About Hastelloy B alloy
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Does anyone have any information on the corrosion resistance of Hastelloy B alloy?
Hastelloy is a type of nickel-based alloy; it is currently divided into three series: B, C, and G. It is primarily used in environments with highly corrosive conditions where iron-based Cr-Ni or Cr-Ni-Mo stainless steels and non-metallic materials cannot be used. Abroad, it is widely applied in various fields such as petroleum, chemicals, and environmental protection. Hastelloy alloy: I. Currently, it is mainly divided into three series: B, C, and G. It is primarily used in environments with highly corrosive media where iron-based Cr-Ni or Cr-Ni-Mo stainless steels and non-metallic materials cannot be used. To improve the corrosion resistance and cold/warm working properties of Hastelloy, it has undergone three major improvements over time. The development process is as follows: Series B: B → B-2 (00Ni70Mo28) → B-3; Series C: C → C-276 (00Cr16Mo16W4) → C-4 (00Cr16Mo16) → C-22 (00Cr22Mo13W3) → C-2000 (00Cr20Mo16); Series G: G → G-3 (00Cr22Ni48Mo7Cu) → G-30 (00Cr30Ni48Mo7Cu). The most widely used materials today are the second-generation ones: N10665 (B-2), N10276 (C-276), N06022 (C-22), N06455 (C-4), and N06985 (G-3). II. Typical Chemical Composition of Hastelloy Materials
Chemical composition of the material:
N10665 (B-2) base: ≤1.0, 26.0–30, ≤2.0, ≤0.02, ≤0.10, ≤1.0, ≤1.0, ≤0.04, ≤0.03
N10276 (C-276) base: 14.5–16.5, 15.0–17.0, 4.0–7.0, ≤0.01, ≤0.08, ≤2.5, ≤1.0, ≤0.04, ≤0.03; 3.0–4.5, ≤0.035
N06007 (G-3) base: 21.0–23.5, 6.0–8.0, 18.0–21, ≤0.015, ≤1.0, ≤5.0, ≤1.0, ≤0.04, ≤0.03, ≤1.5; 1.5–2.5, ≤0.50
III. Mechanical Properties
Hastelloy exhibits excellent mechanical properties, featuring high strength and high toughness. As a result, it is somewhat difficult to machine, and it has a strong tendency to strain harden – when the deformation rate reaches 15%, it is approximately twice that of 18-8 stainless steel. Hastelloy also has a medium-temperature sensitization zone, whose sensitization tendency increases with the increase in strain rate. At higher temperatures, Hastelloy is prone to absorbing harmful elements, which reduces its mechanical properties and corrosion resistance. 1: Hastelloy B-2 alloy 1) Corrosion resistance: Hastelloy B-2 is a Ni-Mo alloy with extremely low levels of carbon and silicon; this low content reduces the precipitation of carbides and other phases in the welds and heat-affected zones, thereby ensuring good corrosion resistance even in welded conditions. As is well known, Hastelloy B-2 exhibits excellent corrosion resistance in various reducing media, and can withstand the corrosion of hydrochloric acid at any temperature and concentration under normal pressure. It exhibits excellent corrosion resistance in non-oxidizing sulfuric acid at moderate concentrations without inflation, phosphoric acids of various concentrations, high-temperature acetic acid, organic acids such as formic acid, bromic acid, and hydrogen chloride gas; moreover, it is also resistant to corrosion by halogen catalysts. Therefore, Hastelloy B-2 alloy is commonly used in various demanding petroleum and chemical processes, such as the distillation and concentration of hydrochloric acid ； In production processes such as the alkylation of ethylbenzene and low-pressure carbonylation to produce acetic acid. However, years of industrial use of Hastelloy B-2 have revealed that: (1) there are two sensitization zones in Hastelloy B-2 that have a significant impact on its resistance to intergranular corrosion: a high-temperature zone of 1200–1300°C and a medium-temperature zone of 550–900°C ； (2) The weld metal and heat-affected zone of Hastelloy B-2 are highly susceptible to intergranular corrosion due to dendritic segregation, with intermetallic phases and carbides precipitating along the grain boundaries ； (3) Hastelloy B-2 has poor medium-temperature thermal stability. When the iron content in Hastelloy B-2 alloy drops below 2%, the alloy becomes sensitive to the transformation of the β phase (i.e., the Ni4Mo phase, an ordered intermetallic compound). When the alloy is held at a temperature in the range of 650–750°C for a slightly longer period, the β phase is formed instantaneously. The presence of the β phase reduces the toughness of Hastelloy B-2, making it susceptible to stress corrosion; this can even lead to cracking in Hastelloy B-2 during raw material production (such as in the hot rolling process), during equipment manufacturing (such as after welding followed by overall heat treatment of Hastelloy B-2 equipment), and in the service environment of such equipment. Today, the standard test methods specified in our country and around the world for evaluating the intergranular corrosion resistance of Hastelloy B-2 are all the atmospheric-pressure boiling hydrochloric acid method, with the evaluation being carried out via weight loss. Since Hastelloy B-2 is an alloy resistant to hydrochloric acid corrosion, the atmospheric boiling hydrochloric acid test for evaluating the intergranular corrosion tendency of Hastelloy B-2 is quite insensitive. Research conducted by domestic scientific institutions using the high-temperature hydrochloric acid method on Hastelloy B-2 alloy has shown that its corrosion resistance depends not only on its chemical composition but also on the control processes involved in its heat treatment. When the hot working process is not properly controlled, in Hastelloy B-2 not only do the grains grow, but a σ phase rich in Mo also precipitates at the grain boundaries. As a result, the intergranular corrosion resistance of Hastelloy B-2 decreases significantly; in high-temperature hydrochloric acid tests, the erosion depth at the grain boundaries of plates with coarse grains is approximately twice that of normal plates. 2) Physical properties: Density: 9.2 g/cm3; Melting point: 1330–1380°C; Magnetic permeability: (°C, RT) ≤ 1.001. 3) Chemical composition: Elements – Ni, Cr, Fe, C, Mn, Si, Cu, Mo, Co, P, S. Minimum allowable amounts: 0.4 for Ni, 1.6 for Cr, 26.0 for Fe; Maximum allowable amounts: 1.0 for Ni, 2.0 for Cr, 0.01 for Mn, 1.0 for Si, 0.08 for Cu, 0.5 for Mo, 30.0 for Co, 1.0 for P, 0.02 for S, 0.010 for Si. 4) Manufacturing and heat treatment: 1) Heating: For Hastelloy B-2 alloy, it is very important to keep the surface clean and free from contaminants before and during heating. If Hastelloy B-2 alloy is heated in an environment contaminated with sulfur, phosphorus, lead, or other low-melting-point metals, it becomes brittle; the sources of these contaminants include marker pen residues, temperature-indicating paints, greases and liquids, and smoke. This flue gas must have low sulfur content ； For example: natural gas and liquefied petroleum gas are considered acceptable if their sulfur content is no more than 0.1%, urban air has a sulfur content of no more than 0.25 g/m3, and fuel oil is acceptable if its sulfur content is no more than 0.5%. The gas environment required for the heating furnace is a neutral or slightly reducing environment, and it must not fluctuate between oxidizing and reducing conditions. The flame in the furnace must not directly impact Hastelloy B-2 alloy. At the same time, the material must be heated to the desired temperature at the fastest possible rate; this means that the temperature of the heating furnace must first be raised to the required level before the material is placed in the furnace for heating. 2: Hot working – Hastelloy B-2 can be hot-worked in the temperature range of 900–1160°C, and it should be quenched in water after processing. To ensure the best corrosion resistance, annealing should be performed after heat treatment. 3: Cold working – Hall’s B-2 alloy that is subjected to cold working must undergo solution treatment. Due to its much higher work hardening rate compared to austenitic stainless steels, special consideration must be given to the shaping equipment. If a cold forming process is employed, inter-stage annealing is necessary. When the cold working deformation exceeds 15%, solution treatment is required before use. 4: Heat treatment – The solubilization heat treatment temperature should be maintained between 1060 and 1080°C; thereafter, water quenching should be carried out, or rapid air cooling can be used when the material thickness is 1.5 mm or more, in order to achieve the best corrosion resistance. During any heating process, precaution must be taken to keep the surface of the material clean. When heat-treating Hastelloy materials or equipment components, the following points should be taken into account: To prevent deformation of the components during heat treatment, stainless steel reinforcement rings should be used ； The charging temperature, as well as the heating and cooling times, must be strictly controlled ； Before loading into the furnace, pre-treat the heat-treated parts to prevent the formation of thermal cracks ； After heat treatment, 100% PT of the heat-treated parts ； If thermal cracks occur during heat treatment and need to be repaired by welding after grinding, a specialized welding process must be employed. 5: Descaling – The oxides on the surface of Hastelloy B-2 alloy, as well as any stains near the welds, must be removed thoroughly using fine grinding wheels or similar tools. Since Hastelloy B-2 is sensitive to oxidizing media, a large amount of nitrogen-containing gases are generated during the pickling process. 6: Machining – Hastelloy B-2 alloy should be machined in its annealed state, and it is important to be aware of its work hardening properties. For example, a slower surface cutting speed should be used compared to standard austenitic stainless steels; a larger feed rate should be employed for the hardened surface layer, and the tool should remain in continuous operation. 7: Welding – The weld metal and heat-affected zone of Hastelloy B-2 are deficient in Mo due to the easy precipitation of the β phase, which makes them susceptible to intergranular corrosion. Therefore, the welding process for Hastelloy B-2 must be carefully planned and strictly controlled. The general welding process is as follows: ERNi-Mo7 is used as the welding material ； Welding method GTAW ； Keep the temperature between layers at no more than 120℃ ； Wire diameter φ2.4, φ3.2 ； Welding current: 90~150A. At the same time, before welding, the welding wire, the groove of the workpiece to be welded, and adjacent areas should be cleaned and degreased. The thermal conductivity of Hastelloy B-2 is much lower than that of steel; therefore, if a single V-groove is used, the groove angle should be around 70°, along with a lower heat input. Post-weld heat treatment can eliminate residual stresses and improve resistance to stress corrosion cracking.
Chemical composition of the material:
N10665 (B-2) base: ≤1.0, 26.0–30, ≤2.0, ≤0.02, ≤0.10, ≤1.0, ≤1.0, ≤0.04, ≤0.03
N10276 (C-276) base: 14.5–16.5, 15.0–17.0, 4.0–7.0, ≤0.01, ≤0.08, ≤2.5, ≤1.0, ≤0.04, ≤0.03; 3.0–4.5, ≤0.035
N06007 (G-3) base: 21.0–23.5, 6.0–8.0, 18.0–21, ≤0.015, ≤1.0, ≤5.0, ≤1.0, ≤0.04, ≤0.03, ≤1.5; 1.5–2.5, ≤0.50
III. Mechanical Properties
Hastelloy exhibits excellent mechanical properties, featuring high strength and high toughness. As a result, it is somewhat difficult to machine, and it has a strong tendency to strain harden – when the deformation rate reaches 15%, it is approximately twice that of 18-8 stainless steel. Hastelloy also has a medium-temperature sensitization zone, whose sensitization tendency increases with the increase in strain rate. At higher temperatures, Hastelloy is prone to absorbing harmful elements, which reduces its mechanical properties and corrosion resistance. 1: Hastelloy B-2 alloy 1) Corrosion resistance: Hastelloy B-2 is a Ni-Mo alloy with extremely low levels of carbon and silicon; this low content reduces the precipitation of carbides and other phases in the welds and heat-affected zones, thereby ensuring good corrosion resistance even in welded conditions. As is well known, Hastelloy B-2 exhibits excellent corrosion resistance in various reducing media, and can withstand the corrosion of hydrochloric acid at any temperature and concentration under normal pressure. It exhibits excellent corrosion resistance in non-oxidizing sulfuric acid at moderate concentrations without inflation, phosphoric acids of various concentrations, high-temperature acetic acid, organic acids such as formic acid, bromic acid, and hydrogen chloride gas; moreover, it is also resistant to corrosion by halogen catalysts. Therefore, Hastelloy B-2 alloy is commonly used in various demanding petroleum and chemical processes, such as the distillation and concentration of hydrochloric acid ； In production processes such as the alkylation of ethylbenzene and low-pressure carbonylation to produce acetic acid. However, years of industrial use of Hastelloy B-2 have revealed that: (1) there are two sensitization zones in Hastelloy B-2 that have a significant impact on its resistance to intergranular corrosion: a high-temperature zone of 1200–1300°C and a medium-temperature zone of 550–900°C ； (2) The weld metal and heat-affected zone of Hastelloy B-2 are highly susceptible to intergranular corrosion due to dendritic segregation, with intermetallic phases and carbides precipitating along the grain boundaries ； (3) Hastelloy B-2 has poor medium-temperature thermal stability. When the iron content in Hastelloy B-2 alloy drops below 2%, the alloy becomes sensitive to the transformation of the β phase (i.e., the Ni4Mo phase, an ordered intermetallic compound). When the alloy is held at a temperature in the range of 650–750°C for a slightly longer period, the β phase is formed instantaneously. The presence of the β phase reduces the toughness of Hastelloy B-2, making it susceptible to stress corrosion; this can even lead to cracking in Hastelloy B-2 during raw material production (such as in the hot rolling process), during equipment manufacturing (such as after welding followed by overall heat treatment of Hastelloy B-2 equipment), and in the service environment of such equipment. Today, the standard test methods specified in our country and around the world for evaluating the intergranular corrosion resistance of Hastelloy B-2 are all the atmospheric-pressure boiling hydrochloric acid method, with the evaluation being carried out via weight loss. Since Hastelloy B-2 is an alloy resistant to hydrochloric acid corrosion, the atmospheric boiling hydrochloric acid test for evaluating the intergranular corrosion tendency of Hastelloy B-2 is quite insensitive. Research conducted by domestic scientific institutions using the high-temperature hydrochloric acid method on Hastelloy B-2 alloy has shown that its corrosion resistance depends not only on its chemical composition but also on the control processes involved in its heat treatment. When the hot working process is not properly controlled, in Hastelloy B-2 not only do the grains grow, but a σ phase rich in Mo also precipitates at the grain boundaries. As a result, the intergranular corrosion resistance of Hastelloy B-2 decreases significantly; in high-temperature hydrochloric acid tests, the erosion depth at the grain boundaries of plates with coarse grains is approximately twice that of normal plates. 2) Physical properties: Density: 9.2 g/cm3; Melting point: 1330–1380°C; Magnetic permeability: (°C, RT) ≤ 1.001. 3) Chemical composition: Elements – Ni, Cr, Fe, C, Mn, Si, Cu, Mo, Co, P, S. Minimum allowable amounts: 0.4 for Ni, 1.6 for Cr, 26.0 for Fe; Maximum allowable amounts: 1.0 for Ni, 2.0 for Cr, 0.01 for Mn, 1.0 for Si, 0.08 for Cu, 0.5 for Mo, 30.0 for Co, 1.0 for P, 0.02 for S, 0.010 for Si. 4) Manufacturing and heat treatment: 1) Heating: For Hastelloy B-2 alloy, it is very important to keep the surface clean and free from contaminants before and during heating. If Hastelloy B-2 alloy is heated in an environment contaminated with sulfur, phosphorus, lead, or other low-melting-point metals, it becomes brittle; the sources of these contaminants include marker pen residues, temperature-indicating paints, greases and liquids, and smoke. This flue gas must have low sulfur content ； For example: natural gas and liquefied petroleum gas are considered acceptable if their sulfur content is no more than 0.1%, urban air has a sulfur content of no more than 0.25 g/m3, and fuel oil is acceptable if its sulfur content is no more than 0.5%. The gas environment required for the heating furnace is a neutral or slightly reducing environment, and it must not fluctuate between oxidizing and reducing conditions. The flame in the furnace must not directly impact Hastelloy B-2 alloy. At the same time, the material must be heated to the desired temperature at the fastest possible rate; this means that the temperature of the heating furnace must first be raised to the required level before the material is placed in the furnace for heating. 2: Hot working – Hastelloy B-2 can be hot-worked in the temperature range of 900–1160°C, and it should be quenched in water after processing. To ensure the best corrosion resistance, annealing should be performed after heat treatment. 3: Cold working – Hall’s B-2 alloy that is subjected to cold working must undergo solution treatment. Due to its much higher work hardening rate compared to austenitic stainless steels, special consideration must be given to the shaping equipment. If a cold forming process is employed, inter-stage annealing is necessary. When the cold working deformation exceeds 15%, solution treatment is required before use. 4: Heat treatment – The solubilization heat treatment temperature should be maintained between 1060 and 1080°C; thereafter, water quenching should be carried out, or rapid air cooling can be used when the material thickness is 1.5 mm or more, in order to achieve the best corrosion resistance. During any heating process, precaution must be taken to keep the surface of the material clean. When heat-treating Hastelloy materials or equipment components, the following points should be taken into account: To prevent deformation of the components during heat treatment, stainless steel reinforcement rings should be used ； The charging temperature, as well as the heating and cooling times, must be strictly controlled ； Before loading into the furnace, pre-treat the heat-treated parts to prevent the formation of thermal cracks ； After heat treatment, 100% PT of the heat-treated parts ； If thermal cracks occur during heat treatment and need to be repaired by welding after grinding, a specialized welding process must be employed. 5: Descaling – The oxides on the surface of Hastelloy B-2 alloy, as well as any stains near the welds, must be removed thoroughly using fine grinding wheels or similar tools. Since Hastelloy B-2 is sensitive to oxidizing media, a large amount of nitrogen-containing gases are generated during the pickling process. 6: Machining – Hastelloy B-2 alloy should be machined in its annealed state, and it is important to be aware of its work hardening properties. For example, a slower surface cutting speed should be used compared to standard austenitic stainless steels; a larger feed rate should be employed for the hardened surface layer, and the tool should remain in continuous operation. 7: Welding – The weld metal and heat-affected zone of Hastelloy B-2 are deficient in Mo due to the easy precipitation of the β phase, which makes them susceptible to intergranular corrosion. Therefore, the welding process for Hastelloy B-2 must be carefully planned and strictly controlled. The general welding process is as follows: ERNi-Mo7 is used as the welding material ； Welding method GTAW ； Keep the temperature between layers at no more than 120℃ ； Wire diameter φ2.4, φ3.2 ； Welding current: 90~150A. At the same time, before welding, the welding wire, the groove of the workpiece to be welded, and adjacent areas should be cleaned and degreased. The thermal conductivity of Hastelloy B-2 is much lower than that of steel; therefore, if a single V-groove is used, the groove angle should be around 70°, along with a lower heat input. Post-weld heat treatment can eliminate residual stresses and improve resistance to stress corrosion cracking.
HB is too expensive. Our company has used HB as a sealing metal component for concentrated sulfuric acid. Imported: 500 per kilogram
Thank you for providing information on Hastelloy stainless steel