Hastelloy Alloys
Hastelloy Alloys
Hastelloy alloy is a corrosion-resistant nickel (Ni) alloy which contains other chemical elements such as chromium (Cr) and molybdenum (Mo). This material has high temperature resistance and outstanding corrosion resistance.
Hastelloy alloy has good sulphfidation resistance and high metallurgical stability, which makes it preferable material for high-temperature applications of thermal energy storing and electricity generating devices such as gas turbines. In addition, it has low cycle fatigue resistance superior to that of most solid solution-strengthened alloys and it has a very good resistance to hot corrosion. The alloy is used to produce high-temperature gas path components such as turbine combustors, flame holders, liners, pressure vessels of some nuclear reactors, chemical reactors, and pipes / valves in the chemical industry.
Hastelloy alloys are widely used across multiple industries because of their improved mechanical properties. Since they can withstand moderate to severe corrosion, Hastelloy alloys are used in several welding, aerospace engineering, and chemical processing applications.
Hastelloy alloys are widely used by the chemical processing industries. The need for reliable performance leads to their acceptance and growth in the areas of energy, health and environmental, oil and gas, pharmaceutical, and flue gas desulphurization (FGD) industries. The attributes of Hastelloy alloys include high resistance to uniform attack, outstanding localized corrosion resistance, excellent stress corrosion cracking resistance, and ease of welding and fabrication.
Along with containing nickel and molybdenum, the different grades of Hastelloy alloys can contain percentages of iron (Fe), aluminum (Al), tungsten (W), carbon (C), titanium (Ti), chromium (Cr), and other elements. The most widely used and versatile Hastelloy alloys are the C-types.
Formulated in 1952, the Hastelloy X alloy is a more recent grade of superalloy compared to others. It contains higher percentages of iron to improve oxidation resistance, formability, and high temperature strength. It can also be cold rolled to meet desired temper properties; however, it cannot be hardened by heat treatments.
Hastelloy B-type alloys are known for their high percentages of nickel and molybdenum. Because of nickel and molybdenum, they offer high resistance to corrosion. The alloys are notable for their ductility and has one of the highest melting points of all the naturally occurring elements. These alloys are formulated to withstand extreme reducing conditions, such as environments with hydrochloric, hydrobromic, and sulphuric acids.
Hastelloy alloys which fall within the C-family have high percentages of nickel, molybdenum, and chromium. The addition of chromium increases the formability of these types of alloys, allowing them to withstand elevated temperatures and reducing atmospheres. Majority of the C-type alloys can be formed using different cold and hot working methods, such as deep drawing, press forming, and punching.
Hastelloy G-type alloys typically contain tungsten, which has the highest melting point of all metals. This family of alloys can be welded using certain techniques, such as gas tungsten arc welding (GTAW), submerged arc welding (SAW), and shielded metal arc welding (SMAW).
Hastelloy alloys are available in different grades. Some of the important Hastelloys alloy grades are B-3 alloy, C-4 alloy, C-22 alloy, C-22HS alloy, C-86 alloy, C-276 alloy, C-2000 alloy, G-3 alloy, G-30 alloy, G-35 alloy, X alloy, Hybrid-BC1 alloy, and N alloy. Hastelloy B-3 alloy possesses outstanding resistance to non-oxidizing acids, such as hydrochloric acid and sulphuric acid. The advantages of B-3 alloy over other B-family alloys are improved thermal stability and improved fabrication characteristics. Hastelloy Hybrid-BC1 alloy handles stronger non-oxidizing acids than C-type alloys and tolerates oxidizing impurities which B-type alloys do not tolerate.
The most versatile of the Hastelloy alloys are the Hastelloy C-type alloys. Hastelloy C-2000 alloy combines outstanding resistance to oxidizing media with superior resistance to non-oxidizing environments and represents a true performance breakthrough for chemical process equipment applications. Hastelloy C-22 alloy is particularly resistant to pitting and crevice corrosion. It has been used extensively to protect against the most corrosive flue gas desulphurization systems and the most sophisticated pharmaceutical reaction vessels.
Hastelloy G-30 alloy has been very successful as phosphoric acid heat exchanger tubing and for other process components in the fertilizer industry. Hastelloy G-35 alloy has been designed as an improved version of Hastelloy G-30 alloy in these applications. The high chromium content of both of these alloys makes them the best choices for strong oxidizing solutions and mixed acid pickling services. The characteristics of the important Hastelloy alloys are described below.
Hastelloy B-3 alloy (UNS N10675) – It is a nickel base wrought alloy. It shows extremely high resistance to hydrochloric acid at all concentrations and temperatures. It also shows extremely high resistance to hydrogen chloride, hydrobromic, acetic, phosphoric, and sulphuric acids. The alloy has excellent resistance to pitting, to stress corrosion cracking, and to knife-line and heat affected zone attack. It resists the grain boundary carbide precipitation in the heat affected weld zone, hence making it suitable for most chemical process applications in the as welded condition. Also, it has greatly improved structural stability compared with some other B-type alloys, leading to fewer concerns during welding, fabrication, and service.
Like other nickel alloys (in the mill annealed condition), it is ductile, can be formed and welded, and resists stress corrosion cracking in chloride-bearing solutions. Also, it is able to withstand fluoride-bearing media and concentrated sulphuric acid, both of which result in damage to zirconium alloys. The alloy composition is nickel – 65 %, molybdenum – 28.5 %, chromium – 1.5 %, iron -1.5 %, cobalt – 3 % maximum, manganese – 3 % maximum, tungsten – 3 % maximum, aluminum – 0.5 % maximum, titanium – 0.2 % maximum, silicon -0.1 % maximum and carbon 0.01 %. It has a density of 9.22 grams per cubic centimeter (g/cc). The mechanical properties of this alloy are ultimate tensile strength (UTS) – 914 MPa, yield strength at 2 % offset – 396 MPa, elongation – 55 %, and Rockwell hardness – B-98.
Hastelloy B-3 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and coated electrodes. It is used in numerous chemical process industry applications, especially in the construction of reaction vessels for pure, reducing acid service.
Hastelloy C-4 alloy (UNS N06455) – It is the most (micro-structurally) stable of the widely used nickel-chromium-molybdenum alloy, which is well known for its resistance to several aggressive chemicals, in particular hydrochloric acid, sulphuric acid, and chlorides. This stability means that the alloy can be welded without fear of sensitization, i.e., the nucleation and growth of deleterious, second phase precipitates in the grain boundaries of the weld heat-affected zone (HAZ).
Like other nickel alloys, Hastelloy C-4 alloy is ductile, easy to form and weld, and possesses exceptional resistance to stress corrosion cracking in chloride-bearing solutions, a form of degradation to which the austenitic stainless steels are prone. With its high chromium and molybdenum contents, this alloy is able to withstand both oxidizing and reducing acids, and is resistant to pitting and crevice attack in the presence of chlorides and other halides.
Hastelloy C-4 alloy has high-temperature stability in the range of 650 deg C to 1,040 deg C as shown by good ductility and corrosion resistance. It has virtually the same uniform corrosion resistance as Hastelloy C-276 alloy. The alloy composition is nickel – 65 %, chromium – 16 %, molybdenum – 16 %, titanium – 0.7 %, iron – 3 % maximum, cobalt – 2 % maximum, manganese -1 % maximum, silicon -0.08 % maximum, and carbon – 0.01 maximum. It has a density of 8.64 g/cc. The mechanical properties of this alloy are ultimate tensile strength (UTS) – 768 MPa, yield strength at 2 % offset – 416 MPa, elongation – 52 %, and Rockwell hardness – B-90.
Hastelloy C-22 alloy (UNS N06022) – It is one of the well-known and well-proven nickel-chromium-molybdenum alloys with better overall corrosion resistance than other nickel-chromium-molybdenum alloys available today, including Hastelloy C-276 alloy, Hastelloy C-4 alloy, and ‘Cabot’ alloy no. 625. The chief attributes of Hastelloy C-22 alloy are its outstanding resistance to both oxidizing and reducing chemicals, and protection from pitting, crevice attack, and stress corrosion cracking. Because of its versality, Hastelloy C-22 alloy can be used where ‘upset’ conditions are likely to occur or in multi-purpose plants. It is the best alloy to use as universal weld filler metal to resist corrosion of weldments.
Hastelloy C-22 alloy has excellent resistance to oxidizing aqueous media including acids with oxidizing agents, wet chlorine, and mixtures containing nitric acid or oxidizing acids with chloride ions. Its high chromium content provides much higher resistance to oxidizing media than the family standard, Hastelloy C-276 alloy, and imparts exceptional resistance to chloride-induced pitting, an insidious and unpredictable form of attack, to which the stainless steels are prone. It also has exceptional resistance to a wide variety of chemical process environments including strong oxidizers such as ferric and cupric chlorides, hot contaminated media (both organic and inorganic), chlorine, formic and acetic acids, acetic anhydride, and sea water and brine solutions.
Like other nickel alloys, Hastelloy C-22 alloy is very ductile, shows outstanding weldability, and is easily fabricated into industrial components. It is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Its use in the typical chemical process industry applications include reactors, heat exchangers, and columns. The composition of the alloy is nickel – 56 %, chromium – 22 %, molybdenum – 13 %, iron – 3 %, tungsten – 3 %, cobalt – 2.5 % maximum, manganese – 0.5 maximum, vanadium – 0.35 maximum, silicon – 0.08 % maximum, and carbon -0.01 maximum. It has a density of 8.69 g/cc. The mechanical properties of this alloy are UTS – 802 MPa, yield strength at 2 % offset – 405 MPa, elongation – 57 %, and Rockwell hardness – B-90.
Hastelloy C-22HS alloy (UNS N07022) – It is a versatile nickel-chromium-molybdenum alloy with excellent resistance to both oxidizing and reducing acids. This alloy has been designed to show corrosion resistance comparable to other Hastelloy C-type alloys, but can be heat treated to achieve around double the yield strength. This alloy has outstanding resistance to sour gas environments. It is used in the oil and gas industry in bar, billet, tube, and pipe product forms for applications which need very high strength and superior corrosion resistance. This alloy is especially suited for high-temperature, high-pressure wells, and is capable of being produced at considerably higher strength levels than other nickel base alloys.
Hastelloy C-22HS alloy is corrosion-resistant material for oil and gas industry use. Cold working of the alloy at levels between 30 % and 65 % results in high room temperature yield strengths. It shows exceptional resistance to sour gas environments and is NACE (National Association of Corrosion Engineers) / ISO (International Organization for Standardization) approved. The alloy is available in the form of plate, sheet, strip, billet, bar, wire, pipe, and tube. Round products in the form of solid bars are available up to 250 mm with different quantities of cold work to achieve high strength and toughness by simultaneously retaining the outstanding corrosion resistance of the alloy. The alloy is available in three very high-strength conditions.
Early testing of Hastelloy C-22HS alloy has been focused on material in the annealed + age-hardened condition where the material was annealed at 1,079 deg C and age-hardened at 704 deg C / 16 hours / furnace cool to 607 deg C / 32 hour / air-cool. In this ‘standard condition’ this alloy typically has strengths around 690 MPa. While this strength level is almost double of ‘Hastelloy C-type alloys’ in the annealed condition, several oil and gas applications need even higher strength. For this reason, a considerable development effort has been carried out on Hastelloy C-22HS alloy in three other ‘very high strength’ conditions namely (i) cold worked, (ii) cold worked + age-hardened at 607 deg C / 10 hours / air cooled, and (iii) low temperature annealed at 1,010 deg C + age-hardened at 704 deg C / 16 hours / fast cooled to 607 deg C / 32 hours / air cooled.
A comparison of yield strengths for the three very high strength conditions is shown in Fig 1 along with that of the annealed and ‘standard’ conditions. It is not recommended to use highly cold worked and aged material since the increase in yield strengths is minimal and the susceptibility to hydrogen embrittlement in severe oil well conditions is increased.
Fig 1 Yield strength of Hastelloy C-22S alloy in three very high strength conditions
Hastelloy C-22S alloy is qualified to NACE MR0175 / ISO 15156 Level VII environment with 5 grams per litre (g/l) elemental sulphur to 205 deg C and modified NACE Level VII, 25 % NaCl + 7000 kPa CO2 + 7000 kPa H2S (hydrogen sulphide) at 288 deg C, the highest level in the specification. The maximum hardness and yield strength covered is HRC 43 and 1,413 MPa. The composition of this alloy is nickel 61 %, chromium -21 %, molybdenum -17 %, iron -2 % maximum, tungsten – 1 % maximum, silicon – 0.08 % maximum, and carbon – 0.01 maximum. It has a density of 8.61 g/cc. The mechanical properties of this alloy are ultimate tensile strength (UTS) – 1,409 MPa, yield strength at 2 % offset – 1,365 MPa, elongation – 16.7 %, and Rockwell hardness – C-42.
Hastelloy C-86 alloy (UNS N06686) – It is the filler metal which is used for the gas metal and gas tungsten arc welding of UNS N06686 and other alloys of similar composition. The filler metal is used as a corrosion-resistant overlay on carbon and low alloy steels and as an overmatching filler metal for alloys of similar compositions, such as Hastelloy C-276 alloy. The matte finish on the spooled wire promotes smooth feeding through welding equipment and reduced tip wear in contact tips. The composition of this alloy is nickel – 59, chromium – 20.5 %, molybdenum -16 %, tungsten – 4 %, iron – 5 % maximum, manganese – 1 % maximum, copper – 0.5 %, titanium – 0.25 maximum. The UTS value of this alloy is 760 MPa, and elongation is 30 %.
Hastelloy C-276 alloy (UNS N010276) – It is the first wrought, nickel-chromium-molybdenum material to ease concerns over welding because of its extremely low carbon (C) and silicon (Si) contents. As such, it has been widely accepted in the chemical process and associated industries, and now has a more than 50-year-old track record of proven performance in a vast number of corrosive chemicals. It has with very good resistance to localized attack. Like other nickel alloys, it is ductile, easy to form and weld, and possesses exceptional resistance to stress corrosion cracking in chloride-bearing solutions, a form of degradation to which the austenitic stainless steels are prone.
Hastelloy C-276 alloy is a versatile, corrosion resistant alloy. With its high chromium and molybdenum contents, it is able to withstand both the oxidizing and the reducing acids, and shows outstanding resistance to pitting and crevice attack in the presence of chlorides and other halides. It has excellent resistance to pitting, stress corrosion cracking, and oxidizing atmospheres up to a temperature of 1,038 deg C. Also, it is very resistant to sulphide stress cracking and stress corrosion cracking in sour, oil field environments.
Hastelloy C-276 alloy has very good resistance to reducing and mildly oxidizing corrosive environments. It has exceptional resistance to a wide variety of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, hot contaminated media (organic and inorganic), chlorine, formic and acetic acids, acetic anhydride, and sea water and brine solutions. It resists the formation of grain boundary precipitates in the weld heat affected zone. Hence, it is suitable for majority of process applications in the as welded condition.
Hastelloy C-276 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Typical chemical process industry applications include reactors, heat exchangers, and columns. The composition of the alloy is nickel – 57 %, chromium – 16 %, molybdenum -16 %, iron – 5 %, tungsten – 4 %, cobalt – 2.5 % maximum, mang anise – 1 % maximum, vanadium – 0.35 % maximum, silicon – 0.08 % maximum, and carbon -0.01 % maximum. It has a density of 8.89 g/cc. The mechanical properties of this alloy are UTS – 792 MPa, yield strength at 2 % offset – 356 MPa, elongation – 61 %, and Rockwell hardness- B -90.
Hastelloy C-2000 alloy (UNS N06200) – It is unique among the nickel-chromium-molybdenum alloys in having a deliberate copper addition. This provides highly improved resistance to sulphuric acid. It also has a high chromium content, to maximize its resistance to oxidizing chemicals and process streams contaminated with ferric ions and dissolved oxygen. It is the most versatile, corrosion resistant alloy with excellent resistance to uniform corrosion in oxidizing or reducing environments.
Like other nickel alloys, it is ductile, easy to form and weld, and possesses exceptional resistance to stress corrosion cracking in chloride-bearing solutions, a form of degradation to which the austenitic stainless steels are prone. It is able to withstand a wide range of oxidizing and reducing chemicals, and shows outstanding resistance to pitting and crevice attack in the presence of chlorides and other halides. It has superior resistance to localized corrosion as compared to Hastelloy C-276 alloy.
Hastelloy C-2000 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Typical chemical process industry applications include reactors and heat exchangers. The composition of the alloy is nickel – 59 %, chromium – 23 %, molybdenum – 16 %, copper – 1.6 %, silicon – 0.08 % maximum, and carbon – 0.01 %. It has density of 8.58 g/cc. The mechanical properties of this alloy are UTS – 752 MPa, yield strength at 2 % offset – 359 MPa, elongation – 64 %, and Rockwell hardness – B-87.
Hastelloy G-3 alloy (UNS N06985) – This alloy is an improved version of Hastelloy G alloy. It has the same outstanding general corrosion resistance as Hastelloy G alloy along with higher resistance to heat affected zone attack and outstanding weldability. It has outstanding resistance to hot sulphuric acid and phosphoric acid, and withstands the corrosive effects of both the oxidizing and reducing agents and can handle both acid and alkaline solutions.
Hastelloy G-3 alloy has outstanding resistance to mixed acids, sulphate compounds, contaminated nitric acid, wet flue gas desulphurization scrubber environments, and hydrofluoric acid. The alloy’s resistance to the formation of grain boundary precipitates in the heat affected zone makes it suitable for use in majority of the chemical process applications in the as-welded condition.
The composition of the alloy is cobalt -5 % maximum, chromium – 21 % to 23.5 %, molybdenum – 6 % to 8 %, tungsten – 1.5 % maximum, iron – 18 % to 21 %, silicon – 1 % maximum, manganese – 1 % maximum, carbon – 0.015 % maximum, and nickel the balance. Others elements which are present are copper – 1.5 % to 2.5 %, Niobium + tantalum – 0.5 % maximum, phosphorus – 0.04 % maximum, and sulphur – 0.03 % maximum. It has a density of 8.3 g/cc. The mechanical properties of this alloy are UTS – 683 MPa, yield strength at 2 % offset – 303 MPa, elongation – 53 %, and Rockwell hardness – B-83.
Hastelloy G-30 alloy (UNS N06030) – It is a nickel-chromium-iron alloy which shows superior corrosion resistance over majority of other nickel base and iron base alloys in commercial phosphoric acid and several complex environments containing highly oxidizing agents such as nitric acid. This alloy is highly resistant to ‘wet process’ phosphoric acid (P2O5). P2O5 is one of the most important industrial chemicals, being the primary source of phosphorus for agri-chemical fertilizers. This alloy is also moderately resistant to chloride-induced localized attack, which can be a problem beneath deposits in the evaporators used to concentrate P2O5. Also, this alloy is less susceptible to chloride-induced stress corrosion cracking than the stainless steels.
As a result of its high chromium content, Hastelloy G-30 alloy is also very resistant to other oxidizing acids, such as nitric, and mixtures containing nitric acid. It possesses moderate resistance to reducing acids, such as hydrochloric acid and sulphuric acid, as a result of its appreciable molybdenum and copper contents. This alloy has several advantages over other metallic and non-metallic materials in handling phosphoric acid, sulphuric acid, nitric acid, fluoride environments and oxidizing acid mixtures.
Hastelloy G-30 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Applications of this alloy include P2O5 evaporator tubes, and nitric acid-based metal pickling hardware. The composition of this alloy is nickel – 43 %, chromium – 30 %, iron – 15 %, molybdenum – 5.5 %, tungsten – 2.5 %, cobalt – 5 % maximum, copper – 2 % maximum, niobium – 1.5 % maximum, manganese – 1.5 maximum, silicon -1 % maximum, and carbon – 0.03 maximum. It has a density of 8.22 g/cc. The mechanical properties of this alloy are UTS – 690 MPa, yield strength at 2 % offset – 324 MPa, elongation – 56 %, and Rockwell hardness – B-88.
Hastelloy G-35 alloy (UNS N06035) – It is an improvement to Hastelloy G-30 alloy in handling phosphoric acid with excellent resistance to corrosion in highly oxidizing media and acidic chloride environments. It has been developed to resist ‘fertilizer-grade’ phosphoric acid (P2O5), which is used in the production of fertilizers.
Tests in real-world solutions indicate that Hastelloy G-35 alloy is far superior to other metallic materials in the phosphoric acid. It has also been developed to resist localized attack in the presence of chlorides, since this can be a problem beneath deposits in evaporators used to concentrate ‘fertilizer-grade’ phosphoric acid. Also, this alloy is much less susceptible to chloride-induced stress corrosion cracking than the stainless steels and nickel-chromium-iron alloys traditionally used in ‘fertilizer-grade’ phosphoric acid.
As a result of its very high chromium content, this alloy is extremely resistant to other oxidizing acids, such as nitric, and mixtures containing nitric acid. It possesses moderate resistance to reducing acids, as a result of its appreciable molybdenum content, and, unlike other nickel-chromium-molybdenum alloys, it is very resistant to ‘caustic de-alloying’ in hot sodium hydroxide. Hastelloy G-35 alloy is available in the form of plates, sheets, strips, billets, bars, wires, pipes, tubes, and covered electrodes. Its applications include P2O5 evaporator tubes.
The composition of this alloy is nickel – 58 %, chromium – 33.2 %, molybdenum – 8.1 %, iron – 2 % maximum, silicon – 0.6 % maximum, copper – 0.3 maximum, and carbon 0.05 maximum. It has a density of 8.22 g/cc. Its thermal conductivity is 10 WE/m.k, specific heat is 450 J/kg.k, and melting range is 1,332 deg C to 1,361 deg C. The mechanical properties of this alloy are UTS – 689 MPa, yield strength at 2 % offset – 317 MPa, elongation – 72 %, and Rockwell hardness – B-87.
Hastelloy X alloy (UNS N06002) – It is a nickel-chromium-iron-molybdenum alloy which possesses an exceptional combination of oxidation resistance, fabricability, and high-temperature strength. It has also been found to be exceptionally resistant to stress corrosion cracking in petrochemical applications. Hastelloy X alloy shows good ductility after prolonged exposure at temperatures of 650 deg C, 760 deg C, and 870 deg C for 16,000 hours.
Hastelloy X alloy has outstanding forming and welding characteristics. It can be forged or otherwise hot-worked, providing it is held at 1,177 deg C for a time sufficient to bring the entire piece to this temperature. As a result of its good ductility, it is also readily formed by cold-working. All hot-worked or cold- worked parts are to be annealed and rapidly cooled in order to restore the best balance of properties. The alloy can be welded by a variety of techniques, including gas tungsten arc welding, gas metal arc welding, shielded metal arc welding, and resistance welding.
Wrought forms of Hastelloy X alloy are furnished in the solution heat-treated condition unless otherwise specified. Hastelloy alloy is solution heat-treated typically at 1,177 deg C and is rapidly cooled. Bright annealed products are cooled in hydrogen. Annealing at temperatures lower than the solution heat- treating can cause precipitation of secondary phases, which can affect the strength and ductility of the alloy.
Hastelloy X alloy is useful for aircraft, furnace and chemical process components. It has wide use in gas turbine engines for combustion zone components such as transition ducts, combustor cans, spray bars, and flame holders as well as in after-burners, tail-pipes, and cabin heaters. It is recommended for use in industrial furnace applications since it has unusual resistant to oxidizing, reducing, and neutral environments. Furnace rolls of this alloy have been still in good condition after operating for 8,700 hours at 1,177 deg C. The alloy is also used in the chemical process industry for retorts, muffles, catalyst support grids, furnace baffles, tubing for pyrolysis operations, and flash drier components.
The chemical composition of this alloy is nickel – 47 %, chromium – 22 %, iron – 18 %, molybdenum – 9 %, cobalt – 1.5 %, tungsten – 0.6 %, carbon – 0.1 %, manganese- 1 % maximum, silicon – 1 % maximum, boron – 0.008 % maximum, niobium – 0.5 % maximum, aluminum – 0.5 % maximum, and titanium – 0.15 % maximum. It has a density of 8.22 g/cc. The mechanical properties of this alloy are UTS – 755 MPa, yield strength at 2 % offset – 385 MPa, elongation – 45 %, and Rockwell hardness – B-92.
Hastelloy Hybrid-BC1 (UNS N10362) – This alloy has good resistance to aging and embrittlement plus good fabricability. It has excellent resistance to hot fluoride salts in the temperature range of 705 deg C to 870 deg C.
Hastelloy Hybrid-BC1 alloy possesses much higher resistance to hydrochloric and sulphuric acids than the nickel-chromium-molybdenum (Hastelloy C-type) alloys, and can tolerate the presence of oxidizing environments. The alloy also shows extremely high resistance to pitting and crevice corrosion. The alloy is suitable for use at temperatures up to around 427 deg C. It excels in reducing acids and acid mixtures (with or without halides) open to oxygen, and other oxidizing residuals / contaminants. It bridges the gap between Hastelloy B and C family of alloys with better reducing acid resistance than Hastelloy C family of alloys and a resistance to oxidizing impurities.
Wrought forms of Hastelloy Hybrid-BC1 alloy are furnished in the solution-annealed condition, unless otherwise specified. The standard solution-annealing treatment consists of heating to 1,149 deg C followed by rapid air-cooling or (preferably) water quenching. Parts which have been hot formed are to be solution annealed prior to final fabrication or installation. The minimum hot forming temperature of this alloy is 954 deg C.
The chemical composition of this alloy is nickel – 62 %, molybdenum – 22 %, chromium – 15 %, iron -2 % maximum, manganese – 0.25 %, silicon – 0.08 % maximum, aluminum – 0.5 % maximum, and carbon – 0.01C maximum. It has a density of 8.83 g/cc. The mechanical properties of this alloy are UTS – 841 MPa, yield strength at 2 % offset – 405 MPa, and elongation – 61.6 %.
Hastelloy Hybrid-BC1 alloy is suitable for the applications in the chemical processing, pharmaceutical, agricultural, food, petrochemical, and power industries. The alloy is used for reaction vessels, heat exchangers, valves, pumps, piping, and storage tanks.
Hastelloy N alloy (UNS N10003) – It is a nickel-base alloy which was invented at Oak Ridge National Laboratories as a container material for molten fluoride salts. It has good oxidation resistance to hot fluoride salts in the temperature range of 704 deg C to 871 deg C.
In tests conducted for over two years duration, corrosion attack on Hastelloy N alloy in molten fluoride salts at temperatures up to 704 deg C was less than 0.025 millimeter per year. It is expected that Hastelloy N alloy will be most useful in environments involving fluorides at high temperatures. However, the alloy compares favourably with other Hastelloy alloys in different corrosive media, as shown in the penetration rates. It is especially suggested that the alloy be tested in molten halides of zirconium, beryllium, lithium, sodium, potassium, thorium or uranium.
Hastelloy N alloy has good oxidation resistance in air. It shows promise for continuous operations at temperatures up to 982 deg C. Intermittent use at temperatures up to 1,038 deg C can also be possible. No discernible oxidation has been measured for this alloy at temperatures up to 649 deg C.
Metallographic examinations have shown that the elements in alloy N remain in solid solution in the 593 deg C to 871 deg C temperature range. Tensile tests have indicated no tendency toward embrittlement for prolonged periods at 816 deg C. Hastelloy N alloy has good weldability and can be readily forged. The hot working range is between 871 deg C to 1,177 deg C. It has been successfully extruded and further processed into high-quality seamless or manufactured as welded and drawn tubing.
Solution heat-treatment is recommended after hot or cold working of Hastelloy N alloy parts. For sheet and plate, this is accomplished by soaking at 1,177 deg C for sections up to 6 mm thick and then cooling rapidly in air, or soaking at 1,185 deg C for sections 6 mm and thicker followed by water quenching.
The chemical composition of this alloy is nickel 71 %, molybdenum – 16 % chromium – 7 %, iron – 5 % maximum, silicon – 1 % maximum, manganese – 0.8 % maximum, tungsten – 0.5 % maximum, aluminum + titanium – 0.5 % maximum, copper – 0.35 % maximum, cobalt – 0.2 % maximum, and carbon – 0.08 % maximum. It has a density of 8.86 g/cc. The melting range is 1,300 deg C to 1,400 deg C. The mechanical properties of this alloy are UTS – 794 MPa, yield strength at 2 % offset – 314 MPa, elongation – 50.7 %, and Rockwell hardness – B-96.
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