Preparing And Properties Research Of Wear Resistance Composite Boiler Tubes

"Four tubes" of the boiler include water wall tubes, superheater tubes, reheater tubes, economizer tubes. They are important components for heat and mass exchange of the power plant. The blowout and leakage accident of "four tubes" caused by wear, however, has been a major threaten to the safe and stable operation of the power plant. To solve this problem, this paper studied the preparation technology of high wear-resisting boiler tubes and deposited pure Ni65clad layer and four TiB2-Ni65clad layers with different contents of TiB2using semiconductor laser cladding. The influence of TiB2content on high temperature erosion wear resistance of clad layers was also talked about.X-ray diffraction (XRD) patterns displayed that matrix phase of y-Ni and hard phases of CrB, Ni3B, Fe23(C,B)6were indentified in the clad layers. Scanning electron microscope (SEM) analysis exhibited a dispersive distribution of hard phases in the light grey particle-shaped γ-Ni phase.2-3mm thick compact clad layers with no porosity, no impurity and metallurgical bonding were obtained. The improvement of hardness and wear resistance of clad layers could be attributed to this microstructure.By comparison, it could be found that the micro-hardness of TiB2-containing clad layers were higher than that of pure Ni65clad layer. The micro-hardness of all clad layers ranged from1100HV to1300HV, among which the micro-hardness of clad layer with a content of20wt%TiB2was highest (1353HV). The thermal erosion and abrasive wear experiments showed that the wear resistance of clad layers increased with the elevated content of TiB2. The performance of high temperature erosion wear resistance of clad layers was improved ten times higher than that of common boiler tube stainless steels, while the abrasive wear resistance was3-5times higher than that of304H stainless steel.