Thermal spraying - Determination of tensile adhesive strength
1 Scope
This standard is applicable to the determination of the strength of the thermal spraying coating or the adhesive strength between the thermal spraying coating and the substrate material.
This standard is applicable to the evaluation of the effects of substrate material and spray material, preparation of the surface of the workpiece, and the spraying conditions on the bond and adhesive strength of thermal spraying coatings, and the routine supervision of the thermal spraying works.
Note: This standard is not applicable to very thin and porous coatings. In this case, a bend test has proved to be more appropriate.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard. For dated references, subsequent amendments (excluding corrections) to, or revisions, of any of these publications do not apply to this standard. However parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. For undated references, the latest editions apply.
GB/T 16825 Verification of tensile testing machines (idt ISO 7500-1)
3 Terms and definitions
For the purposes of this standard, the following terms and definitions apply.
tensile adhesive strength RH
strength obtained in the tension test, calculated from the quotient of the maximum load, Fm, and the cross-sectional area at the fractured face, S, i.e.,
where,
RH——the tensile adhesive strength, N/mm2;
Fm——the maximum load, N;
S——the cross-sectional area at the fractured face, mm2;
4 Equipment
Any type of tensile testing machine in accordance with GB/T 16825 and meeting static loading conditions with an accuracy of not less than ±1%, and a clamping system are to be used to ensure concentric clamping and loading of the specimens. See Figure 1.
5 Specimens
5.1 Shape
For the determination of the tensile strength in the tensile test, specimens of shapes A and B and of 25mm and 40mm diameter are specified in this standard. Different specimen sizes are selected according to the tensile adhesive strength of the specimens and the capacity of the testing machine.
Specimen A (see Figure 2) consists of a substrate block to which the coating is applied at the front face, and a loading block which is adhesively bonded to the flat coating surface.
Specimen B (see Figure 3) consists of two loading blocks and a disc of substrate material. The coating is thermally sprayed to one side of the disc, and the disc is then adhesively bonded to the two loading blocks.
5.2 Preparation
Foreword I
1 Scope
2 Normative references
3 Terms and definitions
4 Equipment
5 Specimens
5.1 Shape
5.2 Preparation
5.3 Number of specimens
6 Procedure
7 Evaluation
8 Test report
9 Possible faults in the preparation of specimens and in testing
