Length High Temperature Phase Stability And Wear Behavior Of Laser Clad Ta Reinforced Nicrbsi Coating

Ta is added to laser clad NiCrBSi coating to improve high-temperature wear resistance. The influence of heat treatment of 700 degrees C on Ta reinforced coating is studied. The microstructure is analyzed by XRD, SEM, EDS, TEM and XPS. The tribological performances were investigated on high temperature pin-on-disk tribometer at temperatures up to 700 degrees C. Ta reinforced coating mainly includes gamma-Ni, TaC, Ni3Fe, CrB, M23C6 and Cr2.8Fe1.2B4. Under heat treatment, most of the phases remain stable except that M23C6 is dissolved and coarsened. CrB formed on TaC particle is evolved into Cr2.8Fe1.2B4. The heat treatment has little influence on the hardness of Ta reinforced coating. It is difficult to form an oxide layer on worn surface of NiCrBSi coating at any temperature. On the contrary, an oxide layer form on worn surface of Ta reinforced coating at 700 degrees C. Ta significantly improves the wear resistance of NiCrBSi coating at high temperatures, which is attributed to Ni matrix strengthened by Ta, TaC with high thermal stability, clean TaC/matrix interface, and compact oxide layer. The main wear mechanism below 600 degrees C is abrasion and adhesion, and oxidization, which transitions to delamination, abrasion, ploughing and oxidization at 700 degrees C.