Abstract
As part of a program to develop a stainless steel (SS) resistant to pitting, intergranular corrosion (IGC), and general corrosion while improving the stress corrosion cracking (SCC) resistance, the influence of silicon additions to an 18Cr-8Ni stainless alloy was investigated. Preliminary corrosion data indicated that an 18Cr-8Ni-5Si composition had not only exceptional resistance to IGC following sensitizing heat treatment but also improved general and pitting corrosion resistance. This paper describes the results of further studies aimed at comparing the SCC resistance of the silicon duplex alloys with that of AISI 304 SSs. In addition, preliminary data were obtained on the weldability and formability of silicon-containing duplex stainless alloys. An experimental alloy (18Cr-8Ni-5Si) was found to be immune to SCC in boiling magnesium chloride solution in the annealed condition. The experimental alloy was also markedly superior to AISI 304 SS when tested in the cold-worked condition. The mechanical properties of the experimental alloy (18Cr-8Ni-5Si) were approximately twice that of AISI 304 SSs. The results of hot twist tests conducted in the range of 2000 to 2400 F (1093 to 1316 C) indicate that the hot formability of the experimental alloy was comparable to that of other duplex SSs, and the welding tests indicated excellent welding characteristics at all heat inputs with no longitudinal or transverse cracking. In addition, preliminary data indicate that this steel can be hot rolled on conventional facilities without undue cracking and may be readily welded.
