Evaluation of thermal aging embrittlement in CF8 duplex stainless steel bysmall punch test

Small punch test was performed on CF8 duplex stainless steel aged at 370 an d 400 degrees C for up to 5000 h to characterize thermal aging embrittlemen t. At room temperature, the small punch (SP) load-displacement curve was si milar in shape to those of ferritic steels and exhibited a good reproducibi lity in spite of ferrite-austenite structure. As the test temperature was l owered to a certain temperature depending on the degree of aging, the SP lo ad show ed a sudden drop followed by curve serration before the SP specimen fractured, resulting from the cracking of ferrite phase. While the aging h eat treatment led to a slight increase of the yield strength, the transitio n appearing in the SP energy versus temperature curves shifted to higher te mperature due to the hardening of ferrite phase. Additionally, phase bounda ry separation was an important factor in the degradation of the steel aged at 400 degrees C. (C) 2000 Elsevier Science B.V. All rights reserved.