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Additive manufacturing, a revolutionary technology, has been at the forefront of innovation for years. In recent times, an age-old process dating back to the 1950s has reemerged as a game-changing enhancement to additive manufacturing. This process, known as Hot Isostatic Pressing (HIPing), is undergoing a remarkable resurgence.
The unique approach to additive manufacturing involves the use of commercially pure titanium in powder form as its raw material instead of expensive titanium-aluminium alloy powders. This choice not only reduces costs significantly but also unlocks the immense potential of titanium, a material celebrated for its high strength-to-weight ratio, impressive mechanical properties, and exceptional corrosion resistance.
However, titanium is notoriously challenging to process into engineered materials due to its sensitivity to external elements, particularly oxygen. An industry expert notes that titanium is very sensitive to the effects of oxygen.
One of the primary challenges in additive manufacturing with titanium is the formation of pores or voids within the layered deposition build-up. These voids can compromise the material’s ductility, and its ability to stretch or bend, and lead to catastrophic fracture modes. Moreover, voids can significantly impact the durability of parts under cyclic loading, posing a serious concern for aerospace components where reliability is paramount.
To address this critical issue, significant efforts have been made to reduce porosity in titanium components to less than one percent. Achieving this level of porosity is crucial as it aligns with industry standards for conventionally produced titanium-aluminium alloys.
Researchers have optimised various parameters, including particle size, particle velocity, and subsequent mechanical behaviour during additive manufacturing. One key discovery in their quest to minimise voids was the use of irregularly shaped particles, rather than spherical ones, in the cold spray deposition process. This innovation not only improved the build speed but also helped reduce void formation, a significant breakthrough in additive manufacturing.
The heart of this innovation lies in the application of Hot Isostatic Pressing. This step involves subjecting the titanium material to a maximum pressure within an argon atmosphere. This process not only reduces porosity but also enhances the overall material performance, making it comparable to the highest-ranked titanium alloys available.
Experts emphasise the importance of science-driven post-processing methods. An understanding of the science behind the post-processing methods is crucial for industry regulators and customers. Material scientists play a pivotal role in selecting parameters like temperature, pressure, and isothermal hold time for the HIPing process, ensuring the highest quality and performance of the titanium components.
The issue of pore generation and induced stresses in additive manufacturing is not unique to these endeavours; it resonates across the additive manufacturing sector. The acquisition of HIP technology was originally to support an innovative waste treatment process.
This application of HIP technology is within the Australian Nuclear Science and Technology Organisation (ANSTO), which boasts over 30 years of operating expertise in HIP technology. Facilities capable of qualifying and characterising the performance of materials before and after the thermal treatment process are considered essential for those in the manufacturing industry.
The resurgence of Hot Isostatic Pressing in the world of additive manufacturing is a testament to the industry’s commitment to pushing boundaries. This innovative approach is not only revolutionising the production of titanium components but also setting new standards for material performance.
By reducing porosity and optimising the manufacturing process, researchers are on a mission to ensure that titanium components meet or even exceed the performance levels of conventional titanium-aluminium alloys. As additive manufacturing continues to evolve, the synergy between cutting-edge technology and time-tested processes like HIPing promises to reshape the future of manufacturing.
