Fractographic Study of Destruction of Composite Coatings After Bending Tests

The paper presents results of fractographic studies of fracture of specimens with coatings obtained by the method of nonvacuum electron-beam cladding of refractory powders on a steel substrate after conducting three-point bending tests. It has been established that brittle fracture of the coating with cracking occurs during specimen bending. The fracture is dendritic in character due to the cast dendritic structure formed in the deposited layer. The important roles of the dendrite grain sizes and of the volume fraction of eutectics have been revealed and justified. The influence of the eutectic volume fraction on the microhardness and strength of the coating has been established.