A common goal for industrial manufacturers is to create a safer working environment and reduce production costs. One common method to achieve this goal is to drastically reduce cutting fluid use in machining. Recent advances in machining technologies have made it possible to perform machining with minimum-quantity lubrication (MQL). Drilling takes a key position in the realization of MQL machining. In this study the effects of using MQL in drilling AISI 1018 steel with HSS tools using a vegetable based lubricant were investigated. A full factorial experiment was conducted and regression models were generated for both surface finish and hole size. Lower surface roughness and higher tool life were observed in the lowest speed and feed rate combination.

Please read the abstract in the section 00front of this document / Dissertation (M Eng (Chemical Engineering))--University of Pretoria, 2005. / Chemical Engineering / unrestricted

During the cold reduction of steel sheet in a rolling mill, rolling oils are used for lubrication to provide the desired steel surface. Rolling oil formulations consist largely of mineral oils, glycerides and/or synthetic esters, fatty acids, emulsifiers and additives. These oils are generally used as 2-5% emulsions and will be subjected to high temperature and pressure during use. This results in chemical changes within the oil that can affect steel surface cleanliness after annealing. It is advantageous to have rolling oils that are stable but easily removed during annealing and leaving a minimal amount of residues. Thus in the field of rolling mill technology the surface quality of rolled product and stability of rolling oils are critical in the selection of lubricants. Additionally, production cost and environmental impact are also critical in the selection of lubricants. In this study, the performance of vegetable-based rolling oils was investigated by recording the FTIR spectra of the oils using Horizontal Attenuated Total Reflectance, an internal reflection accessory, before and after systematic heat treatment. Evidence was found that the vegetable-based oils degraded on heating and the spectroscopic analysis indicated that this was due to rearrangement of unsaturated components from a cis to a trans configuration. / Dissertation (MSc)--University of Pretoria, 2008. / Chemistry / unrestricted

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As a type of steel with notable resistance to thermal fatigue, cracking, and abrasion, AISI H13, is known for its machining ease, high hardness, and consistent heat treatment response. These qualities make AISI H13 a preferred choice for fabricating dies, moulds, and tools exposed to high temperatures, rendering it popular in metalworking. Enhanced cooling technology in die and casting moulds necessitates intricate geometries achievable through additive manufacturing (AM). To further advance part complexity and surface finish in inaccessible regions, the industry is increasingly adopting additive-subtractive hybrid manufacturing (ASHM), showing promising growth. There are, however, some concerns associated with this process, especially with the subtraction part, which is done through machining. These include the low machinability of the workpiece due to the higher hardness of additively manufactured parts compared to conventional methods. These issues are more pronounced in ASHM processes because liquid coolants or lubricants cannot be easily used, nor can the parts be heat-treated before machining. As a first step in this study, we performed a comprehensive literature review on solid lubricants used in machining so far. Their effectiveness, mechanisms, challenges, and recent developments were discussed in detail. The main purpose of this study was to introduce and investigate the effectiveness of our novel metallic solid lubricant coating for machining of AISI H13 additive manufactured parts in ASHM processes. Since the goal of this study was to mimic the ASHM process, the lubricant coating was used in dry machining, without the application of any liquid lubricant or coolant. Moreover, the workpiece was not heat treated and the tests were performed on an as-built additively manufactured AISI H13 part. A detailed study was performed to assess the impact of these lubricant coatings on AISI H13 surface integrity. The findings showed that the soft metallic lubricant coating considerably reduced the machining force and improved the surface roughness subsurface properties of the part. This method proved to be an effective solution for avoiding lubricants in ASHM processes, while significantly improving the machinability of AISI H13 parts in ASHM processes. / Thesis / Master of Applied Science (MASc) / AISI H13 tool steel is extensively utilized in tooling applications due to its exceptional wear resistance, toughness, and capability to maintain hardness at high temperatures, making it an asset for industrial uses, particularly in die and tooling manufacturing. One significant application is in the fabrication of conformal cooling channels, where additive manufacturing (AM) is the preferred method for creating intricate geometries. With the introduction of additive subtractive hybrid manufacturing (ASHM), there's an opportunity to enhance both the surface finish and the complexity of designs. However, ASHM introduces specific challenges, notably in machining. This study aims to tackle these challenges by focusing on a dry machining process for AISI H13, omitting the use of coolant and investigating the impact on surface integrity. By integrating a novel class of solid lubricant coating, the research seeks to bypass traditional methods, aiming for an improvement in machining outcomes. The results indicate that this new class of lubricant coating could significantly enhance the machining process, providing an exceptional alternative to conventional approaches and contributing to the advancement of manufacturing technologies.

The lubrication of ceramic materials is a difficult problem; conventional lubrication techniques are limited or often ineffective. Therefore, the concept of tribopolymerization -- originally proposed by Furey and later modified by Furey and Kajdas -- is used as a new approach to boundary lubrication of ceramics. In this approach, potential polymer-forming compounds are used in minor concentrations in a carrier fluid, which polymerize at the contact region under the sliding action to form a protective layer at the contact. Selected monomers -- including one condensation type, C₃₆ dimer acid/ ethylene glycol monoester, and five addition type, i.e., lauryl methacrylate, diallyl phthalate, vinyloctadecyl ether, vinyl acetate and methyl-2-acrylamido-2- methoxy acetate, were used at 1% concentration in hexadecane in pin-on-disk tests with sliding alumina and zirconia ceramic systems. Results showed that wear reductions of alumina by up to 80% were achieved at room temperature. At elevated temperatures (up to 150°C), the monomers were also effective; one of the monomers reduced wear by over 90% at higher temperatures. In the zirconia system, the monomers in general were also effective in reducing wear, but not to the same extent as with alumina. There was no significant effect of the monomers on friction. Detailed surface analytical studies of the worn surfaces lubricated with the monomer solutions using Fourier transform infrared microspectroscopy, X-ray photoelectron spectroscopy and mass spectrometry showed the complex nature of tribochemistry involved in the antiwear action of these monomers. In addition to the polymerization, evidence of chemical reactions of the monomers with the ceramic substrate was found. Using an advanced infrared microscope system, surface temperatures at the lubricated contacts of alumina-on-sapphireand zirconia-on-sapphiresystems were measured for selected monomers. In general the temperatures were very low. Theoretical estimations of surface temperatures using Vick’s model were also carried out for several systems (including the ones studied in the past) and the role of surface temperature in the anti-wear action of the monomers was examined. The relationship is complex; but the general trend suggests that temperatures are important for tribopolymerization of the monoester, whereas not so much so for the addition monomers. A molecular modeling software -- CHEM-X -- was also used to obtain additional insight into the mechanisms of anti-wear action of the monomers. In this exploratory study, 3-dimensional shapes of the monomers, their polymerization mechanisms, and possible orientation of a selected monomer on polymerization mechanisms, and possible orientation of a selected monomer on a ceramic surface was examined. Possible mechanisms of anti-wear action of these monomers are proposed. For the monoester, the mechanism involves (a) an initial adsorption of the carboxylic end of the molecules on the surface, (b) chemical reaction with the surface to form a soap, and (c) the formation and outward growth of oligomer/polymer chains somewhat similar in structure to a Langmuir-Blodgett multi-layer. The mechanism of anti-wear action of the addition monomers is believed to be connected to the negative-ion radical action mechanism (NIRAM) as proposed by Kajdas. According to this mechanism, exoelectron emitted during sliding initiate tribopolymerization of vinyl monomers, and monomers polymerizing only by anionic or free radical mechanisms are capable of tribopolymerization on the ceramic surfaces. It is proposed that the formed polymeric products act as a binding medium for fine wear debris particles generated during sliding. As a result, a strongly bonded debris layer -- somewhat similar to a ceramic powder reinforced polymer composite -- forms on the surface. This layer provides protection to the sliding surfaces against wear. / Ph. D.

An experimental study of ceramic lubrication through the concept of tribopolymerization from the vapor phase is presented. Four vinyl monomer additives were studied, i.e., vinyl acetate, diallyl phthalate, lauryl methacrylate, and vinyl octadecyl ether. The liquid additives were heated, vaporized, and delivered to an enclosed alumina-on-alumina "pin-on-disk” contact region by a stream of dry nitrogen gas. Alumina ball wear reductions of up to 99% were observed and total wear reductions (ball and disk) of over 70% were also common. Colorful surface films visible to the naked eye were examined. Monomer concentration does not appear to have an effect over the range examined. But, higher monomer delivery temperatures have a significant beneficial effect in reducing wear. Selective FTIRM analysis shows evidence of both polymerization and monomer reactions with the alumina surface. It is believed that the surface films formed reduce adhesion and therefore decrease both wear and friction. The development, design, and construction of a high load, high speed, high frictional heat generation pin-on-disk machine is presented. A very successful geometry has been created and recommendations for added instrumentation and its future use for both liquid and vapor phase tests are presented. / Master of Science

Ceramics have a wide variety of applications due to their unique properties; however, the low fracture toughness leads the formation and propagation of unpredictable cracks, and reduces their reliability. To solve this problem, self-healing adaptive oxides were developed. The aim of the work is to gain new insights into self-healing mechanisms of ceramics and their application. Binary oxide systems were investigated that are at least partially healed through the extrinsic or intrinsic addition of silver or silver oxide to form ternary oxides (e.g., Nb2O5 + Ag → AgNbO3). Sintered pellets and coatings were tested. For self-healing TBCs, model systems that were studied include YSZ-Al2O3-SiC, YSZ-Al2O3-TiC, YSZ-Al2O3-Nb2O5, and YSZ-Al2O3-Ta2O5. Laser cladded samples and sintered pellets were produced to test. The healing process occurs due to the formation of oxidation products and glassy phases depending on the self-healing mechanism. X-ray diffraction was used to explore phase evolution, chemical compositions, and structural properties of these samples. SEM equipped with EDS was used to investigate the chemical and morphological properties for the cross-sectional area. Pin-on-disc test was applied to test tribology performance for Nb2O5-Ag2O system, and infiltration test was applied to test CMAS-resistance for TBCs at elevated temperature. The improvements in the performance of these materials were demonstrated.

by Ha Fu-Lam. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1989. / Bibliography: leaves 61-63.

Resumo: No processo de retificação e utilização de fluidos de corte é uma maneira de implementar a qualidade final ao processo, pois os fluidos têm como finalidade a lubrificação na área de contato entre a peça e ferramenta e a refrigeração das superfícies, assim evitando danificações na superfície da peça. Com isso, a utilização de fluidos de corte tem sido constantemente estudada, visando diminuir a utilização deste, pois a utilização de fluidos de corte tem seus problemas. O custo do produto final aumenta consideravelmente com o uso de fluidos de corte no processo de retificação, além de que os fluidos de corte são substâncias tóxicas e nocivas tanto às pessoas quanto ao meio ambiente. Portanto indústrias, universidades e centro de pesquisas são levados a pesquisar métodos alternativos menos prejudiciais ao meio ambiente. Dentre as alternativas surge e técnica da mínima quantidade de lubrificante (MQL), que também tem suas desvantagens, como por exemplo, a formação de uma borra de óleo na superfície de corte do rebolo, o que gera uma rugosidade maior na peça. Porém, visando minimizar esse problema podem ser usados jatos de ar comprimido incidindo na superfície de corte do rebolo, com o objetivo de limpar a superfície de corte do rebolo, com o objetivo de limpar a superfície do rebolo. Dessa forma, avaliou-se a eficiência desse sistema de ar comprimido para a limpeza e pôde-se verificar que, a utilização da limpeza juntamente com a técnica do MQL, torna-se viável, pois de uma maneira geral a técnica do MQL com limpeza obteve melhores resultados na qualidade da peça e desgaste da ferramenta, em relação ao MQL sem limpeza. A limpeza com um ângulo tangente à superfície do rebolo foi a condição de limpeza que obteve melhores resultados para a limpeza o que comprova que a melhoria na técnica do... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In grinding process the use of cutting fluids is a way to implement the final quality of the process because the fluids are intended for the lubrication in the contact area between the work piece, the tool and the cooling of the surfaces avoiding damages on the work piece surface. However, the use of cutting fluids has been constantly studied in order to reduce its use since this practice brings a lot of problems about. The final product cost increases considerably along with the use of cuting fluids in gringing process, besides those substances are toxic and harmful to people and to the environment as well. Therefore, industries, universities and research center have been taken as sites for investigating less harmfulll alternative methods to the environment. Among such alternatives comes up of minimum quantify of lubricant technique (MQL), which also has some disadvantages, such as the formation of oil sludge on the cut surface of the wheel, which creates a greater surface roughness on the work piece. However, in order to minimize this problem compressed air jets can be used focusing on the cut surface of the wheel, in order to clean it. Thus, we could evaluated the effectiveness of that compressed air system used for cleaning, and it was possible to observe that the use of cleaning with the MQL technique is feasible because from a general view the use of the MQL technique in the cleaning process showed better results in the quality of the work piece and wornout of the tool comparing to the to the MQL with no cleaning. The cleaning with a tangent angle to the surface of the wheel was the condition of cleanliness that showed better results for the cleanliness which proves that the improvements for the MQL techniques does not lead to significant results compared to the conventional technique. However, the MQL technique with cleanliness has its... (Complete abstract click electronic access below) / Orientador: Eduardo Carlos Bianchi / Coorientador: Anselmo Eduardo Diniz / Banca: Carlos Elias da Silva Junior / Banca: Celso Naves de Souza / Mestre