Optimization of several surface treatment processes for alleviating fretting damage of a locking pin

The operational safety and reliability of a variable gauge train are affected by the anti-fretting wear performance of the locking mechanism. The main purpose of this study is to optimize the surface treatment process for a locking pin material under actual service conditions to alleviate fretting damage. Based on the two basic principles of surface strengthening and friction reduction, a substrate (AISI 4135 steel) surface was treated by laser quenching (LQ), plasma nitriding (PN), and bonded MoS2 coating. Systematic fretting wear tests were conducted, and the wear behavior and damage mechanism of various treated surfaces were comprehensively investigated. The results indicate that the wear resistances of the LQ- and PN-treated surfaces were significantly improved, and their main wear mechanisms were abrasive wear, delamination, and oxidation wear. The MoS2 coating exhibits the lowest friction coefficient and energy dissipation due to its self-lubricating property, but it incurs the highest wear rate and failure in the form of plastic deformation. Furthermore, the rough compound layer with a high hardness on the PN-treated surface is conducive to the formation and maintenance of the third-body contact at the fretting interface, consequently resulting in a significant reduction in wear. An optimal surface treatment process for alleviating fretting damage of the locking pin is recommended via comprehensive evaluation, which provides a reference for the anti-fretting protection of related mechanical components.

Nonlinear Vibration Characteristics of the Involute Spline Coupling in Aeroengine with the Parallel Misalignment

In order to control the vibration of the involute spline coupling in aeroengine well and reduce the fretting wear, a bending–torsion coupling nonlinear vibration model of the involute spline coupling with the misalignment was proposed, and a dynamic meshing stiffness function with multiteeth engagement was established. Then, the influence of different misalignment, wear, and rotation speeds with different misalignment on the nonlinear vibration characteristics of the involute aviation spline coupling was explored. The result shows that with an increase of the parallel misalignment, the system experienced the state of a single period, a quasiperiod, multiperiod, and chaos but finally only alternated between the quasiperiod and the chaos state. The uneven wear of each tooth of the spline displayed a significant influence on the vibration of the spline coupling, and the influence of the uniform wear was smaller under given conditions here. Furthermore, with an increase of the speed, the larger the misalignment was, the more times the system entered or left the chaos state were. The model proposed here is found to be closer to the actual working conditions, and the analysis results can provide more accurate external load conditions for the prediction of the fretting damage of the spline coupling in aeroengine.

Finite element analysis of the effects of load amplitude and phase on crack initiation location in fretting fatigue

Fretting fatigue is a major form of fretting damage affected by various factors. In this paper, the Ruiz parameter is used to predict the variation in the initiation location of the fretting fatigue crack with the amplitude of load, providing a reference for the study of the initiation characteristics of fretting fatigue cracks. The influence of the phase difference between loads is also considered. Three numerical models are established using ABAQUS for simulation experiments. Four phase difference angles are involved, i.e. 0°, 90°, 180° and 270°. Results indicate that for 0° phase difference, the maximum of initiation parameter K is always observed at the trailing edge of the contact zone (near the loading side of the strain load) with the increase of load amplitude, such that the fretting fatigue crack initiates at the trailing edge. However, for 90°, 180°, and 270° phase differences, the maximum of initiation parameter K shifts from one edge of the contact to the other with the increase of load amplitude. In addition, it is observed that the maximum and minimum initiation parameter K values are obtained for 0° and 180° phase differences, respectively, while the values of K for 90° and 270° phase differences are approximately equal and between those for 0° and 180°.

Tribological Properties of Steels

This chapter covers the friction and wear behaviors of carbon, alloy, and tool steels. It begins a review of commercially available shapes and forms. It then describes the metallurgy and microstructure of various designations and grades of each type of steel and explains how it affects their performance in adhesive and abrasive wear applications and in environments where they are subjected to solid particle, droplet, slurry, and cavitation erosion and fretting damage.

IMPROVING OF FRETTING RESISTANCE INTERMETALLIC Ti2AlNb ALLOY

The results of research on improving the fretting resistance of a titanium alloy made of orthorhombic titanium aluminide Ti2AlNb by forming a coating consisting of a barrier and an outer layer on the surface using an industrial vacuum-arc installation MAP-3 are presented. The dependences of the total wear and the coefficient of friction of samples made of Ti2AlNb alloy with and without coating in combination with a counterbody made of high-strength welded dispersed-hardening alloy during fretting damage tests at room (20 °C) and elevated (700 °C) temperatures are established. The kinetics of oxygen saturation of the surface of samples made of Ti2AlNb alloy with and without coating at the operating temperature of the alloy based on 200 h is shown. The phase and elemental compositions of the fretting-resistant coating after high-temperature exposure are investigated.

Effects of Dispersant and ZDDP Additives on Fretting Wear

This paper examines the effect of dispersant and anti-wear additives on fretting wear in lubricated bearing steel contacts. Reciprocating sliding ball-on-flat fretting tests with a stroke length of 50 μm have been carried out on steel-to-steel contacts in both dry and lubricated conditions. Wear and friction coefficient have been measured, and surface characterisation has been carried out using optical techniques to investigate fretting wear. The presence of base oil reduces fretting wear markedly compared to dry conditions, but fretting damage is still observed at low reciprocation frequencies. As frequency is increased, there is a transition from oxidative to adhesive/scuffing damage. The anti-wear additive ZDDP is effective in forming a tribofilm on the surfaces and reducing visible oxidation and wear. A succinimide dispersant also reduces the accumulation of solid debris but does not alleviate wear damage. The combination of both ZDDP anti-wear additive and dispersant in base oil appears to provide significant protection against fretting wear.