Standard No.:	GB/T 8642-2025
English Name:	Thermal spraying—Determination of tensile adhesive strength
Chinese Name:	热喷涂 抗拉结合强度的测定
Chinese Classification:	A29    Material Protection
Professional Classification:	GB    National Standard
ICS Classification:	25.220.20 25.220.20    Surface treatment 25.220.20
Source Content Issued by:	SAMR;SAC
Issued on:	2025-12-2
Implemented on:	2026-7-1
Status:	valid
Superseding:	GB/T 8642-2002 Thermal spraying - Determiantion of tensile adhesive strength
Target Language:	English
File Format:	PDF
Word Count:	18200 words
Translation Price(USD):	728.0
Delivery:	via email in 1 business day

Thermal spraying - Determination of tensile adhesive strength 1 Scope This document specifies the procedure to determine the tensile adhesive strength of thermally sprayed coatings under tension in the direction normal to the surface of the coating by applying a tensile test. By using this procedure, comparability of the test results is ensured. The test is intended to determine the tensile adhesive strength between the thermally sprayed coating and the substrate material or between the bond and top coat as well as of the cohesive strength of the related coat of the coating system. In some cases, thermally sprayed coatings might have two or more layers. The method specified in this document applies also to determine the tensile adhesive strength between the interfaces of different layers in a coating system which consists of two or more layers. This test is sufficient to compare coatings manufactured using same or similar feedstock materials and thermal spraying processes. The tensile adhesive strength test is not intended to provide absolute values for evaluation of the durability of coatings under operational use. This document is used to assess the influence of substrate preparation, the spraying conditions and the process parameter on the tensile adhesive strength of thermally sprayed coatings. It can also be employed in order to monitor the consistency of the manufacturing and spraying processes. Note: This tensile test can also be applied to very thin coatings. Moreover, the infiltration of bonding agent into the thermally sprayed coatings containing a required level of porosity can be minimized using an appropriate bonding agent (foil rather than liquid). For further instructions, please refer to 6.5.3. This tensile test is inappropriate for determining the adhesive strength of fused spray coatings deposited using self-fluxing alloys due to their inherent high adhesive strength values. 2 Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB/T 11373 Thermal spraying Pre-treatment of surfaces of metallic parts and components GB/T 16825.1 Metallic materials - Calibration and verification of static uniaxial testing machines - Part 1: Tension/compression testing machines - Calibration and verification of the force-measuring system (GB/T 16825.1-2022, ISO 7500-1: 2018, IDT) GB/T 18719 Thermal spraying - Terminology, classification (GB/T 18719-2002, ISO 14917: 1999, MOD) 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 adhesive strength RH tensile strength measured in the tensile test, which is calculated from the quotient of the maximum load Fmax and the cross-sectional area of the fractured face 3.2 adhesive failure fracture, which runs along the interface between coating and substrate Note 1: The coating will be totally separated away from the substrate. Note 2: The inter-particle cohesive strength is higher than the adhesive strength of the coating. 3.3 cohesive failure fracture, which takes place within the coating Note: The inter-particle bonding (cohesive strength) is lower than the adhesive strength of the coating. 3.4 adhesive-cohesive failure fracture, which is partially located in the interface of the coating to the substrate and partially within the coating 3.5 internal adhesive strength adhesive strength between the layers of a coating system, e.g. between a bond and top coat 3.6 test disc test specimen formed like a disc coated on one side Note: This is to be positioned and bonded between two loading blocks when preparing the tensile test specimen. 3.7 reference specimen specimen for determination of the strength of bonding agent Note: This consists of two uncoated loading blocks bonded together using the same bonding procedure as for all other test specimens.

Foreword i Introduction iii 1 Scope 2 Normative references 3 Terms and definitions 4 General provisions 5 Equipment for testing and measuring and auxiliary equipment 5.1 Test instruments 5.2 Measurement instruments 5.3 Specimen fixing devices for bonding of the tensile test specimen 6 Specimens 6.1 Shape of specimens 6.2 Material of the specimen 6.3 Preparing the substrate and loading blocks 6.4 Preparing and spraying of the specimen 6.5 Manufacture of the specimens for tensile test 6.6 Reference specimen 6.7 Number of test specimens 7 Test procedure 8 Measurement readings and evaluation 9 Test report - Documentation 10 Possible sources of fault when preparing the specimens and on test Annex A (Informative) Recommendations for further auxiliary equipment Annex B (Informative) Work instructions for bonding Annex C (Informative) Function areas on the tensile specimen and possibilities of fracture locations according to ASTM C633-13 Annex D (Informative) Record for the applied tensile test according to this document Bibliography