclear applications, making it necessary to understand how it deforms after irradiation. Ion implantation combined with nanoindentation is commonly used to measure radiation-induced changes to mechanical properties; hardness and modulus can be calculated from load–displacement curves, and fracture toughness can be estimated from surface crack lengths. Further insight into indentation deformation and fracture is required to understand the observed changes to mechanical properties caused by irradiation. This paper investigates indentation deformation using high-resolution electron backscatter diffraction (HR-EBSD) and Raman spectroscopy. Significant differences exist after irradiation: fracture is suppressed by swelling-induced compressive residual stresses, and the plastically deformed region extends further from the indentation. During focused ion beam cross-sectioning, indentation cracks grow, and residual stresses are modified. The results clarify the mechanisms responsible for the modification of apparent hardness and apparent indentation toughness values caused by the compressive residual stresses in ion-implanted specimens.

scholarly journals Laser-Induced Growth of Titanium Nitride Microcolumns on Biased Titanium Targets

2005 ◽  
Vol 20 (1) ◽  
pp. 62-67 ◽  
Author(s):  
E. György ◽  
A. Pérez del Pino ◽  
P. Serra ◽  
J.L. Morenza
Keyword(s):  
Bias Voltage ◽  
Single Pulse ◽  
Laser Pulses ◽  
High Repetition Rate ◽  
Applied Bias ◽  
Applied Bias Voltage ◽  
Surface Microrelief ◽  
High Repetition ◽  
Melting Threshold ◽  
Biased Samples

Titanium targets with a bias voltage ranging from −500 to +500 V were submitted to multipulse high repetition rate Nd:yttrium aluminum garnet (YAG; λ = 1.064 μm, τ ∼ 300 ns, ν = 30 kHz) laser irradiations in nitrogen at intensity values below the single-pulse melting threshold. The morphology of the TiN structures formed under the cumulative action of the laser pulses on the surface of the unbiased and biased targets was investigated by profilometry and scanning electron microscopy. Under these irradiation conditions, a specific columnar surface microrelief developed. The height of the microcolumns reached about 10–15 μm, and their diameter about 1–2 μm. The development of TiN microcolumns was enhanced by the applied bias voltage. The enhancement in the negative biased samples was stronger than that in the positive biased ones.

scholarly journals Through-Thickness Residual Stresses, Microstructure, and Mechanical Properties of Electron Beam-Welded CA6NM Martensitic Stainless Steel after Postweld Heat Treatment

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Sheida Sarafan ◽  
Priti Wanjara ◽  
Jean-Benoît Lévesque ◽  
Javad Gholipour ◽  
Henri Champliaud ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Stainless Steel ◽  
Electron Beam ◽  
Residual Stresses ◽  
Tensile Properties ◽  
Martensitic Stainless Steel ◽  
Postweld Heat Treatment ◽  
Image Correlation ◽  
Postweld Heat

In this study, the integrity of electron beam- (EB-) welded CA6NM—a grade of 13% Cr-4% Ni martensitic stainless steel—was assessed through the entire joint thickness of 90 mm after postweld heat treatment (PWHT). The joints were characterized by examining the microstructure, residual stresses, global mechanical properties (static tensile, Charpy impact, and bend), and local properties (yield strength and strain at fracture) in the metallurgically modified regions of the EB welds. The applied PWHT tempered the “fresh” martensite present in the microstructure after welding, which reduced sufficiently the hardness (<280 HV) and residual stresses (<100 MPa) to meet the requirements for hydroelectric turbine assemblies. Also, the properties of the EB joints after PWHT passed the minimum acceptance criteria specified in ASME sections VIII and IX. Specifically, measurement of the global tensile properties indicated that the tensile strengths of the EB welds in the transverse and longitudinal directions were on the same order as that of the base metal (BM). Evaluation of the local tensile properties using a digital image correlation (DIC) methodology showed higher local yield strengths in the fusion zone (FZ) and heat-affected zone (HAZ) of 727 MPa and 740 MPa, respectively, relative to the BM value of 663 MPa. Also, the average impact energies for the FZ and HAZ were 63 J and 148 J, respectively, and attributed to the different failure mechanisms in the HAZ (dimples) versus the FZ (quasi-cleavage consisting of facets and dimples). This study shows that the application of PWHT plays an important role in improving the weld quality and performance of EB-welded CA6NM and provides the essential data for validating the design and manufacturing process for next-generation hydroelectric turbine products.

Simulating Residual Stresses Using a Modified Wedge-Loaded Compact Tension Specimen

2013 ◽  
Author(s):  
P. Kapadia ◽  
H. Zhou ◽  
C. M. Davies ◽  
R. C. Wimpory ◽  
K. M. Nikbin
Keyword(s):  
Stainless Steel ◽  
Residual Stresses ◽  
Crack Growth ◽  
Crack Tip ◽  
Compact Tension ◽  
Image Correlation ◽  
Internal Stresses ◽  
Fe Model ◽  
Creep Ductility ◽  
Crack Tip Plasticity

Residual stresses are induced in components when fabrication processes produce internal stresses or local deformation and cause accelerated creep damage and cracking during service at elevated temperatures. A method of inducing residual stresses in laboratory fracture specimens is proposed where an oversized wedge is inserted into the crack mouth of a compact tension, C(T), type specimen. In this way the extent of internal stresses can be controlled in order to minimise the level of crack tip plasticity which inherently reduces the remaining strain to failure. Numerical simulations of wedge insertion into specimens made of 316H austenitic stainless steel have been developed to calibrate the wedge insertion process. These models have been experimentally validated using surface strains measured during the wedge insertion, using Digital Image Correlation (DIC), and Neutron Diffraction (ND) measurements. The validated Finite Element (FE) model is used to determine the wedge insertion depth required to maximise the residual stresses without causing significant crack tip plasticity. The validated numerical simulation is used to determine the wedge insertion depths of further wedge-loaded C(T) specimens made from uniformly pre-compressed 316H stainless steel. The reduced creep ductility of this material increases the rate of crack growth under creep conditions. This method of inducing residual stresses with limited crack tip plasticity allows creep crack growth under simulated secondary loading conditions to be investigated without the influence of non-uniform creep ductility caused by work hardening.

scholarly journals Intragranular Residual Stress Evaluation Using the Semi-Destructive FIB-DIC Ring-Core Drilling Method

2014 ◽  
Vol 996 ◽  
pp. 8-13 ◽  
Author(s):  
Alexander J.G. Lunt ◽  
Alexander M. Korsunsky
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Titanium Aluminide ◽  
Ion Beam ◽  
Sample Surface ◽  
Image Correlation ◽  
Near Surface ◽  
Core Drilling ◽  
Drilling Method ◽  
Ring Core

Titanium aluminide (TiAl) is a lightweight intermetallic compound with a range of exceptional mid-to-high temperature mechanical properties. These characteristics have the potential to deliver significant weight savings in aero engine components. However, the relatively low ductility of TiAl requires improved understanding of the relationship between manufacturing processes and residual stresses in order to expand the use of such components in service. Previous studies have suggested that stress determination at high spatial resolution is necessary to achieve better insight. The present paper reports progress beyond the current state-of-the-art towards the identification of the near-surface intragranular residual stress state in cast and ground TiAl at a resolution better than 5μm. The semi-destructive ring-core drilling method using Focused Ion Beam (FIB) and Digital Image Correlation (DIC) was used for in-plane residual stress estimation in ten grains at the sample surface. The nature of the locally observed strain reliefs suggests that tensile residual stresses may have been induced in some grains by the unidirectional grinding process applied to the surface.

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