Wear Characteristics of Superalloy and Hardface Coatings in Gas Turbine Applications–A Review

Abstract

In the gas-turbine research field, superalloys are some of the most widely used materials as they offer excellent strength, particularly at extreme temperatures. Vital components such as combustion liners, transition pieces, blades, and vanes, which are often severely affected by wear, have been identified. These critical components are exposed to very high temperatures (ranging from 570 to 1300 °C) in hot-gas-path systems and are generally subjected to heavy repair processes for maintenance works. Major degradation such as abrasive wear and fretting fatigue wear are predominant mechanisms in combustion liners and transition pieces during start–stop or peaking operation, resulting in high cost if inadequately protected. Another type of wear-like erosion is also prominent in turbine blades and vanes. Nimonic 263, Hastelloy X, and GTD 111 are examples of superalloys used in the gas-turbine industry. This review covers the development of hardface coatings used to protect the surfaces of components from wear and erosion. The application of hardface coatings helps reduce friction and wear, which can increase the lifespan of materials. Moreover, chromium carbide and Stellite 6 hardface coatings are widely used for hot-section components in gas turbines because they offer excellent resistance against wear and erosion. The effectiveness of these coatings to mitigate wear and increase the performance is further investigated. We also discuss in detail the current developments in combining these coating with other hard particles to improve wear resistance. The principles of this coating development can be extended to other high-temperature applications in the power-generation industry.

A Harmonic Balance-based Method to Predict Nonlinear Forced Response and Temperature Rise of Dry Friction Systems Including Frictional Heat Transfer

“…Since turbine blades work at high temperature environment, the initial temperature of the contact interface is close to 600℃ to 800℃ [13]. Due to the frictional heat, the increased contact temperature may lead to melting and ablation of superalloy material on the interface [8]. In addition, the friction coefficient changes with the contact temperature, resulting in unexpected dynamic behavior, such as jamming [14][15].…”

“…It has been observed in aircraft engine tests that the temperature increases drastically (usually over 300℃) on the contact surface of dry friction dampers under high rotational speed and heavy aerodynamic load. The interface temperature rise will change the physical and chemical properties of the contact material, leading to degradation, wear and even melting on the frictional region [6][7][8][9]. In terms of dynamics, the increased temperature alters the normal force level [10][11], contact parameters [12] and further changes the vibration responses [13], producing seriously negative effects like lifting-off and jamming of dampers [14][15].…”

Materials challenges in hydrogen-fuelled gas turbines

“…Commonly applied materials able to meet the mechanical requirements are wrought Ni base superalloys such as Hastelloy X, IN617, Nimonic 263, Haynes 188, or Haynes 230 and SS309 [22,24,25,29]. In order to keep the surface of these alloys sufficiently below their melting point, internal air cooling and thermal barrier coatings (TBC) (see Section 2.4) or ceramic tiles are applied as the combustor lining.…”

The effect of aluminide coating on the steam oxidation behavior of SS321 steel at 700 °C

“…Austenitic steels and nickel-based superalloys are suitable candidates for increasing the efficiency of heat exchangers at temperatures higher than 700 °C [3,4]. If a suitable coating is used, austenitic steels can be a suitable alternative to nickel-based superalloys, which are expensive [5]. A high percentage of superheaters are made of SS321.…”