Tuesday
Keynote Presentation: New Titanium Products via Powder Metallurgy Process
T. Furuta, Toyota Central R&D Labs
Japan
The powder metallurgy (P/M) process is an attractive method for the manufacture of titanium-based materials and products. The prime reason for this is its cost effectiveness, because it can eliminate several production operations such as melting, casting, forging, and machining processes, which are all expensive compared with those for steel. In contrast, the P/M process enables the production of complex materials that are difficult to make via ingot metallurgy processes. High alloyed materials and metal matrix composites (MMCs) are typical examples. Some examples of new materials are presented in this paper. These include TiB particle-reinforced titanium metal matrix composites (Ti-MMCs) for automobile engine exhaust valves [1], heat resistant materials that can endure the high temperatures (>1100 K) of an exhaust atmosphere. Gum metal [2,3], which is a new multi-functional titanium alloy that has an ultra-low elastic modulus (50 GPa), ultra-high strength (1,200–2,100 MPa), ultra-high elastic deformability (2.5%). It also does not undergo a thermo-elastic martensitic transformation at room temperature, and exhibits super-cold formability without work hardening. These superior properties are all due to the unique plastic deformation mechanism peculiar to this alloy. Furthermore, titanium has unique physical properties, such as being nonmagnetic and having relatively high electrical resistance among metals. This is very important for motor components that rotate at high speeds because high electrical resistance reduces eddy current losses, which leads to savings in power consumption and enhancement of the power supply efficiency of the total system. Basic concepts to simultaneously achieve both improvements in the ultra-high strength, high resistivity, and high rigidity of Ti-MMCs are introduced [4]. The objective of this paper is to clarify the mechanism for inducing high resistivity in newly developed TiC(1-X)/Ti-MMCs fabricated by blended elemental reactive sintering with a focus on the effect of the C and Al content.
Keynote Presentation: Fatigue Behavior and Failure Mechanisms of Metal-Injection-Molded Beta Titanium Alloys
T. Ebel, Helmholtz-Zentrum Hereon
Germany
Due to inevitable processing defects, fatigue failure of Metal-Injection-Molded (MIM) titanium alloys is an important concern in applications where structures are subjected to cyclic loading for long periods of time, such as bio-tolerant implants or parts in airplanes or automobiles. This study focuses on the differences in fatigue behavior and failure mechanisms between MIM Ti-6Al-4V and MIM beta-titanium alloys, i.e., between two common medical titanium alloys. It can be shown that the high-cycle fatigue performance of MIM beta-titanium (e.g. Ti-20Nb-10Zr) has inherent advantages over MIM Ti-6Al-4V. Under existing processing conditions the grain size of beta-titanium is three times higher than Ti-6Al-4V and its carbon and oxygen levels are also two times higher. Nevertheless, the fatigue endurance limit of beta-titanium is about 33% higher and its lifespan is more than one order of magnitude longer than that of Ti-6Al-4V. The superior fatigue performance of beta-titanium attributes to the absence of alpha/beta colonies and equiaxed grains, which are typical weak microstructural characteristics.
Comparative Assessment of Wrought PM Ti-6Al-2Sn-4Zr-2Mo Alloy Rods Fabricated Using Cold Spray, Hot Isostatic Pressing, and Spark Plasma Sintering
C. Doblin, CSIRO
Australia
Starting with spherical Ti-6Al-2Sn-4Zr-2Mo alloy feedstock, ~25 mm diameter preforms were produced using three primary solid state consolidation approaches: (1) cold spray, (2) HIP, and (3) SPS. All preforms were converted into ~8 mm rods using similar thermomechanical processing schedules. Detailed metallurgical characterization and evaluation of the rods were preformed to compare capabilities of the three wrought PM product forms with respect to similarly processed wrought Ti-6Al-2Sn-4Zr-2Mo bar. Results obtained to date will be presented, demonstrating the prospects of cold spray as an alternate, potentially lower-cost route for fabrication of Ti alloy near net shape parts with standard-grade mechanical properties.
L-PBF Process Optimization for Ti-6242 (Ti–6Al–2Sn–4Zr–2Mo-0.08Si) - A High Performance Material for High Temperature Critical Applications
J. Arreguin, AP&C, A GE Additive Company
Canada
Titanium alloy powders are known for producing parts with excellent mechanical properties, but different powders alloys from the titanium family are best utilized in specific scenarios. Ti-6242 is a metal alloy that has both light weight and high temperature resistance properties. The processability of this alloy by additive manufacturing (AM) technologies has been a challenge due to the residual stress of this alloy which leads to cracking formation on solidified parts. Ti-6242 plasma atomized powder has been designed to meet the highest quality requirements of additively manufactured parts for aerospace applications. The plasma atomized Ti-6242 powder ensure excellent physical properties and sound control on composition homogeneity which reduce the phase segregation during the deposition process. These powder properties have positive influence on AM process control and cracking suppression. The developed parameters shown excellent stability and printed parts are free of cracks. Developed parameters shown excellent robustness across 37 builds with multiple machines and different powder lots. Printed parts shown outstanding mechanical properties that exceed comparable Ti6Al4V parts at 200 C range and meet and exceed minimum AMS4976 requirements at elevated temperature. Printed parts shown density of 99.9% and higher. Capability assessment of printed parts as surface roughness, thing walls, horizontal holes were determined. In conclusion, Ti-6242 shown to be an excellent alternative for high-temperature applications in the range of 500 C with roughly the half of density of most popular nickel-based alloys.
Sinter Based Additive Manufacturing of Titanium, Binder, and Processing Technology
J. G. Schaper, Element22 GmbH
Germany
Sinter based additive manufacturing technologies are gaining more interest and are getting established in certain applications. However, the focus has mainly been concentrated on common materials and alloys like 316L and 17-4-PH due to their relatively uncomplex thermal debinding and sintering processability. When it comes to Titanium and other reactive materials, the thermal debinding and sintering is much more challenging. This is due to the reactivity of the metals during thermal debinding of the polymeric binders that are needed for the shaping process. For each shaping progression, different requirements need to be addressed e.g., green part strength, flexibility (filaments), flowability (MIM) and crosslinking (stereolithography (LMM)) etc. When it comes to reactive metals, thermal removal with minimal residuals and reactivity with the metals are major requirements. The main challenge to meet material standards like the ASTM F2885-17 is the control of the interstitial elements C and O. Another challenge is the choice of the optimal shaping technology for each individual part. Critical requirements can be mechanical properties, final density, acceptance of interstitials, complexity, minimum and maximum wall thicknesses, overhangs, open or closed internal structures and so on. To make this choice, a good understanding of the benefits and drawbacks of each shaping technology is needed. An overview of the most common shaping technologies like MIM, FFF, CMF, MBJ and LMM will be presented.
Tribocharging Behavior of Commercially Pure Ti and Ti-6Al-4V Powders with Different Oxidation Levels
E.R.L. Espiritu, McGill University
Canada
Due to their high strength, low weight, and excellent corrosion resistance, Titanium and its alloys are attractive to aerospace and automobile industries. The typical fabrication method for Titanium parts is by subtractive manufacturing, which requires additional cost for machining. In addition, complex geometries that these industries demand, may be impossible to produce with subtractive manufacturing. This is where additive manufacturing becomes useful since it can produce net or near-net structures and significantly reduces the machining leading to lower cost high integrity products. Additive manufacturing, specifically powder bed processes, uses metal powders that is spread in a thin layer, and is fused using a heat source. The process is repeated in a layer-by-layer fashion until a predesigned geometry is achieved. Due to the high cost of Ti powders, recycling them for the next print cycle is the current trend in the industry, however, the powder’s oxygen content is known to increase with each recycling step. Controlling the oxygen content is extremely important as this affects feedstock quality, which then affects final part quality. Rapid testing of oxygen content using the typical characterization methods, during manufacturing process is not practical and is not possible. This work explored the possibility of using a tribocharging analyzer as a quick and easy method of indirectly assessing oxygen content of commercially pure Ti and Ti6Al4V powders. In this work, powders with different levels of oxidation were evaluated for their morphology, size distribution, flow characteristic, and triboelectric charging behavior coupled with surface oxidation assessment via XPS. The results showed some degree of tribocharging variability between different oxidation levels. This demonstrates that this new method of characterization has a promising future in the additive manufacturing industry.
Panel Discussion: Standardization & Ti Powder MetallurgyModerator - L.P. Lefebvre, Conseil National de Recherche du Canada Panelists - Matthias Scharvogel (Element 22), Javier Arreguin (AP&C), Shane Collins (ASTM), Matthew Di Prima (FDA), Cindy Ashforth (FAA), Benoit Julien (Stryker), and Francois Girard (Pratt & Whitney Canada) PMTi2022 will be hosting a panel discussion on the effect of interstitials, their role and impact on standardisation. Panelists from different regulatory agencies, OEMs, powder and part producers will discuss the requirements and challenge related to the control of interstitials in titanium parts produced by additive manufacturing and powder metallurgy. The discussion will cover the impact of the current requirements on the acceptance and growth of new processes and technologies, the economics, safety as well as opportunities for the development of new materials. The discussion (hybrid) will take place August 30th, during the PMTi2022 conference in Montreal, (PMTi2022 Conference (mpif.org)).
Production of Ti64 Powders for Medical AM Applications
K. Bensaid, Tekna
Canada
Selecting metallic powders is an important consideration in Additive Manufacturing (AM) applications. This presentation will discuss technology to produce AM powders with focus on low-oxygen content Ti64 powders designed for medical applications. We will review the advantages of using a quality feedstock for laser powder bed fusion (L-PBF) processes including a case study of a Ti64 powder lot re-sieved over 50 times over 9 months during the production of orthopedic implants.
A Novel Testing Bench for the Assessment of Metal Powder Spreading Behavior for Powder Bed-Based AM Applications
S.E. Brika, Ecole de technologie superieure
Canada
Given the sensitivity of powder bed-based AM (PBAM) processes to feedstock variations, there is the need for new testing instruments simulating the powder spreading conditions in existing and prospective PBAM systems. Conventional powder characterization techniques test powders under conditions that differ from the ones involved in the PBAM processes, thus limiting their use for the optimization of powder feedstock and the improvement of powder spreading mechanisms. A novel testing apparatus is developed to replicate the powder spreading procedure and measure the powder bed density, spreading forces, and surface uniformity as a function of the powder size and shape distributions, layer thickness, powder spreading speed and type of the recoating mechanism. A comparative study case using Ti6Al4V powders is presented to validate the capabilities of the apparatus and its relevance for the powder feedstock quality control and as a research and development tool dedicated for PBAM applications.
A Scoping Review on the Additive Manufacturing of Ti6Al4V Metal Matrix Composite with Carbides as Reinforcement
N. Nkosi, Stellenbosch University
South Africa
The use of selective laser melting (SLM) has become common in the manufacturing of titanium metal matrix composites (MMC). However, there is a need to increase some of the mechanical properties of these composites in order improve the lifespan of the materials as well as increasing their industrial application range. In this scoping literature review, an update on the status of SLM and its application to the manufacturing of titanium metal matrix composites reinforced with carbides is provided. The scoping review was conducted using the Arksey and O’Malley framework. The main purpose of this review was to explore and understand the SLM process and its employment in the manufacture of carbide reinforcement of titanium alloys for industrial applications by (i) identifying the scope of relevant and available literature, (ii) studying and choosing a suitable reinforcement carbide for further investigative studies based on relevant literature, (iii) identifying and summarizing SLM processing parameters to produce MMCs and lastly, (iv) identifying a suitable design of experiments matrix for the SLM of the MMCs. The sourced publications were reviewed and analysed using Atlas.ti software. The analyses showed that the most commonly used carbide is TiC followed by SiC due to their compatibility with the Ti6Al4V matrix, desired properties and availability of powder. The main SLM process parameters were scanning strategy, laser power, scanning speed, hatch distance and powder layer thickness which all played key roles in determining the quality of the final SLM-produced materials. A central composite design of experiments method was widely used to design and model the research work involving SLM experiments. The review analysis confirmed the increasing demand of research in producing MMCs using different carbides and optimizing SLM parameters and their application in several industries.
On the potential of Eutectoid β Stabilizing Elements to Develop New PM Ti Alloy Compositions
L. Bolzoni, The University of Waikato
New Zealand
The widespread application of titanium alloys is still hindered by their high cost. Powder metallurgy offers the advantage of using cheaper alloying elements, than the ones currently used in wrought titanium alloys, for the development of new alloys with enhanced mechanical behaviour for structural engineering applications. This work discusses strategies and presents the latest initiatives taken to reduce the materials and manufacturing costs of Ti alloys primarily investigating the use of multiple eutectoid β stabilising elements without and with the simultaneous addition of isomorphous β stabilisers. It is demonstrated that the combination of new alloy chemistries and alternative powder metallurgy processing method is a promising and viable sound approach to achieve Ti alloys with good mechanical performance at lower cost.
Comparison of Fatigue Properties of Ti-6Al-4V, Processed by Metal Injection Molding and Composite Extrusion Modelling
W. Limberg, Helmholtz-Zentrum Hereon
Germany
Additive Manufacturing techniques are very interesting for the production of customized titanium alloy implants. However, especially for long-term implants, fatigue properties play an important role.
For this study, rectangular shaped fatigue test specimens were produced by Composite Extrusion Modelling (CEM) using fine gas atomized Ti-6Al-4V powder < 20 µm and 10 wt.% binder. For comparison, the same feedstock was also used to produce specimens of the same shape and size by Metal Injection Moulding (MIM).
Due to the high sinter activity of the fine powder, residual porosity after debinding and sintering for one hour at 1300 °C was only 1.8% for the MIM-specimens. For the CEM-specimens, the residual porosity was only slightly higher with 1.9%. This small difference correspondence to the results of the X-ray investigations, where only few larger defects like pores of less than 100 µm in diameter were found.
The fatigue tests were conducted by 4-point bending at room temperature with a load ratio of 0.2. The microstructures and fracture surfaces were observed by SEM and light optical microscope. Oxygen and nitrogen contents were analysed by a melt extraction technique. While the MIM-specimens achieved a fatigue endurance limit of 450 MPa, the value drops down to 425 MPa for the CEM-specimens. However, the main difference between the two different production routes is the scattering of the fatigue values. While the individual values of the MIM samples show only a slight deviation from the mean, the scatter of the individual values of the CEM samples is significantly larger.
Opportunities of Powder Metallurgy Titanium in the Hydrogen Technologies: The Case of Bipolar Plates
C. Romero, Universidad Carlos III de Madrid
Spain
The fast development of hydrogen energy in the recent and coming years means that there is a window of opportunity for many industries to develop new products, which can also be the case for the titanium powder metallurgy industry. Bipolar plates for fuel cells and electrolyzers are good candidates for this industry, as titanium shows outstanding potential for the application but presents strong limitations. In this work, the application of specific PM routes to manufacture bipolar plates with advanced designs will be discussed, including approaches to improve their performance.
Characterization of Powder Spreadability for Additive Manufacturing Optimization
S. Caubergh, Granutools
Belgium
Additive Manufacturing (AM) becomes more and more popular in industrial manufacture processes and allow complex 3D structures production. Metallic powders such as titanium or titanium alloys are commonly used for Selective Laser Melting (SLM). This AM method consists of a succession of thin layers of powder spread by a recoater and sintered by laser melting. For this process, the powder must exhibit good spreadability as the resolution is controlled by the thickness and the regularity of the layer. Therefore, characterizing this spreadability is crucial to optimize the Additive Manufacture process. Moreover, the powder excess, after the passage of the recoater, is often recovered for reuse (recycling). However, recycling can change properties of this powder. Evaluating the impact of used powder for Additive Manufacturing is then of great importance for Additive Manufacturing improvement. We measured the spreadability of titanium alloy powders with a rotating drum, called GranuDrum. This method allows characterizing the spreadability of powders without applying compressive load during the powder testing, which fits with the process conditions encountered in Additive Manufacturing. We found that the spreadability of the powders is directly related to the quality of the recoated bed layers and thus on the quality of the expected parts. Moreover, a comparison between measurements performed with fresh powder and used powder highlight the effect of recycling on the quality of the powder. These results linking powder rheology, recycling and flowing properties of powders can be valuable for the optimization of Additive Manufacturing processes.
Current Research in Binder Jet Printing of Titanium Powders
N. Jump, University of Utah
USA
Binder Jet (BJ) printing has recently emerged as a feasible manufacturing method for small to large scale parts, but at the current moment, the full capabilities of this technology are restricted by the materials available. Titanium is one of the most desirable materials used in manufacturing due to its low density, high strength, high elongation %, and corrosion resistance, yet at this time the material cannot successfully be utilized within the BJ system. This discontinuity exists due to titanium having a high affinity for both carbon and oxygen impurities. These impurities, which are abundant within the polymeric binders utilized in the BJ system, can significantly reduce the highly desired mechanical properties of titanium. Current research is being conducted to produce Ti-64 parts from both pre-alloyed and hydride elemental blends on the BJ system, with relatively low carbon and oxygen contents. The oxygen and carbon pickups from each step are investigated.
Tailoring Hot Isostatic Pressing Treatments to Homogenize Process-Dependent Microstructures and Mechanical Properties of Electron Beam Melted Ti-6Al-4V Parts
J. Bonini, Lucideon M+P
USA
Materials of known, repeatable properties that are resistant to fracture are of prime importance for structural applications, but additively manufactured parts often contain internal porosity and heterogeneities in the grain structure which reduce strength and reliability. Post-manufacture, hot isostatic pressing (HIP) treatments are commonly employed to seal the internal porosity. In this work, Ti-6Al-4V parts were manufactured by electron beam melting powder bed fusion and subjected to a range of HIP treatments that were carried out at temperatures above and below the β transus for Ti-6Al-4V. Super-β transus HIP treatments eliminate microstructural.
Titanium Metal Injection Molding and 3D Binderjet Printing
R. Swenson, Tritech Titanium Parts, LLC, The University of Texas at El Paso
USA
This presentation will discuss the pros and cons for each process, and the effect on the process selection for specific parts. There are many considerations including cost, process flow, and properties. In this study, we will go through the current standing of titanium metal injection molding, the current achievements of the new binder jet printing process for Ti64.