Study of Influence of the Peak Current Time in Microstructure of a Coating Hard Made by GTAW-P Process

摘要

This paper presented analysis in order to show the influence of welding pulse parameters on the microstructure of the deposit, where a coating performed by GTAW-P process (Tungsten Arc Welding with the Atmosphere Gas with deposition Powder). The coating was an alloy of cobalt based on a substrate of a steel SAE 1020. The coating was performed with pulsed current between 120 and 180 A, and the variations of pulse parameters occurred between the time base and peak currents. Metallographic analysis by electronic scanning microscopy (SEM), micro hardness testing and determination of the dilution rate of the material were carried out. Thus, the results demonstrated that sample 3 showed better results, such as the size of finer grains, medium high hardness about 65 HRC, 4.3% dilution rate and a lower heat transfer. Therefore, the spectrum shown by scanning electron microscopy revealed the presence of hard carbides (Co, Cr and W) in interdendritic region of the deposit, which explained the high levels of hardness.