This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

Recent developments in stainless steels

Infrared thermography for condition monitoring – A review

Effect of initial pH and temperature of iron salt solutions on formation of magnetite nanoparticles

Advanced structural health monitoring of concrete structures with the aid of acoustic emission

Magnetic flux leakage (MFL) detection is one of the most popular methods of pipeline inspection. It is a nondestructive testing technique which uses magnetic sensitive sensors to detect the magnetic leakage field of defects on both the internal and external surfaces of pipelines. This paper introduces the main principles, measurement and processing of MFL data. As the key point of a quantitative analysis of MFL detection, the identification of the leakage magnetic signal is also discussed. In addition, the advantages and disadvantages of different identification methods are analyzed. Then the paper briefly introduces the expert systems used. At the end of this paper, future developments in pipeline MFL detection are predicted.

https://www.mdpi.com/1424-8220/15/12/29845/pdf

Theory and Application of Magnetic Flux Leakage Pipeline Detection

A review of the application of acoustic emission techniques for monitoring forming and grinding processes

Pulsed eddy current (PEC) technique is used for the detection of sub-surface defects in electrically conducting materials. In order to extend the application of PEC technique for the detection of defects in thick non-magnetic materials, the detection sensitivity of the probe need to be enhanced. Detection sensitivity of the probe mainly depends on the probe configuration. In view of this, optimisation of probe configuration for deeper penetration of magnetic field in the material is carried out through finite element modelling. Present study focuses on model based design optimisation of PEC probe for the detection of sub-surface defects located more than 4 mm from surface in a 8 mm thick AISI type 316 stainless steel plate. The performance of ferrite cored absolute probe, ferrite cored send-receive probe and ferrite cored send-receive probe with outer shielding has been compared and optimised probe has been fabricated. The detection sensitivity of the optimised probe has been studied using machined notches introduced at different depths.

Optimisation of pulsed eddy current probe for detection of sub-surface defects in stainless steel plates

The tensile data involving austenitic Alloy C-276 suggest that this alloy is capable of maintaining appreciable structural strength at temperatures relevant to the sulfuric acid decomposition process related to the nuclear hydrogen initiative. Reduced failure strain and formation of serrations, characteristics of dynamic strain ageing (DSA), were noted within susceptible temperature regimes. An average activation energy of 55 kJ/mol, and work hardening index ranging from 0.68 to 0.75 were determined as functions of different testing temperature and strain rates. The occurrence of DSA was also associated with enhanced dislocation density. Depending on the testing temperature, a combination of ductile and intergranular brittle failures was observed with the tested specimens.

Dynamic strain ageing of an austenitic superalloy—Temperature and strain rate effects

Influence of fly ash and curing on cracking behavior of concrete by acoustic emission technique

A set of experiments has been carried out to examine the characteristics of the acoustic emission (AE) generated during tensile deformation of AISI type 304 stainless steels. Two grades of steels—nuclear and commercial; and two types of specimens—unnotched and notched, have been used in this study. The AE total counts obtained in different specimens for specific strain levels have been analysed by regression analysis approach of data analysis. The results indicate that the AE counts from notched specimens are usually higher than those from unnotched specimens in the nuclear grade steel, unlike the opposite results obtained for the commercial grade steel in the present study and also reported results for other materials. These results have been explained with the help of the different sources of AE in the two grades of stainless steels.

C. K. Mukhopadhyay

Papers

A review of the application of acoustic emission techniques for monitoring forming and grinding processes

Optimisation of pulsed eddy current probe for detection of sub-surface defects in stainless steel plates

Dynamic strain ageing of an austenitic superalloy—Temperature and strain rate effects

Influence of fly ash and curing on cracking behavior of concrete by acoustic emission technique

Acoustic emission from tensile deformation of unnotched and notched specimens of AISI type 304 stainless steels