How NASA Uses PIP to Uncover Hidden Mechanical Variation in AM Parts

However, the same design flexibility that makes AM so powerful also introduces sensitivity: small variations in printing parameters, geometry, or heat treatment can lead to significant differences in mechanical performance. Understanding and controlling these sensitivities is essential for qualifying high-performance AM parts.

At the ASTM International Conference on Advanced Manufacturing (ICAM) 2025, Marcus Gaiser-Porter of Plastometrex presented collaborative work with NASA, demonstrating how Profilometry-based Indentation Plastometry (PIP) can be used to rapidly uncover and quantify

Mapping Mechanical Performance in NASA HR-1 and HR-2

One of the most challenging environments for materials is found inside liquid rocket engines, where components must retain exceptional strength at elevated temperatures and withstand high-pressure hydrogen exposure.

To meet these demands, NASA developed NASA HR-1, and later NASA HR-2, an iron-nickel alloy engineered to resist corrosion and hydrogen embrittlement while maintaining ease of printability. Both alloys are compatible with Directed Energy Deposition (DED) and Laser Powder Bed Fusion (LPBF), making them ideal candidates for advanced AM applications (Figure 1).

PIP testing was performed on a c-ring specimen manufactured from NASA HR-1 using LPBF with varying thickness around its arc (Figure 2). The fine spatial resolution of PIP allowed local yield stress to be mapped across the ring down to 3 mm intervals radially. When the local yield stress was mapped, it revealed a strong correlation between part thickness and local mechanical strength.

These results underscore a critical insight: small variations in AM processing or geometry can drive significant shifts in material behaviour. Even small changes in section thickness can produce localised shifts in yield behaviour that would be invisible to bulk testing.

Conventional testing methods, such as tensile testing, simply cannot provide this level of spatial resolution. Without this, qualification risks being based on incomplete or misleading mechanical data.

High temperature PIP testing was also carried out on NASA HR-2 samples. These components were produced via DED under two closely spaced heat-treatment conditions that differed by only 28°C during initial heating. High temperature mechanical behaviour was rapidly characterised up to 800°C using the PLX-HotStage. The results revealed a pronounced sensitivity to thermal processing: a small 4% change in heat treatment temperature resulted in a ~15% shift in mechanical properties across the tested temperature range (Figure 3).

Understanding components’ hyper-sensitivity to process conditions emphasises the importance of both accurate process monitoring and frequent quality assurance checks throughout manufacture.

PIP testing provides a rapid, fine scale means of detecting these sensitivities early in the development cycle, without the time and cost burdens of traditional testing. Further, as an ASTM-standardised test method, the reliable, repeatable results provided by PIP testing can be utilised with confidence from qualification all the way through to production.

As organisations like NASA continue to push the limits of material performance, techniques such as PIP testing will play a central role in validating and optimising AM processes, ensuring that next-generation alloys like NASA HR-1 and NASA HR-2 meet the extreme demands of future missions.

This work was done in collaboration with Thomas Southern, Applications Engineer at Plastometrex, and Colton Katsarelis, Materials Engineer at the NASA Marshall Space Flight Center.

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