Abstract

Austenitic stainless steels are the wide-spread materials, used mainly in the power industry. In that kind of engineering application, structural parts of rotating elements reach during their lifetime very high numbers of loading cycles, exceeding 107 numbers of cycles. With regard to this fact, the data of ultra-high cycle fatigue properties are needed to be used in the qualified design. Increasing demands on the efficiency cause the increase of the operating temperature, and exposition of these materials to the elevated temperatures can cause some important structural changes, which result in the sensitising of the structure. In this study authors present their own experimental results about fatigue properties of AISI 316Ti austenitic stainless steel after sensitising, in the ultra-high cycle region (Nf = 106 ~ Nf = 3×109 cycles). Fatigue tests were carried out using ultrasonic fatigue testing device with frequency f = 20 kHz at the coefficient of cycle asymmetry R = -1, and temperature T = 20±5°C. In the ultra-high cycle region was observed the continuous decrease of the fatigue properties of the AISI 316Ti, and there was recorded the negative effect of the sensitising on the ultra-high cycle fatigue properties of the AISI 316Ti.

Highlights

  • Austenitic stainless steels are the important category of the technical materials, which have found the wide range of the applications

  • Authors in this study present their own experimental results of the influence of sensitisation on the ultra-high cycle fatigue properties of the AISI 316Ti austenitic stainless steel

  • The degree of sensitisation was evaluated as a ditch, because the careful observation taken on the multiple places shows a high degree of intergranular attack and individual grains were wholly surrounded by the pits (Fig. 4)

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Summary

Introduction

Austenitic stainless steels are the important category of the technical materials, which have found the wide range of the applications. In special cases where these steels are exposed to increased temperatures for some time (after welding or in the application in the power industry), significant changes of the microstructure can occur, which affect and decrease the ability to create the protective passive layer. This phenomenon is called sensitisation [1, 2]. Authors in this study present their own experimental results of the influence of sensitisation on the ultra-high cycle fatigue properties of the AISI 316Ti austenitic stainless steel

Material
Sensitisation treatment and evaluation
Fatigue tests
Results
Fractography analysis
Sensitisation
Fatigue properties
Conclusions

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