Brazing of Alumina/304 Stainless Steel for rotating joint applications – Master Thesis Davide Carniani

Author: Davide Carniani; Type of thesis: Master Thesis
Abstract: Mechanical face seal is a type of seal widely used in rotating equipment. They apply in all instances where movement is required, from robotics to automotive. Among the many existing fields of application, pumping systems are quite demanding in terms of performance, especially when the device has to be used in harsh environments.
The aim of the project was the development of the process for alumina (Al2O3) and 304 stainless steel in one piece for the realization mechanical systems (mechanical face seals) working in chemically aggressive environments.
Vacuum brazing technique was selected as joining technique to overcome incompatibility in the nature of chemical bonds of the materials involved. Home-made copper-based active brazing alloy (ABA) prepared starting from powders and binder was used to join two materials. A custom oven heated by IR-lamp until 1000°C was used to perform the brazing process.
The objective of the work was to study the process parameters: time of brazing, ramps of heating and cooling, temperature of brazing, issues in the join of chemically and thermo-mechanically different materials, amount of ABA to be applied and types of the binder.
Particular attention was given to the binder, changing the ease of brazing paste application and paste stability during storage, which are important factors for the industrialization of the process.
The process developed was shown to provide good integrity of the samples produced.