Effect of Mo/Nb ratio variations on the microstructure and cryogenic impact toughness of NiCrMo deposited metals

Abstract

Effects of varying the Mo/Nb (in weight percent) ratio in ENiCrMo-6-deposited metals on the microstructure and cryogenic impact toughness of the metals were investigated. When the Mo/Nb ratio decreased from 6.09 to 3.28, the Nb-rich phase on the grain boundaries was transformed from un-continuous precipitation to continuous precipitation, the area fraction and average size of the precipitates within the grains were significantly increased, and a eutectic-type Laves phase appeared. Although the austenitic matrix of the deposited metals indicated a ductile fracture mode, the precipitates significantly deteriorated the cryogenic impact toughness. As the average size and area fraction of the precipitates increased, the cryogenic impact value decreased significantly.

Keywords

• Cryogenic impact toughness
• 9%Ni steel
• Nickel-base alloy
• Deposited metal
• ENiCrMo-6