Ingot to Stent Part I – Multiple Source NiTi Characterization via a Single Tube Processing Path

This first of a multi-year installment provides an updated and limited NiTi grade characterization for tube-based devices. Good design with NiTi requires keeping up to date with the metallurgical quality and functional performance of modern grades. This work brings a tube-based view of several NiTi grades from ingot to laser-machined stent with equivalent intermediate processing and final stent form. Into the 2000’s, mitral valve repair was an inpatient surgery. Largely due to NiTi-based frames and stents with streamlined delivery technique, transcatheter mitral valve replacement is becoming an outpatient procedure with improved healing times. Such NiTi valves, as do all structural metals, contain a variety of microscale defects that are dependent on production variables from ingot to final form. The work here is not exhaustive but is intended to expand knowledge of said defect distributions.

A key aim of the present study is to help differentiate between materials and processing variables. This is accomplished by uniquely bringing together several ingot manufacturing sources and one renowned medical-grade, tube manufacturer. Focus is placed on commercially available VIM and PAM melt grades inserted into a typical standard 3.5 x 0.165 mm stent tube production process.

The presentation of Part I will include: ingot and processed-subcomponent transformation temperature data, particle-void assembly size distributions of melted bars and tubes, post-electropolish topographical information, corrosion performance data, and mechanical properties of final tubes in as delivered and post processed condition.