Ion beam processing of high-temperature solid-lubricating coatings

Ion bean assisted deposition (IBAD) and ion beam mixing (IBM) were utilized to fabricate self-lubricating coatings of CaF{sub 2}/Ag and BaF{sub 2}/CaF{sub 2}/Ag composites. In IBAD, a low energy ({approximately}500 eV) Ar{sup +} bombardment was used in combinations with electron beam evaporation of coating materials. In ion beam mixing, magnetron sputter deposition was used to deposit a mixed composite coating of CaF{sub 2} + Ag which was subsequently ion beam mixed with 1 MeV Ag{sup +} at a fluence of 1 x 10{sup 16} cm{sup {minus}2}. The deposited coatings were characterized for composition and microstructure using Rutherford back-scattering spectrometry (RBS) and transmission electron microscopy (TEM). The friction and wear tests were carried out in a high-temperature controlled-atmosphere test system utilizing pin-on-disc wear test geometry. Uncoated Si{sub 3}N{sub 4} (NBD-100) spheres were used as the pin-on coated NBD-100 Si{sub 3}N{sub 4} and Rene 41 Ni-base superalloy discs. Both IBAD and sputtering of BaF{sub 2} and CaF{sub 2} resulted in a near stoichiometric composition with a very fine microstructure. Friction coefficients below 600{degrees}C were approximately 0.2-0.3 in the case of coated Rene 41 alloy, but were reduced to about 0.1-0.15 at 800{degrees}C for coated Si{sub 3}N{sub 4}. 13 refs., 15 figs., 2more » tabs.« less