2013 Volume 54 Issue 9 Pages 1851-1856
Plasma transferred arc welding (PTAW) is widely employed to improve the quality of components whose surface is subjected to severe wear conditions. However, the wear properties of these coatings is significantly affected by the welding process adopted during the deposition of the coatings. This paper details an investigation of the microstructure, composition, hardness and wear characteristics of Stellite12 Co-based coatings with different welding currents. Optical microscopy (OP), scanning electron microscopy/energy dispersive spectrum analysis (SEM/EDS), X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the microstructure. An increase in the arc current increased the dilution of the DSS and changed the composition as well as the dendritic arms coarsening of the Co-based coatings. Increasing the arc current gives rise to a reduction in the hardness of the coatings, whereas reduction in the hardness of the coatings is accompanied by a reduction in their wear resistance with the exception of the lowest current sample. Additionally, the microstructure of the welding heat affected zone (HAZ) during PTAW was also studied. The heat affected zone was decorated with some needle-type austenites nucleated from grain boundary austenite, but without σ-phase. Moreover, some chromium-rich precipitates were also detected in the welding heat affected zone of the specimens during PTAW.
