Corrosion behavior of HVOF sprayed coatings of Ni-TiC and Ni-(Ti, W)C SHS produced composite powders and Ni+TiC mixed powder

摘要

In this research, the corrosion behavior of different types of (Ni-TiC) coatings produced by high velocity oxy-fuel (HVOF) technique was studied. Ni-TiC and Ni-(Ti, W)C composite powders were produced by self-propagation high temperature synthesis (SHS). These powders as feedstock were thermally sprayed on steel substrates in comparison with a conventional powder mixture of Ni+TiC. The microstructures of the produced coatings were characterized using SEM micrographs. The presence of different phases in the microstructure was investigated using EDS analysis and XRD patterns. Also, the behavior of the coatings against a corrosive media was studied using Tafel polarization tests. The results show that the Ni-TiC and Ni(W-Ti)C coatings exhibited better corrosion resistance than conventional Ni+TiC mixture coating due to the increment of the homogeneity of the structure and the decrement of the porosity level. In addition, the presence of W in the microstructure of Ni(W-Ti)C coating provided the least pitting and highest general corrosion.