Analysis of Deformation of a Fireclay Refractory

Abstract

l a 1 T=1009'c U-718 P S I j I I / I I Rate process theory was applied in a study of the creep behavior of a fireclay refractory (firebrick) after different heat treatments. The analysis was based on the assumption that, in the absence of phase changes, equivalent deformation substructures are produced for a given strain at constant stress independent of temperature. An activation energy of about 170 kcal/mole was determined for the flow process in a heattreated firebrick, which corresponds closely to the value for mullite specimens. Varying but higher values obtained under different test conditions indicated that phase changes were also occurring during the creep tests. The effect of the amount and texture of the components on the creep behavior and strength of the firebrick specimens is discussed. Useful correlations based on this approach are presented, making it possible to predict creep behavior at constant or variable temperatures and also to calculate stress distributions through a wall containing a temperature gradient after a given strain is reached in a given time.

Tribofilm Formation As a Result of Complex Interaction at the Tool/Chip Interface during Cutting

“…It has been found that there are two types of tribofilms that are formed on the frictional body as a result of structural modification and interaction with the environment: (1) super-ductile and lubricating films [12]; and (2) tribo-ceramics with thermal barrier properties and increased hardness and strength [10,24,26,27,[30][31][32][33][34][35][36][37][38][39]. Tribofilms (SS) of the first type (SS-I) are observed as a result of structural activation marked by an increase in the density of atomic defects at the surface.…”

Nanocrystalline coating design for extreme applications based on the concept of complex adaptive behavior

“…Figure 4 presents TEM data on the microstructure of the surface of worn coated ball-nose end mill within a zone of the workpiece material buildup. [33][34][35][36][37] The 2.6 eV positive chemical shift of the XPS line Al 2s component can be interpreted as being related to the formation of Al 6 Si 2 O 13 mullite films. The first zone presents a tetragonal martensite structure of the adhered workpiece material ͑tool steel H13͒ that is related to EDX spectra ͑region 1͒.…”

Hierarchical adaptive nanostructured PVD coatings for extreme tribological applications: the quest for nonequilibrium states and emergent behavior

“…That is why this coating can sustain even ultrahigh-speed [207][208][209][210][211][212][213][214][215][216], which is two times higher compared to the monolayered coating (table 2). XPS data indicates the formation of Al-Si-O bonds in Al 6 Si 2 O 13 mullite tribofilms [209][210][211][212]. The nonstoichiometric titanium tribo-oxide (7.3%) and rutile TiO 2 (5.5%, table 2) are also formed on the friction surface.…”

“…This leads to formation of a nonstoichiometric titanium oxide films and rutile TiO 2 (table 2). XPS indicate formation of sapphire-like [207] triboceramics and nanofilms with a phase composition close to Al 6 Si 2 O 13 mullite [209][210][211][212][213][214]. A partial chemical transformation of aluminum in the TiAlCrSiYN monolayer coating has taken place: 28.6% of Al was retained in the complex nitride, 17.6% of aluminum oxidized with the formation of Al-Si-O oxide (mullite) and 8.8% of aluminum oxidized with the formation of trivalent Al 2 O 3 (sapphire, table 2).…”

“…Sapphire is the hardest oxide possessing an excellent thermal shock resistance at high temperatures [207,222], and mullite is a refractory compound that has similar high-temperature properties [209][210][211]214]. Both materials, especially sapphire, have excellent ability to accumulate energy from external impact [216,[222][223][224] that leads to reduction of entropy production during friction.…”