Effects of microstructure and inclusions on very high cycle fatigue properties of compressor blade steels

Article type: Research Article

Authors: Wang, Pengfei^{a; b} | Wang, Weiqiang^{a; b; *} | Li, Aiju^c | Zhang, Ming^{a; b} | Li, Jianfeng^{a; d}

Affiliations: [a] School of Mechanical Engineering, Shandong University, 17923 Jingshi Road, Jinan, China | [b] Engineering and Technology Research Center for Special Equipment Safety of Shandong Province, 17923 Jingshi Road, Jinan, China | [c] School of Materials Science and Engineering, Shandong University, 17923 Jingshi Road, Jinan, China | [d] Key Laboratory of High Efficiency and Clean Mechanical Manufacture of Ministry of Education, 17923 Jingshi Road, Jinan, China

Correspondence: [*] Corresponding author. E-mail: wqwang@sdu.edu.cn.

Abstract: The fatigue behaviour of two steels, FV520B and KMN, with different heat treatment (marked as S and I) used in compressor blades was investigated in a very high cycle fatigue regime. It was found that the S-N curve of FV520B-I continuously declined with increasing the number of fatigue cycles and the cracks initiated from interior mostly, while the S-N curve of KMN-I had a slow decline after 107 cycles and surface fracture was observed mostly. Fatigue limit was observed in both low strength steels (FV520B-S and KMN-S). In order to explain the difference between the two steels, mechanical property tests, metallographic observation, and SEM analysis were carried out. The results showed that the very high cycle fatigue behaviour tended to occur in bimodal microstructure compared with basket weave microstructure and high strength steels were more obvious. Besides, inclusions of FV520B-I made the crack initiation sites shift from surface to interior of specimen.

Keywords: Compressor blade steels, very high cycle fatigue, S-N curve, fatigue strength, microstructure

DOI: 10.3233/SFC-170196

Journal: Strength, Fracture and Complexity, vol. 10, no. 1, pp. 1-9, 2017