Structure and Mechanical Properties of a Copper Combustion Chamber throughout Its Life Cycle

Abstract

The material of a combustion chamber is subjected to high thermal and mechanical fatigue that can result in premature failure. Nevertheless, there is very little information in the literature concerning its characterization. In this work, the study of some properties of the copper combustion chambers in water heaters throughout their life cycle is described. The microstructure, hardness, morphology, mechanical strength and roughness were evaluated, from the pristine copper sheet to a chamber subjected to 53,000 cycles. Throughout the whole cycle, changes were detected in the organization of the crystalline structure. Both after conformation and after completing the manufacturing process, the material exhibits a preferential orientation according to the direction [110], which is the most favorable to degradation of the material by thermal fatigue. The prevalence of the less dense crystallographic planes of the material in all stages of the life cycle allowed a better diffusion of the oxidant species facilitating the corrosion of the material. The oxidation products did not form a passivated layer and detached from the bulk copper, causing a progressive deterioration of the material.