Thesis (M.Sc.)--Chulalongkorn University, 1998

An attempt was made to correlate the susceptibility to intergranular stress corrosion cracking (IGSCC) of type AISI 304 austenitic stainless steel to the degree of sensitization determined using the doppler broadened positron annihiltion (DBPA) spectroscopy. The specimens were sensitized by isothermal exposure from 2 to 16 hours at 650 ํC and strained in 0.5 mole per liter sodium thiosulfate pentahydrate (Na2S2O3.5H2O) solution at an initial strain rate of 1.73x10 -6 per second and at ambient temperature. The microstructure of the specimens was examined in scanning electron microscope (SEM) revealing different density of carbides precipitate along grain boundaries of the various sensitized specimens. The ultimate tensile strength (UTS) of the sensitized specimens was used to evaluate the susceptibility to stress corrosion cracking (SCC) in the specimens and it was found that, the UTS of the specimens decrease while increasing the sensitization time. The UTS values obtained from SSRT test were found to have an inverse correlation with the S parameters obtained from DBPA spectroscopy. Thus the DBPA spectroscopy may be nondestructively used to evaluate the susceptibility to SCC in type AISI 304 austenitic stainless steel.