Friction and wear behavior of in-situ reinforced silicon nitride. Final report

Specimens of in-situ-reinforced silicon nitride (ISRSH) have been wear tested in lubricated, reciprocating, sliding motion against a silicon nitride counterface. Only mild wear of the ISRSN was observed at contact pressures up to 4.8 GPa at an average sliding velocity of 0.3 m/s. At 0.6 m/s, a wear mode transition was observed in ISRSN at 4.2 - 4.4 GPa. In comparison, the wear mode transition in silicon carbide whisker reinforced silicon nitride at both velocities was evident at about 2.2 - 2.4 GPa. Scanning electron microscopy of the ISRSN wear surfaces revealed the presence of a 40 pm thick debris layer on the mild wear tracks. The ISRSN wear mode transition response indicated a potential for an improved wear resistance in this material as compared to whisker reinforced silicon nitride

Reciprocating sliding wear of in-situ reinforced silicon nitride

The reciprocating sliding wear response of two in-situ reinforced-silicon nitride compositions provided by AlliedSignal have been evaluated. The materials were prepared by AlliedSignal-Ceramic Components Division and were tested at conditions of interest to the Bendix Engine Controls Division (South Bend, IN) and AlliedSignal Research and Technology (Des Plaines, IL). The materials are being considered for a variety of new applications, and the current tests provide critical friction and wear values under anticipated operating conditions. Both pin and disk specimens of GS-44 and GN-10 in-situ reinforced silicon nitride of specified dimensions for wear testing were provided by the AlliedSignal participants. An initial series of tests examined the unlubricated behavior of these materials at elevated temperature (up to 900 C) in an inert atmosphere. The results revealed excessive levels of both friction and wear in the unlubricated condition. The test conditions were modified to include the use of jet fuel as a lubricant because of an intended application in that medium. The introduction of the lubricant resulted in very limited wear of both the pin and disk specimens

(Tribology conferences and forums)

The principal meeting attended during this trip was the Japan International Tribology Conference Nagoya 1990. The conference encompassed a wide range of topics, including the tribology of ceramics, the tribology in high-performance automobiles, and many aspects of lubrication technology. Associated forums were also held on the tribology of advanced ceramics, on solid lubrication, and on automotive lubricants. Presentations made during the latter forum discussed anticipated trends in engine development and anticipated improvements in lubricants required for the next generation of engines. In addition to meetings, site visits were made to five industrial organizations to discuss ceramic tribology. Nippon Steel Corporation and Toshiba Corporation are both very active in the ceramic area, Nippon Steel from their interest in research on new materials and Toshiba from both an interest in new materials and in support of their work in electronic devices. Two engine manufacturers were also visited, Toyota Motor Corporation, and Nissan Motor Co., Ltd. These companies were somewhat reserved in their discussion of progress in the utilization of ceramics in automobile engines

Preparation and friction characteristics of self-lubricating TiN- MoS{sub 2} composite coatings

Composite coatings consisting of distinctly discrete phases of TiN and MoS{sub 2} were codeposited on graphite and Ti-6Al-4V substrates from Ti((CH3)2N)4/NH3/MoF6/H2S gas mixtures. Chemical composition and microstructure of the coatings were studied by Auger electron spectroscopy, XRD, and TEM. Friction coefficients at room temperature in air were typically in the range of 0.07 to 0.3; they remained comparable at 573 K, but increased to 0.7 to 1.0 at 673 K. A friction coefficient of {similar_to}0.3 was, however, obtained from a composite coating tested at 973 K

Friction and wear of self-lubricating TiN-MoS{sub 2} coatings produced by chemical vapor deposition

The purpose of the work reported here was to develop special chemical vapor deposition (CVD) methods to produce self-lubricating ceramic coatings in which the lubricating and structural phases were co-deposited on Ti-6Al-4V alloy substrates. These novel composite coatings are based on a system containing titanium nitride and molybdenum disulfide. The method for producing these coatings and their sliding behavior against silicon nitride counterfaces, in the temperature range 20--700 C in air, are described. The initial sliding friction coefficients for the composite coatings at room temperature were 0.07--0.30, but longer-term transitions to higher friction occurred, and specimen-to-specimen test variations suggested that further developments of the deposition process are required to assure repeatable friction and wear results. Friction and wear tests at 300 and 700 C produced encouraging results, but tests run at an intermediate temperate of 400 C exhibited friction coefficients of 1.0 or more. Oxidation and a change in the nature of the debris layers formed during sliding are believed to be responsible for this behavior