Titanium carbide (TiC) and titanium carbonitride (Ti(C,N)) are both common components in hard, wear resistant ceramic-metal composites, or cermets. In this study the intermetallic nickel aluminide (Ni3Al) has been used as a binder for the production of TiC and Ti(C,N) based cermets. These cermets offer several improved characteristics relative to conventional WC-based ‘hardmetals’, such as lower mass and improved oxidation resistance, which are also combined with high fracture resistance, hardness and wear resistance. The cermets were produced using an in-situ, reaction sintering procedure to form the stoichiometric Ni3Al binder, with the binder contents varied from 20 to 40 vol%. However, for high N content Ti(C,N) cermets, the wettability of molten Ni3Al is relatively poor, which leads to materials with residual porosity. Therefore various amounts of Mo2C (1.25, 2.5, 5 and 10 vol%) were incorporated into the Ti(C0.3,N0.7)-Ni3Al cermets, with the aim of improving the densification behaviour. Mo2C was found to improve upon the wettability during sintering, thus enhancing the densification, especially at the lower binder contents. The tribological behaviour of TiC and Ti(C,N) cermets have been evaluated under reciprocating sliding conditions. The wear tests were conducted using a ball-on-flat sliding geometry, with a WC-Co sphere as the counter-face material, for loads from 20 to 60 N. The wear response was characterised using a combination of scanning electron microscopy, energy dispersive X-ray spectroscopy, and focused ion beam microscopy. Initially, two-body abrasive wear was observed to occur, which transitions to three-body abrasion through the generation of debris from the cermet and counter-face materials. Ultimately, this wear debris is incorporated into a thin tribolayer within the wear track, which indicates a further transition to an adhesive wear mechanism. It was found that Mo2C additions had a positive effect on both the hardness and indentation fracture resistance of the samples, but had a detrimental effect on the sliding wear response of the cermets. This behaviour was attributed to increased microstructural inhomogeneity with Mo2C additions.

Baigiamajame magistro darbe apžvelgti laboratoriniai ir praktiniai abrazyvinio dėvėjimosi tyrimų metodai. Sumontuotas ekskavatoriaus kaušo dantų abrazyvinio dėvėjimosi stendas, sudaryta nauja tyrimo metodika. Tyrimas buvo atliktas su šešiais ekskavatoriaus kaušo dantimis: trys aplydyti „Anykščių vario“, du ESAB firmų elektrodais, vienas dantis neaplydytas. Darbe ištirtos neaplydyto ir aplydytų skirtingais elektrodais ekskavatoriaus kaušo dantų abrazyvinio dėvėjimosi charakteristikos, pateiktos išvados ir rekomendacijos. / The final magistracy work review laboratory and field abrasive wear test methods. New excavator bucket teeth abrasive wear tester was mounted and new research method was created. Research was developed with six excavator bucket’s teeth: three teeth were coating with “Anyksciu varis” company electrodes, two teeth were coating with ESAB company electrodes and one tooth wasn’t coating. In this work are analysing teeth that are coating with several types electrodes or without them, abrasive wear performances. It was present conclusion and recommendation.

The cutting action of a single abrasive grain was investigated using a combination of high-speed scratch tests and finite element models. The high-speed scratch tests were unique in that the cutting conditions of a grinding operation were closely replicated. Two geometries were tested: a round-nosed stylus to approximate a 15-grit abrasive grain and a flat-nosed stylus to approximate a worn 46-grit abrasive grain. The three-dimensional finite element model was unique in that a hybrid Euler-Lagrange method was implemented to efficiently model the interaction between an abrasive grain and a workpiece. The finite element model was initially validated using indentation tests to remove the complexities of relative motion from the validation process. The validation was completed through comparisons to the experimental scratch tests. The results of the analysis revealed several key findings. Rubbing, plowing, and cutting do not display distinct transitions; rather, they coexist with different weightings depending on the scratching speed and the depth of cut. The normal forces increased for a given depth of cut as the scratching speed was increased due to strain-rate hardening of the workpiece. The tangential forces decreased for a given depth of cut as the scratching speed was increased due to a reduction in the coefficient of friction and a change in the cutting mechanics from plowing to cutting. The change in the cutting mechanics was investigated by analyzing the evolution of the scratch profiles as the depth of cut and scratching speed were changed. It was found that higher scratching speeds produced less material pile-up and this was attributed to a change in the cutting mechanics. Due to the change in the cutting mechanics, the specific energy decreased as the depth of cut and scratching speed were increased. A numerical case study revealed that reducing the grain size resulted in: lower forces, lower specific energies, and smaller volumes of subsurface stresses. The finite element model was adapted to work in conjunction with the flat-nosed stylus creating the first model capable of simulating the cutting of an abrasive grain in three dimensions.

Titanium carbonitride (Ti(C,N)) cermets have become more popular in recent research due to their mix of high hardness, high hot hardness, good ductility, chemical stability, and low densities. These mechanical properties make Ti(C,N)-cermets especially desirable as a replacement for current ‘hardmetals’, such as tungsten carbide cobalt (WCCo), as it is known that WC-Co exhibits poor mechanical behaviour at elevated temperatures. Additional interest and research has been conducted in reference to binders which enhance the cermet’s capability to retain strength at high temperatures while remaining ductile. One such binder, Ni3Al actually increases in yield strength up to a temperature of ~900°C. In this thesis, the production method utilizing melt infiltration for TiC, Ti(C0.7,N0.3), Ti(C0.5,N0.5), and Ti(C0.3,N0.7)-based cermets with Ni3Al binder contents of 20, 30 and 40 vol. % have successfully been developed and utilized. This process produced high density samples at each nitrogen content for all binder contents, excluding Ti(C0.3,N0.7). Ti(C0.3,N0.7)-Ni3Al samples at 20 and 30 vol. % suffered from poor infiltration and could not be tested. The reciprocating wear mechanisms were examined, using a ball-on-flat test, utilizing WC-Co spheres with a diameter of 6.35 mm as a counter-face, and test parameters of 20 Hz, 2 hrs., and applied loads of 20, 40, 60 and 80 N. The wear tracks were examined using optical profilometry, SEM, and EDS to determine the volumetric wear rate, and the dominant wear mechanisms. The wear volume, and wear mechanisms were compared with the effect of binder content, nitrogen content, and applied load.

No description available.

The present study investigated the effect of dilute polymer solutions on the size, shape, and roughness of channels and holes, machined in metal and glass using a novel abrasive slurry-jet micro-machining (ASJM) apparatus. The apparatus consisted of a slurry pump and a pulsation damper connected to an open reservoir tank to generate a 140-micron turbulent jet containing 1 wt% 10-micron alumina particles. With the addition of 50 wppm of 8-M (million) molecular weight polyethylene oxide (PEO), the widths of the channels and diameters of holes machined in glass decreased by an average amount of 25%. These changes were accompanied by approximately a 20% decrease in depth and more V-shaped profiles compared with the U-shape of the reference channels and holes machined without additives. The present results demonstrate that a small amount of a high-molecular-weight polymer can significantly decrease the size of machined channels and holes for a given jet diameter.

The present study investigated the effect of dilute polymer solutions on the size, shape, and roughness of channels and holes, machined in metal and glass using a novel abrasive slurry-jet micro-machining (ASJM) apparatus. The apparatus consisted of a slurry pump and a pulsation damper connected to an open reservoir tank to generate a 140-micron turbulent jet containing 1 wt% 10-micron alumina particles. With the addition of 50 wppm of 8-M (million) molecular weight polyethylene oxide (PEO), the widths of the channels and diameters of holes machined in glass decreased by an average amount of 25%. These changes were accompanied by approximately a 20% decrease in depth and more V-shaped profiles compared with the U-shape of the reference channels and holes machined without additives. The present results demonstrate that a small amount of a high-molecular-weight polymer can significantly decrease the size of machined channels and holes for a given jet diameter.

The wear process in three-body contact causes problems of abrasion such as volume loss and changes of geometry of the triboelements. The wear problem leads to increased failure and high costs for repairing or replacing equipment. To understand the nature of the wear behaviour and to predict the wear rate in advance, experimental investigation and numerical simulation of the wear process are required. In this work, the wear process is analysed and the influencing parameters governing the wear behaviour are investigated experimentally to develop a new wear model. Main influential factors are considered such as kinematics of abrasive particles, contact stiffness of the particle layer, friction characteristics, and wear factors. The experiments to study kinematics of particle layers are performed on a new observation tester. To define the contact stiffness of abrasive particles, experiments are conducted by the uniaxial spindle compression tester. Moreover, a tribometer test rig with applied load up to 200 N and velocity up to 1000 mm/s is used to investigate the friction characteristics and the wear behaviour of three-body tribosystem. Analyses of influential factors on the wear behaviour in dependency of predefined process parameter are carried out. Additionally, based on the results of the experimental investigations, approximation equations representing the relation of the influential factors and the process parameters are determined. A three-body wear model is build up to represent the wear behaviour by physical wear laws. Furthermore, these approximation equations and the relevant parameters obtained by experimental investigations are included in the Fleischer’s wear equation to simulate the wear process. With the coupled model the wear process of the sample can be simulated twodimensional over the sliding distance. It is possible to predict the wear depth and the wear intensity, which can be used to estimate the wear rate. Additionally, from the results of the wear simulation the worn surface and the local contact pressure in the contact region are determined which provide a deeper insight into the wear process. With this simulation the understanding of the wear behaviour can be improved which is important to solve wear problems.

Surface preparation is the key factor in determining the success of a protective coating system and its ultimate objective is to create proper adhesion of a coating over an underlying substrate. Abrasive blast cleaning involves mechanical cleaning by the continuous impact of abrasive particles at high velocities on to the substrate in a jet stream of compressed air. Industries that use abrasive blasting include the shipbuilding industry, automotive industry, and other industries that involve surface preparation and painting. Materials from different origins can be used as a blasting media including coal slag, smelter slag, mineral abrasives, metallic abrasives, and synthetic abrasives. Purpose of this thesis is to investigate the usability of industrial wastes (coal slag, smelter slags, etc.) of Turkey as abrasives in surface preparation technologies. Four different slag samples of three sources, namely coal furnace slag sample from &Ccedil / ayirhan thermal power plant, ferrochrome slag sample from Eti Krom A.S., granulated blast furnace and converter slag sample from Eregli Iron and Steel Works were studied within the scope of this thesis work. The samples were prepared by crushing and screening. The chemical composition and physical characteristics of the samples were determined. All the samples were tested in industrial scale. Test results showed that the converter slag meet all the specifications for abrasives and it can be used in blast cleaning operations. However, coal furnace slag, granulated blast furnace slag and ferrochrome slag are not suitable to be used as abrasive in surface preparation technologies.

O objetivo desta pesquisa é realizar um estudo sobre o desgaste abrasivo do ferro fundido branco alto cromo de acordo com a norma ASTM A532 II D, submetidas à diferentes faixas de temperatura de austenitização, decompondo a faixa de 950 a 1.150 ºC, amplamente usada nas fundições, em intervalos de 50 ºC. Esta liga foi escolhida para estudo em virtude de sua extensa aplicação na indústria de mineração, possuindo como principal característica a utilização em revestimentos de moinhos e martelos de britadores, onde a resistência ao desgaste abrasivo é exigida. Os corpos de prova foram caracterizados através de análise química, dureza, e estrutura metalográfica, avaliando as mudanças na microestrutura, e consequentemente, alterações nas propriedades de resistência ao desgaste abrasivo do material. Na avaliação das amostras, foi utilizada a microscopia ótica e, para simular a condição de desgaste abrasivo, determinando a perda de massa, foi empregando o abrasômetro do tipo roda de borracha, seguindo a norma ASTM G65. Os testes práticos demostraram que o ciclo de temperatura é uma etapa importante na determinação da dureza, que por sua vez, é uma característica fundamental à resistência ao desgaste abrasivo, visto que para o material estudado, quanto maior a dureza, maior foi a resistência ao desgaste abrasivo. / The objective of this research is to perform a study on the abrasive wear of high chromium white cast iron according to ASTM A532 II D, submitted to different austenitizing temperatures, in the range of 950 to 1150 ºC with 50 ºC steps, widely used in foundries. This alloy was chosen for study because of its extensive application in the mining industry, having as main characteristic the use in mill and hammer coatings of crushers where abrasive wear resistance is required. The specimens were characterized by chemical analysis, hardness, and metallographic analysis, evaluating the changes in the microstructure, and consequently changes in the abrasive wear properties of the material. In the evaluation of the samples, optical microscopy was used and, to simulate the abrasive wear condition, determining the mass loss, the rubber wheel type abrasive test was used, following the ASTM G65 standard. The practical tests demonstrated that the temperature cycle is an important step in determining the hardness, which in turn is a fundamental characteristic to the abrasive wear resistance, since for the material studied, the higher the hardness, the higher the resistance to abrasive wear.