[ Column ]
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To compare the performance of SDSS and HDSS , the PREN values of ferrite and austenite calculated using Thermo- Calc software are shown in Figure 1 . As may be seen at a temperature range of 1100-1200 ° C , PRE N of both ferrite and austenite is more than those for SDSS , exceeding 48 . Thanks to its great alloy design , optimum PRE N of ferrite and austenite is achieved when their content is almost equal . It should be noted that we used typical alloy composition for the calculations , and the PRE N of ferrite and austenite might vary based on the actual composition .
Welding filler metal The unique alloying design of HDSSs requires highly engineered filler metal to deliver the required properties for different high-performance applications . Exaton 27.7.5 . L has been designed to deliver high mechanical and corrosion resistance performance in complex welding thermal cycles . The typical microstructure of the root pass fabricated using this HDSS filler wire is shown in Figure 2 . The weld shows a balanced fraction of ferrite and austenite , and no indication of fine secondary austenite clusters and detrimental intermetallic phases was found .
Stress / pressure
HDSSS SDSS
Standard DSS
Figure 3 : The application map of duplex stainless steel grades .
Figure 2 . Typical microstructure of root pass using HDSS ( 27 % Cr , 7 % Ni , 5 % Mo ) wire . The bright phase is austenite , and the dark phase is ferrite .
In addition to the welding of HDSS products , welding wires provide the opportunity to use HDSS in a wide range of applications . Weld overlays , root passes of super duplex stainless steel welds , and welding of 13 % Cr stainless steels are a few applications that can locally enhance the performance of different components using HDSS welding wire . Some applications of HDSS welding wires will be explored in upcoming issues of Stainless Steel World .
Corrosivity or service temperature
Application The schematic comparison of service temperature , corrosivity of environment , and stress / pressure level applied on the components for different duplex stainless steels is shown in Figure 3 . Thanks to the high strength-to-weight ratio , as well as high critical pitting temperature , HDSS products are great candidates where a combination of high pressure , high temperature , and highly corrosive environment are present . This includes tropical seawater , components for chemical and petrochemical applications , and heat exchangers . The alloy is a great alternative to nickel alloys for the above-mentioned applications . To sum up , HDSS has a great potential to be used in highly corrosive and load-bearing conditions thanks to their excellent composition and microstructure design , making them sustainable choices in many different applications .
References
1 . Alleima product datasheets for different duplex stainless steel grades .
2 . ESAB product datasheet for Exaton 27.7.5 . L
3 . Guocai Cha , Pasi Kangas , Hyper- Duplex Stainless Steels , How A New Generation of High-Alloy Stainless Steels Is Helping To Overcome Challenges In The Offshore Oil And Gas Industry , Sandvik white paper .
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