Search Results for hydrogen damage

This article provides an overview of the classification of hydrogen damage. Some specific types of the damage are hydrogen embrittlement, hydrogen-induced blistering, cracking from precipitation of internal hydrogen, hydrogen attack, and cracking from hydride formation. The article focuses on the types of hydrogen embrittlement that occur in all the major commercial metal and alloy systems, including stainless steels, nickel-base alloys, aluminum and aluminum alloys, titanium and titanium alloys, copper and copper alloys, and transition and refractory metals. The specific types of hydrogen embrittlement discussed include internal reversible hydrogen embrittlement, hydrogen environment embrittlement, and hydrogen reaction embrittlement. The article describes preservice and early-service fractures of commodity-grade steel components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also reviewed.

Waterwall tube failure samples removed from a coal- and oil-fired boiler in service for 12 years exhibited localized underdeposit corrosion and hydrogen damage. EDS and XRD revealed that bulk internal deposits collected from the tubes contained metallic copper which can accelerate corrosion through galvanic effects and can promote hydrogen damage. Ultrasonic testing was recommended to locate tubes with severe gouging and corrosion, which are suspect locations for hydrogen damage. The source of the copper should be identified and future chemical cleaning of the boiler should address its presence in the waterwall tubes.

The rear wall tube section of a boiler that had been in service for approximately 38 years was removed and examined. Visual examination of the tube revealed a small bulge with a through-wall crack. Metallography showed that the microstructure of the bulged area consisted of a few partially decarburized pearlite colonies in a ferrite matrix. The microstructure remote from the bulged area consisted of pearlite in a ferrite matrix. EDS analysis of internal deposits on the tube detected a major amount of iron, plus trace amounts of other elements. The evidence indicated that the bulge and crack in the tube resulted from hydrogen damage. Examination of the remaining water circuit boiler tubing using nondestructive techniques and elimination of any heavy deposit buildup was recommended.

The power-type counterbalance spring, formed from hardened-and-tempered carbon steel strip and subsequently subjected to phosphating treatment, fractured at the two locations during fatigue testing. A rust colored dark band at the inside edge of the fracture surface was disclosed during investigation. Etch pits were revealed by the cleaned surface which were never observed on properly phosphated coating. It was interpreted that the spring had been subjected to an abnormal acid attack in pickling or phosphating which had resulted in considerable absorption of hydrogen by the metal and hence embrittlement. The part was concluded to have cracked during phosphating or excessive acid pickling before phosphating.

Hydrogen damage is a term used to designate a number of processes in metals by which the load-carrying capacity of the metal is reduced due to the presence of hydrogen. This article introduces the general forms of hydrogen damage and provides an overview of the different types of hydrogen damage in all the major commercial alloy systems. It covers the broader topic of hydrogen damage, which can be quite complex and technical in nature. The article focuses on failure analysis where hydrogen embrittlement of a steel component is suspected. It provides practical advice for the failure analysis practitioner or for someone who is contemplating procurement of a cost-effective failure analysis of commodity-grade components suspected of hydrogen embrittlement. Some prevention strategies for design and manufacturing problem-induced hydrogen embrittlement are also provided.

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.

A 75 mm OD x 7.4 mm wall thickness carbon steel boiler tube ruptured. A substantial degree of corrosion on the water-side surface leaving a rough area in the immediate vicinity of the rupture was revealed by visual examination. Decarburization and extensive discontinuous intergranular cracking was revealed by microscopic examination of a cross section through the tube wall at the fracture. It was concluded that the rupture occurred because of hydrogen damage involving the formation of methane by the reaction of dissolved hydrogen with carbon in the steel. Hydrogen was produced by the chemical reaction that corroded the internal tube surface. Steel embrittled by hydrogen can be restored only if grain boundary cracking or decarburization had not occurred but since the material embrittled in this manner, its replacement was recommended.

A high-pressure steam pipe specified to be P22 low-alloy steel failed after 25 years of service. Located at the end of the steam line, the pipe reportedly received no steam flow during normal service. Visual examination of the failed pipe section revealed a window fracture that appeared brittle in nature. Specimens from the fracture area and from an area well away from the fracture were examined metallographically and chemically analyzed. Results indicated that the pipe had failed by hydrogen damage that resulted in brittle fracture. Chemical analysis indicated that the pipe material was 1020 carbon steel, not P22. The misapplication of pipe material was considered to be a contributing factor. Position of the pipe within the system caused the localized damage.

Welds in two CMo steel catalytic gas-oil desulfurizer reactors cracked under hydrogen pressure-temperature conditions that would not have been predicted by the June 1977 revision of the Nelson Curve for that material. Evidence of severe cracking was found in five weld-joint areas during examination of a naphtha desulfurizer by ultrasonic shear wave techniques. Defect indications were found in longitudinal and circumferential seam welds of the ASTM A204, grade A, steel sheet. The vessel was found to have a type 405 stainless steel liner for corrosion protection that was spot welded to the base metal and all vessel welds were found to be overlaid with type 309 stainless steel. Long longitudinal cracks in the weld metal, as well as transverse cracks were exposed after the weld overlay was ground off. A decarburized region on either side of the crack was revealed by metallurgical examination of a cross section of a longitudinal crack. It was concluded that the damage was caused by a form of hydrogen attack. Installation of a used Cr-Mo steel vessel with a type 347 stainless steel weld overlay was suggested as a corrective action.

After four months at a temperature of 400 to 5000 C, pipes at a gas generating plant were so heavily eroded they had to be replaced. Three sections of pipe, from different locations, were analyzed to determine whether mechanical wear or corrosion caused the damage. Samples of corrosion product from each pipe section were analyzed for carbon, sulfur, and iron and were found to consist mainly of iron sulfide mixed with soot and rust. The damage resulted from a high content of hydrogen sulfide in the gas (6% CO2, 20% CO, 8 to 12% H2, 0.5 to 1.5% CH4, remainder N2). To process the coal in question, the pipes material should be a heat-resistant steel that contains more chromium and has greater resistance to hydrogen sulfide.

Brittle intergranular fracture, typical of a hydrogen-induced delayed failure, caused the failure of an AISI 4340 Cr-Mo-Ni landing gear beam. Corrosion resulting from protective coating damage released nascent hydrogen, which diffused into the steel under the influence of sustained tensile stresses. A second factor was a cluster of non-metallic inclusions which had ‘tributary’ cracks starting from them. Also, eyebolts broke when used to lift a light aircraft (about 7000 lb.). The bolt failure was a brittle intergranular fracture, very likely due to a hydrogen-induced delayed failure mechanism. As for the factors involved, cadmium plating, acid pickling, and steelmaking processes introduce hydrogen on part surfaces. As a second contributing factor, both bolts were 10 Rc points higher in hardness than specified (25 Rc), lessening ductility and notch toughness. A third factor was inadequate procedure, which resulted in bending moments being applied to the bolt threads.