Darren Fraser

Effect of processing conditions on porosity formation in cold gas dynamic spraying of copper

The cold gas dynamics process is a promising low-temperature spray process in which particles are accelerated in a supersonic flow before impacting with substrate to be coated. In this study the effect of spray temperature, spray pressure, and particle size on porosity formation in cold spray coatings are investigated. Results show that an increase in spray temperature and a decrease in particle size lead to a decline in volume fraction of porosity. Furthermore, particle velocity and particle temperature are determined to be the significant parameters for elimination of porosity. A model is proposed for estimation of the volume fraction of porosity for alloy of this study.

Direct Manufacturing of Titanium Parts by Cold Spray

Titanium has excellent properties as an engineering material such as light weight, high strength and high resistance to corrosion and fracture. However, the high cost associated with the materials and current process technologies is not conducive to higher-volume production for consumer industry. It appears near net shape manufacturing has to be used to manufacture titanium and titanium alloys parts. Investigators are exploring several near net shape technologies. However, most of these technologies involve melting and solidification. Each new layer starts out molten, solidifies, and must eventually cool to room temperature. Oxygen sensitive material such as titanium needs to be processed under vacuum. There is a great need for revolutionary coating and direct Manufacturing technology to extend the application of titanium and titanium alloys from top end, aerospace and biomedical to lower end consumer use. It appears Cold Spray Technology can deliver a suitable and cost effective coating and direct manufacturing solution for titanium industry. CSIRO Light Metals Flagship has pioneered in developing direct manufacturing technologies to fabricate titanium parts using Cold Spray. Mechanical properties of Cold Spray titanium in as sprayed and heat treated conditions are presented and compared with wrought titanium. Some of technologies such as Cold Spray for direct manufacturing of seamless titanium pipes are discussed.

Microstructure and mechanical properties of Ti–6Al–4V manufactured by electron beam melting process

Abstract Electron beam melting (EBM) is a powder based additive manufacturing technology used to produce parts with high geometrical complexity directly from a three-dimensional computer aided design model. It is one of the most promising methods of additive manufacturing for a wide range of industrial applications, especially the medical implant and aerospace industries. This paper presents the microstructures and mechanical behaviour of as fabricated and hot isostatic pressing (HIP) processed parts, which are made by an Arcam A1 EBM system. The biocompatible titanium alloy Ti6Al4V was used as the material for the specimens. Characterisation of the parts after manufacturing and after tensile and fatigue tests was conducted by scanning electron microscopy. The mechanical properties, including tensile stress–strain, Vickers microhardness (HV), surface roughness and fatigue cycles, have been measured and compared with similar literature relevant to EBM made Ti6Al4V parts. The results highlight the advantage and disadvantage of HIP processing on the mechanical properties and microstructure of the EBM made parts.

Residual Stresses and Deformations in Electron Beam Melting process Using Finite Element Analysis

The simulation of residual stress in Electron Beam Melting (EBM) process is critical for optimization of process conditions. However, there is no published literature on the simulation of residual stresses in this process. This paper considers finite element modeling of the temperature distribution through transient thermal analysis. The measured temperature and total heat flux from transient thermal analysis are then used as initial input parameters to the structural analysis. Consequently, deformations and residual stresses in structural analysis were measured. The titanium alloy, Ti6Al4V has been used, which is one of the most common materials for biomedical implants due to its high strength to weight ratio, corrosion resistance, and its biocompatibility features.

Mechanical Properties Investigation of HIP and As-Built EBM Parts

Electron beam melting (EBM) is a direct metal additive manufacturing technique which has been recently utilized for fabrication of biomedical implants. This paper represents an investigation into the mechanical properties of both as-built and hot isostatic pressing (HIP) processed samples manufactured in EBM process. The titanium alloy, Ti6Al4V was used, which is one of the most common materials for biomedical implants due to its high strength to weight ratio, corrosion resistance, and its biocompatibility features. Tensile properties, surface roughness, and Vickers microhardness have been investigated.

Synchrotron X-ray CT characterization of titanium parts fabricated by additive manufacturing. Part II. Defects.

Synchrotron X-ray tomography (SXRT) has been applied to the study of defects within three-dimensional printed titanium parts. These parts were made using the Arcam EBM(®) (electron beam melting) process which uses powdered titanium alloy, Ti64 (Ti alloy with approximately 6%Al and 4%V) as the feed and an electron beam for the sintering/welding. The experiment was conducted on the Imaging and Medical Beamline of the Australian Synchrotron. The samples represent a selection of complex shapes with a variety of internal morphologies. Inspection via SXRT has revealed a number of defects which may not otherwise have been seen. The location and nature of such defects combined with detailed knowledge of the process conditions can contribute to understanding the interplay between design and manufacturing strategy. This fundamental understanding may subsequently be incorporated into process modelling, prediction of properties and the development of robust methodologies for the production of defect-free parts.

Compressive Properties of Ti-6Al-4V Built by Electron Beam Melting

Electron beam melting (EBM) is a direct metal additive manufacturing technique in which a 4 kW electron beam is utilized to manufacture the parts in a layer by layer fashion. This paper represents an investigation into the quasi-static compressive deformation behavior of EBM made specimens. The mechanical testing was carried out at strain rate of 10-3 s-1 by a numerically controlled hydraulic MTS machine on both as-built and machined samples manufactured by this high-tech process. The Vickers micro-hardness of the samples has been measured before and after the compression test. The microstructure of the compressed sample was characterized. The particle size distribution, morphology, and chemical composition of the Ti6Al4V, which is one of the most common materials for biomedical implants because of its high strength to weight ratio, corrosion resistance, and its biocompatibility features, have been investigated. The fracture surface has been characterized by scanning electron microscope.

Investigation of Wear Properties of EBM Processed Ti6Al4V with UHMWPE for Biomedical Applications

The wear of polymeric bearing material in contact with metallic biomedical implant has often been the main cause of long-term clinical failure of such implants. Very few studies seem to have been undertaken to investigate the wear behaviour of Ultra-High-Molecular-Weight-Propylene (UHMWPE) bearing material in contact with titanium alloy implant material under various loading conditions. This research paper presents an investigation on the wear properties of UHMWPE under dry and wet sliding conditions at different loading conditions. In this study, the well-known pin-on-disk equipment was used to carry out the sliding wear test. The titanium pin was made by Electron Beam Melting (EBM) technology and machined to rub on the UHMWPE disk. The aim is to understand the wear characteristics of UHMWPE in relation to Ti6Al4V alloy under various loading and lubricating conditions. Results include volume loss and wear rate analysis.