Influence of Crystal Structure on Friction Characteristics of Rare-Earth and Related Metals in Vacuum to 10-10 Millimeter of Mercury
Abstract
The friction, wear, and metal-transfer characteristics were determined for rare-earth and related metals in vacuum to 10-10 millimeter of mercury. The metals studied were lanthanum, neodymium, praseodymium, cerium, holmium, erbium, gadolinium, dysprosium, samarium, yttrium, and thallium. Friction and wear experiments were conducted with the rare-earth or related metals generally sliding against 440-C stainless steel at sliding velocities to 2000 feet per minute and loads to 3000 grams. The rare-earth or related metals were the rider specimens (3/18-in. -rad. hemisphere) sliding on flat 2 1/2 -inch-diameter disk specimens of 440-C stainless steel. Factors studied were the effects of crystal structure and crystalline phase changes on the friction, wear, and metal-transfer characteristics of these metals in vacuum. The results of the investigation indicate that crystal structure markedly influences friction, wear, and metal-transfer characteristics of the rare-earth and related metals in vacuum. Close-packed hexagonal crystal forms of the rare earths and of thallium had much lower friction, wear, and metal transfer characteristics than face-centered or body-centered cubic structures. The lowest friction coefficients were obtained with those rare-earth metals that have the largest c-axis (crystal height), that is, those metals with the lanthanum- and samarium-type crystal structures. With neodymium a crystal transformation was observed at a temperature below that reported in the literature.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1964
- Accession Number
- ADA397106
Entities
People
- Donald H. Buckley
- Robert L. Johnson
Organizations
- National Aeronautics and Space Administration