EN 4128:2016

Overview

EN 4128:2016 is a European Standard under the auspices of CEN, detailing specifications for aerospace-grade bolts. This standard applies to bolts featuring a normal hexagonal head, a coarse tolerance shank, and a short threaded section. These bolts are made from a heat-resistant nickel-base alloy and feature an aluminium IVD (ion vapor deposition) coating. Classified for strength and performance, they have a minimum tensile strength of 1,250 MPa at ambient temperature and withstand temperatures up to 425 °C without permanent degradation of properties.

This standard is critical for aerospace manufacturing and maintenance where high-strength, temperature-resistant fasteners are required.

Key Topics

• Bolt Design and Dimensions: Bolts covered by EN 4128 have a normal hexagonal head and comply with dimensional and tolerance requirements aligned with ISO 3193, ensuring interchangeability and compatibility within aerospace assemblies.

• Material Properties: The bolts are manufactured from a heat-resistant nickel-base alloy, ensuring exceptional strength and durability in high-temperature aerospace environments.

• Surface Treatment: An aluminium IVD coating (per MIL-DTL-83488 type II, class 3, thickness 4 µm to 12 µm or EN 6118) provides corrosion resistance and extended service life. Post-coating surface treatments include mechanical blasting and chromate conversion, with optional lubrication to aid assembly.

• Mechanical Performance: The tensile strength requirement is set at 1,250 MPa at room temperature. The bolts maintain mechanical properties up to 425 °C. The standard also specifies adaptations to fatigue and double shear test loads, applying a coefficient for accurate stress evaluation.

• Marking & Identification: Bolts must be marked in accordance with EN 2424 for aerospace products, ensuring traceability. The marking includes diameter codes and locking hole designations for wire or split pins when applicable.

• Manufacturer Requirements: Compliance includes adherence to EN 9100 for quality management and EN 9133 for part qualification, guaranteeing the reliability of these critical components.

Applications

EN 4128 bolts are primarily used in aerospace and defense industries where components are exposed to extreme temperatures and mechanical stresses. Key applications include:

• Aircraft engines and structural assemblies requiring high-temperature fasteners that maintain integrity under thermal cycling.

• Spacecraft components exposed to harsh environments demanding durability and corrosion resistance.

• High-performance aerospace systems including turbines and exhaust assemblies, which depend on nickel-base alloy bolts for safety and longevity.

• Maintenance and repair operations in aviation, where replacement fasteners must meet stringent performance and material classifications.

Using bolts conforming to EN 4128 ensures standardized quality, enhanced safety, and compatibility within critical aerospace applications.

Related Standards

• EN 2424 – Aerospace series - Marking of aerospace products: Defines marking protocols for traceability and certification.

• EN 6118 – Aerospace series - Process specification - Aluminium base protection for fasteners: Alternative specification for aluminium coating processes.

• EN 9100 – Quality management systems - Requirements for aviation, space, and defense organizations: Quality framework applicable to manufacturers.

• EN 9133 – Aerospace series - Qualification procedure for aerospace standard parts: Ensures components meet qualification criteria.

• ISO 3193 – Aerospace bolts - Dimensions and tolerance standards for hexagonal head bolts.

• ISO 7913 – Aerospace bolts and screws - Tolerances for form and position applicable to these bolts.

• MIL-DTL-83488 – Military specification for aluminium coatings, referenced for surface treatment compliance.

Keywords: EN 4128:2016, aerospace bolts, nickel base alloy bolts, aluminium IVD coating, heat resistant fasteners, aerospace standard bolts, hexagonal head bolts, aerospace standardization, bolt tensile strength, high-temperature bolts.