Introduction

Abstract

Testing of solid thin film lubricants for tribology applications that operate in vacuum presents unique challenges not encountered when testing in air. The end use of the lubricant film will determine the level of vacuum needed for testing. For example, if the application use of the lubricant requires high-vacuum conditions, then the film should be tested in those conditions as well. Testing in the milli-Torr range is significantly easier than testing in high-vacuum conditions, so long as the presence of some gas is permissible for accurate evaluation of the film. If the system under test will not have continuous pumping and still requires high-vacuum operating conditions, then all gasses from the coating and hardware components inside the test chamber must be removed before testing begins. For example, if the system and coating under test will be sealed, that is, isolated from the vacuum pumping system, then all outgassing must take place before isolation from the pumping system. Rotating anode x-ray tubes, which are high-voltage and high-vacuum devices and require a high-vacuum operating environment, do not operate with constant pumping, and it is therefore required to have all components sufficiently outgassed before disconnecting from the pumping system. However, outgassing all components prior to testing requires significant preparation. Alternatively, all components required for testing coatings would not need to be fully outgassed provided that continuous vacuum pumping is used to remove outgassing molecules during the test.