A T-piece from a copper hot water system failed. Microscopic examination of a polished section revealed a main crack and branching transcrystalline cracks running from the outer surface of the pipe into the pipe wall. The crack appearance indicated disintegration by stress-corrosion cracking. Although copper is not susceptible in the pure state, it is prone to stress-corrosion cracking under tensile stress in the presence of other elements in a damp ammoniacal atmosphere. The material was not defective, but a phosphorus-deoxidized copper type. The residual phosphorus combined with oxygen to form phosphorus pentoxide. Hard soldering in turn prevented the formation of cuprous oxide, and hydrogen embrittlement occurred.

A batch of bimetal foil/epoxy laminates was rejected because of poor peel strength. The laminates were manufactured by sintering a nickel/phosphorus powder layer to a copper foil, cleaning, then chromate conversion coating the nickel-phosphorus surface, and laminating the nickel-phosphorus side of the clad bimetal onto an epoxy film, so that the end product contained nickel-phosphorus sandwiched between copper and epoxy, with a chromate conversion layer on the epoxy side of the nickel-phosphorus. Peel testing showed abnormally low adhesion strength for the bad batch of peel test samples. Comparison with normal-strength samples using XPS indicated an 8.8% Na concentration on the surface of the bad sample; the good example contained less than 1% Na on the surface. After 15 min of argon ion etching, depth profiling showed high concentrations of sodium were still evident, indicating that the sodium was present before the chromate conversion treatment was performed. A review of the manufacturing procedures showed that sodium hydroxide was used as a cleaning agent before the chromate conversion coating. Failure cause was that apparently the sodium hydroxide had not been properly removed during water rinsing. Thus, recommendation was to modify that stage in the processing.

Eddy-current inspection was performed on a leaking absorber bundle in an absorption air-conditioning unit. The inspection revealed crack-like indications in approximately 50% of the tubes. The tube material was phosphorus-deoxidized copper. Investigation (visual inspection, chemical analysis, 0.75x images, 2x macrographs after light acid cleaning to remove corrosion product, and 75x micrographs) supported the conclusion that the absorber tubes failed by SCC initiated by ammonia contamination in the lithium bromide solution. No recommendations were made.

Pendant-style reheater, constructed of ASME SA-213, grade T-11, steel ruptured. A set of four tubes, specified to be 64 mm OD x 3.4 mm minimum wall thickness was examined. A small quantity of loose debris was removed from the inside of one of the tubes. The major constituent was revealed by EDS analysis of the debris to be iron with traces of phosphorus, manganese, sodium, calcium, copper, zinc, potassium, silicon, chromium, and molybdenum. Thus the debris was interpreted to be the scale from ID of the tube with boiler feedwater chemicals from the attemperation spray. The likely cause of failure was concluded to be exfoliation of the scale from the ID surface of the tube. Creep failures were interpreted to be caused by localized temperatures higher than the maximum service temperature. Replacement of the affected tubes was recommended. Inspection of the tubes by radiography to find the circuits with the greatest accumulation of debris and replacing them as necessary was recommended on an annual basis.

The results of a failure analysis of a series of Cr-Mo-V steel turbine studs which had experienced a service lifetime of some 50,000 h are described. It was observed that certain studs suffered complete fracture while others showed significant defects located at the first stress bearing thread. Crack extension was the result of marked creep embrittlement and reverse temper embrittlement (RTE). Selected approaches were examined to assess the effects of RTE on the material toughness of selected studs. It was observed that Auger electron microscopy results which indicated the extent of grain boundary phosphorus segregation exhibited a good relationship with ambient temperature Charpy data. The electrochemical polarization kinetic reactivation, EPR, approach, however, proved disappointing in that the overlapping scatter in the minimum current density, Ir, for an embrittled and a non-embrittled material was such that no clear decision of the toughness properties was possible by this approach. The initial results obtained from small punch testing showed good agreement with other reported data and could be related to the FATT. Indeed, this small punch test, combined with a miniature sample sampling method, represents an attractive approach to the toughness assessment of critical power plant components.

A section of cast iron water main pipe contained a hole approximately 6.4 x 3.8 cm (2.5 x 1.5 in.). The pipe was laid in clay type soil. Examination revealed severe pitting around the hole and at the opposite side of the outside diam. A macroscopic examination of a pipe section at the hole area showed that the porosity extended a considerable distance into the pipe wall. Metallographic examination revealed a graphite structure distribution expected in centrifugally cast iron with a hypoeutectic carbon equivalent. Chemical analyses of a nonporous sample had a composition typical of cast iron pipe. Chemical analyses of the porous region had a substantial increase in carbon, silicon, phosphorus, and sulfur. The porous appearance and the composition of the soft porous residue confirmed graphitic corrosion. The selective leaching of iron leaves a residue rich in carbon, silicon, and phosphorus. The high sulfur content is attributed to ferrous sulfide from a sulfate reducing bacteria frequently associated with clay soils. Reinforced coal tar protective coating was recommended.

Persistent leakage was experienced from copper tube heaters which formed part of dairy equipment. Metallurgical examination of the brazed joints showed them to have suffered a preferential corrosion attack. This resulted in the phosphide phase of the brazing alloy being corroded away, leaving a weak, porous residual structure. The brazing alloy was of type CP 1 as covered by BS 1845. Header and tube materials were basically copper-nickel alloys for which the use of a phosphorus bearing brazing alloy is not recommended owing to the possibility of forming the brittle intermetallic compound, nickel phosphide. The use of a brazing alloy containing phosphorus was unsuitable on two counts and a quaternary alloy containing silver, copper, cadmium and zinc, such as those in group AG1 or AG2 of BS 1845 would be more suitable. However, because corrosive problems experienced in these units indicated severe service conditions, a proprietary alloy similar to AG1, but containing 3% nickel, was recommended.

A natural gas pipeline explosion and subsequent fire significantly altered the pipeline steel microstructure, obscuring in part the primary cause of failure, namely, coating breakdown at a local hard spot in the steel. Chemical analysis was made on pieces cut from the portion of the pipe that did not fracture during the explosion and from piece 5-1 which contained the fracture origin site. Both pieces were found to have 0.30% carbon and 1.2% Mn with sulfur and phosphorus impurities acceptably low. Fracture mechanics analysis used in conjunction with fractographic results confirmed the existence of a very hard spot in the steel prior to the explosion, which was softened significantly in the ensuing fire. This finding allowed the micromechanism leading to fracture to be identified as hydrogen embrittlement resulting from cathodic charging.

The paper discusses the analysis of a coating defect on a high phosphorus electroless nickel (Ni-11 wt. % P) deposit plated on an aluminum alloy substrate. Preliminary investigations had indicated that the elongated defects were possibly caused by the entrapment of long fibers or particles during the plating. The possible sources of fibers were identified. The SEM/EDS analysis of fibers collected from the air duct filters correlated very well with the defect shape and the EDS profile collected from under the defect site. It appears that the fibers from air duct filters directly above the plating line were blown into the plating tank and getting co-deposited. The paper describes the step-by-step analysis of the defect that led to successful identification of the root cause of the defect.

An SB407 alloy 800H tube failed at a 100 deg bend shortly after startup of a new steam superheater. Three bends failed and one bend remote from the failure area was examined. Visual examination showed that the fracture started on the outside surface along the inside radius of the bend and propagated in a brittle, intergranular fashion. Chemical analysis revealed that lead contamination was a significant factor in the failure and phosphorus may have contributed. The localized nature of the cracks and minimum secondary cracking suggested a distinct, synergistic effect of applied tensile stress with the contamination. Stress analysis found that stress alone was not enough to cause failure; however the operating stresses in the 100 deg bends were higher than at most other locations in the superheater Reduced creep ductility may be another possible cause of failure. Remedial actions included reducing the tube temperature, replacing the Schedule 40 100 deg bends with Schedule 80 pipe, and solution annealing the pipe after bending.

A type 321 stainless steel downcomer expansion joint that handled process gases was found to be leaking approximately 2 to 3 weeks after installation. The expansion joint was the second such coupling placed in the plant after failure of the original bellows. The failed joint was disassembled and examined to determine the cause of failure. Energy-dispersive x-ray analysis revealed significant peaks for chlorine and phosphorus, indicating failure by chloride stress-corrosion cracking (SCC). Cracks in the liner and bellows exhibited a branched pattern also typical of SCC. Cracks through the inner liner initiated on the outer surface of the liner and propagated inward, whereas cracks in the bellows originated on the inner surface and propagated outward. Stress-corrosion cracking of the assembly was caused by chloride contaminants trapped inside the bellows following hydrostatic testing. Checking the test fluid for chloride and removing all fluids after hydrostatic testing were recommended to prevent further failure.

An HK-40 alloy tubing weld in a reformer furnace of a petrochemical plant failed by leaking after a shorter time than that predicted by design specifications. Leaking occurred because of cracks that passed through the thickness of the weldment. Analysis of the cracked tubing indicated that the sulfur and phosphorus contents of the weld metal were higher than specified, the thickness was narrower at the weld, and the mechanical resistance of the weld metal was lower than specified. Cracking initiated at the weld root by coalescence of creep cavities. Propagation and expansion was aided by internal carburization. Quality control of welding procedures and filler metal was recommended.

An I-beam of IS-226 specification—I-section dimensions of 450 x l50 x 10 mm (17.7 x 5.9 x 0.4 in.) and a length of 12.41 m (40.7ft)—was flame cut into two section in an open yard near these a coast under normal weather conditions. After approximately 112h, the shorter section of he I-beam split catastrophically along the entire length through the web. Detailed investigation revealed segregation of high levels of carbon, sulfur and phosphorus in the middle of the web and high residual stresses attributed to rolling during fabrication. Flame cutting caused a change in the distribution of the residual stresses, which, aided by low fracture toughness due to the poor quality of the beam, resulted in failure. It was recommended that segregation be avoided in cast ingots used for I-beam manufacture by implementing a better quality-control procedure.

A large number of electropolished copper parts showed evidence of discoloration (tinting) after electropolishing. Because these parts are used in a high-vacuum application, even trace amounts of organic materials would be problematic. Scanning electron microscopy of nondiscolored and discolored areas both showed trace amounts of residue in the form of adherent deposits. EDS, FTIR spectroscopy, XPS, and secondary ion mass spectroscopy (SIMS) analyses indicated that the discoloration to the copper components was due to the development of CuO at localized regions. It was recommended that process changes be made to completely remove residual processing fluids from the part surfaces before electropolishing. The use of more aggressive detergents was suggested, and it was recommended also that a filtering and recirculating system be considered for use in the cleaning and electropolishing tanks.

Two acrylic-coated polymeric motorcycle components exhibited fisheye blemishes after painting. SEM and EDS results showed relatively high levels of sulfur and chlorine associated with the blemishes in both parts. This suggested some adherent residual substances, possibly in the form of processing fluids and/or cleaning agents, were left on the surface just prior to painting and resulted in the observed fisheye blemishes. One of the components also showed evidence of mechanical damage, in addition to detectable iron, which suggests that the part surface may have been damaged from contact with a ferrous material, such as a steel chip.