Bouzid MAAMACHE

In this paper, the effect of tow thermal sprayed interlayers in torch brazing of WC based cermet to steel is investigated. The interface cermet/brazing/steel was characterized by SEM, EDS and XRD. Microhardness measurements and shear test were also done.Preliminary experimental results have shown that good bonding between cermet/brazing/steel was achieved and no voids were detected in the brazing junction. The use of the interlayer promotes the formation of interdiffusion zone, which possessed positive effects on the bond strength of the brazing joint. In the case of brazing without interlayert, this interdiffusion zone is minimal.Having performed line and surface micro analyses of various zones, post-brazing diffusions of Co and Ni and other elements were determined. The hardness distribution in microhardness measurements on this zone confirms the existence of element diffusion.

This paper examines the microstructure and the mechanical proprieties of WC-Co and low carbon steel joints obtained by Tungsten Inert Gas (TIG) brazing using two different thermal sprayed interlayers. On the connection zone, the characterizations of the WC–Co/interlayer/steel joints were studied by SEM, EDS and XRD. Microhardness measurements and shear test were made. The interlayer promoted the formation of interdiffusion zone, which possessed positive effects on the bond strength of the WC– Co/interlayer/steel joints. Having performed line and surface micro analyses of various zones, postbrazing diffusions of Co and Ni and other elements were determined. The hardness distribution in microhardness measurements on this zone shows the existence of element diffusion.

This work presents the study of the influence of successive repairs on the microstructure and mechanical behavior of the HAZ in a welded HSLA steel API X52. The results show that the succession of repairs in the same area has a direct influence on the microstructure morphology for all the welded joints samples when the mechanical properties by means of tension tests agree well with standards. However, the obtained values of the tensile strength of the various welded pipes are acceptable by the standards which imply the qualification of the welding process for all the repairs. Therefore, the previous investigations lead to the conservation of the same mechanical properties, i.e. the possibility of making more repairs that the standards specify. The grain size of the HAZ obtained after the first repair decrease in impact strength value as the number of repairs increases.