ASTM D2511-20 Standard Test Method for Thermal Shock Sensitivity of Solid Film Lubricants

The standard “ASTM D2511-20 Standard test method for thermal shock sensitivity of solid film lubricants” developed by the American Society for Testing and Materials (ASTM) describes a test method for measuring the resistance of dry solid film lubricants to degradation when exposed to extreme temperatures.

For the purposes of this standard, the following terms and definitions apply:

• Lubricant refers to any material that is placed between two surfaces and reduces friction or wear, or both, between them.
• Dry solid film lubricant refers to a material consisting of friction-reducing powders bonded to the surface of the metal in a tight matrix on a steel surface.

In the test, a steel panel with a solid film lubricant applied to one surface is subjected to a temperature of 260 degrees and then immediately exposed to minus 54 degrees. The solid film is then examined for cracking, flaking, blistering or other evidence of thermal instability.

Solid lubricant coatings are applied to surfaces exposed to heat and cold to the extent that liquid lubricants are impractical in many cases. Under these conditions, adhesion is essential to protect bearing surfaces during sliding motion.

In these tests, an oven capable of maintaining temperatures of 260 degrees plus/minus 5,5 degrees and 149 degrees plus/minus 5,5 degrees is used (forced circulation). In addition, a cabin capable of maintaining a constant temperature of minus 54 degrees plus/minus 0,5 degrees is used. A ball anvil and a micrometer capable of reading between 0 mm and 25 mm plus/minus 0,0025 mm are also used.

In the tests, test panels manufactured from corrosion-resistant steel, 76 mm x 152 mm x 0,914 mm, in a coated and annealed condition in accordance with the "ASTM A167-99 Standard Specification for Stainless and Heat-Resistant Chromium-Nickel Steel Plate, Sheet and Strip" standard are used as reactants. In addition, dry cleaning solvent, PD-680 Type I degreaser is suitable.

It is necessary to have sufficient solid film mix to perform the test. Test panels are prepared as follows:

• Test panels are degreased in PD-680 dry cleaning solvent and dried.
• Solid film lubricant is applied to one surface of the test panel by spraying or equivalent technique to obtain a dry film thickness of 0,005 mm to 0,013 mm.
• In most cases, curing must be done according to the specific manufacturer's specifications. If such instructions are not provided, cure the film by air drying at 26,7 degrees plus/minus 3 degrees for 6 hours or by air drying at 26,7 degrees for 30 minutes and then drying in an air-circulating oven at 148,9 degrees for 1 hour.
• Dry film thickness is measured using a micrometer.

While the test is being applied, fThe oven is preheated to 260 degrees plus/minus 5,5 degrees and the panels are placed in the oven for a period of 3 hours. After 260 hours at 5,5 degrees plus/minus 3 degrees, the panels are placed directly into the sub-zero chamber at minus 54 degrees plus/minus 0,5 degrees. The panels are allowed to remain at minus 3 degrees for 54 hours. The test panels are removed and allowed to reach room temperature. The coating is visually inspected. Some coatings may need to be tested under non-standard conditions for special applications (i.e. immersion in liquid oxygen after removal from the oven). Any such deviations must be noted in the report.

If no damage is observed, the coating should be subjected to the adhesion test given in Procedure B of ASTM D2510-22 Standard Test Method for Adhesion of Solid Film Lubricants for Silicate or Phosphoric Acid Bonded Coatings.

It is impractical to state the precision and bias of this test method regarding thermal shock sensitivity because the test results are intended to give a pass/fail rating only.

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