Boron micro alloying of stainless steels increases their hardenability, hot workability and creep ductility . Boron has a tendency to form chromium rich-iron borides at the grain boundaries, as the solubility limit of boron is very low in stainless steels. The size of the precipitates is usually very fine . Studies have shown that high free boron content will result in chromium boride precipitation on annealing at grain boundaries in mill scale production. The formation of these precipitates cannot be suppressed by water quenching. They are reported to adversely affect corrosion resistance . In the present work, the influence of boron micro alloying (5-40 ppm) in low carbon grade EN 1.4307 (AISI 304L) stainless steel is studied. The effect of boron on etching with oxalic acid, which is a pre-test for inter-granular corrosion of stainless steel according to ASTM A262, is demonstrated. The etch test was carried out on samples with different boron concentration in as-received and in annealed condition. The etch test results were complemented with FEG-SEM examinations. The results indicate the presence of boron rich precipitates near the grain boundaries. In order to determine the influence of boron precipitates on the corrosion properties of the steel, pitting potentials of samples with different boron levels were performed. In addition, corrosion rates in sulphuric acid, Strauss test solution, and Huey test solution were determined.
|Title of host publication||7th European Stainless Steel Conference: Science and Market, Proceedings|
|Place of Publication||Bergamo|
|Publisher||Associazione Italiana di Metallurgiana|
|Publication status||Published - 2011|
|MoE publication type||B3 Non-refereed article in conference proceedings|