BACKGROUND
The purpose of this project is to investigate the ability of SwRI’s Renishaw AM250 to print shape memory alloy (SMA) components, specifically nickel-titanium (NiTi, nitinol). Nitinol has become a popular alloy due to its unique elastic and shape memory properties and has numerous applications, ranging from biomedical to aerospace. While nitinol has many uses, there are drawbacks that have limited its use to select applications. Nitinol is readily available in smaller stock sizes but there are few suppliers of large stock material. This makes the bulk material prohibitively expensive in small quantities. Additionally, nitinol can be difficult and expensive to machine due to work hardening. Its elastic properties also make it challenging to form into complex shapes. To date, additive manufacturing of shape memory alloys (AM-SMA) appears to be limited to academic institutions based on an initial survey of published research. While the published research provides a good starting point, none of the groups specifically used an AM250. Also, these institutions are focused on basic research, without a good way to transition the technology to industry.
APPROACH
The objective of this research is to develop parameters at SwRI for additive manufacturing with NiTi powder to reduce the issues of working with standard nitinol material. This can also help establish SwRI as a leader in a technology that is growing but remains underdeveloped in industry due to manufacturing and cost limitations.
Small-scale test builds will help establish ideal build parameters for the NiTi powder. Preliminary tests are shown in Figure 1. Initial tests (a) show a completely failed build while later tests (c) showed promising results after adjusting parameters based on the earlier builds. Once build parameters are established, further testing will be done on tensile specimens. These specimens will be used to investigate the mechanical properties, as well as the shape memory properties, of the printed NiTi. Comparisons will also be made to NiTi specimens fabricated from stock material.
Figure 1: a) Failed build, b) partially completed build, and c) completed build with some cracking.
ACCOMPLISHMENTS
Initial tests have helped bound build parameters. Additional small-scale builds are in process with recently received powder to continue to refine the build parameters to an ideal set.