The Effect of Heat Treatment on the Microstructure and Phase Composition of Plasma Sprayed Al2O3 and Al2O3-TiO2 Coatings for Applications in Biomass Firing Plants

Airingas Šuopys,Romualdas Kėželis,Rolandas Uscila,Viktorija Grigaitienė,Simona Tučkutė,Martynas Lelis,Liutauras Marcinauskas,Mindaugas Aikas

doi:10.3390/coatings11111289

Abstract

This study presents the thermal and chemical resistance of plasma-sprayed Al2O3 and Al2O3 doped with 13 wt.% of TiO2 coatings and their suitability for the fire grate of straw pellet furnaces. Coatings were deposited on steel substrates using direct current atmospheric pressure plasma spraying. The surface structure, elemental, and phase composition of formed coatings were analyzed before and after the thermal treatment, imitating natural application conditions. For the experiment, the annealing temperature was 500 °C for twenty-five cycles (80 min each). It was found that the steel substrate oxidized after five thermal cycles, and the formation of iron oxides was observed. The elemental composition of the Al2O3 and Al2O3-13 wt.% TiO2 coatings remained unchanged even after 25 cycles of heat treatment. The X-ray diffraction (XRD) results revealed that the alpha-Al2O3 to gamma-Al2O3 phase ratio in the Al2O3-TiO2 coating was reduced by only 8.7% after 25 cycles.

Highlights

The need for functional materials always increases—many systems and their parts or sections must be durable and resistant to chemical or thermal effects and corrosion.Inevitably, surface treatment is necessary for performance, longevity, and quality purposes.One of the most effective ways to prolong the lifetime of certain parts or systems is protective coatings
Al2 O3 and Al2 O3 -13 wt.% TiO2 coatings were deposited on steel (P265GH) substrate at atmospheric pressure using a direct current (DC) plasma torch developed at Lithuanian
Al2O3 and Al2O3-13 wt.% TiO2 coatings were formed via atmospheric pressure plasma spray technology using air as the plasma forming gas

Summary

Introduction

The need for functional materials always increases—many systems and their parts or sections must be durable and resistant to chemical or thermal effects and corrosion.Inevitably, surface treatment is necessary for performance, longevity, and quality purposes.One of the most effective ways to prolong the lifetime of certain parts or systems is protective coatings. The need for functional materials always increases—many systems and their parts or sections must be durable and resistant to chemical or thermal effects and corrosion. Surface treatment is necessary for performance, longevity, and quality purposes. One of the most effective ways to prolong the lifetime of certain parts or systems is protective coatings. Ceramic coatings deposited employing plasma spray technology become a viable alternative to organic and polymer-based coatings for surface protection applications. The most frequently used metal oxide ceramics are alumina, zirconia, titania, yttria, and their composites materials. Thermal and plasma spraying methods appear as the most common ways to form a protective ceramic coating on the material surface [1]

Methods

Discussion

Conclusion