Alloy Hastelloy Research Articles

HASTELLOY ALLOY G-3

Abstract HASTELLOY Alloy G-3 is a nickel-base alloy with outstanding corrosion resistance in the as-welded condition. It is an improved wrought version of HASTELLOY Alloy G. Alloy G-3 has the same excellent general corrosion resistance as Alloy G, along with improved resistance to heat-affected zone (HAZ) attack and excellent weldability. Alloy G-3 is a logical choice for many chemical applications, particularly those involving sulfuric and phosphoric acids, as well as applications where Alloy G has been used successfully. This datasheet provides information on composition, physical properties, hardness, tensile properties, and bend strength. It also includes information on corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-277. Producer or source: Cabot Corporation.

最近のハステロイ合金の特性と用途

最近のハステロイ合金の特性と用途

A fracture mechanics analysis of ultrasonic fatigue

The method of ultrasonic fatigue finds increasing interest in materials science. Especially, fatigue crack growth rates near the threshold stress intensity range, ΔK 0 , can be determined with this method in reasonable times providing no frequency and corrosion effects exist. But for an accurate application of this technique it is necessary to improve the testing systems and also the determination of the dynamic cyclic stress intensity range, ΔK. In this paper, fatigue crack growth experiments at ultrasonic frequencies with different mean stresses and also the calculation of the dynamic stress intensity range with finite elements are treated. On this basis fatigue crack growth curves at room temperature of the alloys Hastelloy X and IN 800 were measured and compared with results obtained at low frequencies. No significant influence of frequency could be found in these materials.

Long-term ageing characteristics of some commercial nickel-chromium-molybdenum alloys

The long-term ageing characteristics of some commercial Ni-Mo-Cr alloys (the high-temperature HASTELLOY alloy S and the corrosion resistant HASTELLOY alloys C-4 and C-276) at 810 K were investigated. It was found that the three alloys undergo the following long-range ordering reaction: disordered f c c lattice → ordered orthorhombic, Pt2Mo-type superlattice. Ordering was found to cause considerable strengthening without severe loss of tensile elongation. Deformation in the ordered state occurred predominantly by twinning. The corrosion rates of alloys C-4 and C-276 in boiling sulphuric-ferric sulphate solution did not seem to be greatly affected by the long-range ordering reaction. In addition to ordering, the three alloys were also found to undergo grain boundary reactions. The resulting phase in alloys S and C-4 assumed a dispersed morphology and was identified as carbide, probably of the Type M12C. In alloy C-276, however, which contains higher amounts of iron and tungsten, the boundary precipitate was in the form of a continuous layer consisting of M12C and Mu-phase. This could account for the reduced tensile elongation of alloy C-276 relative to alloys S and C-4 and also to its high corrosion rate.

High temperature behaviour of the alloy hastelloy B in a hydrogen chloride/water vapour atmosphere

Specimens of the alloy Hastelloy B were tested at 600 and 700°C in an atmosphere of 21% HC1 containing some free oxygen. The results are related to continuous weight-change measurements up to 100 h and long-term tests of 500 h. During the tests the samples lost weight initially at a constant rate which then decreased. An adherent oxide scale was developed. In the outer part of the scale formation of a compact layer, in which the impurities Si, Mn, Co and Cr became enriched, was observed. In the inner part MoO 2 was formed, the growth of which was irregular as a result of phase transformations. This investigation was carried out in connection with a proposed thermochemical method of splitting water, involving the use of nuclear heat.

A model for H-Absorption by metals

An analytical technique has been developed for studying hydrogen (H) absorption in cathodically charged metals. The technique combines computer modeling of H-motion with simple total H-content measurements, and yields the precise H-concentration profiles produced by galvanostatic charging. Although the technique was developed for one particular nickel-base superalloy, it is quite general and can be applied to a wide range of alloy systems. The technique was used to study H-absorption by HASTELLOY Alloy C-276, a single phase alloy whose hydrogen embrittlement (HE) tendency depends on thermomechanical state. The study indicated that H-absorption also depends on thermomechanical state. However, no clear cut relationship was obtained between H-absorption and embrittlement behavior of Alloy C-276.

Hydride formation in a Ni-base superalloy

X-ray diffraction, optical- and scanning-electron metallographic and microhardness studies have been conducted in pure Ni and a Ni-base alloy (HASTELLOY Alloy C-276) in an effort to determine if hydrides form in the alloy during cathodic charging in the presence of a strong H-recombination poison. The studies indicate that hydrides do form and that the extent of surface damage caused by them is a function of the alloy thermomechanical state. In the annealed alloy, hydrides produce a network of crystallographic cracks. In the 50 pct cold-worked alloy, extensive intergranular blistering and lamellar peeling are observed in addition to the crack network. In the cold-worked and aged alloy, damage similar to, but less extensive than, that of the cold-worked alloy is found. The average depth of damage penetration may be accounted for by the bulk diffusion of H in the alloy. It is not clear whether the observed susceptibility of the cold-worked and aged alloy to H embrittlement can be attributed to hydride formation.

Precipitation of NiMo in a Ni-Mo base alloy

A study, using electron microscopy and diffraction techniques, was made to characterize a minor second phase present in a corrosion resistant Ni-Mo base alloy (Hastelloy alloy B containing 27.8 wt% Mo and less than 0.002 wt% C. The effect of second phase distribution in the microstructure on tensile properties and corrosion resistance was determined. The only second phase that could be identified by electron diffraction was found to be the intermetallic NiMo δ phase. It was found that during aging of previously solution treated material, selected grain boundary segments migrate and leave behind NiMo particles. This grain boundary reaction was found to have no detrimental effect on ductility and corrosion resistance.

The Effect of Scan Rate on Pitting Potentials of High Performance Alloys in Acidic Chloride Solution

Abstract The effect of potential scan rate on the pitting potential determination of several high performance alloys in acidic chloride solution at 70 C was documented. Materials from several alloy classifications were examined including austenitic stainless steel, duplex stainless steel, 20-type stainless steel, and nickel base alloys. The functional relationship of pitting potential versus scan rate was dependent on the material studied. Results at intermediate and rapid scan rates were dependent on the material studied and on the experimental procedure. The response of the pitting potential of a given alloy to intermediate and rapid scan rates appears to be a function of the kinetics of passive film formation at the corrosion potential and at applied potentials. Therefore, the most promising accelerated electrochemical tests for localized corrosion resistance are the slow scan rate and constant potential pitting tests. Hastelloy alloy G was found to be resistant to pitting corrosion at all applied potentials in this environment. Additionally, the microstructural sites most susceptible to stable pit initiation were determined for the alloys investigated.

Pitting Resistance of Engineering Materials in Geothermal Brines—I. Low Salinity Brine

Abstract The resistance of carbon steel, E-Brite 26-1, Type 316L stainless steel, Haynes Alloy 20 Mod, Carpenter Alloy 20 Cb-3, Inconel Alloy 625, Hastelloy Alloy G, Hastelloy Alloy C-276, Titanium 50A, and TiCode 12 to pitting in a low salinity geothermal brine (Nowlin No. 1) was determined. The behavior of coupons exposed to the “fresh,” unflashed wellhead brine was compared with the behavior of coupons exposed to unflashed brine collected at the wellhead and transported to the laboratory. Pitting potentials were also determined in laboratory tests. There was excellent agreement between laboratory and field test data. The two titanium alloys were completely resistant to pitting under all experimental conditions, Hastelloy Alloy C-276 was the nickel base alloy most resistant to pitting, and Haynes Alloy 20 Mod was the most resistant iron base alloy. The breakdown potentials for the high chromium ferrous alloys satisfy the thermodynamic requirements for pit initiation via oxidative dissolution of manganese sulfide inclusions in the passive film.

The Use of Potential-pH Diagrams for the Interpretation of Corrosion Phenomena in High Salinity Geothermal Brines

Abstract Corrosion potentials and cyclic voltammograms are reported for AISI 1010 carbon steel, E-Brite 26-1 stainless steel, AISI 316L stainless steel, Haynes Alloy 20 Mod, Carpenter 20 Cb-3, Inconel Alloy 625, Hastelloy Alloy G, Hastelloy Alloy C-276, Titanium 50A, and TiCode 12 in high salinity geothermal brine at 250 C. Potential-pH diagrams for the component metals (Fe, Ni, Cr, Ti) in the brine at 25 and 250 C are also derived, and are used to interpret the corrosion behavior and cyclic voltammetric responses of the alloys in the elevated temperature brine environment.

Factors Influencing the Embrittlement of Cold Worked High Alloy Materials in H2S Environments

Abstract The resistance of several high strength nickel and cobalt base alloys to embrittlement in aqueous H2S containing environments was examined. The alloys evaluated were Hastelloy Alloy C-276 and Alloy C-4, Inconel 625, and MP35N. All materials were received as tubing in the cold reduced condition and were subjected to various heat treatments ranging from 148 to 593 C (300 to 1100 F) for times from 10 minutes to over 500 hours. The effect on cracking susceptibility of: (1) cold working, (2) aging time and temperature, (3) sample orientation, (4) galvanic interaction with steel, and (5) environmental temperature and composition were determined. It was found that aging for very short periods at high temperature [482 to 593 C (900 to 1100 F)/10 minutes] or for longer times at low temperatures [148 to 204 C (300 to 400 F)/~500 hours] significantly reduced the resistance of these materials to hydrogen embrittlement. This behavior was greatly dependent on galvanic interaction with steel and on sample orien...

HASTELLOY ALLOY B-2

Abstract HASTELLOY alloy B-2 has outstanding corrosion resistance in the as-welded condition. It is an improved wrought version of HASTELLOY alloy B with the same excellent corrosion resistance as alloy B, but with improved resistance to knife line and heat-affected zone attack. Alloy B-2 resists the formation of grain-boundry carbide precipitates in the weld heat-affected zone, thus making it suitable for most chemical process applications in the as-welded condition. This alloy also has excellent resistance to pitting and stress-corrosion cracking. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on high temperature performance and corrosion resistance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-249. Producer or source: Stellite Division, Cabot Corporation.

Stress Corrosion Behavior of Fe-Cr-Ni and Other Alloys in High Temperature Caustic Solutions

Abstract The resistance of various commercial alloys to stress corrosion cracking (SCC) in 50% NaOH has been evaluated at temperatures in the range 284 to 332 C. Austenitic alloys tested included Type 300 series stainless steels, Monel Alloy 400, Inconel Alloys 600, 625, 690, Incoloy Alloys 800, 804, 825, Hastelloy Alloy C, and Nickel 201. Other materials tested were Croloy 2¼Cr-1Mo steel, ferritic stainless steels Type 446, 26-1S, and EB 26-1, and commercial purity titanium. The effects of alloy composition, heat treatment, and test temperature on the severity of SCC were examined. Increasing the nickel content increased the resistance of SCC in deaerated 50% NaOH. In an aerated 50% NaOH solution, both high chromium and high nickel contents were necessary to increase stress corrosion resistance. In deaerated 50% NaOH, ferritic alloys exhibited high corrosion rates and displayed structure sensitive cracking behavior. Titanium corroded rapidly but did not crack. The greatest overall resistance to SCC in de...

Effects of solidification substructure on the mechanical properties of a nickel base superalloy

Rod specimens of HASTELLOY alloy X were unidirectionally solidified by the floating zone method in an electron-beam zone melter. Temperature gradient (▽ T) and growth rate ( R) were controlled to produce three types of solidification substructures: cellular, cellular-dendritic, and dendritic. Qualitative agreement with the solidification treatment of Tiller and Rutter was obtained, in that a decrease in the parameter ▽ T/ R changed the solidification mode away from cellular toward dendritic. Room- and elevated-temperature tensile tests indicate that the dendritic form of the alloy is stronger and more ductile than the cellular form, probably because there is less tendency for brittle, low-melting grain-boundary phases to form during dendritic solidification.

An Improved Ni-Cr-Mo Alloy for Corrosion Service

Abstract A new Ni-Cr-Mo corrosion resistant alloy, Hastelloy alloy C-4, has been developed that does not precipitate an intermetallic Mu phase upon aging in the 650 to 1090 C temperature range. This further improvement of Hastelloy alloy C-276 has evolved from a detailed study of the effects of the substitutional and interstitial elements on the precipitation of intermetallic and carbide phases. Data have been generated to show that Hastelloy alloy C-4 is basically equivalent in corrosion resistance to its predecessors in both oxidizing and reducing media.

Effect of Composition and Structure on Crevice, Intergranular, and Stress Corrosion of Some Wrought Ni-Cr-Mo Alloys

Abstract The relationship of composition and microstructure to the occurrence of localized corrosion in Hastelloy alloys C, C-276, and C-4 was investigated. One hour exposures of these alloys in th...

Phase transformations in the alloy hastelloy B

The alloy Hastelloy B undergoes phase transformations in the temperature range of ∼600°–800° C. These phase transformations were studied in some detail by electron microscopy. The essential result of this study was the observed formation of the DO 22 structure as an intermediate phase. The DO 22 structure is relatively stable in Hastelloy B and its further transformations are easily observable. At 600°C it is transformed to Ni 4 Mo followed by a partial transformation to Ni 3 Mo, whereas at 700°C Ni 3 Mo is formed from DO 22 directly.

Carburization of Hastelloy alloy X

The carburization of Hastelloy alloy X has been studied by the standard tracer techniques using 14C over the temperature range 700 to 1100°C in vacuo and helium environment. The 14C activity in the specimen decreases exponentially with the depth of penetration and increases with carburization time. It is observed that carbon diffusion in the alloy is dominated by grain-boundary diffusion. The effect of oxygen in helium gas on carburization is observed. Oxygen has two opposite types of action on carburization of the alloy. One is inhibitive action and the other is accelerative action.

Effect of Aging on the Anodic Behavior of Ni-Cr-Mo Alloys

Abstract The precipitation response of corrosion resistant alloys based on the Ni-Cr-Mo phase diagram is complex with both intermetallic and carbide phases being formed during aging in the 650 to 1090 C (1202 to 1994 F) range. Although these phases markedly affect the corrosion resistance, their composition and structure have not been fully defined. Data are presented to show that the precipitating intermetallic phase in Hastelloy alloy C-276 is a (Ni, Fe, Co)3 (W, Mo Cr)2 Mu phase and the carbide is an M6C. Both phases have been shown to significantly increase the anodic dissolution rate of the passive region in boiling 10% sulfuric acid. Intergranular attack on aged alloy C-276 samples occurred due to attack of depleted regions in reducing acids and direct dissolution of precipitates under oxidizing conditions.