THE DESIGN AND ANALYSIS OF EXPERIMENTS. By Oscar Kempthorne. New York, John Wiley and Sons, Inc., 1952. 631 pp. $8.50. This book by a teacher of statistics (as well as a consultant for \"experimenters\") is a comprehensive study of the philosophical background for the statistical design of experiment. It is necessary to have some facility with algebraic notation and manipulation to be able to use the volume intelligently. The problems are presented from the theoretical point of view, without such practical examples as would be helpful for those not acquainted with mathematics. The mathematical justification for the techniques is given. As a somewhat advanced treatment of the design and analysis of experiments, this volume will be interesting and helpful for many who approach statistics theoretically as well as practically. With emphasis on the \"why,\" and with description given broadly, the author relates the subject matter to the general theory of statistics and to the general problem of experimental inference. MARGARET J. ROBERTSON

The Design and Analysis of Experiments

Inconel 718 is one of the most commonly employed alloys for metal additive manufacturing (MAM) and has a wide range of applications in aircraft, gas turbines, turbocharger rotors, and a variety of other corrosive and structural applications involving temperatures of up to ∼700 °C. Numerous studies have investigated different aspects of the mechanical behaviour of additively manufactured (AM) Inconel 718. This study analyses the observations from more than 170 publications to provide an unbiased engineering overview for the mechanical response of AM Inconel 718 (and its variations and spread among different reports). First, a brief review of the microstructural features of AM Inconel 718 is presented. This is followed by a comprehensive summary of tensile strength, hardness, fatigue strength, and high-temperature creep behaviour of AM Inconel 718 for different types of MAM techniques and for different process and post-process conditions.

A review of mechanical properties of additively manufactured Inconel 718

Machine learning-based image processing for on-line defect recognition in additive manufacturing

Powder Bed Fusion (PBF) techniques constitute a family of Additive Manufacturing (AM) processes, which are characterised by high design flexibility and no tooling requirement. This makes PBF techniques attractive to many modern manufacturing sectors (e.g. aerospace, defence, energy and automotive) where some materials, such as Nickel-based superalloys, cannot be easily processed using conventional subtractive techniques. Nickel-based superalloys are crucial materials in modern engineering and underpin the performance of many advanced mechanical systems. Their physical properties (high mechanical integrity at high temperature) make them difficult to process via traditional techniques. Consequently, manufacture of nickel-based superalloys using PBF platforms has attracted significant attention. To permit a wider application, a deep understanding of their mechanical behaviour and relation to process needs to be achieved. The motivation for this paper is to provide a comprehensive review of the mechanical properties of PBF nickel-based superalloys and how process parameters affect these, and to aid practitioners in identifying the shortcomings and the opportunities in this field. Therefore, this paper aims to review research contributions regarding the microstructure and mechanical properties of nickel-based superalloys, manufactured using the two principle PBF techniques: Laser Powder Bed Fusion (LPBF) and Electron Beam Melting (EBM). The ‘target’ microstructures are introduced alongside the characteristics of those produced by PBF process, followed by an overview of the most used building processes, as well as build quality inspection techniques. A comprehensive evaluation of the mechanical properties, including tensile strength, hardness, shear strength, fatigue resistance, creep resistance and fracture toughness of PBF nickel-based superalloys are analysed. This work concludes with summary tables for data published on these properties serving as a quick reference to scholars. Characteristic process factors influencing functional performance are also discussed and compared throughout for the purpose of identifying research opportunities and directing the research community toward the end goal of achieving part integrity that extends beyond static components only.

Powder Bed Fusion of nickel-based superalloys: A review

CoCr alloy processed by Selective Laser Melting (SLM): effect of Laser Energy Density on microstructure, surface morphology, and hardness

In the frame of additive manufacturing of metals, laser powder-bed fusion is investigated in this paper as an advanced industrial prototyping tool to manufacture Inconel 718 turbine blades at a predesign stage before flow production. Expediting of the evaluation of any upgrade to the part is aimed. To this purpose, possible anisotropy of manufacturing is preliminarily investigated via tensile testing at room and elevated temperature as a function of the sloping angle with the building plate; the normalized strength is given and compared with similar studies in the literature. Positioning and proper supporting in manufacturing are discussed; the parts are further investigated to assess their compliance with the intended nominal geometry.

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Laser powder-bed fusion of Inconel 718 to manufacture turbine blades

Titanium alloys are employed for several applications, ranging from aerospace to medicine. In particular, Ti-6Al-4V is the most common, thanks to an excellent combination of low density, high specific strength and corrosion resistance.Laser welding has been increasingly considered as an alternative to traditional techniques to join titanium alloys. An increase in penetration depth and a reduction of possible welding defects is achieved indeed; moreover a smaller grain size in the fused zone is benefited in comparison to either TIG and plasma arc welding, thus providing an increase in the tensile strength of the welded structures.The aim of this work is to develop the regression model for a number of responses which are crucial for the feature of the joint. The study was carried out on 3 mm thick Ti-6Al-4V plates; a square butt welding configuration was considered employing a disk-laser source. A 3-level factorial plan was hence arranged in a face-centred cubic scheme. The responses were analyzed referring to the governing parameters. Then, an optimization was carried out via statistical tools, in order to find the optimal welding set-up for the alloy under examination.Copyright © 2013 by ASME

Investigation and Optimization of Laser Welding of Ti-6Al-4 V Titanium Alloy Plates

Titanium and its alloys are increasingly being used in aerospace, although a number of issues must be addressed. Namely, in the framework of welding to produce complex parts, the same mechanical strength and a reduced buy-to-fly ratio are desired in comparison with the same components resulting from machining. To give grounds to actual application of autogenous laser beam welding, Ti–6Al–4V L- and T-joints have been investigated in this paper, as they are a common occurrence in general complex components. Discussions in terms of possible imperfections, microstructure, and microhardness have been conducted. Then, a real part consisting of a support flange for aerospace application has been chosen as a valuable test-article to be compared with its machined counterpart both in terms of strength and buy-to-fly. The feasibility and the effectiveness of the process are shown.

Laser Beam Welding of a Ti–6Al–4V Support Flange for Buy-to-Fly Reduction

Possible anisotropy resulting from Additive Manufacturing of metals is investigated. Superalloy Inconel 718 is considered and a number of specimens are manufactured by means of Selective Laser Melting, with different direction of growing. Tensile testing both at room and elevated temperature are conducted.

Mechanical properties of Inconel 718 in additive manufacturing via selective laser melting: An investigation on possible anisotropy of tensile strength

Both technical and economic reasons suggest to join dissimilar metals, benefiting from the specific properties of each material in order to perform flexible design. Adhesive bonding and mechanical joining have been traditionally used although adhesives fail to be effective in high-temperature environments and mechanical joining are not adequate for leak-tight joints. Friction stir welding is a valid alternative, even being difficult to perform for specific joint geometries and thin plates. The attention has therefore been shifted to laser welding. Interest has been shown in welding titanium to aluminum, especially in the aviation industry, in order to benefit from both corrosive resistance and strength properties of the former, and low weight and cost of the latter. Titanium alloy Ti-6Al-4V and aluminum alloy 2024 are considered in this work, being them among the most common ones in aerospace and automotive industries. Laser welding is thought to be particularly useful in reducing the heat affected zones and providing deep penetrative beads. Nevertheless, many challenges arise in welding dissimilar metals and the aim is further complicated considering the specific features of the alloys in exam, being them susceptible to oxidation on the upper surface and porosity formation in the fused zone. As many variables are involved, a systematic approach is used to perform the process and to characterize the beads referring to their shape and mechanical features, since a mixture of phases and structures is formed in the fused zone after recrystallization.

Gaetano Corrado

Papers

Laser powder-bed fusion of Inconel 718 to manufacture turbine blades

Investigation and Optimization of Laser Welding of Ti-6Al-4 V Titanium Alloy Plates

Laser Beam Welding of a Ti–6Al–4V Support Flange for Buy-to-Fly Reduction

Mechanical properties of Inconel 718 in additive manufacturing via selective laser melting: An investigation on possible anisotropy of tensile strength

Characterization of disk-laser dissimilar welding of titanium alloy Ti-6Al-4V to aluminum alloy 2024