Excellent Seizure and Friction Properties Achieved with a Combination of an a-C:H:Si DLC-Coated Journal and an Aluminum Alloy Plain Bearing

Abstract

Friction occurring between the crank journal and main bearings accounts for a large share of the mechanical losses of automotive engines. The effects of higher in-cylinder pressures and narrower bearings have raised the specific load applied to bearings, making it essential to secure sufficient seizure resistance as well. For the purpose of meeting both requirements, we have endeavored to reduce friction and improve seizure resistance by applying a diamond-like carbon (DLC) coating to the crank journal. In the present study, a bearing tester was used that has received international standard certification from the International Organization for Standardization for reproducing the sliding behavior occurring between the crank journal and main bearings in actual engines. Test results indicated that a silicon-containing hydrogenated amorphous carbon (a-C:H:Si) DLC-coated journal showed a definite friction reduction and a marked improvement in seizure resistance. An acoustic emission (AE) analysis revealed that an adhesion-induced AE peak observed for a steel journal was not seen for the DLC-coated journal. Additionally, tin and aluminum elements in the bearing material that were transferred to and observed on the sliding surface of the steel journal were not seen on the DLC-coated journal. Accordingly, the low affinity of the DLC coating with these metal elements presumably led to the clear friction reduction and superior seizure resistance displayed by the DLC coating.

A review of advances in tribology in 2020–2021

“…www.Springer.com/journal/40544 | Friction For DLC films serving in special environments, such as parts with high load and high speed, appropriate doping will be carried out on DLC films to change the bonding mode of the cross-linked carbon matrix hybrid network inside the film and the chemical state of the film surface, as well as the surface texturing, so as to improve the performance of the film and realize the application in actual working conditions. Doping of hydrogenated amorphous carbon DLC exhibited significant improvement of tribological properties further, such as single-layer tungsten-doped (a-C:H:W) [171] and multilayer silicon oxide containing (a-C:H:Si:O/a-C:H) 25 amorphous carbon coatings [172], silicon-containing hydrogenated amorphous carbon DLC (a-C:H:Si) [173], and so on. The friction and wear behavior of DLC was revealed to mainly depend on their surface topography [174], and a considerably lower friction coefficient was achieved under severe working conditions by DLC coatings combination with the texturing [175].…”

AI‐Enabled Metal‐Polymer Plain Bearing Based on the Triboelectric Principle

“…Si-incorporated diamond-like carbon (Si-DLC) films have been applied to bearings, drillers, and so on [16,17] due to their outstanding performance, such as anti-abrasion abilities, hightemperature stability, low surface roughness, and exceptional adhesion with the substrates. [16,[18][19][20][21] Besides, Si-DLC films can be an ideal candidate as a triboelectric dielectric material for sensing due to their anti-abrasion abilities and higher electrical output than DLC films [22] Metal-polymer plain bearings (MPPB) have found increasing applications in various types of machinery owing to specific favorable characteristics, such as high load-carrying capacity, the possibility of use in dry friction and boundary conditions, damping ability, etc. [23] These advantages make them attractive for various applications, such as high-speed turbo-machinery, machine tool spindles, compressor pumps, and precision grinder spindles.…”

Running-in for Low Friction between Silicon-Containing Aluminum Alloy and Bearing Steel in Engine Oil

“…Aluminum is an attractive material for engine components owing to its lightweight, high strength, high stiffness-to-weight ratio, and good corrosion resistance. However, soft aluminum easily adheres to its counterpart [8][9][10][11] and exhibits severe wear [9,12] under boundary lubrication. Nevertheless, the addition of silicon to aluminum improves its wear-resistant properties [13,14] and extends its application to sliding components in internal combustion engines (i.e., sliding bearings [8], engine blocks [13,14], and piston assembly [15,16]).…”