Analysis on High Temperature Fretting Wear Behaviour of 20Cr13 Stainless Steel

Fretting wear has been widely found in various fields, such as mineral mining, petrochemical, water conservancy and hydropower engineering, rail transit, and aerospace. The low reactivity character of 20Cr13 stainless steel and its superior mechanical properties make it a candidate of choice for the end-stage turbine blade. However, fretting wear and fatigue crack are induced in the turbine blade for complicated operating conditions (high speed, high stress, and high temperature). High temperature is one of the most basic challenges faced by stainless-steel blade in the power serving of gas turbines. In this paper, the effect of ambient temperature on the fretting wear behaviour of 20Cr13 stainless steel with distinctive fretting displacements was studied, the time-vary characteristics of friction coefficient with distinctive temperatures were analyzed. Fretting running regime, wear morphology, debris behaviour and wear mechanism within different ambient temperatures was discussed. This work holds future promise for providing a reference in the theoretical results and the analyzed method for the design of wear resistance and corrosion resistance at high temperature condition. The result demonstrated that the fretting running regime for the smaller displacement was not modified by raising the temperatures. Clearly, worn center was prone to maintain an excellent sticking state. Conversely, abrasive wear and material spalling characteristics were significantly observed on the edge of worn surfaces. Time-varying curve of friction coefficient was experiencing wild swings in this condition. As the medium displacement condition at normal temperature, the F_t–D curves all turn to the irregular oval, which corresponded a fretting running status to mixed regime (MFR) in whole contact zone. Mixed fretting regime for the medium displacement had transformed from a slip regime after the ambient temperature exceeds than 100 ℃. Moreover, the friction coefficient and wear volume first ascended and then descended with increasing temperature. Wear debris from the adherent third layer evolved into the rolling micro-particle, which had also benefited from temperature raising. A significant decrease in friction coefficient and wear volume were also observed with a decrease in dissipated energy should be credited with a sliding lubrication effect from finely debris. Accordingly, some abrasive wear characteristics such as ploughing were typical observed in worn surface. As the large displacement condition at normal temperature, the F_t-D curves all turn to the parallelogrammatic, which corresponds a fretting running status to slip regime (SR) in whole contact zone. Time-varying curves of friction coefficient showed an elevated-stable, this phenomenon had been attributed to the dynamic balance between debris production and removal. In slip regime, large fretting displacement made it difficult to maintain the compact debris layer in the worn center, and undergo severe wear and a drastic friction increase. Wear debris from the slip regime which could be formed a special ‘glaze layer’ with high-temperature induction. After the glaze layer was formed, the tribo-system transitioned in fact to a two-body contact configuration between Si₃N₄ ball and glaze layer, and adhesive wear and abrasive wear were the dominant wear mechanism. As a result, the material loss could be alleviated more effectively via ‘glaze layer’, while the problem of abrasive wear and adhesive wear on the ceramic counterpart could not be ignored.