Master Bond Case Study

Overview of EP15

Master Bond EP15 is a one-component, thermally-curing epoxy with a tensile strength in excess of 12,000 psi (82.7 MPa) due to the formation of rigid, dimensionally stable bonds upon curing. This bulk tensile strength makes it ideal for testing the adhesive and cohesive strengths of various thermal spray coatings according to ASTM C633, which requires the use of a high tensile strength adhesive that does not fail until after the coating.

ASTM C633 to Test the Bond Strength of Thermal Spray Coatings

This test evaluates the adhesive strength of a coating to a substrate or the cohesion strength of the coating when tension is applied perpendicular to a surface. During the test, a coating is applied to one side of a substrate, and this coated surface is attached to a loading fixture, followed by the application of a tensile force perpendicular to the coating's plane. This test is specifically designed for examining coatings applied through thermal spray processes, such as combustion flame, plasma arc spraying, two-wire arc, high-velocity oxygen fuel, and detonation methods, using wire, rod, or powder feedstocks. Several parameters may critically affect the test results, including but not limited to:

  • Surface preparation method
  • Cure schedules
  • Pull rates
  • Substrates

The Role of EP15 in ASTM C633 Testing

To ensure the success of bonding strength according to ASTM C633, it is necessary to select an adhesive with a bond strength greater than the expected bonding strength so that the specimens fail before the adhesive. As shown below in Table 1, EP15 has been used to test the bond strength of a wide variety of coating and substrate pairs. The case studies below highlight the importance of preparing each substrate surface to optimize the bonding of EP15 for ASTM C633 tensile tests.

In this paper we present 6 case studies, which provide an overview of the uses of EP15 for ASTM C633 testing. This chart provides an overview of these case studies.

Case Study Thermal Spray Technique Coating Substrate Bond Strength
Case Study 1 DC-Magnatron Sputtering Ti, Nb, or uranium-8 wt% molybdenum alloy Aluminum,
niobium, tantalum, titanium, and zirconium
70 MPa
Case Study 2 Cold Gas Dynamic
Spraying (CGDS)
Al-6061 alloy N/A
Case Study 3 Cold Gas
Dynamic Spraying (CGDS)
SiC-reinforced, Al-12Si alloy 6061-T6 aluminum 82 ± 10 MPa
Case Study 4 High Velocity Oxy-Fuel (HVOF) Thermal
Inconel 625 Mild Carbon Stainless Steel (304) 45-60 MPa
Case Study 5 Chemical
Densified Coating (CDC)
Cr2O-SiO2 SS316 N/A
Case Study 6 Arc Spraying Alpha-1800 (iron-boron cored wire) Mild steel N/A


To read the in-depth details of both the ASTM C633 testing requirements and the case studies, please download.


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