Failure Analysis of First and Second Stage Gas Turbine Blades

  • PDF / 2,758,242 Bytes
  • 10 Pages / 595.276 x 790.866 pts Page_size
  • 62 Downloads / 329 Views

DOWNLOAD

REPORT


TECHNICAL ARTICLE—PEER-REVIEWED

Failure Analysis of First and Second Stage Gas Turbine Blades Hassan Kazempour-Liasi . Ali Shafiei . Zahra Lalegani

Submitted: 2 July 2019 / in revised form: 20 August 2019 Ó ASM International 2019

Abstract Failures of vanes and blades of a dual-fueled GE Frame 5001 gas turbine are investigated in the present work. Mechanical tests and metallurgical analysis were performed to identify the mechanisms and causes of the failures. According to visual inspections and microstructural analyses, the failure mode of the blades was determined to be stress-rupture due to high-temperature exposures. The main reason for high-temperature exposure was the gathering and combustion of the fuel in the second stage vanes. Keywords Gas turbine  Vanes  Blades  Failure analysis  Superalloys

Introduction Turbine blades are one of the critical components of a gas turbine and are subjected to high temperatures and high stresses during their operation. These conditions can lead to premature failure of blades and consequently failure of the turbine [1, 2]. In-service failure of gas turbine blades occasionally occurs, and several cases are reported in the literature [3–5]. Turbine blades can fail by different mechanisms. These mechanisms include creep [3], fatigue [4], and oxidation and corrosion [5]. When a gas turbine blade failure occurs, failure analysis is usually performed to avoid the reoccurrence of the failure. The failure analysis of gas turbine blades can be carried out by

H. Kazempour-Liasi (&)  A. Shafiei  Z. Lalegani Metallurgy Department, Niroo Research Institute (NRI), Tehran 14665-517, Iran e-mail: [email protected]

metallurgical and mechanical analysis to determine the failure mechanism and the causes of the failure [3]. In the present work, the failure analysis of vanes and blades of a gas turbine is performed and the results are reported.

Background In this study, the failure of vanes and blades of a dualfueled GE Frame 5001 gas turbine with an average nominal capacity of 25 MW is reported. The turbine has two rows of vanes and two rows of blades. The blades are made from nickel-based superalloys, and vanes are made from cobaltbased and iron-based superalloys. All of the blades were made by precision casting method, and only the first stage blades had a diffusion coating. Also, the first and second stage vanes were cooled by air supplied from the compressor. The turbine had 7 unsuccessful start-ups before being started. After being started, the turbine worked for 185 h and then a decrease in the turbine speed was noticed. The gas turbine was inspected, and it was observed that the vanes and blades were severely damaged (Fig. 1). The details of the damage and the results of the failure analysis which was performed are presented here.

Experimental Works and Results Visual Inspections Visual inspections of the turbine and its components including blades, vanes, transition pieces, shrouds, and liner were performed. The results of the visual inspections are given as follows:

123

Data Loading...