Drilling Process in γ-TiAl Intermetallic Alloys

Gamma titanium aluminides (gamma-TiAl) present an excellent behavior under high temperature conditions, being a feasible alternative to nickel-based superalloy components in the aeroengine sector. However, considered as a difficult to cut material, process cutting parameters require special study to guarantee component quality. In this work, a developed drilling mechanistic model is a useful tool in order to predict drilling force (Fz) and torque (Tc) for optimal drilling conditions. The model is a helping tool to select operational parameters for the material to cut by providing the programmer predicted drilling forces (Fz) and torque (Tc) values. This will allow the avoidance of operational parameters that will cause excessively high force and torque values that could damage quality. The model is validated for three types of Gamma-TiAl alloys. Integral hard metal end-drilling tools and different cutting parameters (feeds and cutting speeds) are tested for three different sized holes for each alloy.RTC-2014-1861-4, INNPACTO DESAFIO II. Spanish Governmen

Sensitivity Analysis of Tool Wear in Drilling of Titanium Aluminides

In the aerospace industry, a large number of holes need to be drilled to mechanically connect the components of aircraft engines. The working conditions for such components demand a good response of their mechanical properties at high temperatures. The new gamma TiAl are in the transition between the 2nd and 3rd generation, and several applications are proposed for that sector. Thus, NASA is proposing the use of the alloys in the Revolutionary Turbine Accelerator/Turbine-Based Combined Cycle (RTA/TBCC) Program for the next-generation launch vehicle, with gamma TiAl as a potential compressor and structural material. However, the information and datasets available regarding cutting performance in titanium aluminides are relatively scarce. So, a considerable part of the current research efforts in this field is dedicated to process optimization of cutting parameters and tool geometries. The present work is framed in the study of wear when machining holes in these difficult-to-cut alloys. In particular, the work presents the results from drilling tests on three types of gamma TiAl alloys, extruded MoCuSi, ingot MoCuSi, and TNB type, to define an optimal set of cutting parameters. Maintaining uniform, gradual wear is key to avoiding tool breakage and enabling good hole dimensional accuracy. So, this paper proposes a model based on ANOVA analysis to identify the relationships between cutting conditions and resulting wear and estimate tool life. The best cutting parameters were found at v(c) = 10-15 m/min and f(n) = 0.025 mm/rev.Thanks are addressed to the UFI in Mechanical Engineering of the UPV/EHU for its support to this project, and to Spanish project DPI2016-74845-R, ESTRATEGIAS AVANZADAS DE DEFINICION DE FRESADO EN PIEZAS ROTATIVAS INTEGRALES, CON ASEGURAMIENTO DE REQUISITO DE FIABILIDAD Y PRODUCTIVIDAD and project RTC-2014-1861-4, INNPACTO DESAFIO II

Hole Making by Electrical Discharge Machining (EDM) of -TiAl Intermetallic Alloys

Due to their excellent strength-to-weight ratio and corrosion and wear resistance, gamma-TiAl alloys are selected for aerospace and automotive applications. Since these materials are difficult to cut and machine by conventional methods, this study performed drilling tests using Electro Discharge Machining (EDM) to compare the machinability between two different types of gamma-TiAl: extruded MoCusi and ingot MoCuSi. Different electrode materials and machining parameters were tested and wear, surface hardness, roughness and integrity were analyzed. The results indicate that extruded MoCuSi is preferable over MoCuSi ingots.Thanks are given to the UFI in Mechanical Engineering of the UPV/EHU for its support to this project, and to Spanish project DPI2016-74845-R, ESTRATEGIAS AVANZADAS DE DEFINICION DE FRESADO EN PIEZAS ROTATIVAS INTEGRALES, CON ASEGURAMIENTO DE REQUISITO DE FIABILIDAD Y PRODUCTIVIDAD and project RTC-2014-1861-4, INNPACTO DESAFIO II

Prediction Methods and Experimental Techniques for Chatter Avoidance in Turning Systems: A Review

The general trend towards lightweight components and stronger but difficult to machine materials leads to a higher probability of vibrations in machining systems. Amongst them, chatter vibrations are an old enemy for machinists with the most dramatic cases resulting in machine-tool failure, accelerated tool wear and tool breakage or part rejection due to unacceptable surface finish. To avoid vibrations, process designers tend to command conservative parameters limiting productivity. Among the different machining processes, turning is responsible of a great amount of the chip volume removed worldwide. This paper reports some of the main efforts from the scientific literature to predict stability and to avoid chatter with special emphasis on turning systems. There are different techniques and approaches to reduce and to avoid chatter effects. The objective of the paper is to summarize the current state of research in this hot topic, particularly (1) the mechanistic, analytical, and numerical methods for stability prediction in turning; (2) the available techniques for chatter detection and control; (3) the main active and passive techniques.Thanks are addressed to Basque country university excellence group IT1337-19. The authors wish to acknowledge also the financial support received from HAZITEK program, from the Department of Economic Development and Infrastructures of the Basque Government and from FEDER funds. This research was funded by Tecnologico de Monterrey through the Research Group of Nanotechnology for Devices Design, and by the Consejo Nacional de Ciencia y Tecnologia (CONACYT), Project Numbers 242269, 255837, 296176, and the National Lab in Additive Manufacturing, 3D Digitizing and Computed Tomography (MADiT) LN299129