Tribological behaviour of colloidally processed sialon ceramics sliding against steel under dry conditions

Abstract

Advanced structural ceramics are presently used in several tribological applications such as precision instrument bearings, water pumps, automotive engine parts and cutting tools inserts. In the present work, the tribological behaviours of colloidally processed and pressureless sintered sialon ceramics with different phases (a and b) have been studied, aiming at increasing the industrial applications of sialon ceramics. The friction and wear behaviour of sialon ceramics against steel DIN-Ck45K were investigated using a pin-on-disk tribometer under dry conditions. Scanning electron microscopy (SEM), and energy dispersion spectroscopy (EDS) were used to analyse the worn surfaces of the sialon ceramics. Under the conditions used, sialon ceramics exhibited a typical mild wear (10 )6 mm 3 N )1 m )1 ) and the dominant wear mechanisms present were adhesive and abrasion. The results confirmed that colloidal processing and pressureless sintering are effective methods to prepare wear resistant sialon ceramic components.

Microstructure–Mechanical Properties–Wear Resistance Relationship of SiAlON Ceramics

“…The unreacted a/b-Si 3 N 4 phase undergoes oxidation to form a SiO 2 -rich layer, as per Reaction [10]. The observation of a thick SiO 2 layer suggests the nonprotectiveness (thick oxide layers are known to be nonprotective in the case of pure oxidation), and this is reflected in cracking/spalling around the tribochemical layer.…”

“…The thermodynamic feasibility of Reaction [10] in the temperature range 333 to 388 K (maximum rise in contact temperature during wear (Table V)) is assessed from the free-energy calculations using commercial HSC software, [31] which follows the Barin et al [32] data compilation. In Figure 10, the DG values for Reaction [10] to occur from left to right are plotted as a function of temperature.…”

“…In Figure 10, the DG values for Reaction [10] to occur from left to right are plotted as a function of temperature. The free-energy plot in Figure 10 indicates that Reaction [10] is feasible in the temperature range obtained from Archard's model. Therefore, it can be said that formation of the silica layer can occur through oxidation of the silicon nitride phase present in the SiAlON ceramics.…”

The effect of the wet-milling process on sintering temperature and the amount of additive of SiAlON ceramics

“…The solvent compositions were determined according to literature studies [7][8][9][10][11][12]. The sedimentation method was used for determination of an adequate dispersion in order to use ball milling energy to decrease the particle size of the starting powders.…”

“…Thus, in an agglomerate-free system, energy will be transferred to the powder to decrease particle size. There are few studies [7][8][9][10] investigating well-dispersed suspension systems for SiAlON ceramics but these did not include any comparison between solvent and dispersant types. In this study, SiAlON powders milled in different solvent mediums (toluene, methyl ethyl ketone, and ethanol) with different kinds of dispersants (oleic acid, poly ethylene glicol, sodium tripolyphosphate) and sedimentation tests were performed.…”