Mechanical Investigations of ASTM A36 Welded Steels with Stainless Steel Cladding

Pavaret Preedawiphat,Sedthawatt Sucharitpwatskul,Mai Noipitak,Numpon Mahayotsanun,Keerati Sa-Ngoen,Kuniaki Dohda,Pongsak Tuengsook

doi:10.3390/coatings10090844

Abstract

The in-service life of ASTM A36 welded steel pipes in power plants is often shortened by ash corrosion. During the heating condition, the ash deposition on the welded steel pipes gradually reduces the thickness of the pipes, thus, reducing the lifetime. Instead of replacing the pipes with new ones, the cost could be significantly reduced if the lifetime could be further extended. Weld cladding was the method selected in this study to temporarily extend the service life of welded pipes. This paper performed the mechanical investigations of A36—A36 welded steel plates after coating the surfaces with 309L stainless steel with a cladding method. The residual stress was also tested to observe the internal stresses developed during the welding processes of A36—A36 specimens. The comparison between the coated and non-coated surfaces of welded steels was performed by using the tensile tests (at room and elevated temperatures), corrosion (pitting corrosion, intergranular corrosion, and weight-loss corrosion) tests, and wear (shot blasting) tests. The life-extension of both coatings was evaluated based on the tensile tests and the corrosion and wear tests provided the qualitative evaluations of the coating performance. The results showed that surfaces coated by cladding could be used to temporarily extend the life of ASTM A36 welded steel under the studied conditions.

Highlights

ASTM A36 is a carbon structural steel generally used in welded constructions and power plants [1].In coal-fired and biogas power plants, ash can deposit on steel surfaces and cause severe corrosion [2,3].Under cyclic thermal conditions coupled with ash corrosion, the lifetime of these structural components is significantly reduced [4], and one of the main reasons is the thickness reduction or weight loss on steel surfaces [5]
The 309L stainless steel layer in weld direction (WD)-25 provided lower tensile strength
On the cladding sites (P1 and P2), pitting corrosion occurred both on the 309L stainless steel layer

Summary

Introduction

ASTM A36 is a carbon structural steel generally used in welded constructions and power plants [1].In coal-fired and biogas power plants, ash can deposit on steel surfaces and cause severe corrosion [2,3].Under cyclic thermal conditions coupled with ash corrosion, the lifetime of these structural components is significantly reduced [4], and one of the main reasons is the thickness reduction or weight loss on steel surfaces [5]. ASTM A36 is a carbon structural steel generally used in welded constructions and power plants [1]. In coal-fired and biogas power plants, ash can deposit on steel surfaces and cause severe corrosion [2,3]. Under cyclic thermal conditions coupled with ash corrosion, the lifetime of these structural components is significantly reduced [4], and one of the main reasons is the thickness reduction or weight loss on steel surfaces [5]. The corrosion consequences can lead to component failures, safety and environment hazards, downtime, and high maintenance costs. One of the standard techniques to prevent such failures or extend the lifetime is surface coating [6]. Stainless steels have been widely coated on Coatings 2020, 10, 844; doi:10.3390/coatings10090844 www.mdpi.com/journal/coatings

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