The machining of a new alloy often presents a challenge. While useful assumptions can be drawn from materials of similar properties, there will always be unpredictable outcomes. Titanium alloys have been employed in the aerospace industry due to their high mechanical properties and good strength-to-weight ratio. Ti-64 (Ti-6Al-4V) was the standard choice until recently, when Ti-555.3 (Ti-5Al-5V-5Mo-3Cr) began to take its place. Ti-555.3 has improved resistance to fatigue and higher mechanical properties compared to Ti-64 and is able to maintain its strength when exposed to high temperatures, which warrants its acceptance for many applications. However, its chemical reactivity, low thermal conductivity and high mechanical properties are known to cause challenges when cutting this alloy. Making use of both experimental procedures and computational resources, this work presents a comparison between these two aerospace alloys under different process conditions, setting the ground for further academic development and optimization strategies. Determining that these alloys are substantially different from a machinability standpoint (lower tool life, abrasion & chipping as dominant wear mechanisms and nonuniform chip formation for Ti555.3 versus Ti-64). Based on this further investigation should be carried out for optimal tooling selection to improve the machining of Ti555.3. / Thesis / Master of Applied Science (MASc)

Orientador: Anselmo Eduardo Diniz / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-07T07:00:53Z (GMT). No. of bitstreams: 1 Micaroni_Ricardo_D.pdf: 2196403 bytes, checksum: 4db1f057fa92acc55a6677b56f01f72d (MD5) Previous issue date: 2006 / Resumo: Na usinagem dos metais, a aplicação do fluido de corte otimizada é um recurso que pode aumentar a taxa de remoção de material. Dentre os beneficios pode-se citar a redução da temperatura da ferramenta e melhor formação dos cavacos. Na primeira fase deste trabalho foi estudada a viabilização do corte a seco, da aplicação do fluido de corte em fluxo abundante ou convencional e em alta pressão em diferentes direções no torneamento do aço ABNT 1045, empregando-se ferramentas de metal duro em operação de acabamento. Para isso, foi montado um sistema composto por uma bomba de alta pressão e injetores direcionados para a superficie de saída, para a superficie de folga e simultaneamente para estas duas direções. As variáveis de saída foram: desgaste e vida da ferramenta, rugosidade da peça, potência e temperatura de corte. Na segunda fase será estudada a influência do uso ou não do fluido de corte na dilatação térmica de corpos de parede fina. Foi observado que a redução da vazão e o aumento da pressão do fluido de corte aumentaram a vida da ferramenta em relação às outras condições de refrigeração e, que a redução da vazão não alterou significativamente a temperatura de corte da ferramenta. Por outro lado, nos ensaios de dilatação térmica ficou constatado que a ausência do fluido de corte influenciou significativamente a variação diametral dos corpos de prova de parede fina / Abstract: In machining, the suitable use of cutting fluid is a resource that can increase the rate of material removal. Among the benefits it is possible to mention the tool temperature decrease and better chip formation. In the first stage of this work, several cooling/lubrication conditions were compared in finish turning operations of ABNT 1045 steel. These conditions were: dry cutting, the application of a abundant flow of cutting fluid in a conventional way (high flow rate and small pressure) and application of high pressure fluid in different directions. With this purpose, it was assembled a system containing a high pressure pump and injectors directed. to rake face, flank face and simultaneously in both directions. The output parameters were: tool wear an tool life, workpiece surface roughness, cutting power and temperature. In the second phase will be study the influence of the cutting fluid in the thermal expansion of worpieces with thin wall. The flow reduction and cutting fluid pressure increase the lifetime of the tool compared to other cooling conditions and that the flow reduction did not significant1y affected the tool temperature. On the other hand, the diameter variation of the workpiece with thin walls was larger in the absence of the cutting fluid / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

The diploma thesis is aimed to the influence of the high-pressure and low-pressure coolant system according to the machining operation. The comparison was carried out with different types of materials and cutting tools using the main machining operations – turning, milling, and drilling. The study is focused on the chip and heat removal from the cutting zone, tools life and wear of the tools. A description of the basic principle of the high-pressure coolant system meant is described in this thesis. The economical analysis of the high-pressure compared to low-pressure system was determined in the last part of this work.

Heat generated in a machining process is a common and critical obstacle faced in today's machining industries. The heat generated in the cutting zone has a direct negative influence on the tool life which, in turn contributes to increase the manufacturing costs. Especially, in machining of Heat Resistant Super Alloys, HRSA this is a very limiting factor. HRSA are capable of retaining their mechanical strength and hardness at elevated temperatures. This property is advantageous in the application in e.g. aero-engines but also a disadvantage, since it also lowers the machinability significantly. This work is an attempt to improve the heat transfer from the cutting zone, which would lead to an increase in the tool life. To achieve this goal, the cutting tool has been modified to create an improved interface between the coolant and tool in the high-temperature areas. Two generations of inserts have been designed and investigated. Firstly, an insert with surface texture features has been created with the purpose of increasing the available surface area for heat dissipation: First generation, Gen I. Secondly, a GenII was designed as a further improvement of Gen I. Here, several channel features on the rake face were added, reaching out from the contact zone to the near proximity of the cutting edge. This with the purpose of improving access of the coolant closer to the cutting edge. The experiments were conducted in facing operations of Alloy 718 with uncoated round carbide inserts. All experiments were carried out with high-pressure coolant assistance, with a pressure of 16 MPa on the rake face and 8 MPa on the flankface, respectively.The two generations of inserts, Gen I and Gen II, were experimentally evaluated by tool wear analysis in comparison with a regular insert. The results shows that the tool life increased significantly for the Gen I insert, compared to a catastrophic failure of the regular insert at the same conditions. Regarding the Gen II insert,an increase in tool life by approximately 30 to 40 percent compared to Gen I insert was observed.