Process, Chemistry, and Property Relations for Spray Formed NiCr Alloys
Abstract
A series of NiCr spray forming runs were completed in order to investigate the mechanisms for exceptional high strength and ductility in previous spray formed 5ONi-5OCr (all compositions in wt%) tubes. Although tests showed good strength results, the best mechanical properties of these spray formed alloys were not achieved in this series. The mechanical properties of this eutectic region alloy were found to be sensitive to small changes in processing parameters and chemical composition. More specifically, it was found that slight increases in chromium and nitrogen content can increase strength but decrease ductility and fracture toughness. Crevice corrosion testing was also performed on a spray formed 5ONi-5OCr disk. After a six month exposure in coastal seawater, the alloy showed no evidence of crevice corrosion. This result may be a result of one or all of three different known corrosion resistance enhancements: small scale spray formed microstructure, increased chromium, and increased nitrogen. Slow strain rate (SSR) tests were also performed on 5ONi-5OCr samples, which showed good performance under freely corroding conditions, but experienced a reduction in maximum load under polarized conditions. Based on the results of this series of NiCr spray forming experiments, it is proposed that future work includes NiCr alloys with slightly higher nickel and lower chromium contents (52Ni-48Cr). These changes are likely to increase fracture toughness values without compromising strength and corrosion resistance It is also suggested that future corrosion tests compare spray formed and cast NiCr alloys, as well as varying the chromium and nitrogen components in order to pinpoint and capitalize on the reason for the excellent crevice corrosion resistance of the 5ONi-5OCr material.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 2002
- Accession Number
- ADA406761
Entities
People
- Leslie K. Kohler
- Louis F. Aprigliano
Organizations
- Naval Surface Warfare Center Carderock Division