Study On High Temperature Sulfur Corrosion Characteristics Of Nickel-Based Alloy Cladding Layer

In the process of coal-fired power generation,due to its complicated working environment,severe high-temperature sulfur corrosion of the superheater tubes of the pulverized coal furnace will occur.However,the traditional superheater pipe is difficult to meet the overall corrosion resistance requirements of the boiler.Laser cladding technology plays an important role in the research of wear-resistant and corrosion-resistant coatings due to its unique advantages.The use of laser cladding technology to prepare corrosion-resistant alloy coatings on the surface of superheater tubes not only meets the requirements of corrosion resistance but also reduces production costs.Considering the synergistic effect of Cr and Mo elements in the actual high temperature sulfur corrosion working environment,this paper used laser cladding technology to prepare four different Ni-Cr-Mo alloy cladding layers with different Cr and Mo contents.And the phase composition,microstructure,Vickers hardness and sulfate-resistant high-temperature corrosion resistance of the cladding layer were characterized.The experimental results show that the four Ni-Cr-Mo alloy cladding layers form a good metallurgical bond with the matrix.The main phases are nickel-based solid solution formed by Cr,Mo,Fe and Ni and the retained metastable phase MoNi4.The Mo element in the microstructure of the Ni-Cr-Mo alloy cladding layer is segregated at the grain boundary.As the content of Cr and Mo increases,the Vickers hardness increases gradually.Isothermal corrosion experiments were carried out at 650? and 750? with Na2SO4 and K2SO4 as corrosion reagents.The corrosion period was 12 h for 14 cycles.At 650?,the maximum corrosion loss of the cladding decreases with the increase of Cr and Mo content.However,when the mass fraction of Mo element reaches 19%,the maximum corrosion weight loss of the sample increases,which is caused by the appearance of microcracks on the surface of the cladding layer.The corrosion product at 650? is mainly metal oxide Cr2O3.At 750?,the corrosion products are mainly metal oxide Cr2O3 and a small amount of metal sulfide MoS2.The maximum corrosion weight loss law at 750? is similar to that at 650?,and the corrosion rate is increased.