This paper presents a study of the standard post-weld heat treatment （PWHT） behaviour of autogenous laser welded γ＇ age-hardenable precipitation strengthened nickel based superalloy Haynes 282 （HY 282）. The stud...This paper presents a study of the standard post-weld heat treatment （PWHT） behaviour of autogenous laser welded γ＇ age-hardenable precipitation strengthened nickel based superalloy Haynes 282 （HY 282）. The study involves a careful and detailed microstructural characterisation as well as an analysis of the weld cracking susceptibility during welding and Gleeble thermo-mechanical physical simulation. Various factors that could influence post-weld cracking in superalloys weld were experimentally examined. Our microstructural exami- nation of the as-solution heat treated （SHTed） material and the thermo-mechanically refined grain material shows that intergranular heat affected zone （HAZ） cracking is observable in only the as-welded SHTed material. There was no indication of post-weld heat treatment cracking in all welded materials. Our conclusion, in this study, is that the chemistry of superalloy HY 282 which aids the preclusion/formation of deleterious so- lidification microconstituents during welding as well as its relatively slow aging kinetics enhances its resistance to PWHT cracking.展开更多
The stress rupture properties and deform ation mechanism s of K4750 alloy at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ were investigated. As the decrease of tem perature and stress, the stress rupture life gradually increased...The stress rupture properties and deform ation mechanism s of K4750 alloy at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ were investigated. As the decrease of tem perature and stress, the stress rupture life gradually increased. A Larson-Miller Parameter (LMP) method was used for analyzing the stress rupture life under different conditions. The linear fitting formula between stress (σ) and LMP was derived as σ= 3166.455-119.969 ×LMP and the fitting coefficient w as 0.98. After testing, the dislocation configurations of all stress rupture samples w ere investigated by transm ission electron microscopy (TEM). The tem perature and stress had a significant impact on the deform ation m echanism, thereby affected the stress rupture life of K4750 alloy. As the increasing stress at a given tem perature, the deform ation m echanism gradually transform ed from Orowan looping to stacking fault shearing. Based on experim ental results, the threshold stress at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ for the transition of deformation mechanism was estimated to be about 650 MPa, 530 MPa, 430 MPa and 350 MPa, respectively. Below the threshold stress,γ phase effectively hindered dislocation motion by Orowan looping mechanism, K4750 alloy had along stress rupture life. Slightly above the threshold stress, Orowan looping combining stacking fault shearing was the dom inant mechanism ,the stress rupture life decreased. As the further increase of stress, stacking fault shearing acted as the dominant deformation mechanism , the resistance to dislocation motion decreased rapidly, so the stress rupture life reduced significantly.展开更多
文摘This paper presents a study of the standard post-weld heat treatment （PWHT） behaviour of autogenous laser welded γ＇ age-hardenable precipitation strengthened nickel based superalloy Haynes 282 （HY 282）. The study involves a careful and detailed microstructural characterisation as well as an analysis of the weld cracking susceptibility during welding and Gleeble thermo-mechanical physical simulation. Various factors that could influence post-weld cracking in superalloys weld were experimentally examined. Our microstructural exami- nation of the as-solution heat treated （SHTed） material and the thermo-mechanically refined grain material shows that intergranular heat affected zone （HAZ） cracking is observable in only the as-welded SHTed material. There was no indication of post-weld heat treatment cracking in all welded materials. Our conclusion, in this study, is that the chemistry of superalloy HY 282 which aids the preclusion/formation of deleterious so- lidification microconstituents during welding as well as its relatively slow aging kinetics enhances its resistance to PWHT cracking.
文摘The stress rupture properties and deform ation mechanism s of K4750 alloy at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ were investigated. As the decrease of tem perature and stress, the stress rupture life gradually increased. A Larson-Miller Parameter (LMP) method was used for analyzing the stress rupture life under different conditions. The linear fitting formula between stress (σ) and LMP was derived as σ= 3166.455-119.969 ×LMP and the fitting coefficient w as 0.98. After testing, the dislocation configurations of all stress rupture samples w ere investigated by transm ission electron microscopy (TEM). The tem perature and stress had a significant impact on the deform ation m echanism, thereby affected the stress rupture life of K4750 alloy. As the increasing stress at a given tem perature, the deform ation m echanism gradually transform ed from Orowan looping to stacking fault shearing. Based on experim ental results, the threshold stress at 650 ℃, 700 ℃, 750 ℃ and 800 ℃ for the transition of deformation mechanism was estimated to be about 650 MPa, 530 MPa, 430 MPa and 350 MPa, respectively. Below the threshold stress,γ phase effectively hindered dislocation motion by Orowan looping mechanism, K4750 alloy had along stress rupture life. Slightly above the threshold stress, Orowan looping combining stacking fault shearing was the dom inant mechanism ,the stress rupture life decreased. As the further increase of stress, stacking fault shearing acted as the dominant deformation mechanism , the resistance to dislocation motion decreased rapidly, so the stress rupture life reduced significantly.
