Studying the Erosion Corrosion Behavior of NiCrAlY Coating Layer Applied on AISI 446 Stainless Steel Using Thermal Spray Technique

Ghufran Matrood,Hussain Yousif,Ahmed Al-Gaban

doi:10.30684/etj.v38i11a.1691

Abstract

Erosion-Corrosion behavior of NiCrAlY coatings deposited on 446 stainless steel samples by flame thermal spraying was performed in this research. The hardness of uncoated and coated sample is measured, using HVS-1000 Digital Micro hardness Tester. The results of hardness show that the coated samples have higher hardness than uncoated samples. Microstructure and phase analysis of the coating layer was observed by using optical microscope, X-ray diffraction (XRD), and SEM respectively. Erosion –Corrosion test was performed in different period of time (6, 12, and 18 hr.) using the erosion-corrosion system. The result shows that because of uniform distribution and homogeneous of coating layer, weight loss was very low and approximately equal in all period of testing time.

Highlights

The coating layer- substrate cross section which represented in( Figure 6, b) shows the thin line between coating layer and the substrate, this thin line related to the fusion that creates along the coating layer- substrate inter face
The NiCrAlY coatings were successfully deposited on 446 stainless steel by using flame thermal sprayed process
Microhardness test showed that the hardness of the coated samples was in the range between (600-650 Hv), while the hardness of uncoated samples was in the range between (300-330 Hv)

Summary

Introduction

Erosion–corrosion of metallic materials describes the material degradation process where mechanical wear by solid particles, liquid or the combination of both processes interacts with corrosion caused by dissolution or surface oxidation [1].In high-temperature acidic environments, erosion can increase corrosion by removing the protective passive film and exposing the underlying metal surface to the corrosive medium [1,2,3] or by creating less protective surface films with embedded particles [4] and increasing the mass transfer coefficient by creating turbulent conditions or by creating a rough surface [5].The resistance to abrasion, erosion, and corrosion of the components are greatly increasing by depositing a protective coating layer and this is growing industry of developing economic significance [6, 7]. Erosion–corrosion of metallic materials describes the material degradation process where mechanical wear by solid particles, liquid or the combination of both processes interacts with corrosion caused by dissolution or surface oxidation [1]. Nickel based alloys coating is utilized in applications that require resistance to wear combined with hot corrosion or oxidation resistance [8]. MCrAlY (where M = Co or Ni ) series are used as a part of TBC (Thermal barrier coating ) coating system as a bond coat bonding aiding layer and protective oxides former or as a final coating layer to protect the super alloy and steels from the harsh and hot environments [9, 10]. There are many techniques available, e.g. electroplating, vapor depositions, thermal spraying etc

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