ASTM C633-24 PDF

Full title and description

ASTM C633-24 — Standard Test Method for Adhesion or Cohesion Strength of Thermal Spray Coatings. This standard specifies a tensile test procedure to determine the adhesion (bonding) of a thermal‑spray coating to a substrate or the cohesion strength of the coating when loaded in tension normal to the coating surface.

Abstract

Provides a reproducible laboratory method for applying a tensile load normal to a coated specimen by bonding a coated substrate fixture to a loading fixture and pulling until failure; used to quantify and compare adhesion or cohesion strength of thermal‑spray coatings (metals, metal‑oxides, carbides, etc.). Limits, precautions and typical applications are described.

General information

• Status: Active.
• Publication date: November 2024 (active/last updated Nov 19, 2024).
• Publisher: ASTM International.
• ICS / categories: 25.220.40 (metallic coatings).
• Edition / version: C633‑24.
• Number of pages: 8.

Scope

The test covers determination of adhesion (bond strength at the coating–substrate interface) or cohesion (failure within the coating) by coating one face of a substrate fixture, bonding that coated face to a loading fixture with an adhesive, and subjecting the bonded assembly to a tensile load perpendicular to the coating plane until failure. The method is adapted for thermal‑spray processes (flame, plasma, two‑wire arc, HVOF, detonation) and is limited to coatings thicker than about 0.015 in (0.38 mm) because of adhesive penetration concerns. Tests are usually performed at ambient temperature unless a suitable adhesive allows elevated‑temperature testing.

Key topics and requirements

• Specimen and fixture geometry: substrate and loading fixtures (commonly cylindrical) prepared and coated per the standard; careful fixturing and self‑aligning fixtures recommended to ensure axial loading.
• Adhesive bonding: selection and curing of an adhesive that is stronger than the minimum expected coating bond so adhesive failure is not the limiting factor.
• Test execution: crosshead speed and data capture must be controlled to record peak load accurately (typical pull speeds cited in practical guidance are in the range ~0.030–0.050 in/min).
• Minimum coating thickness: coatings thinner than ~0.015 in (0.38 mm) are excluded unless special adhesives or methods prevent adhesive penetration.
• Result interpretation: report maximum tensile stress (load normalized by area) and describe fracture locus — adhesive (interface) vs cohesive (within coating) — to classify adhesion vs cohesion strength.
• Use for comparative and QC purposes (not as an absolute service‑life prediction due to geometry and residual stress effects).

Typical use and users

Used for quality control, acceptance testing, equipment and process qualification, and materials development for thermal spray coatings. Typical users include thermal‑spray operators, coatings engineers, materials laboratories, aerospace and power‑generation component manufacturers, and research organizations.

Related standards

Complementary or related documents include other adhesion/adhesion‑type test methods and thermal‑spray guidance, for example ASTM D4541 (portable pull‑off adhesion testers), ASTM C1624 (scratch testing for ceramic coatings), and international guidance such as ISO/EN 12679 (thermal‑spraying recommendations and best practices). These standards are often used together when assessing coating performance in different service or field conditions.

Keywords

adhesion, cohesion, bond strength, thermal spray, tensile adhesion test, coating‑substrate interface, HVOF, plasma spray, bond strength test.

FAQ

Q: What is this standard?

A: ASTM C633‑24 is the ASTM test method that defines a tensile procedure to measure adhesion or cohesion strength of thermal‑spray coatings by pulling a bonded coated fixture and recording the fracture stress.

Q: What does it cover?

A: It covers specimen preparation, bonding of a coated substrate to a loading fixture, tensile testing normal to the coating plane, minimum coating thickness limits (~0.015 in / 0.38 mm), result reporting, and interpretation of adhesive vs cohesive failure.

Q: Who typically uses it?

A: Coatings laboratories, materials and process engineers, thermal‑spray operators, aerospace, power‑generation and automotive manufacturers, and researchers performing comparative adhesion testing or qualification.

Q: Is it current or superseded?

A: Current — the active version is ASTM C633‑24 (listed active and last updated in November 2024). Users should reference the C633‑24 document for the authoritative text and check ASTM for any amendments.

Q: Is it part of a series?

A: It is maintained under ASTM’s thermal‑spray committee structure (Committee B08, Subcommittee B08.12) and relates to other ASTM and international standards addressing coating testing and thermal‑spray practice. The document appears in ASTM’s Book of Standards (Vol. 02.05).

Q: What are the key keywords?

A: Adhesion, cohesion, bond strength, thermal spray, tensile test, coating adhesion, fracture locus.