Abstract
In order to optimize the well control equipments of nitrogen drilling, the wellhead equipments have been inspected and analyzed systematically, and the failure analysis has been performed for the fracture at the through hole of two valve plates of flat valve at the side outlet of the multi-function four-way valve in this paper. The fracture reason of the valve plates is explored from macroscopic morphology analysis, chemical composition analysis, mechanical property test, SEM analysis and macroscopic analysis respectively. SEM scanning shows that more precipitates have been separated out nickel-based solid solution in Ni60 welded alloy layer. The spectrum analysis shows that these precipitate phases are rich chromium evolution phases. The valve plate cracks are originated in the welded alloy layer. The final fracture of valve plate is a cleavage fracture and the mechanism is brittle fracture.
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