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Additive Manufacturing
particularly titanium alloys such as Ti64 . Since 2017 , Airbus have fitted 3D printed titanium shafts to the doors of A350 airliners and recently opened an Additive Manufacturing Centre in Germany to produce parts for helicopters and lightweight Urban Air Vehicles ( UAV ) [ 3 ] . While IndyCar utilise 3D printed titanium for the frame that supports its aeroscreen driver protection device . It also exhibits high corrosion resistance , which can be further enhanced with oxide coatings .
AlSi10Mg is common in 3D printing because of its ability to solidify consistently , but new aluminium powders are being developed that are more printable .
The key to achieving high quality builds is to use powders with consistent particle size distribution and optimum composition . To guarantee this , Conflux follow strict quality control procedures where they track the composition of new and recycled powder using spectrometry analysis and mechanical testing of tensile bars . This not only monitors the levels of each alloy within a powder , but also the amount of oxide layers built up during recycling , which can then be accounted for with printing parameters . Once the powder has been deemed printable , the focus shifts to analysing the physical properties of the printed material . The alloys used for some heat exchangers need to cope with temperatures above 800 ° C . Alongside this , they also need to have a high fatigue life and corrosion resistance due to the variety of coolants used in automotive , aerospace and energy applications . “ When it comes to thermal performance , the most important property for us is strength ,” explains Fordyce . “ If we can use a higher strength material , then we can have thinner walls which shortens the path for heat transfer and ultimately means a higher performing heat exchanger .” “ Most people assume that thermal conductivity is also important , but we ’ ve found it becomes less significant at the wall thicknesses we are dealing with . Copper , for example , has higher thermal conductivity than aluminium , but if we have to make the walls thicker to make the copper part strong enough , that results in a worse preforming heat exchanger overall . So , we can sacrifice thermal conductivity if it means we can achieve a part with thinner walls .”
Types of metal printing powders
Stainless Steel Alloys One of the materials in Conflux ’ s repertoire is 316 stainless steel which is a relatively stable alloy suitable for both high and low temperature harsh environments that require high corrosion resistance . This makes it perfect for manufacturing tools and machinery components for the oil and gas industry as well as engine components that come into contact with corrosive substances . However , it is relatively heavy and therefore not suited for lightweight applications in aerospace or motorsport . It can also experience higher warping and residual stresses during printing then aluminium .
Titanium Alloys An extremely strong and lightweight material ideal for aerospace and motorsport applications is titanium ,
Copper Alloys The high thermal conductivity of copper makes it ideal for thermal applications such as heat sinks and heat exchangers as well as electronic components like busbars and induction coils . Unfortunately , it can be difficult to print with the type of laser wavelengths used in most additive manufacturing printers . Material manufacturers have recognised this and are now adding alloy elements to create high percentage copper alloys such as copper zirconium and copper chromium . These are much more printable and retain high thermal conductivity .
Aluminium Alloys Aluminium alloys such as AlSi10Mg are the most commonly used material in 3D printing . This is mainly because aluminium solidifies with lower tendency to residual stress cracking compared to other alloys , which is why it has been used in casting for decades . It is a cheaper alternative to titanium and so often used in aerospace , automotive and motorsport . Companies such as Airbus and Boeing continue to manufacture 3D printed aluminium components for its aircraft , helicopter and satellites – with the latter often featuring more than 500 additively manufactured parts . Aluminium can also be used to print Formula 1 heat exchangers and automotive pistons such as for Porsche ’ s 911 GT2 RS model . Recently , there has been a lot of development to improve the printability of aluminium alloys that have a higher strength and corrosion resistance than AlSi10Mg . This has led to a variety of new powders that weren ’ t on the market a few years ago .
Nickel Alloys Nickel alloys such as Inconel and Monel K500 maintain their strength at extreme temperatures and are resistant to highly corrosive fluids , making them perfect for rocket applications , gas turbine engine parts and other aerospace turbomachinery . However , printability can be an issue , as nickel alloys tend to develop residual stress and cracking during the printing process . These risks of build failures make this material expensive to print and so is typically only used for very specific applications .
Nickel alloys , such as Monel K , have unique properties making them suited to high temperature rocket applications . www . heat-exchanger-world . com Heat Exchanger World June 2024
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