Sigma () phase embrittlement - Man y stainl ess steels and other iron-chromium alloys are susceptible to a grain boundary phenomenon known as sigma-phase embrittlement. Sigma phase is An Investigation on the Cracking of Air Tubes of Rotary Sep 28, 2011 · Cracking of an air tube used for supplying air in rotary kiln of a sponge iron plant is investigated in this paper. The material of the air tube is ASTM A297 HK 40, a member of the heat-resistant cast alloy family (H series) steels widely used for enhanced high-temperature properties. Microstructural degradation occurring at high temperature affects mechanical and corrosion-resistance
However, 304 and 304H tubing are not subject to this embrittlement mechanism in normal boiler use. Factors contributing to the formation of sigma phase include the progressive solidification, and the presence of ferritizers particularly molybdenum, columbium and titanium. Sigma phase may also form in the ferritic stainless steels. Corrosion of Cast Steels IspatGuruJul 30, 2016 · Corrosion of cast stainless steels. The main alloying element in the high alloy family of cast stainless steels is generally Cr, which, through the formation of protective oxide films, is the first step for these cast steels in achieving stainless quality. For all practical purposes, stainless behaviour requires a minimum of 12 % Cr. Cracking of an austenitic stainless steel lance pipe in a Dec 01, 2013 · Sigma phase is an ironchromium intermetallic compound and it forms in stainless steel with long-time exposure in the temperature range of 6001000 °C. K. Al-Jumayiah, F. HabibySigma phase formation and embrittlement of cast ironchromiumnickel (FeCrNi) alloys. J Min Mater Charact Eng, 7 (2008), pp. 127-145. CrossRef View
embrittlement resulting from changes generated by the interaction between the metal and its environment. These types of embrittlement are:hydrogen embrittlement, stress-corrosion cracking and liquid metal embrittlement. Environmental embrittlement of Ductile Iron is usually not a concern for designers. However, more attention Hau, J., and Seijas, A., Sigma phase embrittlement of Hau, J., and Seijas, A., Sigma phase embrittlement of stainless steel in FCC service, CORROSION2006, paper 06578. has been cited by the following article:TITLE:Sigma Phase Formation and Embrittlement of Cast Iron-Chromium-Nickel (Fe-Cr-Ni) Alloys Homogenization Heat Treatment to Reduce the Failure of Jan 18, 2012 · One of the most affected mechanical properties of steels by formation of the sigma phase is impact energy. Effect of sigma phase on the impact energy of austenitic steel Fe-25Cr-20Ni is shown in Fig. 8 . By increasing the time of exposure at formation temperature range of sigma phase (760870°C), toughness value decreases by 85%.
The sigma phase can form in a wide range of FeCr systems. Traditionally, precipitation of sigma phase under an elevated temperature environment (such as during casting, rolling, welding, forging, aging, and so forth) would enhance the strength but reduce the ductility of an iron based alloyaccordingly, it would generally be avoided. Sigma phase-induced failure of AISI 310 stainless steel Dec 01, 2017 · Sigma phase in this case has formed at the interface of carbide with the matrix. Areas around the carbides are to some extent depleted from carbon and this facilitates the formation of sigma phase. Formation of sigma-phase is accompanied with excessive brittleness and eventually intergranular crack opening and fracture. Sigma-phase is a Fe Cr intermetallic compound, which forms mostly in Stainless Steel - High Temperature ResistanceJan 08, 2002 · These grades are all prone to sigma phase formation if exposed for long periods to a temperature of about 590 to 870°C. Sigma phase embrittlement refers to the formation of a precipitate in the steel microstructure over a long period of time within this particular temperature range. The effect of the formation of this phase is to make the steel extremely brittle and failure can occur because of
Dec 01, 2013 · The precipitation sites of sigma-phase consist of delta/gamma interface boundary, triple conjunction, grain corner and cellular . In this work, formation and morphology of sigma-phase in the failed rollers and the effect of homogenization heat treatment Suitable materials for pressure vessels - Heanjia Super The high chromium based stainless steels produce sigma phase at high temperature and are attacked by embrittlement at lower temperature limits. Sigma phase is hard, fragile and non-magnetic in nature and its chemistry is based on an alloy in which it is produced. TABLE OF CONTENTS - Stainless Steel Worldretard the kinetics of sigma phase formation. Additions of sulfur, selenium, and lead in stainless steel improve machinability. Columbium additions can improve high-temperature creep strength. Copper additions improve resistance to sulfuric acid. A combination of manganese and nitrogen may be used as a partial substitute for nickel in
Temper embrittlement is caused by the presence of specific impurities in the steel, which segregate to prior austenite grain boundaries during heat treatment. The main embrittling elements (in order of importance) are antimony, phosphorus, tin and arsenic. The fracture surface of a material embrittled by these elements has an intergranular cast irom Metallurgy for DummiesGrey cast iron. Grey cast iron is characterized by its graphitic microstructure, which causes fractures of the material to have a grey appearance. It is the most commonly used cast iron and the most widely used cast material based on weight. Most cast irons have a chemical composition of 2.5 to 4.0% carbon, 1 to 3% silicon, and the remainder is phase diagram iron carbon Metallurgy for DummiesFigure 1. Iron Carbon Phase Diagram. At the low-carbon end of the metastable Fe-C phase diagram, we distinguish ferrite (alpha-iron), which can at most dissolve 0.028 wt. % C at 738 °C, and austenite (gamma-iron), which can dissolve 2.08 wt. % C at 1154 °C.
Vol.7, No.2 Sigma Phase Formation And Embrittlement 145 S31803 duplex s tainless steel aged treated at 850°C, Materials Research, July/Sept. 2002, vol.5, no.3, p.385-389.