| 51. |
- Reeve, P. A. P., et al.
(författare)
-
Radical Functionalization of Unsaturated Amino Acids : Synthesis of Side-Chain-Fluorinated, Azido-Substituted, and Hydroxylated Amino Acids
- 2019
-
Ingår i: ACS Omega. - : American Chemical Society. - 2470-1343. ; 4:6, s. 10854-10865
-
Tidskriftsartikel (refereegranskat)abstract
- A range of enantiomerically pure protected side-chain-fluorinated amino acids has been prepared (13 examples) by treatment of protected amino acids containing unsaturated side chains with a combination of Fe(III)/NaBH4 and Selectfluor. The modification of the conditions by replacement of Selectfluor with NaN3 allowed the preparation of side-chain azido-substituted amino acids (five examples), which upon catalytic hydrogenation gave the corresponding amines, isolated as lactams (four examples). Radical hydration of the unsaturated side chains leading to side-chain-hydroxylated protected amino acids has also been demonstrated.
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| 52. |
- Rogström, Lina, et al.
(författare)
-
Decomposition routes and strain evolution in arc deposited TiZrAlN coatings
- 2019
-
Ingår i: Journal of Alloys and Compounds. - : ELSEVIER SCIENCE SA. - 0925-8388 .- 1873-4669. ; 779, s. 261-269
-
Tidskriftsartikel (refereegranskat)abstract
- Phase, microstructure, and strain evolution during annealing of arc deposited TiZrAlN coatings are studied using in situ x-ray scattering and ex situ transmission electron microscopy. We find that the decomposition route changes from nucleation and growth of wurtzite AlN to spinodal decomposition when the Zr-content is decreased and the Al-content increases. Decomposition of Ti0.31Zr0.24Al0.45N results in homogeneously distributed wurtzite AlN grains in a cubic, dislocation-dense matrix of TiZrN consisting of domains of different chemical composition. The combination of high dislocation density, variation of chemical composition within the cubic grains, and evenly distributed wurtzite AlN grains results in high compressive strains, -1.1%, which are retained after 3 h at 1100 degrees C. In coatings with higher Zr-content, the strains relax during annealing above 900 degrees C due to grain growth and defect annihilation. (C) 2018 Elsevier B.V. All rights reserved.
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| 53. |
- Salamania, Janella, 1992-, et al.
(författare)
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Elucidating dislocation core structures in titanium nitride through high-resolution imaging and atomistic simulations
- 2022
-
Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 224
-
Tidskriftsartikel (refereegranskat)abstract
- Although titanium nitride (TiN) is among the most extensively studied and thoroughly characterizedthin-film ceramic materials, detailed knowledge of relevant dislocation core structures is lacking. Byhigh-resolution scanning transmission electron microscopy (STEM) of epitaxial single crystal (001)-oriented TiN films, we identify different dislocation types and their core structures. These include, besidesthe expected primary a/2{110}h110i dislocation, Shockley partial dislocations a/6{111}h112i and sessileLomer edge dislocations a/2{100}h011i. Density-functional theory and classical interatomic potentialsimulations complement STEM observations by recovering the atomic structure of the different disloca-tion types, estimating Peierls stresses, and providing insights on the chemical bonding nature at the core.The generated models of the dislocation cores suggest locally enhanced metal–metal bonding, weakenedTi-N bonds, and N vacancy-pinning that effectively reduces the mobilities of {110}h110i and {111}h112idislocations. Our findings underscore that the presence of different dislocation types and their effects onchemical bonding should be considered in the design and interpretations of nanoscale and macroscopicproperties of TiN.
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| 54. |
- Salamania, Janella, et al.
(författare)
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High temperature decomposition and age hardening of single-phase wurtzite Ti1−xAlxN thin films grown by cathodic arc deposition
- 2024
-
Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 8:1
-
Tidskriftsartikel (refereegranskat)abstract
- Wurtzite TmAlN (T-m = transition metal) themselves are of interest as semiconductors with tunable band gap, insulating motifs to superconductors, and piezoelectric crystals. Characterization of wurtzite TmAlN is challenging because of the difficulty to synthesize them as single-phase solid solution and such thermodynamic, elastic properties, and high temperature behavior of wurtzite Ti1-xAlxN is unknown. Here, we investigated the high temperature decomposition behavior of wurtzite Ti1-xAlxN films using experimental methods combined with first-principles calculations. We have developed a method to grow single-phase metastable wurtzite Ti1-xAlxN (x = 0.65, 0.75, 085, and 0.95) solid-solution films by cathodic arc deposition using low duty-cycle pulsed substrate-bias voltage. We report the full elasticity tensor for wurtzite Ti1-xAlxN as a function of Al content and predict a phase diagram including a miscibility gap and spinodals for both cubic and wurtzite Ti1-xAlxN. Complementary high-resolution scanning transmission electron microscopy and chemical mapping demonstrate decomposition of the films after high temperature annealing (950 degrees C), which resulted in nanoscale chemical compositional modulations containing Ti-rich and Al-rich regions with coherent or semicoherent interfaces. This spinodal decomposition of the wurtzite film causes age hardening of 1-2 GPa.
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| 55. |
- Sangiovanni, Davide, et al.
(författare)
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Strength, transformation toughening, and fracture dynamics of rocksalt-structure Ti1-xAlxN (0 <= x <= 0.75) alloys
- 2020
-
Ingår i: Physical Review Materials. - : AMER PHYSICAL SOC. - 2475-9953. ; 4:3
-
Tidskriftsartikel (refereegranskat)abstract
- Ab initio-calculated ideal strength and toughness describe the upper limits for mechanical properties attainable in real systems and can, therefore, be used in selection criteria for materials design. We employ density-functional ab initio molecular dynamics (AIMD) to investigate the mechanical properties of defect-free rocksalt-structure (B1) TiN and B1 Ti1-xAlxN (x = 0.25, 0.5, 0.75) solid solutions subject to [001], [110], and [111] tensile deformation at room temperature. We determine the alloys ideal strength and toughness, elastic responses, and ability to plastically deform up to fracture as a function of the Al content. Overall, TiN exhibits greater ideal moduli of resilience and tensile strengths than (Ti,Al)N solid solutions. Nevertheless, AIMD modeling shows that, irrespective of the strain direction, the binary compound systematically fractures by brittle cleavage at its yield point. The simulations also indicate that Ti0.5Al0.5N and Ti0.25Al0.75N solid solutions are inherently more resistant to fracture and possess much greater toughness than TiN due to the activation of local structural transformations (primarily of B1 -amp;gt; wurtzite type) beyond the elastic-response regime. In sharp contrast, (Ti,Al)N alloys with 25% Al exhibit similar brittleness as TiN. The results of this work are examples of the limitations of elasticity-based criteria for prediction of strength, brittleness, ductility, and toughness in materials able to undergo phase transitions with loading. Comparing present and previous findings, we suggest a general principle for design of hard ceramic solid solutions that are thermodynamically inclined to dissipate extreme mechanical stresses via transformation toughening mechanisms.
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| 56. |
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| 57. |
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| 58. |
- Stjernberg, Jesper, et al.
(författare)
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Study of the degradation process of refractory bricks in rotary kilns
- 2008
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Ingår i: Global roadmap for ceramics & ICC2 proceedings. - Faenza : Institute of Science and Technology for Ceramics. - 9788880800842
-
Konferensbidrag (refereegranskat)abstract
- Iron ore pellets are commonly sintered in a kiln insulated with bricks, which wear and need to be replaced regularly. It is desirable to increase the lifetime of those bricks. Slag/brick compatibility tests have been performed in a laboratory furnace. Slag collected from a production kiln, three commercial bricks and additions of alkali were used. Alkali dissolves the mullite in the bricks, and form the phases nepheline and kalsilite. Characterization of the microstructure showed that the degradation of the bricks was enhanced by increased temperature and amount of alkali. The slag penetration depth is more affected by increased temperature than increased dwell time.
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| 59. |
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| 60. |
- Talyzin, A V, et al.
(författare)
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Superhard and superelastic films of polymeric C60
- 2001
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Ingår i: Diamond and related materials. - 0925-9635 .- 1879-0062. ; 10:11, s. 2044-2048
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Tidskriftsartikel (refereegranskat)abstract
- The C60 thin film deposited on steel substrate was transformed by high pressure-high temperature treatment to a superhard and superclastic material. The films were studied by Raman spectroscopy in situ at 20 GPa after heating at 300░C and ex situ after the quenching. The hardness and elastic properties of the high-pressure phases have been characterized with nanoindentation. The hardness of the films were determined to be 0.5 ▒ 0.1 GPa and 61.9 ▒ 9 GPa for unmodified C60 and HPHT treated films, respectively. The hardness of the pressurized film is higher than for cubic BN but lower than hardness values reported for ultrahard fullerite samples prepared from powders. An interesting observation was that the HPHT treated film showed an extreme elastic response with an elastic recovery of approximately 90%. ⌐ 2001 Elsevier Science B.V. All rights reserved.
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| 61. |
- Tisell, L E, et al.
(författare)
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The Ki67 index a prognostic marker in medullary thyroid carcinoma.
- 2003
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Ingår i: British journal of cancer. - : Springer Science and Business Media LLC. - 0007-0920 .- 1532-1827. ; 89:11, s. 2093-7
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Tidskriftsartikel (refereegranskat)abstract
- Our objective was to examine the usefulness of the Ki67 proliferation index as a prognostic marker in patients with medullary thyroid carcinoma (MTC). It is difficult to predict the prognosis of MTC by using conventional prognostic factors. Immunocytochemical analysis of tumour proliferation has been used as a prognostic tool in some tumours, but only rarely in MTC. In all, 71 tumours from 36 patients were investigated, by using a semiautomatic image analysis programme. On average 10,000 nuclear profiles were counted per tumour, and the percentage of tumour cells expressing the proliferation marker, Ki67, was calculated. Primary tumours that had metastasised had higher Ki67 indices than primary tumours that had not metastasised. Recurrent lymph node metastasis had higher Ki67 indices than the primary tumours. By using a Poisson model, it was possible to estimate the median survival time for individual patients if the Ki67 index for the primary tumour and the age at surgery were known. The higher the Ki67 index and the age at operation were, the shorter was the survival. Estimating the median survival of individual patients will be of help for planning the patients' life and postoperative follow-up and treatment.
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| 62. |
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| 63. |
- Welin, L., et al.
(författare)
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Aspirin increases mortality in diabetic patients without cardiovascular disease: a Swedish record linkage study.
- 2009
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Ingår i: Pharmacoepidemiology and Drug Safety. - : Wiley. - 1099-1557 .- 1053-8569. ; 18:12, s. 1143-9
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: Aspirin is effective in secondary prevention of cardiovascular disease. The results are less convincing when aspirin is used for primary prevention even in high-risk patients (i.e., patients with diabetes). We therefore analyzed the effect of aspirin on mortality and serious bleeding in diabetic patients with and without cardiovascular disease. METHODS: We performed a record linkage study of the patient registry of the Västra Götaland region in south-western Sweden, the Swedish mortality register and the Swedish register of dispensed drugs. All diabetic patients (n = 58 465) from 1 July 2005 to 30 June 2006 were followed up with respect to bleeding until 31 October 2006, and mortality until 31 December 2006. RESULTS: When 19 confounding factors (diseases and interventions) were assessed, aspirin significantly increased mortality in diabetic patients without cardiovascular disease from 17% (95% confidence interval; 95%CI, 1-36) at age 50 years to 29% (16-43) at age 85 years. In contrast aspirin tended to decrease mortality among elderly diabetic patients with cardiovascular disease. Theoretical calculations indicated that aspirin caused 107 excess deaths among diabetic patients without cardiovascular disease and prevented 164 deaths among diabetic patients with cardiovascular disease. Aspirin also increased the risk of serious bleeding by 46% (95%CI, 22-75) in diabetic patients without cardiovascular disease but decreased the risk among those with cardiovascular disease. CONCLUSION: Aspirin use in diabetes patients without cardiovascular disease remains controversial and current guidelines should be revised until results from ongoing large randomized controlled trials become available.
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| 64. |
- Wilhelmsen, Lars, 1932, et al.
(författare)
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Factors associated with reaching 90 years of age : a study of men born in 1913 in Gothenburg, Sweden
- 2011
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Ingår i: Journal of Internal Medicine. - : Wiley. - 0954-6820 .- 1365-2796. ; 269:4, s. 441-451
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Tidskriftsartikel (refereegranskat)abstract
- Objectives. Increasing numbers of people reach old age. We wanted to identify variables of importance for reaching 90 years old and determine how the predictive ability of these variables might change over time. Setting and subjects. All men in the city of Gothenburg born in 1913 on dates divisible by 3, which is on the 3rd, 6th, 9th etc., were included in the study. Thus, 973 men were invited, and 855 were examined in 1963 at age 50. Further examinations were made at age 54, 60 and 67. Anthropometric data, lifestyle and parental factors, blood pressure, lung function, X-ray of heart and lungs and maximum work performance were recorded. The area under the receiver operating characteristic curve was used to analyse the predictive capacity of a variable. Results. A total of 111 men (13%) reached 90 years of age, men who reached 90 years were more likely at age 50 to be nonsmokers, consume less coffee, have higher socio-economic status and have low serum cholesterol levels than those who did not reach this age; however, at age 50 or 62, parents' survival was of no prognostic importance. Variables of greatest importance at higher ages were low blood pressure and measures related to good cardiorespiratory function. In multivariable analysis, including all examinations, being a nonsmoker, consuming small amounts of coffee, having high housing costs at age 50, good maximum working capacity and low serum cholesterol were related to a better chance of survival to age 90. Conclusions. Low levels of cardiovascular risk factors, high socio-economic status and good functional capacity, irrespective of parents' survival, characterize men destined to reach the age of 90.
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| 65. |
- Wilhelmsen, Lars, 1932, et al.
(författare)
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Saving lives, money and resources: drug and CABG/PCI use after myocardial infarction in a Swedish record-linkage study
- 2010
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Ingår i: European Journal of Health Economics. - : Springer Science and Business Media LLC. - 1618-7598 .- 1618-7601 .- 1439-6637. ; 11:2, s. 177-184
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Tidskriftsartikel (refereegranskat)abstract
- Drug costs are increasing despite the introduction of cheaper generic drugs. The aim of the present study was to analyse the entire costs of hospital care, out-patient care, and the cost of drugs for 16 months following a myocardial infarction (MI) to see to what extent drug costs contribute to the overall costs of care. Diagnoses and costs for care as well as mortality data obtained from the Vastra Gotaland Region, Sweden, and drug costs from the Swedish Board of Health and Welfare, were merged in a computer file. Patients registered from 1 July 2005 to 30 June 2006 were followed from 28 days after an MI, with follow-up until 31 October 2006. Of 4,725 patients, 711 died before the start of the study and 721 during follow-up. Higher age [hazard ratio (HR, 95%CI) = 1.06 (1.05-1.07)], previous MI [HR = 1.31 (1.13-1.53)] and diabetes mellitus [HR = 1.34 (1.13-1.58)] were associated with increased mortality, which decreased with coronary interventions: CABG/PCI [HR = 0.19 (0.14-0.27)]. In a multivariable analysis, mortality was lower for patients taking simvastatin [HR = 0.62 (0.50-0.76)] and clopidogrel [HR = 0.58 (0.46-0.74)]. Costs for out-patient care accounted for 25% and drugs for 5% of total costs. If patients not treated with simvastatin or clopidogrel had received these drugs, an additional 154-306 lives might have been saved. Drug costs would be higher, but total costs lower. Thus, even expensive drugs may reduce overall costs.
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| 66. |
- Yang, Jing, et al.
(författare)
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Contact damage resistance of TiN-coated hardmetals: Beneficial effects associated with substrate grinding
- 2015
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Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 275, s. 133-141
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Tidskriftsartikel (refereegranskat)abstract
- Contact loading is a common service condition for coated hardmetal tools and components. Substrate grinding represents a key step within the manufacturing chain of these coated systems. Within this context, the influence of surface integrity changes caused by abrasive grinding of the hardmetal substrate, prior to coating, is evaluated with respect to contact damage resistance. Three different substrate surface finish conditions are studied: ground (G), mirror-like polished (P) and ground plus heat-treated (GTT). Tests are conducted by means of spherical indentation under increasing monotonic load and the contact damage resistance is assessed. Substrate grinding enhances resistance against both crack nucleation at the coating surface and subsequent propagation into the hardmetal substrate. Hence, crack emergence and damage evolution is effectively delayed for the coated G condition, as compared to the reference P one. The observed system response is discussed on the basis of the beneficial effects associated with compressive residual stresses remnant at the subsurface level after grinding, ion-etching and coating. The influence of the stress state is further corroborated by the lower contact damage resistance exhibited by the coated GTT specimens. Finally, differences observed on the interaction between indentation-induced damage and failure mode under flexural testing points in the direction that substrate grinding also enhances damage tolerance of the coated system when exposed to contact loads.
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| 67. |
- Yang, Jing, et al.
(författare)
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Grinding effects on surface integrity and mechanical strength of WC-Co cemented carbides
- 2014
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Ingår i: 2ND CIRP CONFERENCE ON SURFACE INTEGRITY (CSI). - : ELSEVIER SCIENCE BV. ; , s. 257-263
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Konferensbidrag (refereegranskat)abstract
- In this study, the correlation existing among grinding, surface integrity, and flexural strength is investigated for WC-Co cemented carbides (hardmetals). A fine-grained WC-13 wt % Co grade and three different surface conditions: (1) ground, (2) mirror-like polished (reference), and (3) ground plus high-temperature annealed, are investigated. Surface integrity and mechanical characterization is complemented with fractography. The grinding strongly affects both surface integrity and flexural strength. During grinding, a damaged thin layer together with high compressive residual stresses is introduced. The layer results in considerable strength enhancement compared to the reference polished surface condition. Fractography reveals that the improved strength mainly stems from grinding-induced changes on effective location, from surface into subsurface levels, of the strength-controlling flaw.
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| 68. |
- Yang, Jie, et al.
(författare)
-
Grinding-induced metallurgical alterations in the binder phase of WC-Co cemented carbides
- 2017
-
Ingår i: Materials Characterization. - : ELSEVIER SCIENCE INC. - 1044-5803 .- 1873-4189. ; 134, s. 302-310
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Tidskriftsartikel (refereegranskat)abstract
- The metallic binder phase dictates the toughening behavior of WC-Co cemented carbides (hardmetals), even though it occupies a relative small fraction of the composite. Studies on deformation and phase transformation of the binder constituent are scarce. Grinding represents a key manufacturing step in machining of hardmetal tools, and is well-recognized to induce surface integrity alterations. In this work, metallurgical alterations of the binder phase in ground WC-Co cemented carbides have been assessed by a combination of electron back scattered diffraction and transmission electron microscopy techniques. The Co-base binder experiences a martensitic phase transformation from fcc to hcp crystal structure, predominantly in the first 5 mu m below the surface. The hcp fraction decreases gradually along a depth of 10 mu m. Surface Co displays severe plastic deformation under the highest strain, resulting in formation of nanocrystalline grains in the first micrometer below the surface. Microstructural refinement within the binder phase is observed even at greater depth. Stacking faults were detected in most of the refined grains. The metallurgical alterations of the binder phase modify the local stress distribution during grinding, which affects the discerned subsurface microcracking. The resulting residual stress profile is the sum of multiple subsurface changes, such as phase transformation, severe plastic deformation and grain refinement, where it is discerned that the depth profile of the transformed hcp-Co fraction coincides with the grinding-induced residual stress profile.
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| 69. |
- Yang, Jie, et al.
(författare)
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Implementation of advanced characterisation techniques for assessment of grinding effects on the surface integrity of WC-Co cemented carbides
- 2018
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Ingår i: Powder Metallurgy. - : Taylor & Francis. - 0032-5899 .- 1743-2901. ; 61:2, s. 100-105
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Tidskriftsartikel (refereegranskat)abstract
- Grinding is a key step on the manufacturing process of WC-Co cemented carbides (hardmetals). In this work, an investigation of grinding effects on the surface integrity of hardmetals is conducted. It is done by combining diverse advanced characterisation techniques: X-ray diffraction, field emission-scanning electron microscopy, electron back scatter diffraction, focused ion beam - 3D tomography and transmission electron microscopy. The study is carried out in a fine-grained WC-Co grade. Besides ground state, polished surface finish condition is assessed for comparison purposes. It is evidenced that grinding induces significant alterations: 3D tomography illustrates microcracking exists down to 2.5 mu m depth with a highly anisotropic distribution at the subsurface, large compressive residual stresses extending until subsurface levels of about 12 mu m, and phase transformation of binder from the original fcc phase into the hcp one, as well as severe plastic deformation observed within the binder at the surface level.
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| 70. |
- Yang, Jing, et al.
(författare)
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Influence of substrate microstructure and surface finish on cracking and delamination response of TiN-coated cemented carbides
- 2016
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Ingår i: Wear. - : ELSEVIER SCIENCE SA. - 0043-1648 .- 1873-2577. ; 352-353, s. 102-111
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Tidskriftsartikel (refereegranskat)abstract
- The cracking and delamination of TiN-coated hardmetals (WC-Co cemented carbides) when subjected to Brale indentation were studied. Experimental variables were substrate microstructure related to low (6 wt% Co) and medium (13 wt% Co) binder content, and surface finishes associated with grinding and polishing stages before film deposition. Brale indentation tests were conducted on both coated and uncoated hardmetals. Emphasis has been placed on assessing substrate microstructure and subsurface finish effects on load levels at which cracking and delamination phenomena emerge, the type of cracking pattern developed, and how fracture mechanisms evolve with increasing load. It is found that polished and coated hardmetals are more brittle (radial cracking) and the adhesion strength (coating delamination) diminishes with decreasing binder content. Such a response is discussed on the basis of the influence of intrinsic hardness/brittleness of the hardmetal substrate on both cracking at the subsurface level and effective stress state, particularly regarding changes in shear stress component. Grinding promotes delamination compared to the polished condition, but strongly inhibits radial cracking. This is a result of the interaction between elastic-plastic deformation imposed during indentation and several grinding-induced effects: remnant compressive stress field, pronounced surface texture and micro cracking within a thin altered subsurface layer. As a consequence, coating spallation prevails over radial cracking as the main mechanism for energy dissipation in ground and coated hardmetals. (C) 2016 Elsevier B.V. All rights reserved.
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| 71. |
- Yang, J., et al.
(författare)
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Mechanical strength of ground WC-Co cemented carbides after coating deposition
- 2017
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Ingår i: Materials Science & Engineering. - : ELSEVIER SCIENCE SA. - 0921-5093 .- 1873-4936. ; 689, s. 72-77
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Tidskriftsartikel (refereegranskat)abstract
- Manufacturing of hardmetal tools often involves surface grinding, ion etching and final coating. Each stage throughout the manufacturing chain introduces surface integrity changes which may be critical for defining the final mechanical behavior of the coated tools. Within this context, an experimental test program has been developed to assess the influence of a coating (TiN) deposition on surface integrity and transverse rupture strength of a previously ground fine-grained WC-Co grade substrate. Four different substrate surface finish conditions (prior to ion etching and coating) were evaluated: as sintered (AS), ground (G), polished (P), and ground plus high temperature annealing (GTO. Surface integrity and fracture resistance characterization, complemented with a detailed fractographic analysis, were performed on both uncoated and coated samples. Results show that the surface integrity after grinding has been partly modified during the ion etching and film deposition processes, particularly in terms of a reduced compressive residual stress state at the substrate surface level. Consequently, the grinding induced strength enhancement in hardmetals is reduced for coated specimens. Main reason behind it is the change of nature, location and stress state acting on critical flaw: from processing defects existing at the subsurface (uncoated G specimens) to grinding-induced microcracks located close to the interface between coating and substrate, but within the subsurface of the latter (coated G specimens). This is not the case for AS and P conditions, where flexural strength does not change a result of ion etching and coating. Finally, fracture resistance increases slightly for GTT specimens after coating process, possibly caused by a beneficial effect of the deposited film on the residual stress state at the surface.
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| 72. |
- Yang, J., et al.
(författare)
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Substrate surface finish effects on scratch resistance and failure mechanisms of TiN-coated hardmetals
- 2015
-
Ingår i: Surface & Coatings Technology. - : Elsevier. - 0257-8972 .- 1879-3347. ; 265, s. 174-184
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the influence of substrate surface finish on scratch resistance and associated failure mechanisms is investigated in the case of a TiN-coated hardmetal. Three different surface finish conditions are studied: as-sintered (AS), ground (G), and mirror-like polished (P). For G conditioned samples, scratch tests are conducted both parallel and perpendicular to the direction of the grinding grooves. It is found that coated AS, G and P samples exhibit similar critical load for initial substrate exposure and the same brittle adhesive failure mode. However, the damage scenarios are different, i.e. the substrate exposure is discrete and localized to the scratch tracks for G samples while a more pronounced and continuous exposure is seen for AS and P ones. Aiming to understand the role played by the grinding-induced compressive residual stresses, the study is extended to coated systems where ground substrates are thermal annealed (for relieving stresses) before being ion etched and coated. It yielded lower critical loads and changes in the mechanisms for the scratch-related failure; the latter depending on the relative orientation between scratching and grinding directions. (C) 2015 Elsevier B.V. All rights reserved.
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| 73. |
- Yang, Jie, et al.
(författare)
-
Thermally induced surface integrity changes of ground WC-Co hardmetals
- 2016
-
Ingår i: 3RD CIRP CONFERENCE ON SURFACE INTEGRITY. - : Elsevier. ; , s. 91-94
-
Konferensbidrag (refereegranskat)abstract
- Ground hardmetals are exposed to high temperatures during both processing (e.g. coating deposition) and use (e.g. as a cutting tool). However, studies on thermally induced changes of surface integrity are limited. Here we address this by means of FIB/FESEM and EBSD investigation, with special focus on the binder phase characterization. Our findings indicate that thermal treatment causes two main surface modifications. First, an unexpected microporosity appears in the binder within the subsurface layer when ground surfaces are heated. Second, the metallic phase underneath the ground surface experiences metallurgical changes, in terms of grain and crystallographic phase structures. The mechanisms responsible for these modifications of the binder are discussed in terms of grinding-induced and thermally-reversed phase transformation as well as recrystallization phenomena. We also note that no additional heat treatment related changes such as microcracking and carbide fragmentation in the subsurface layer, are discerned. (C) 2016 The Authors. Published by Elsevier B.V.
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