Joe Elambasseril

High-Value SLM Aerospace Components: From Design to Manufacture

Today additive manufacturing is shaping the future of global manufacturing and is influencing the design and manufacturability of tomorrows products. With selective laser melting (SLM), parts can be built directly from computer models or from measurements of existing components to be re-engineered, and therefore bypass traditional manufacturing processes such as cutting, milling and grinding. Benefits include: 1) new designs not possible using conventional subtractive technology, 2) dramatic savings in time, materials, wastage, energy and other costs in producing new components, 3) significant reductions in environmental impact, and 4) faster time to market. SLM builds up finished components from raw material powders layer by layer through laser melting. SLM removes many of the shape restrictions that limit design with traditional manufacturing methods, thereby allowing computationally optimised, high performance structures to be utilised. Functional engineering prototypes and actual components can then be built in their final shape with minimal material wastage. Samples and small product runs can be produced quickly at comparatively low cost to test and build market acceptance without major investment. In this chapter we present and discuss some of the concepts and findings involved in the design, manufacture and examination of high-value aerospace components from Ti-6Al-4V alloy produced at the RMITs Advanced Manufacturing Precinct.

The Effect of Manufacturing Defects on the Fatigue Behaviour of Ti-6Al-4V Specimens Fabricated Using Selective Laser Melting

Additive Manufacturing (AM) technologies are considered revolutionary because they could fundamentally change the way products are designed. Selective Laser Melting (SLM) is a metal based AM process with significant and growing potential for the manufacture of aerospace components. Traditionally a material needs to be listed in the Metallic Materials Properties Development and Standardization (MMPDS) handbook if it is to be considered certified. However, this requires a considerable amount of test data to be generated on the materials mechanical properties. Therefore, the MMPDS certification process does not lend itself easily to the certification of AM components as the final component can have similar mechanical properties to wrought alloys combined with the defects associated with traditional casting and welding technologies. These defects can substantially decrease the fatigue life of a fabricated component. The primary purpose of this investigation was to study the fatigue behaviour of as-built Ti-6Al-4V (Ti64) samples. Fatigue tests were performed on the Ti-6Al-4V specimens built using SLM with a variety of layer thicknesses and build (vertical or horizontal) directions. Fractography revealed the presence of a range of manufacturing defects located at or near the surface of the specimens. The experimental results indicated that Lack-of-Fusion (LOF) defects were primarily responsible for fatigue crack initiation. The reduction in fatigue life appeared to be affected by the location, size and shape of the LOF defect.

SLM additive manufacture of H13 tool steel with conformal cooling and structural lattices

Purpose Additive manufacture (AM) such as selective laser melting (SLM) provides significant geometric design freedom in comparison with traditional manufacturing methods. Such freedom enables the construction of injection moulding tools with conformal cooling channels that optimize heat transfer while incorporating efficient internal lattice structures that can ground loads and provide thermal insulation. Despite the opportunities enabled by AM, there remain a number of design and processing uncertainties associated with the application of SLM to injection mould tool manufacture, in particular from H13/DIN 1.2344 steel as commonly used in injection moulds. This paper aims to address several associated uncertainties. Design/methodology/approach A number of physical and numerical experimental studies are conducted to quantify SLM-manufactured H13 material properties, part manufacturability and part characteristics. Findings Findings are presented which quantify the effect of SLM processing parameters on the density of H13 steel components; the manufacturability of standard and self-supporting conformal cooling channels, as well as structural lattices in H13; the surface roughness of SLM-manufactured cooling channels; the effect of cooling channel layout on the associated stress concentration factor and cooling uniformity; and the structural and thermal insulating properties of a number of structural lattices. Originality/value The contributions of this work with regards to SLM manufacture of H13 of injection mould tooling can be applied in the design of conformal cooling channels and lattice structures for increased thermal performance.

Effect of loading phase angle on interfacial fracture toughness for Circumferentially Notched Tensile specimens

Coatings often used as a covering to enhance the quality and protect the material to which they are applied to. The interface between the coating and substrate is the weakest part of the material system. Understanding the characteristics of the interfacial fracture toughness is important as it is the bimaterial property that has the most significant impact on the performance of the system. Through accurate prediction of the interfacial fracture toughness, coatings can be produced that are more reliable as unanticipated failures are less likely to occur. This paper analyses the new experimental method-Circumferentially Notched Tensile (CNT) test, using numerical finite element analysis, in order to create a global testing method that can determine interfacial fracture toughness of bimaterial systems.

Mechanical properties of selective laser melted Ti-6Al-4V with different layer thickness

Laser-based metal deposition process such as selective laser melting (SLM) is one of Direct Metal Deposition (DMD) or Additive Manufacturing (AM) processes. Due to the nature of its layer-by-layer process, the microstructures from the bottom layers to the top layers are significantly different due to highly thermal gradient induced by laser beam combined with different cooling rates at each built layer. The SLM process parameters such as laser power, scan speed, layer thickness, hatch spacing etc have a major influence on the mechanical properties of the material fabricated. The relationship between mechanical properties associated with microstructure and process parameters is critical for the manufacture of functional components. The understanding of this relationship will help to facilitate future studies on manufacture and repair of titanium alloy parts/components with SLM technology. Increase in layer thickness will lead to increase in productivity. However, such an increase may impact on the mechanical properties of the material.This paper presents the effect of powder layer thickness on the mechanical properties (tensile and fatigue) of manufactured specimens. The experimental results in this investigation showed that the increase in layer thickness from 30 to 90 µm did not affect the tensile strengths but the ductility was dramatically reduced. The fatigue life was also significantly decreased. The results indicate that the SLM process needs to be optimised for a thicker powder layer case.Laser-based metal deposition process such as selective laser melting (SLM) is one of Direct Metal Deposition (DMD) or Additive Manufacturing (AM) processes. Due to the nature of its layer-by-layer process, the microstructures from the bottom layers to the top layers are significantly different due to highly thermal gradient induced by laser beam combined with different cooling rates at each built layer. The SLM process parameters such as laser power, scan speed, layer thickness, hatch spacing etc have a major influence on the mechanical properties of the material fabricated. The relationship between mechanical properties associated with microstructure and process parameters is critical for the manufacture of functional components. The understanding of this relationship will help to facilitate future studies on manufacture and repair of titanium alloy parts/components with SLM technology. Increase in layer thickness will lead to increase in productivity. However, such an increase may impact on the mechanic...