The Effect of Multi-Walled Carbon Nanotubes Additives on the Tribological Properties of Austempered AISI 4340 Steel

Abstract

Due to a combination of optimal properties such as great strength, high hardness, good process ability, and good mechanical properties, AISI 4340 steel is widely used in many critical industrial applications such as nuclear, military, defense, and aerospace. It is also widely used in hydraulic forged machine tools, forged automotive crankshaft systems, shafts and gears, because of their improved characteristics, and its good tribological properties. The purpose regarding this work is to check the tribological characteristics of austempered AISI 4340 steel while dry and lubricated with machinery oil of SAE 30 grade as base oil. As received, AISI 4340 steel samples have been austempered to four definitely austenitic phase temperatures (850℃, 900℃, 1000℃, and 1050℃) for 90 minutes before being immersed in a mixture of potassium nitrite and sodium nitrite at 400℃ for 45 minutes. Friction and wear tests were then performed on austempered samples. Multi-walled carbon nanotube particles were blended at weight concentrations of 0.055, 0.1, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, and 0.45 with typical machinery oil of 30 grade as base lubricant oil. A pin on the disc wear configuration was used in the experimental investigation. The use of Multi-Walled Carbon Nanotube (MWCNTs) additives in the base oil resulted in a decrease in both friction coefficients and wear rates values when compared to typical base oil lubricant. The results also showed a reduction in both friction coefficients and wear rates as the sample's austempering temperatures were raised. Sliding surfaces were also photo micro graphed, and when the volume concentrations of Multi-Walled Carbon Nanotube particles in the normal base oil lubricant were increased, smoother surfaces with less damage were shown.

Dynamic Processes of Self-Organization in Nonstationary Conditions of Friction

“…One of the most important processes taking place in the tribocontact zone at extreme friction is undoubtedly the process of supramolecular self-organization in the lubricating layer [7]. Such signifcant characteristics of the friction process as the wear intensity of the materials of the friction pair, the temperature in the tribocontact, and the force of friction will depend on the peculiarities of the processes of supramolecular self-organization, which determine the thickness, structure, and shielding capabilities of the boundary lubricating layer [8,9]. Under the conditions of dominance of the limiting lubrication mode, an ordered structure of molecules or reaction products is formed on the surfaces of tribo-coupling elements, and surface friction is carried out between two weakly bonded adsorbed layers in an ordered structure.…”

Study the Machining Accuracy in Hole Reaming of Medium Carbon Steel Using Ultrasonic Vibration Method

“…near the drilled hole exit, expansion increment of hole diam., surface roughness of drilled hole, and burr height of drilled hole exit decreased by 16.79 to 20.2%, 31.5 to 33.6%, 18.54 to 21.68%, 24.87 to 25.36%, 46.75 to 57.63%, and 82.27 to 89.18%, respectively; compared with the common drilling of (Ti6Al4V), Furthermore, the experimental outcome also proved that the drilling technology of (RUAD) of (Ti6Al4V) using the 8-facet drill was practical and the cutting effects were excellent." There are many researches that dealt with this topic, and the uses of different variables, and reached results of scientific interest on this topic [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Sharma et al [26] studied the influence of cutting force and drilling temperature on glass hole surface integrity during rotary ultrasonic drilling.…”

The Effect of Stress Ratio on Fatigue Cracks Growth Rate in Aluminum Alloy

“…The study of the mechanical characteristics of aluminum alloys has been the subject of extensive research [21][22][23][24][25][26][27]. Other models that have been created thus far include [28], [29], [30,31], and [32]. However, the complete models created do not account for the influence of all parameters simultaneously and are not relevant to all materials [28][29][30][31][32].…”

“…Other models that have been created thus far include [28], [29], [30,31], and [32]. However, the complete models created do not account for the influence of all parameters simultaneously and are not relevant to all materials [28][29][30][31][32]. In order to understand the fatigue crack growth at various stress ratios and compare them, we will analyze the fatigue crack growth of the aluminum alloy (AA-AA-6063T832) used to make helicopter wings in this article.…”