STUDY, DESIGN AND DEVELOPMENT OF A VACUUM FURNACE TO PERFORM PRESSURING DIFFUSION WELDING OF LIGHTWEIGHT ALLOYS

Abstract

The joining process carried out in the solid state, named Pressuring Diffusion Welding (PDW), is a modified and not well studied version of Diffusion Welding (DW). In PDW, the load applied to the samples to be joined varies in a sine wave pattern during the whole process instead of being kept constant as in DW. The PDW process produces high strength joints with a significant reduction of the processing time at the joining temperature, due to the fact that the load wave pattern enhances rupture of the oxide scales during the initial stages of the joining process. The oxides scales that are spontaneously formed in most lightweight materials such as Al and Ti alloys difficult joining since they limit atomic diffusion between the samples to be joined. Thus, prompt rupture and/or destabilization of the scales will hasten the joining procedure. Therefore, the objective of this project is to upgrade an existing vacuum furnace, currently used to produce joints by DW, in order to enable PDW joining; the joining apparatus should be capable of developing cycling loads ranging from 70 N to 11.2 kN, with an operative frequency comprised between 0.5 and 5 Hz. The mechatronic project of this new equipment has already started and this paper will present and summarize the main steps of the study, design and development of this equipment which allows joining of materials by the PDW technique. The selection and the dimensioning of the mechanical systems, the selection of the sensors and actuators and of an adequate data acquisition system to acquire, monitor and analyse the signals obtained to perform the automatic control of the furnace will also be discussed in the paper. Keywords: mechanical design; mechatronics; diffusion welding; pressuring diffusion welding; transition joints