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A comprehensive introducion for hastelloy and its grades

By Thomas Huang December 8th, 2023 101 views
Contents
I, What is Hastelloy?

I, What is Hastelloy?

Hastelloy is a nickel-based corrosion-resistant alloy, mainly divided into two categories: 
Nickel-chromium alloys.
Nickel-chromium-molybdenum alloys. 

II, Why Hastelloy is developed?

It is developed to use under strong corrosive media circumstances, that the materials such as iron-based Cr-Ni or Cr-Ni-Mo stainless steel, non-metallic materials can not withstand.
photo of metal developing

III, Grades of Hastelloy

Different grades of Hastelloy have different chemical compositions. Their physical properties, corrosion resistance, machinability, and applications are varied.
Hastelloy grades include the following grades:
 Grades Name  Description
 Hastelloy B-2  Excellent corrosion resistance in reducing environments. 
 Hastelloy B-3  An upgraded version of B-2 with excellent corrosion resistance to hydrochloric acid at any temperature and concentration.
 Hastelloy C-4  It has better thermal stability, good toughness, and corrosion resistance at 650-1040 degrees Celsius.
 Hastelloy C-22   It has better homogeneous corrosion resistance than C-4 and C-276 in oxidizing media and excellent resistance to localized corrosion. 
 Hastelloy C-276   It has better resistance to oxidizing and moderately reducing corrosion, and excellent resistance to stress corrosion.
 Hastelloy C-2000  The most versatile corrosion-resistant alloy with excellent resistance to uniform corrosion in both oxidizing and reducing environments.
 Hastelloy G-30  High chromium content nickel-based alloy with excellent performance in phosphoric acid and other strong oxidizing mixed acid media.
 Hastelloy G-35  Upgraded product of G-30 with better corrosion resistance and thermal stability.
 Hastelloy  It has comprehensive high-strength, oxidation resistance, and easy processing.

IV, Chemical composition of commonly used Hastelloy grades

 Grades  Ni  Cr  Fe  C  Mn  Si  Cu  Mo  Co  P  S  V  W  Other
 Hastelloy B-2  Bal.  ≤1.0  ≤2.0  ≤0.02  ≤1.0  ≤0.1  0.5  30  ≤1.0  ≤0.04  ≤0.03
 Hastelloy C-276  Bal.  14.5~16.5 4.0 ~ 7.0  ≤0.01  ≤1  ≤0.08  15~17  ≤2.5  ≤0.04  ≤0.03  ≤0.035  3.0~4.5
 Hastelloy G-3
 Bal.
 21.0~23.5  18.0~21  ≤0.015  ≤1  ≤1.0  6.0~8.0  ≤5  ≤0.04  ≤0.03    1.5  Nb+Ta ≤0.5
  Hastelloy C-22  Bal.  20.0~22.5  2~6  ≤0.015
   ≤0.08  12.5~14.5  ≤2.5    ≤0.02
 ≤0.35
 2.50~3.5
  Hastelloy C-59  Bal.
 22.0~24  1.5  0.01  0.5  0.01    15.0~16.5  0.3  0.015  0.005  Al 0.1~0.4
 Hastelloy C-4  Bal.
 14.0~18  3.0  0.015  1.0  0.08    14.0~18  2.0  0.04  0.03  Ta 0.70

V, Corrosion Resistance

5.1 General Corrosion Resistance of Hastelloy

5.1.1

Excellent corrosion resistance to most corrosive media in oxidizing and reducing atmosphere states.

5.1.2

Excellent resistance to pitting, crevice corrosion, and stress cracking corrosion.

5.2 Specific corrosion resistance of commonly used Hastelloy grades

 Grades name  Description

5.2.1 Hastelloy B-2

 Hastelloy B-2 alloy is a Ni-Mo alloy with a very low content of carbon and silicon. 
 
5.2.1.1
It has excellent corrosion resistance in a variety of reducing media and resists corrosion by hydrochloric acid with any concentration at any temperature under normal pressure.
 
5.2.1.2
It has excellent corrosion resistance in the non-gas medium concentration of non-oxidizing sulfuric acid, various concentrations of phosphoric acid, high-temperature acetic acid, formic acid, and other organic acids, bromic acid, as well as hydrogen chloride gas, and halogen catalysts.
 

5.2.2 Hastelloy C-276


 Hastelloy C-276 is a nickel-molybdenum-chromium-iron-tungsten nickel-based alloy with extremely low silicon and carbon content. It is one of the most corrosion-resistant of modern metallic materials.
 
5.2.2.1
Excellent corrosion resistance to most corrosive media in oxidizing and reducing atmosphere states.
 
5.2.2.2
Excellent resistance to pitting, crevice corrosion, and stress corrosion. The higher molybdenum and chromium content makes the alloy resistant to chloride corrosion, and the tungsten element further improves the corrosion resistance.
 
5.2.2.3
C-276 alloy is one of only a few materials resistant to corrosion by moist chlorine, hypochlorite, and chlorine dioxide solutions, and has significant corrosion resistance to high concentrations of chlorinated salt solutions such as ferric chloride and copper chloride.
 
5.2.2.4
Suitable for sulfuric acid solutions of various concentrations, is one of the few materials that can be used for hot concentrated sulfuric acid solutions.
 
5.2.2.5
Often used in most corrosive environments of flue gas desulphurization systems and the most complex pharmaceutical reactors.
 

5.2.3 Hastelloy C-22

 Hastelloy C-22 Alloy is a Ni-Cr-Mo alloy.
 
5.2.3.1
It is extremely resistant to pitting, crevice corrosion, intergranular corrosion, and stress corrosion fracture.
 
5.2.3.2
It has excellent corrosion resistance over a wide range of oxidizing and reducing environments.
 

5.2.4 Hastelloy C-59

 C-59 is an ultra-low carbon Ni-Cr-Mo alloy with excellent corrosion resistance and high mechanical strength.
 
5.2.4.1
Wide range of corrosion resistance under oxidizing and reducing conditions.
 
5.2.4.2
Good resistance to pitting and crevice corrosion, as well as immunity to chlorine-induced stress corrosion fracture.
 
5.2.4.3
Good corrosion resistance to inorganic acids such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, and mixed sulfate acids.
 
5.2.4.4
Good corrosion resistance to inorganic acids containing impurities.
 
5.2.4.5
Good corrosion resistance to hydrochloric acid at any concentration below 40°C.
 
5.2.4.6
Licensed for use on pressure vessels between -196 and 450°C.
 
5.2.4.7
Licensed for use in sour gas environments by NACE Standard MR-01-75 Class VII.
 

5.2.5 Hastelloy C-4

 
5.2.5.1
Hastelloy C-4 alloy is resistant to a wide range of chemical media, including reducing media such as phosphoric acid, hydrochloric acid, sulfuric acid, chlorine, and organic or inorganic chloride-containing media.
 
5.2.5.2
Due to the high nickel content, HastelloyC-4 effectively resists stress corrosion cracking due to chlorine, even in hot chloride solutions.

VI, Manufacturing and thermal processing for Hastelloy grades

6.1 Hastelloy B-2

6.1.1 Heating

For Hastelloy B-2 alloys, surfaces must be kept clean and away from contaminants before and during heating. Hastelloy B-2 alloys become brittle if heated in an environment containing sulfur, phosphorus, lead, or other low melting point metal contaminants. Sources of these contaminants include, among other things, marker marks, temperature indicating paints, grease and liquids, and fumes.
photo of heating process

6.1.2 Thermal Processing

Hastelloy B-2 alloys can be hot worked in the range of 900 to 1160°C. After machining, they should be quenched in water. To ensure the best possible corrosion resistance, it should be annealed after hot working.

6.1.3 Cold working

If a cold-forming process is carried out, an interstage annealing is necessary. Cold-worked distortions exceeding 15% should be solution-treated before use.

6.1.4 Heat treatment

The solid solution heat treatment temperature is to be controlled between 1060 and 1080°C, followed by water-cooled quenching or rapid air-cooling if the material thickness is 1.5mm or more to obtain the best corrosion resistance.
Surface cleaning of the material during any heating operation should be pre-empted.

6.1.5 Descaling

Oxides on the surface of the Hastelloy B-2 alloy and stains near welds are to be polished off with a fine grinding wheel, etc. Since the Hastelloy B-2 alloy is sensitive to oxidizing media, more nitrogen-containing gases are generated during the pickling process.

6.1.6 Machining

Hastelloy B-2 is to be machined in the annealed condition.
Relative to the standard austenitic stainless steel is used for slower surface cutting speed, for the surface of the hardened layer to be used for a larger amount of feed, and to place the tool in a continuous state of operation.

6.1.7 Welding

Welding processes for Hastelloy B-2 alloys should be carefully developed and strictly controlled.
The general welding process is as follows:
1) Welding material selection ERNi-Mo7; welding method GTAW;
2) Control interlayer temperature is not greater than 120 ℃; welding wire diameter φ2.4, φ3.2;
3) Welding current 90~150A.
4) At the same time, before welding, the wire, the bevel of the welded part, and adjacent parts should be decontaminated and degreased. 
5) Hastelloy B-2 alloy heat conduction coefficient is much smaller than steel, such as the choice of single V-bevel, the bevel angle should be about 70 °, using a lower heat input. 
6) Residual stresses can be eliminated and resistance to stress corrosion fracture is improved by post-weld heat treatment.

6.2 Hastelloy C-276

C-276 alloy welding performance and ordinary austenitic stainless steel are similar, in the use of a welding method on the C-276 welding, must take measures to minimize the decline in the corrosion resistance of the weld and the heat-affected zone, such as tungsten gas-shielded welding (GTAW), metal-pole gas-shielded welding (GMAW), submerged-arc welding, or some other can minimize the decline in the corrosion resistance of the weld and the heat-affected zone Welding method.
Matching welding consumables: welding rod (ENiCrMo-4), welding wire (ERNiCrMo-4)
Welding bevels should preferably be machined, and pre-welding grinding of machined bevels is necessary. 
Appropriate heat input speed should be used during welding to prevent hot cracking.
The welding of C-276 alloy can choose itself as a welding material or filler metal.

6.3 Hastelloy C-22

6.3.1 Weldability

The welding properties of Hastelloy C-22 alloy are very good, it can be easily welded by tungsten-pole gas-shielded welding, metal-pole gas-shielded welding, submerged-arc welding, etc. The filler metal requires a matching chemical composition.
Photos of submerged-arc welding
                                                            Submerged-arc welding

6.3.2 Mechanical Properties

Hastelloy C-22 alloy has good hot working properties.

6.4 Hastelloy C-59

C-59 alloy can be readily processed by ordinary fabrication processes.

6.4.1 Heating

C-59 alloy should not come into contact with any contaminants before and during heat treatment.

6.4.2 Thermal Processing

C-59 alloy can be heat processed between 950 and 1180°C. The temperature of the alloy must be kept at a constant temperature. Cooling should be done sharply with water. Annealing after hot working ensures that the material has good corrosion resistance.

6.4.3 Cold working

Annealed C-59 alloys should only be used for cold working.

6.4.4 Heat treatment

Solid solution heat treatment should be carried out at temperatures between 1100 and 1180°C, preferably at 1120°C. The temperature of the solid solution heat treatment should be set at 1180°C, preferably at 1120°C. Water cooling is an essential point in ensuring that the material has the best possible corrosion resistance. The surface of the material must be clean during any thermal operation.

6.4.5 Descaling

Oxides in the vicinity of welds in C-59 alloy are much tighter than in other stainless steels and can be cleaned off by grinding with a fine abrasive wheel. Before pickling, oxides and stains on the surface of the material can be polished clean with a fine grinding wheel or stainless steel wire brush.

6.4.6 Machining

Machining C-59 alloy should be in the solution-treated condition.
Relative to low alloy austenitic stainless steels, use lower surface cutting speeds with high feeds to ignore the harder surfaces. Also, keep the tool in continuous operation.

6.4.7 Welding

photo of GTAW
C-59 alloy can be welded by a variety of conventional welding processes such as TIG/GTAW, MIG/MAG, hand metal welding, plasma arc welding, etc.
Cleaning before welding is necessary, using acetone.
Welding parameters and related influencing factors The heat input should be carefully selected when welding, and generally lower heat input should be used, and the interlayer temperature should not exceed 150℃. At the same time using a thinner weld channel welding process.
Generally, the oxidized parts should be brushed off with a stainless steel wire brush immediately after welding.

6.5 Hastelloy C-4

HastelloyC4 alloy has excellent mechanical properties and maintains stable performance in extreme environments.

VII, Uses of Hastelloy

7.1 Hastelloy B-2

It is commonly used in a variety of demanding petroleum and chemical processes, such as distillation of hydrochloric acid, concentration;
photo of Hydrochloric acid equipments
                                                                  Hydrochloric acid equipments
Alkylation of ethylbenzene and low pressure carbonyl synthesis of acetic acid and other production processes.

7.2 Hastelloy C-276

In harsh corrosive environments, such as chemical, petrochemical, flue gas desulfurization, pulp and paper, environmental protection and other industrial fields have quite a wide range of applications:
Heat exchangers, bellows compensators, chemical equipment, flue gas desulfurization and denitration, paper industry, equipment and components in acidic environments, reactors for acetic acid and acidic products, scrubbing towers in FGD systems, sulfuric acid condensers, ferric chloride and copper dichloride, hot contaminated solutions (organic or inorganic), strong oxidizing agents such as formic and acetic anhydride, as well as seawater and brine solution environments.
photo of Scrubbing towers
                                                                      Scrubbing towers 

7.3 Hastelloy C-22

Hastelloy C-22 alloy is used in a wide range of industrial applications such as flue gas desulphurization systems, bleaching systems in the pulp and paper industry, waste incinerators, chemical plants, pharmaceutical plants and radioactive waste storage.

7.4 Hastelloy C-59

C-59 alloy in chemical, petrochemical, energy and environmental engineering.

7.4.1

Equipment for chlorine-containing organic processes, especially in the presence of halogenated acid catalysts;

7.4.2

Equipment for dissolving and bleaching systems in the pulp and paper industry;

7.4.3

Preheaters, valves, impellers and other components of incinerators and flue gas desulphurization systems;

7.4.4

Sour gas treatment system equipment and components;

7.4.5

Acetic acid and acetic anhydride reactors;

7.4.6

Sulphuric acid condensers.

7.5 Hastelloy C-4

HastelloyC-4 is used in most chemical applications and in high temperature environments.
Included:
Flue gas desulfurization systems, pickling and acid regeneration plants, acetic acid and agrochemical production, titanium dioxide production (chlorine method), electrolytic plating, etc.
photo of Titanium dioxide producte plant
                                           Titanium dioxide producte plant
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