430 The material condition, manufacturing details, and surface roughness can all influence the wear behavior.  The details of the roller conditions are given in Table I and additional details follow. The qualification test unit has rollers made from 440F steel in the annealed condition and the working surface specified to have a roughness of 0.4 µm maximum. The qualification test rollers were passivated per ASTM A-380-06. The 440F alloy is similar to 440C but includes the introduction of either selenium and/or additional sulfur to alter the machining characteristics relative to 440C. From x-ray photoelectron spectroscopy both the qualification test unit rollers and the 440F laboratory test rollers were found to have selenium as a constituent. The surface hardness of a 440F laboratory test roller was measured as 24 RC. Laboratory test rollers were made intending to enhance resistance to adhesive wear and to reduce debris generation. These rollers were made from 440C, hardened to RC 58, and provided a fine ground surface. Roughness of the test rollers was documented by stylus profilometer inspections. Typical roughness profiles in the rolling direction are provided in Fig. 6. The roughness data of Fig. 6 were prepared filtering the data using 0.8 millimeter cutoff and 300:1 bandwidth ISO standard filter. The roughness of the 440F rollers (0.15   micrometer Ra) was significantly larger than the roughness of the 440C rollers (0.07 micrometer Ra).  The test rollers that mated with the 440 series rollers were made of Ti6Al4V. The Ti6Al4V rolling surfaces of the qualification unit were observed to have distinctive machining marks, and so the laboratory Ti6Al4V rollers were made using a turning operation as the resulting surface texture of the test rollers were judged similar to the surfaces of the qualification unit. The rollers were stress relieved per AMS 2801 after machining. The roller hardness was RC 35. Some of the Ti6Al4V rollers were anodized per Tifin 200 matching the qualification unit treatment. A typical roughness profile for the Ti6Al4V rollers after anodizing is provided in Fig. 6. The typical roughness average value was 0.44 micrometer Ra. Some testing was done with Ti6Al4V rollers that were not anodized to make project progress previous to the completion of the anodize process. 

Procedure to Install Test Rollers  Test specimens were cleaned and installed using careful procedures to provide clean test surfaces. The test rollers were cleaned just prior to installation into the rig using de-ionized water and 0.05 micron alumina powder. After appropriate hand scrubbing, the cleaning powder was rinsed with deionizer water making sure that the entire roller surface wetted uniformly to confirm complete cleaning of surface oils. The water was removed from the roller using dried pressurized nitrogen. Test rollers and mounting hardware were handled only with gloved hands and clean tools to complete installation into the test apparatus. 

Procedure for Testing Rollers  The first step for testing after installation of the test rollers was to immediately isolate the testing chamber  and provide a vacuum, using the scroll roughing pump, to approximately 50x10-3 Torr chamber pressure.  This isolation step was done even if test scheduling required some delay between the time of installation of rollers and the time for testing to minimize exposure of the cleaned surfaces to any contaminants that might be present in the atmosphere. Prior to testing the turbomolecular pump was used to bring the testing chamber to approximately 3x10 -7 Torr.