ISSN:
1662-9752
Source:
Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Precipitation hardened nickel-based superalloys are widely used in aero and industrial gasturbine engines due to their excellent high temperature strength and remarkable hot corrosionresistance. A drawback of many of these alloys is that they are very difficult to weld due to their highsusceptibility to heat affected zone (HAZ) cracking, both during welding and post weld heattreatments (PWHT). Weld cracking in many of these alloys has been attributed mostly toconstitutional liquatioin of grain boundary NbC precipitates. however, HAZ cracking has beenobserved in carbon-free superalloys as well, Therefore, research was initiated to examine grainboundary liquation and cracking in HAZs in a variety of Ni-based superalloys. It was found thatintergranular cracking of grain boundaries involved liquation of several other phases, in addition toNbC, that were present in pre-weld microstructure of the alloy. These even included the primarystrengthening phase,γ’, in a very widely used superalloy, Inconel 738. In addition, segregation ofmelting point depressant element B was also observed at gain boundaries in other superalloys, whichalso caused grain boundaries in HAZ to liquate and resulting in their cracking. An overview ofmicrostructural aspects of different liquation phenomena involved and characteristics of the liquidfilm contributing to the HAZ microfissuring of nickel superalloys will be discussed in thispresentation
Type of Medium:
Electronic Resource
URL:
http://www.tib-hannover.de/fulltexts/2011/0528/02/16/transtech_doi~10.4028%252Fwww.scientific.net%252FMSF.546-549.1163.pdf
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