Hastelloy Fasteners

Hastelloy Grades Comparison

Corrosion Media Selection Guide

Types of Hastelloy Fasteners We Supply

Hastelloy Bolts

Hastelloy Nuts

Hastelloy Stud Bolts

Hastelloy Washers

Hastelloy Screws

Hastelloy Product Range Matrix

Specifications & Standards of Hastelloy Fasteners

Chemical Composition of Hastelloy Fasteners

Mechanical Properties of Hastelloy Fasteners

Applications of Hastelloy Fasteners

The Hastelloy Fasteners come with high strength and corrosion resistance, which is why they’re used by many industries, as given below. 

• Chemical Processing : Hastelloy fasteners are popularly used in reactors, acid plants, chlorination systems, and scrubbers with frequent exposure to hydrochloric acid, sulfuric acid, wet chlorine and mixed oxidizing and reducing media. Hastelloy C276 and C22 are graded alloy grades with good pitting, crevice corrosion, and stress corrosion cracking resistance, which guarantee the high service life of such equipment in the process.
• Pollution Control / FGD Systems : The wet scrubbers, stacks, and ducting are subject to a very corrosive environment that contains chlorides and acidic condensates in flue gas desulfurization (FGD) systems. Hastelloy screws have been mostly used in these applications because they are able to remain in the mechanical and corrosive conditions characterized by constant wet and acidic conditions.
• Pharmaceutical and Specialty Chemicals : In the case of pharma and specialty chemical plants, Hastelloy fasteners are a good choice as they provide both high corrosion resistance and cleanliness, and therefore are applicable in reactors and process equipment where a high level of contamination is a major concern. Surface finish and adequate fabrication will further promote appropriateness for hygienic use.
• Pulp and Paper (Pulp Chemicals) : The bleaching process entails the use of chloride environments and harsh chemicals like chlorine dioxide. Hastelloy fasteners are applied in digesters, washers, and bleaching units in order to provide resistance to localized corrosion and extend the life of equipment.
• Oil and Gas / sour/offshore chemicals : Presence of chlorides, process chemicals, and the harsh operating conditions in the oil & gas applications, particularly sour service and offshore chemical handling, requires more selective alloys. The Hastelloy fasteners provide dependable performance where regular alloys might fail.

Industry–Grade Selection Guide of Hastelloy Fasteners

Hastelloy vs Other Materials

Hastelloy vs Stainless Steel

Stainless steel fasteners are commonly used for general corrosion protection and have cost-efficient industrial applications. Nevertheless, in the cases of service conditions with severe acids, wet chlorine or mixed oxidizing and reducing media, Hastelloy fasteners are used because their pitting and crevice corrosion, as well as stress corrosion cracking resistance, are better. Where grade stainless steel might fail too soon, Hastelloy offers long-term services.

Hastelloy vs Inconel

The use of Inconel fasteners is mostly used in positions that need high-temperature strength, as well as resistance to oxidation, like furnaces and gas turbines. On the other hand, Hastelloy fasteners are designed to be resistant to acid corrosion and are therefore more applicable in chemical processing and in aggressive media. This selection is based on temperature or corrosion being the service condition of preeminence.

Hastelloy vs Monel

Monel bolts will also be used effectively in seawater and in certain conditions in hydrofluoric acid, and are therefore a niche marine alloy. Depending on the grade of Hastelloy fasteners, they provide a wider range of versatility, particularly in mixed acid systems, and in environments involving both oxidizing and reducing environments. This renders Hastelloy more adaptable in complicated chemical exposures.

Common Challenges with Nickel Alloy (Hastelloy) Fasteners

There are many challenges present that many manufacturers ignore while making these fasteners, and some of the common challenges are given below. 

Galling / Seizing

An issue with nickel alloy and Hastelloy fasteners is galling, particularly when installing under high load or in dry environments. This may cause thread seizing and damage to fasteners. Anti-seize compounds, controlled values of the torque and a slower rate of tightening should be used to mitigate the risk. Surface treatments like PTFL (Teflon) coating also reduce friction and enhance the reliability of assembly.

Crevice Corrosion / Deposits

Even though Hastelloy has a good corrosion-resistant behavior, in stagnant regions, crevices corrosion or deposits may occur due to the accumulation of process chemicals or contaminants. The correct design of joints, minimizing tight crevices, and frequent cleaning and inspection are also means of long-term performance, particularly in chloride-or-acid-contaminated environments.

Wrong-Grade Failures

The use of the wrong grade of Hastelloy in the service environment is one of the most serious reasons for failure. The grades react differently in either oxidizing media or reducing media or both. Grade verification is a critical decision criterion because to avoid expensive mix-ups, Positive Material Identification (PMI) should be strictly followed, full traceability of heat-numbers and material should be certified- this necessitates grade verification, especially during engineers and procurement level.

Manufacturing Process of Hastelloy Fasteners

The step-by-step procedure given below explains how high-quality Hastelloy fasteners are made.

• Raw Material Sourcing: Hastelloy raw material is sourced through certified nickel alloy mills and therefore, the right grade, chemical composition, and complete heat traceability. Production is done by checking the incoming materials using inspection and PMI.
• Forging / Cold Heading: Then the material is either hot forged or cold headed, depending on the size and design of fasteners so as to obtain the necessary shape, strength, and grain structure that is suitable in harsh corrosive environments.
• Machining: Machining is another process that is performed under the control of parameters since Hastelloy is a work-hardening nickel alloy. It is imperative that proper tooling, speed, and cooling are used to ensure that it does not gall and retain the integrity of the surface.
• Threading: Threads are made through thread rolling or thread cutting and they are chosen according to their diameter, load demands and their standards to maintain their dimensional consistency and performance.
• Heat Treatment: Controlled heat treatment is done where both the corrosion resistance and necessary mechanical properties are required, without losing either.
• Cleaning / Passivation: Good cleaning and passivation are done to eliminate the contamination and increase the corrosion resistance, particularly where chemical services are to be used.
• Final Inspection & Packaging: Every batch is finally inspected, marked, documented and packed in an export grade to be distributed safely to all parts of the world without violating international standards.

Quality Assurance & Testing

The quality assurance and other testing are important to know about the strength and corrosion resistance of the hastelloy fasteners. All the methods and testing that we apply are given below. 

• PMI Verification: Positive Material Identification (PMI) is done to verify accurate Hastelloy grade and chemical composition. This eliminates any chance of material traceability and eliminates mix-ups of grades in vital service applications.
• Dimensional Inspection: Dimensional inspection is done by use of calibrated measuring instruments to measure the diameter, length, tolerance and overall perfection with the specified values to ensure that the fit and assembly is correct.
• Mechanical Testing: Mechanical tests like proof load, tensile strength and hardness testing are done under the ordered specification to confirm the strength and performance of the fastener under the service load.
• Thread Gauging (GO / NO-GO): The precision of threads is verified by GO and NO-GO gauges to verify the correct pitch, class and engagement so as to ensure stable installation and load bearing capacity.
• Third-Party Inspection: In cases where it is needed, the third-party inspection is provided by certified agencies to give external quality and compliance checks.
• Certification: Every supply comes with full documentation of its quality, with EN 10204 3.1 or 3.2 certificates where necessary, to provide transparency, traceability and confidence where needed in the most demanding industrial purposes.

Size Range & Availability of Hastelloy Fasteners

Why Choose Unifit Fastener for Hastelloy?

Unifit Fasteners specializes in providing the Hastelloy and other exotic nickel alloys, which offer reliable solutions to industries that require a highly corrosive or demanding environment. Each batch is subjected to Positive Material Identification (PMI) testing as per stringent QA plans to make sure that the batch is of the right grade and is completely traceable. We provide specialized production with the use of drawings or a specifications list, producing one-of-a-kind project orders with accuracy. With a fast turnaround for shutdowns or critical spares, clients can rely on timely delivery. Export-grade packing is done on all its fasteners, and the staff does the technical selection support of severe acids, wet chlorine, and mixed media. Extensive documentation, such as MTC 3.1 or 3.2 certificates, is provided where necessary.

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