Search Results for Sulfides

A number of failures involving carbon and alloy steels were analyzed to assess the effects of inclusions and their influence on mechanical properties. Inclusions, including brittle oxides and more ductile manganese sulfides (MnS), affect fatigue endurance limit, fatigue crack propagation rates, fracture toughness, notch toughness, and transverse tensile properties, and do so in an anisotropic manner with respect to rolling direction. Significant property anisotropy has been documented in the failures investigated, providing evidence that designers failed to account for it. Typical fracture morphologies observed in such cases and metallographic appearances of MnS-containing materials are illustrated.

An Incoloy 800H (UNS N08810) transfer line on the outlet of an ethane-cracking furnace failed during decoking of the furnace tubes after nine years in service. A metallographic examination using optical and scanning electron microscopy as well as energy-dispersive x-ray spectroscopy revealed that the failure was due to sulfidation. The source of the sulfur in the furnace effluent was either dimethyl disulfide, injected into the furnace feed to prevent coke formation and carburization of the furnace tubes, or contamination of the feed with sulfur bearing oil.

The spontaneous breakage of tempered glass spandrel panels used to cover concrete wall panels on building facades was investigated. Between January 1988 and August 1990, 19 panel failures were recorded. The tinted panels were coated on their exterior surfaces with a reflective metal oxide and covered on the back surfaces with an adherent black polyethylene plastic. Macro fractography, SEM fractography, EDX analysis, and photo elasticimetry were conducted on four of the shattered panels. Small nickel sulfide inclusions were found at the failure origins. Failure of the panels was attributed to growth of the inclusions, coupled with high residual stresses. Fracture mechanics analysis showed that the residual stresses alone were high enough to cause fracture of the glass, with a flaw of the size observed.

An aluminum brass seawater surface condenser failed due to pitting after less than one year of service. Large pits filled with a green deposit were evidenced under the nonuniform black scale present over the entire inside surface of the tube. The black deposit was identified as primarily copper sulfide, with zinc and aluminum sulfides while the green deposit was revealed to be copper chloride. The combination of sulfide and chloride attack on the tubes was concluded to have resulted in the failure. Injection of ferrous sulfate upstream of the condenser which could aid the formation of protective oxide films was recommended.

Coiled tubing with 80 ksi yield strength manufactured to a maximum hardness of 22 HRC to meet NACE Standard MR0175 requirement for sour gas service failed after being on 38 jobs (70% of its estimated fatigue life). A transverse crack where a leak occurred was identified as the primary failure point. Numerous OD surface fissures were revealed by a low-power microscope. A brittle zone near the OD, identified as a sulfide stress crack with additional fatigue cracking was revealed by SEM. Sulfide stress cracking defined as brittle failure by cracking under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide was concluded to have initiated the failure which was propagated by fatigue. It was recommended that in the presence of known corrosive environments the tubing should not be used above 50% of its theoretical fatigue life.

During natural gas drilling in the EMS region in 1956, considerable numbers of longitudinal cracks and transverse fractures occurred in the connecting pieces of the bore rods. The connectors were screwed onto the rods by means of a fine thread and tightly joined with it by shrinkage at 530 deg C. The connectors were made of SAE 4140 Cr-Mo steel. The material for the rod pipes was Fe-0.4C-1Mn steel. Structural stresses played a role in the cracking. Iron sulfide formed on the fracture planes and flake-like stress cracks occurred in the steel. The hydrogen sulfide content of the gas was the cause of damage. Hydrogen liberated by reaction with the iron caused the formation of iron sulfide after penetration of the steel, which had an explosive effect during molecular separation under high pressure. This in turn caused the crack formation in conjunction with the external and residual stresses.