Effects of yttria content and sintering temperature on the microstructure and tendency to brittle fracture of yttria-stabilized zirconia

2021 ◽  
Vol 2 (109) ◽  
pp. 65-79
Author(s):  
V.V. Kulyk ◽  
Z.A. Duriagina ◽  
B.D. Vasyliv ◽  
V. Vavrukh ◽  
T.M. Kovbasiuk ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Brittle Fracture ◽  
Fracture Surface ◽  
Physical And Mechanical Properties ◽  
Ceramic Materials ◽  
Optical Microscope ◽  
Operating Conditions ◽  
Vickers Indentation ◽  
Indentation Method ◽  
Young’S Moduli

Purpose: The purpose of this work is to evaluate the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria, based on a study of changes in the microstructure, phase composition, and fracture micromechanisms. Design/methodology/approach: The series of 3YSZ, 4YSZ, and 5YSZ ceramic specimens were sintered in an argon atmosphere. Three sintering temperatures were used for each series: 1450°C, 1500°C, and 1550°C. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The fracture toughness of the material was estimated using both the Vickers indentation method and a single-edge notch beam (SENB) test performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, and mechanical characteristics of YSZ ceramic materials of different chemical and phase compositions sintered in a temperature range of 1450°C to 1550°C are found. Research limitations/implications: To study the actual behaviour of YSZ ceramic materials under operating conditions, it is necessary to evaluate their Young’s moduli, strength, microhardness, and fracture toughness in an operating environment of the corresponding parameters (temperature, pressure, etc.).Practical implications: Based on the developed approach to estimating the propensity to brittle fracture of the formed YSZ ceramic microstructure, it is possible to obtain YSZ ceramic material that will provide the necessary physical and mechanical properties of a wide variety of precision ceramic products. Originality/value: An approach to estimating the propensity to brittle fracture of YSZ ceramics stabilized by the various amount of yttria is proposed based on two methods of evaluating crack growth resistance of materials, namely, the Vickers indentation method and SENB method.

The effect of water vapor containing hydrogenous atmospheres on the microstructure and tendency to brittle fracture of anode materials of YSZ–NiO(Ni) system

2021 ◽  
Vol 2 (108) ◽  
pp. 49-67
Author(s):  
V.V. Kulyk ◽  
B.D. Vasyliv ◽  
Z.A. Duriagina ◽  
T.M. Kovbasiuk ◽  
I.A. Lemishka
Keyword(s):  
Fracture Toughness ◽  
Water Vapor ◽  
Brittle Fracture ◽  
Fracture Surface ◽  
Anode Material ◽  
Optical Microscope ◽  
Processing Technique ◽  
Image Processing Technique ◽  
Three Point Bending ◽  
Partial Pressures

Purpose: The purpose of this work is to estimate the tendency to brittle fracture of the YSZ–NiO(Ni) anode cermet in a hydrogenous environment with various concentrations of water vapor. Design/methodology/approach: YSZ–NiO ceramic plates were fabricated by sintering in an argon atmosphere. The treatment of material was performed in a hydrogenous environment with various concentrations of water vapor. The strength test was performed under three-point bending at 20°C in air. The microstructure and morphology of the fracture surface of the specimens were studied using a scanning electron microscope (SEM) Carl Zeiss EVO-40XVP. The chemical composition was determined using an INCA ENERGY 350 spectrometer. Microhardness measurements were performed on a NOVOTEST TC-MKB1 microhardness tester. The configuration of the imprints and cracks formed was studied on an optical microscope Neophot-21. The porosity of the materials was investigated by analysing the SEM micrographs using the image processing technique. Findings: Peculiarities of changes in the microstructure, the morphology of specimens fracture surface, physical and mechanical characteristics of YSZ–NiO(Ni) material for solid oxide fuel cell (SOFC) anodes of different preconditioning modes aged under various partial pressures of water vapor in a hydrogenous environment are found. Research limitations/implications: To study the actual behaviour of the YSZ–NiO(Ni) anode material in the operating environment, it is necessary to evaluate its strength, Young’s modulus, microhardness, and fracture toughness by changing with a certain step the partial pressure of water vapor in the whole range noted in this work. Practical implications: Based on the developed approach to assessing the propensity to brittle fracture of the formed cermet microstructure, it is possible to obtain an anode material that will provide the necessary functional properties of a SOFC. Originality/value: An approach to estimating the propensity to brittle fracture of a formed cermet structure is proposed based on the microhardness and fracture toughness characteristics obtained by the Vickers indentation method.

The Influence of Some Technological Parameters on the Fracture Toughness of Ceramic Materials

2010 ◽  
Vol 446 ◽  
pp. 11-21
Author(s):  
Viorel Goanta ◽  
Marian Mares
Keyword(s):  
Fracture Toughness ◽  
Low Cost ◽  
High Hardness ◽  
Fem Analysis ◽  
Ceramic Materials ◽  
Indentation Load ◽  
Test Material ◽  
Vickers Indentation ◽  
Technological Parameters ◽  
Material Fracture

In order to determine the fracture toughness of the materials presenting high hardness values in the superficial layers, the Vickers micro-indentation was imposed as a reliable procedure. That method became attractive because of the relative simplicity of the experimental technique and because of its low cost. There are several calculus relationships that could be applied using the data provided by that method, in order to determine the material fracture toughness. The determination of fracture toughness using the Vickers indentation method is based on the analysis of radial cracks propagation, from the corners of the indentation trace. The length of these cracks is connected with the material fracture toughness, on the basis of some semi-empirical calculus relations that are taking into account the indentation load and some physical characteristics of the test material, as Young’s modulus and Poisson’s coefficient. In the present paper, fracture toughness was determined on a series of ceramic samples, made of the same material, but with different geometrical shapes and obtained by applying different technological procedures. The influence of some technological parameters on the fracture toughness was evaluated. The material fracture toughness was determined, into the vicinity of the propagated cracks (in a sample that could be a final product), on an area with a specified geometric contour. As a preliminary stage, a step by step FEM analysis was made, into the Vickers indentation material region, for different values of indentation load. In this manner, it was proved that the maximum stress value, on the perpendicular direction, as related to the crack diagonal plane, is always located at the peak of the indentation trace, and that is the effective start-point of cracking, for this type of indentation.

The Effects of MgO Content on the Mechanical Properties and Microstructures of Al2O3-TiN-TiC Ceramic Materials

2012 ◽  
Vol 500 ◽  
pp. 623-628 ◽  
Author(s):  
Yu Huan Fei ◽  
Chuan Zhen Huang ◽  
Han Lian Liu ◽  
Bin Zou
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Composition ◽  
Flexural Strength ◽  
Crack Path ◽  
Ceramic Materials ◽  
Optical Microscope ◽  
Volume Percent ◽  
Sintered Ceramic ◽  
Microstructure Morphology

Al2O3-TiN-TiC ceramic materials with different MgO content were fabricated by hot-pressing technique. The MgO volume percent was varied from 0vol% to 5vol%. The mechanical properties such as flexural strength, Vickers hardness and fracture toughness were tested. The phase composition of the sintered body was analyzed by XRD while the microstures of the sintering body were observed by OM (Optical Microscope) and SEM. The effects of MgO content on the mechanical properties and microstructures of Al2O3-TiN-TiC were investigated. The results shows that the addition of MgO can change the phase composition of the sintered ceramic materials which displayed with diverse solid solutions and intermetallic compounds. Meanwhile the new sintering products changed the the microstructure morphology which made the crack path complex and affected the mechanical properties.

Fracture Toughness of HVOF Sprayed WC-Co Coatings

2000 ◽  
Author(s):  
S. De Palo ◽  
M. Mohanty ◽  
H. Marc-Charles ◽  
M. Dorfman
Keyword(s):  
Fracture Toughness ◽  
Gas Turbines ◽  
Wear Behavior ◽  
Physical And Mechanical Properties ◽  
Mean Free Path ◽  
Vickers Indentation ◽  
Centrifugal Pumps ◽  
Compressor Blades ◽  
Fracture Properties ◽  
Spray Process

Abstract Tungsten carbide-cobalt coatings are extensively used to protect surfaces from wear in many types of applications, such as compressor piston rods, pump plungers, shaft sleeves on centrifugal pumps and fans, and midspans of compressor blades in gas turbines. The wear behavior in any application is strongly influenced by the basic physical and mechanical properties of such coatings. Fracture toughness as a mechanical property indicates the resistance to fracture in the presence of a sharp crack, and thus provides a measure of the intrinsic strength of the cemented carbides coatings. In this study, Vickers indentation tests have been used to quantify the in-plane fracture behavior of various WC-based coatings deposited by the High Velocity Oxy-Fuel (HVOF) spray process. The indentation cracks are analyzed in terms of standardized relations that utilize radial-median crack geometries. It is shown that the fracture properties of HVOF WC-Co coatings are anisotropic, and depend strongly on the microstructure and composition of the coatings. The crack propagation is determined by the porosity, binder mean free path, and the shape, size, and distribution of the reinforcing carbide particles. The erosion resistances of the coatings have also been discussed as a function of the fracture properties and mechanisms. It is shown, in this study, that the Vickers indentation method is a useful and convenient technique for determining the in-plane fracture toughness of HVOF sprayed WC-based coatings.

Mechanical properties of single-quasicrystalline AlCuCoSi

1991 ◽  
Vol 6 (6) ◽  
pp. 1165-1168 ◽  
Author(s):  
R. Wittmann ◽  
K. Urban ◽  
M. Schandl ◽  
E. Hornbogen
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Friction Coefficient ◽  
Modulus Of Elasticity ◽  
Vickers Indentation ◽  
Indentation Method ◽  
Abrasive Friction ◽  
Highly Strained ◽  
First Time

The mechanical properties of single-quasicrystals of decagonal AlCoCuSi have been studied for the first time by applying the Vickers indentation method. The hardness has been determined as H ≃ 9.6 MPa. Estimates for the modulus of elasticity and the fracture toughness are given. The quasicrystals are highly strained internally. Scratching experiments show slight anisotropies in the abrasive friction coefficient. The dominant abrasive mechanism is microplowing.

The Effects of MgO Addtion on the Mechanical Properties and the Phase Composition of Al2O3-TiC-TiN Ceramic Materials

2012 ◽  
Vol 457-458 ◽  
pp. 3-6
Author(s):  
Yu Huan Fei ◽  
Chuan Zhen Huang ◽  
Han Lian Liu ◽  
Bin Zou
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Phase Composition ◽  
Flexural Strength ◽  
Ceramic Materials ◽  
Bending Test ◽  
Vickers Indentation ◽  
Volume Percent ◽  
Sintered Ceramic ◽  
Three Point Bending

Al2O3-TiN-TiC ceramic materials with different MgO content were fabricated by hot-pressing technique. The MgO volume percent was varied from 0vol% to 5vol%. Three point bending test was applied to get the flexural strength and the Vickers indentation was applied to get the Vickers hardness and the fracture toughness. The phase composition of the ceramics was analyzed by XRD. The effects of the content of MgO on the mechanical properties and the phase composition of Al2O3-TiN-TiC were investigated. The results shows that the addition of MgO can change the phase composition of the sintered ceramic materials which displayed with diverse solid solutions and intermetallic compounds. The convertion of the mechanical properties can also be explained by the XRD results.

Evaluation of Fracture Toughness of Tantalum Carbide Ceramic Layer: A Vickers Indentation Method

2016 ◽  
Vol 25 (7) ◽  
pp. 3057-3064 ◽  
Author(s):  
Ke Song ◽  
Yunhua Xu ◽  
Nana Zhao ◽  
Lisheng Zhong ◽  
Zhao Shang ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Tantalum Carbide ◽  
Ceramic Layer ◽  
Vickers Indentation ◽  
Indentation Method
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