The Effects of Elevated Ambient Temperatures on the Friction and Wear Behavior of Some Commercial Nickel Base Alloys

Abstract

Measurements of friction and wearduring sliding of specimens of Nimonic 75, C263, Nimonic 108 and Incoloy 901 on like specimens i n air at temperatures from 20 t o 800 C are presented. Under the sliding conditions used, all the alloys show a transition temperature, above which low wear and a low coeficient of friction during sliding are observed after a time and below which these parameters remain relatively high throughout. These temperatures are about 150 C for N75, about 200 C for C263 and N108 and between 200 and 300 for Incoloy 901. At given temperatures above the transition temperatures, the coeficient of friction-time loci show sharp, generally very reproducible, changes from relatively high to low coeficients of friction. The times at which these occur decrease with increasing temperature for a given alloy. Such changes can be closely correlated to the formation of a stable, adherent, therma2ly softened, oxide layer or glaze on the load-bearing areas during sliding. Once the glaze is established, very little further wear takes place. These tribological properties of the glaze are associated with its low shear strength and the high strength of the underlying alloy substrate. They depend more on its physical properties than on its precise chemical composition. It is concluded that high strength, relatively rapid transient oxidation rates, and appropriate physical properties of the resulting oxide films are important qualities in alloys employed under sliding conditions i n air at elevated temperatures.

Do heat shock proteins provide protection against freezing?

“…Several studies have shown that cryoprotectant acts as a proleetive agent during heat treatment. Glycerol increases the survival of cultured mammalian cells during hyperthermia [14][15][16][17][18]. Protection of cells from heat by glycerol is thought to result from its ability to stabilize cellular macromolecules [19][20][21].…”

The development of wear-protective oxides and their influence on sliding friction

“…The development of oxide layers on metal surfaces during sliding often leads to re duced friction and wear (Barnes et al 1977;Bisson i960;Lin et al 1974;S tott et al 1973;S to tt et al 1976;Welsh 1965) and clear th a t such oxides play an im portant p art in various practical wear situations, such as during the operation of gas-turbine engines. There have been relatively few detailed studies of the influence of oxides on friction and wear processes, and rela tively little is known about the modes of formation and operation of such oxides or of their role in reducing friction and wear.…”

Strategies for enantioseparations of catecholamines and structurally related compounds by capillary zone electrophoresis using sulfated β-cyclodextrins as chiral selectors

“…In CE, the use of CDs and their derivatives as chiral selectors is the most common strategy employed for the separation of chiral compounds [1][2][3][4][5]. Enantioseparation of charged compounds has often been achieved with the use of neutral or charged CDs [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], or with dual CD systems consisting of a charged CD and a neutral CD [21][22][23][24][25][26][27][28][29], or two oppositely charged CDs [30]. Among many charged CDs studied to date, sulfated CDs have demonstrated the widest application range [6][7][8].…”