Top PDF Indentation Size Effect for the Hardness of Refractory Carbides

Indentation Size Effect for the Hardness of Refractory Carbides

Indentation Size Effect for the Hardness of Refractory Carbides

The sintering temperature, relative density, Young’s modulus, and Poisson’s ratio of sintered bodies are shown in Table 2. The sintered bodies were polycrystalline and have no preferential texture. Therefore, the elastic modulus values are regarded as those of isotropic materials. The relative density of the specimens sintered in this study ranged from 98 to 100%. These small porosity values have a negligible influence on Young’s modulus. Young’s modulus of the prepared refractory carbides ranged from 400 to 712 GPa. Young’s modulus of the carbides has been reported in the literature as 460 GPa for B 4 C, 10,11) 223–534 GPa for
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Structure and properties of high hardness silicide coatings on cemented carbides for high temperature applications

Structure and properties of high hardness silicide coatings on cemented carbides for high temperature applications

The substrate micro-hardness values in Figure 9 are higher than those macro-hardness values reported in Table 1. This difference is now considered in detail: The hardness of the substrate at 500 mN of load, 23.6 GPa, is about 60% higher than the macro-hardness value at 30 kgf (294 N), which was 14.6 GPa (see Table 1). This indentation size effect is commonly observed in cWCs when indented at different length scales [3]. For example, Roebuck et al. [35] reported an order of magnitude increase in the hardness of WC-11 wt.% Co when tested at 1 mN vs. its macro-hardness value. In a less extreme range of indenter sizes, Nabarro et al. [36] indented a WC-11 wt.% Co sample over a load range of about 50 mN–10 N, and observed a hardness rise of about 50%, i.e., a similar increase to the present study, for a similar load change (200-fold vs. 600-fold for our study). Thus, the indenter size effect in WC-FeCr materials appears to be roughly in keeping with similar materials indented across a comparable range of loads.
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Mechanical Properties of Porosity Free Beta Tricalcium Phosphate (β TCP) Ceramic by Sharp and Spherical Indentations

Mechanical Properties of Porosity Free Beta Tricalcium Phosphate (β TCP) Ceramic by Sharp and Spherical Indentations

Instrumented indentation has been developed for determining the mechanical properties of materials but an accurate determination of these properties requires attention on contact stiffness analysis, indentation size effect, elastic modulus mode of calculation, role of stress distribution around the indent and its introduction in expanding cavity models for tensile mechanical properties determination. In the present work, models for hardness, elastic modulus and plastic properties determination by indentation are briefly reviewed and applied for the characterization of a porosity-free β-TCP bioceramic. As a main result the elastic modulus is found to be equal to 162 GPa resulting from the application of different approaches based on the use of various sharp and spherical indenters. Additionally, Martens and contact macrohardnesses were found to be independent on the dwell-time and equals to 4.1 and 6.3 GPa, respectively. Finally, models based on Hollomon’s and Ludwik’s laws as well as expanding cavity models were critically analyzed in light of their capacity to determine the yield stress and to represent the behavior law of the material. As a main result, the yield stress of the β-TCP is found to be equal to 2 GPa.
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Assessment of the Kinetics of Local Plastic Deformation of Zr-2.5%Nb CANDU Pressure Tube Material

Assessment of the Kinetics of Local Plastic Deformation of Zr-2.5%Nb CANDU Pressure Tube Material

induced defects, scratches, usually caused by debris from the coolant entrapped between the fuel bundles and the pressure tube wall or by excessive rubbing of fuel bundle bearing pads against the pressure tube wall, can be produced. The local stress ahead of these scratches can be high enough to potentially result in premature failure of the tube [13]. During service, high local stress ahead of the scratches on the inside surface of the pressure tube can cause the precipitation of Zr-hydrides and thus the start of brittle fracture via a delayed hydride cracking process. It is often observed that brittle failure does not occur at these scratches and this puzzles researchers/engineers. They hypothesize that thermal creep in the region of the scratch causes it to blunt and thereby reduce the local stress ahead of the flaw. However, not much is known about the local thermal creep of Zr-2.5%Nb when it is with or without irradiation damage. It is therefore necessary to develop test techniques to predict the local plastic deformation parameters under the high stress state associated with the sharp scratches on the inside surface of these pressure tubes in order to make accurate flaw assessments. Also, a proper understanding for the effect of neutron irradiation hardening on the local thermal creep rate needs to be gained to accurately predict the deformation of this material in irradiated condition. One characteristic feature of the indentation test results is the indentation size effect i.e. depth-dependence of the indentation hardness of metals below indentation depths of about 10 m. Although the indentation depth dependence of hardness of relatively isotropic (FCC) metals has been studied widely, it has not been investigated in detail for mechanically anisotropic metals such as the highly textured Zr-2.5%Nb pressure tube alloy.
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Experimental and Finite Element Simulation of Nano-indentation on Metal Matrix Composites: Hardness Prediction

Experimental and Finite Element Simulation of Nano-indentation on Metal Matrix Composites: Hardness Prediction

In the last two decades, the use of finite element methods (FEM) for modeling different engineering problems really increased. Indentation process was investigated with FEM by many researchers, to investigate the stress and strain fields under the indenter tip which are used to determine the basic mechanical properties of materials [12-14]. Regarding an appropriate value for the dimension of specimen, as an economic factor in both experimental and numerical simulation. Also, regarding the size effect of the specimens on the precision of the results, finite element modeling can also be used for simulating the nano-indentation process. Some researchers have compared the results obtained from the FE simulation of nano-indentation and the experiment to validate finite element modeling of the nano-indentation process [15-18]. They have shown that the finite element simulation could be an appropriate method for determination of bulk material hardness.
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Effect of Inoculation on Phase Formation and Indentation Hardness Behaviour of Zr47 5Cu45 5Al5Co2 and Zr65Cu15Al10Ni10 Bulk Metallic Glass Matrix Composites

Effect of Inoculation on Phase Formation and Indentation Hardness Behaviour of Zr47 5Cu45 5Al5Co2 and Zr65Cu15Al10Ni10 Bulk Metallic Glass Matrix Composites

DOI: 10.4236/eng.2018.108039 545 Engineering crystals are observed in wider portion of sample. Once again, increase in their size may be attributed to ample time available for diffusion in this region which not only promotes growth of one crystal but may also lead towards emergence of multiple crystals into a large one by dissolution of grain boundaries into each other. Emergence of these hexagonal structures may also be attributed to in- creased toughness due not only to their evolution but their growth in wider re- gions which provide sites to hindrance of motion of shear bands (explained in next section). As the percentage of inoculant increase to 1.0%, similar type of trend is observed in which almost no crystallinity is observed at tip and appreci- able amount of it starts appearing as point of observation in a field of view is moved away from tip towards the inside of wedge (Figure 10(a) and Figure 10(b)). Once again, not enough crystallinity is observed as point of observation is moved to middle but few hints of formation of crystals starts appearing in this region. However, as point of view moves away from this further towards widest part of specimen (Figure 10(e) and Figure 10(f)), visible hexagonal type crystals are witnessed. Once again, their size is large as compared to their quantity. This may again be attributed to diffusion which might have happened in this region which not only allowed individual crystal to develop but also became the reason of grain boundary dissolution resulting in emergence of one large grain than a lot of small ones. This is not desired situation and become the reason of decrease in hardness of material without increasing its toughness. “River like” or “flower like” pattern is again observed which may be attributed to onset of nucleation or metal flow pattern in mold cavity. This again is confirmed by compositional contrast observed in adjacent back scatter images in which areas of higher or lower atomic weight generates a contrast. This is typically related to earlier wit- nessed nature (Zr 2 Cu) of these precipitating crystals [56]. Size of these crystals
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Effects of Initial Powder Size on Microstructure and Corrosion Resistance of in situ (Ti-V)C Reinforced Fe-based Laser Cladding Layers

Effects of Initial Powder Size on Microstructure and Corrosion Resistance of in situ (Ti-V)C Reinforced Fe-based Laser Cladding Layers

The average hardness from the S1 to the S6 cladding layer is 700 HV0.2, 820 HV0.2, 510 HV0.2, 670 HV0.2, 560 HV0.2 and 380 HV0.2, respectively, as shown in Fig. 9. It can be observed that the hardness increases first and then descends later as initial alloy particle sizes of the powders are reduced. It can be known that the strength and the toughness increased as reducing the average grain size according to the Hall-Petch relationship[41], which in turn enhanced the fine-grain strengthening effect. Therefore, the finer matrix grains and more uniformly distribution of the carbides in S2 cladding layer increased its hardness. Zou et al.[18] also found that the microhardness increased with the average grain size of Fe-based cladding layer and the carbide particle size decreased. Although the size of the carbides decreased, the growth of the cladding layer matrix grains and the appearance of the retained austenite in S3 cladding layer caused its hardness to decrease 190 HV0.2 compared with S1 cladding layer. Moreover, the reason for the S6 cladding layer shows the lowest hardness can be attributed to the maximum layer matrix grain size.
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Nano indentation Analysis of Multi Stage Spark Plasma Sintered
Hydroxyapatite-Calcium Titanate Biocomposite

Nano indentation Analysis of Multi Stage Spark Plasma Sintered Hydroxyapatite-Calcium Titanate Biocomposite

matrix of HA results decreasing in the slop and depth of indentation of the curve of HACT ceramics, which implies increasing in stiffness and hardness as decreasing the depth of indentation as shown in Fig.2 (b).The present study has combined consideration of the elastic modulus, flexural strength and fracture toughness data to express the overall effects of processing and microstructure. An optimal sintering profile is chosen in order to control the grain size and porosity. The highest density of 98% of theoretical density was obtained in most of the HA-CT composites with fine grained microstructural features. However, it was reported that above 95% of theoretical density, the grain size is the dominant factor for mechanical properties.
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Effect of Mold Preheating on the Microstructure of the Investment Cast Astm F-75 Implant Alloy

Effect of Mold Preheating on the Microstructure of the Investment Cast Astm F-75 Implant Alloy

temperatures of 550, 700, 850 and 1000 °C. The as-cast microstructures were characterized by optical microscopy and scanning electron microscopy (SEM Philips X230). The SEM image was randomly captured from different zones of the specimens obtained in each condition. Electrolytic etching with a 5% hydrochloric acid solution in water was used to reveal the microstructure. During etching, dc voltage of 5 V was applied for 1 s. Phase identification of the samples was carried out by X-ray diffraction (Philips X’Pert-MPD) with CuKα radiation (λ=1.54 Å) in a 40 kV voltage and 30 mA current. The quantitative determination of grain and carbide sizes was performed using the Image Tool software. For each mold preheating temperature, about 15-20 images was captured and used for the calculation of the grain size and volume fraction of carbides. Hardness of specimens was measured by Rockwell C method.
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Effect of grain size on hardness, bending strength and indentation toughness of multi-doped zirconia ceramics Yonggang Hoo, a, b,* Yusheng Shi aand Wenzhong Lub

Effect of grain size on hardness, bending strength and indentation toughness of multi-doped zirconia ceramics Yonggang Hoo, a, b,* Yusheng Shi aand Wenzhong Lub

were prepared via powder processing and pressure-less sintering to investigate the mechanical properties such as flexural strength, hardness, and fracture toughness. One of the purposes was to evaluate the influence of heating treatment on the mechanical properties of our new material system and then find a more optimized processing to obtain the best mechanical properties. The flexural strength and hardness of sintered ceramics were measured at room temperature. The null hypothesis was that no distinct tendency was found. In addition, the other purpose was to estimate the fracture
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Effect of carbide size in hardfacing on abrasive wear

Effect of carbide size in hardfacing on abrasive wear

The minimum of the abrasive wear rate was de- termined in the overlay depth of 0.8–1.4 mm. This range corresponds to the maximal overlay hard- ness, to the maximal carbides surfaces A, and to the maximal proportion of the latter in the matrix. With regard to the fact that the occurrence of hypereutec- tic carbide particles influences mostly the abrasive wear resistance, the relation between the abrasive resistance and carbides surfaces A was determined. This relation is shown in Figure 16. The variable matrix hardness was respected and therefore, the interlay was divided into the carbide surfaces A from 0 mm to 1.4 mm and those from 1.4 mm to 3.4 mm (Figure 17).
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Assessment of Surface Caking of Powders Using the Ball Indentation Method

Assessment of Surface Caking of Powders Using the Ball Indentation Method

The experiments were carried out at 25 °C and 45 °C under 75% RH; the results are shown in Figure 8. The hardness values are much larger at 45 °C than those at 25 °C, particularly for PVP and to a lesser extent for HPC, but the changes are still orders of magnitude, even though there is less moisture sorption at the higher temperature (Figure 2). This implies that temperature and relative humidity have a coupled effect on powder caking. When PVP is exposed at 45 °C to 75% RH, the hardness value increases first and reaches the highest value at 2-day with a value of almost 13 MPa. Then it decreases significantly by an order of magnitude with time. The states of the PVP powder beds at 45 °C and 25 °C after 8-day exposure to 75% RH are very different. The particles are regarded as “transformed” at the higher temperature, whilst they are simply “bonded” at the lower temperature (Oksanen and Zografi, 1990). For HPC and CaHPO 4 , the hardness of both samples increases with temperature, albeit to a minor extent for the latter.
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Rockwell Based Hardness Testing Machine

Rockwell Based Hardness Testing Machine

P. Rockwell invented the Rockwell hardness test to get more accurate and rapid measurement. After that Charles H. Wilson expanded on Rockwell’s invention. The Rockwell is a hardness scale based on indentation hardness of material. The Rockwell hardness test based upon Measurement of depth to which an indenter is forced by major load beyond the depth resulting from a previous load(minor) load. The principle of working is firstly minor is applied. A zero position is recorded. After that major load is applied and the maximum penetration position is recorded. After that remove the major load until minor load is reached. Resulting Rockwell no. displayed. It is difference between major load and minor load . The indenter may be either a diamond cone &tungsten carbide ball, depending upon the characteristics of the material being tested. In this project paper, this machine is designed for measuring hardness of metals & alloys, whether round, flat or irregular in shapes. This machine is ideally suitable for laboratories, tool rooms, heat treatments shops, R&D departments, inspection departments, foundries& educational institutions. Automatic weight selection with automatic zero setting dial guage. Motorized versions are also available.
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Micro-Mechanical Assessment of the Local Plastic Strain Invoked During a Splined Mandrel Flow Forming Operation

Micro-Mechanical Assessment of the Local Plastic Strain Invoked During a Splined Mandrel Flow Forming Operation

In the Section 3 of Chapter 3, the effect of strain-hardening rate on the grain-to-grain variability of local plastic strain in spin-formed fcc are investigated. To study the effect of work hardening rate and stacking fault energy (SFE) two fcc materials, pure copper and 70/30 brass, with completely different SFEs than 5052 and 6061 aluminum alloys were subjected to the SMFF operations. Micro-indentation hardness was used to assess the local equivalent plastic strain distribution in four fcc metals subjected to identical splined mandrel flow forming processes. Both the maximum local equivalent plastic strain and the grain-to-grain variability in the equivalent plastic strain increased with increasing strain-hardening rate of the work piece material. The deformed microstructure of the formed work pieces indicated that considerably more grain-to-grain variability in the dislocation slip step and deformation twin densities exist in the material with a high strain-hardening rate (i.e. 70/30 brass). These findings are of considerable importance and should be considered when assessing the suitability of high strain forming processes for producing reliable, and homogeneous, parts from fcc metal alloys that display high strain hardening rates.
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Difference in the Effect of Cold Working and Tempering on Microstructure of Mod 9Cr 1Mo Steel

Difference in the Effect of Cold Working and Tempering on Microstructure of Mod 9Cr 1Mo Steel

The microstructure of this steel is tempered martensite structure and it has been reported that creep strength of the steel depends on the tempering conditions. 6 ­ 8) For instance, it has been reported that the creep strength of the steel tempered at low temperatures is larger than that of the steel tempered at high temperatures due to larger hardness and higher dislocation density. 6­9) On the other hand, when this steel is cold worked, the hardness and dislocation density increase. However, unlike in the steel tempered at low temperatures, in cold-worked steel the creep strength decreases. 8­12) Therefore, when cold working and tempering are applied to the Mod.9Cr­1Mo steel, there is commonality that the high dislocation density is retained in the steel and the hardness of the steel is larger, but the effect of tempering and cold working on creep strength is different. One reason for this may be the difference in microstructure. However, there have been no studies focusing on the difference in the effect of cold working and tempering on the microstructure of Mod.9Cr­1Mo steel. Therefore, in this study the difference in the effect of cold working and tempering on the microstructure of Mod.9Cr ­
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Focused Ion Beam and Nanomechanical Tests for High Resolution Surface Characterisation: New Resources for Platinum Group Metals Testing3-19

Focused Ion Beam and Nanomechanical Tests for High Resolution Surface Characterisation: New Resources for Platinum Group Metals Testing3-19

The results of TEM-SAED analysis on dualbeam prepared thin foils are reported in Figure 9. Figures 9(a) and 9(e) show detail of the grain structure at the sample surfaces. It is clear that the grain structure has been maintained almost identically after heat treatment and that the dislocation density is similar in both cases, confirming the results obtained by nanoindentation and dualbeam cross-section observation. In addition, a very thin surface hardened layer (characterised by a finer grain size) is clearly shown in Figures 9(b) and 9(f). Figures 9(c)–(g) show details of the intragrain morphology, which are significantly different for the two samples. In the case of the heat treated sample the ordered domains are clearly visible confirming that the phase transition happens at a subgrain level.
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The influence of the indentation size in relation to the size of the microstructure of three polycrystalline materials indented with a Berkovich indenter

The influence of the indentation size in relation to the size of the microstructure of three polycrystalline materials indented with a Berkovich indenter

In order to bridge the gap between the micro- and macro-scale properties, microhardness measurements at decreasing loads have been performed with the aim of determining the load independent hardness, i.e. the macroscopic hardness. Therefore, a Vickers microhardness test has been carried out at indentation loads over the range of 25 to 1000 gram force in specimens of Ti-6Al-4V, CrMoV and C110. Hardness measurements at loads below 100 gram force in CrMoV were neglected as the indentation impressions exceeded the limits of spatial resolution of the built-in optical microscope. Five indentations per load were performed at an offset of at least three times the diagonal of the residual imprint. The macroscopic hardness was compared with the Martens hardness computed from each P-h curve in order to assess the suitability of a depth-sensing indentation experiment to represent the mechanical behaviour of the bulk material, or otherwise.
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Study of Dam Concrete Mechanical Properties Using Nano-indentation

Study of Dam Concrete Mechanical Properties Using Nano-indentation

Take into consideration that the dam in this study was built decades ago and have been exposed to air for a long time, the samples taken from the dam can be considered as the set of samples which suffer carbonation effect. Also the Han, Pan and Sun samples are more completely carbonated compared to the dam samples taken in 8” depth and in 16” depth, as a result, the Han, Pan and Sun samples are used as object of reference for dam samples taken from the surface. According to the indentation results of modulus of the dam samples fall in the region in 34-83 GPa, which means the carbonation process is the reason why modulus and hardness change during time and this effect is done by chemistry reaction with water and CO 2 . Also, the degree of this reaction process changes with depth change in the concrete structure.
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Studies on Hybrid Composite Material

Studies on Hybrid Composite Material

Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. The Brinell hardness test method as used to determine Brinell hardness, is defined inASTM E10. . Brinell testing often use a very high test load (3000 kgf) and a 10mm wide indenter so that the resulting indentation averages out most surface and sub-surface inconsistencies.

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Theoretical investigation of the zirconium carbide nano-sheet: A study of NMR, NBO, EPR and Polar

Theoretical investigation of the zirconium carbide nano-sheet: A study of NMR, NBO, EPR and Polar

out to explore zirconium carbide nano- sheet (ZrC nano-sheet). ZrC nano-sheet is similar to that of graphene, except that Zr is one among the alternative carbons. Zirconium carbide, due to its unique physical and chemical properties, such as high melting point (~3540°C), high hardness (~25 Gpa), wear resistance, high thermal conductivity, excellent mechanical properties and good chemical stability at high temperature, is used in industries, especially for high temperature applications 31-41 . It is used in different

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