A Mechanics Analysis Of Formation And Expansion Of Fatigue Crack In Laser Cladding On Repeated Impact Load

摘要

Coating samples prepared by laser cladding were subjected to repeated impact fatigue experiment. It is observed through phenomenological analysis that most coating cracks are original from the surface. And then, the cracks extend by the combined action of coating inner stress and repeated impact compression stress. The formation of crack is close related to performance of coating material. It can be divided to traversed crack and reticular crack from surface side; it also can be divided to vertical extend crack and reticular extend crack from the cross section side. Rigid and brickie coating has a shorter repeated impact life because a kind of linear crack is formed easily in it. On the other hand, tougher coating has a long life. Mechanics of nucleation and expansion of crack was explained by using stress concentration theory and vacancy concentration theory. The anti-repeated impact fatigue performance of laser cladding part could be improved by increasing toughness and reducing hardness of the coating material. Furthermore, suitable dispersion strengthening and fine-crystal strengthening can obtain the same purpose.