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ML00040 - Apr.2017

Brittle Fracture of a Valve Stem

Detail of the cleavage micromechanism.

2

195
Detail of the cleavage micromechanism.
M

Material

Nodular Cast Iron
  • UNS F32800
  • ASTM A 536 60-40-18
Ds

Description

During maintenance of the hydraulic in the an unsuitable assembling condition imposed a non expected to the stem, that broke in a brittle way. The matrix opened by cleavage from a raiser (the region of diameter variation).

C

Chemistry (% in weight)

Product Analysis

3.40C; 2.70Si; 0.30Mn; 0.023P; 0.019S.

Associated Images
The fracture surface is flat, shows the graphite nodules and cleavage of the ferritic microstructure, indicating that the material have exceeded the capacity to acomodate the stress.
944
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Cleavage Facets
Detail of the cleavage micromechanism.
195
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Fractography by SEMDf - Cleavage Facets
The cast iron microstructure is predominatly ferritic with graphite nodules.
169
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Graphite in Nodules
The micrography of the stem at the fracture region shows a flat fracture with transgranular clevage at the ferritic structure.
137
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture
Micrography presenting a detail of the fracture surface opening to the graphite nodules.
139
VIEW
ML00040 / Apr.2017
Brittle Fracture of a Valve Stem
M - Nodular Cast IronP - Valve StemAp - ShipCd - Brittle Fracture
Cm - Nital Etched Micrography by OMDf - Fracture