The effects of applied stress and heat treatment on the stress corrosion cracking behaviour of manganese bronze.

Type of content
Theses / Dissertations
Publisher's DOI/URI
Thesis discipline
Mechanical Engineering
Degree name
Master of Engineering
Journal Title
Journal ISSN
Volume Title
Manz, Olaf

Stress corrosion cracking (SCC) is a cracking mechanism requiring a tensile stress on a susceptible material in a corrosive environment. Changes to, or the removal of, any of these three conditions can cause significant impacts on the SCC susceptibility. The propagation of SCC is typically described as being predominately transgranular (TG) or intergranular (IG).

AW Fraser is an original equipment manufacturer (OEM) that produces extrusions and precision machined components from bronze alloys. The particular alloy used for this project’s investigations is a manganese bronze designated as UNS C86300, which is primarily used in high-wear engineering applications such as bushings in earthmoving equipment due to its excellent strength and wear resistance. The material consists of equiaxed grains of the BCC β-phase, with iron-rich κ-phase precipitates within the grains and at grain boundaries. Cracks were discovered in parts of rough-machined UNS C86300 after as little as 24 hours when stored outside. A failure analysis determined the cracking mode to be intergranular SCC due to the residual stresses from rough machining. A preliminary project found UNS C86300 to be susceptible to SCC in an environment of deionised water. The current method AW Fraser uses to prevent SCC in these parts is to cast sections far thicker than the final part to reduce the residual stresses induced by the clamping force of the lathe chuck, yet this process increases production time and cost significantly.

SCC in copper-based alloys has been extensively researched after first being documented in the late 19th century, and the effects of the environment, material, and stress are well understood. However, the majority of the research focuses on α-phase alloys. Although there are some documented cases of β-phase brass alloys experiencing SCC in deionised water, there is a gap in the literature concerning this phenomenon.

To contribute towards filling this gap in the literature and to provide valuable data to AW Fraser, the effects of applied stress and heat treatment on the SCC behaviour of UNS C86300 have been investigated. As-received, stress-relieved, annealed, and quenched C-ring specimens were tested in deionised water at applied stresses ranging from 25–95% of the material’s yield strength. Dezincification susceptibility tests and various analytical methods have been conducted on selected specimens to determine any relationships between failure time and applied stress or heat treatment.

Ngā upoko tukutuku/Māori subject headings
ANZSRC fields of research
All Right Reserved