Effects of temperature and atmosphere on microstructure and tribological properties of plasma sprayed FeCrBSi coatings

FeCrBSi coatings were deposited using an atmospheric plasma spray (APS) technique. The coated specimens were heat-treated at temperatures varying from 300 to 700 °C for 1 hour in air or nitrogen atmospheres. Effects of heat treatment on microstructures, phase compositions, hardness and tribological performance of the coatings were investigated. It was discovered that depending on the temperature and atmosphere, the heat treatment led to intersplat oxidation and caused recrystallization of the coatings. The as-sprayed FeCrBSi coating was mainly consisted of α (Fe, Cr) solid solution phases, while Cr7C3 and Fe3B phases gradually precipitated especially at high temperature, resulting in significantly enhanced hardness. In comparison to the as-sprayed coatings, the coatings heat-treated in nitrogen atmosphere showed lower friction coefficients. With increasing the treatment temperature, the wear resistance exhibited decrease first and then increase. Worn surface analyses suggested that the wear failure was governed by abrasion wear and intersplat debonding of the coatings. Thus, hardness increment and intersplat oxidation became competing factors influencing the wear resistance. When compared to the coatings heat-treated in air, the coatings heat-treated in nitrogen exhibited a significantly higher wear resistance due to the prevention of intersplat oxidation.