Failure Analysis and Prevention: Metallography for Failure Analysis
Program Organizers: Larry Hanke, Materials Evaluation and Engineering, Inc; Tom Ackerson, IMR Metallurgical Services
Tuesday 2:00 PM
October 9, 2012
Room: Room 330
Location: David L. Lawrence Convention Ctr
Session Chair: Dustin Turnquist, ESI; Burak Akyuz, ATS, Inc.; Tom Ackerson, IMR Metallurgical Services
2:00 PM
Failure of Blast Furnace Fuel Injection Lances Via Sulfur-Induced Hot Corrosion: Amber Dalley1; Jerry Capo1; 1U. S. Steel Corporation
In blast furnace operations, hydrocarbon fuels are commonly injected into the hot blast stream to control the flame temperature and replace some of the metallurgical coke. Fuel injection has the dual benefit of decreasing operating costs and/or increasing productivity. Metal lances are used to inject the solid, liquid, or gaseous fuels into the blast furnace. Common lance metals include Inconel 600 nickel-based alloy and various grades of stainless steel. At times, perforations develop in the lance walls as far as 20 inches from the tip. Once this occurs, fuel may escape and prematurely ignite inside the hot blast delivery system, leading to equipment damage and loss of production. Metallographic examination of several perforated fuel lances revealed the presence of severe sulfidation/hot corrosion attack and accelerated localized thinning. This paper examines the potential sources of sulfur and metallurgically documents the progression of this damage mechanism.
2:20 PM
Metallographic Analysis of Thread Damage in Iron Alloy Components: Frederick Schmidt1; Mark Hineman1; Michael Danko1; 1Engineering Systems, Inc.
The ultimate failure mode of threaded connections is often the “root cause” of more serious mechanical failures. Often maintenance personnel perform replacement therapy with little regard for a permanent solution to a problem. At ESI, we have examined a diverse collection of failure types of threaded components that were evaluated by others prior to metallography. Typically, an incorrect diagnosis of the failure mode is made which will most likely lead to a repeated occurrence. The paper will present examples of “black iron" pipe, cast iron, steel and stainless steels parts where use of destructive testing, metallography and micro-hardness evaluation was required to discover the correct “root cause”. Metallography must be performed correctly. In some of the samples prepared by others, incorrect preparation, creation of artifacts, and improper etching were observed. The importance of peer review in completing and comparing metallographic analysis results will be illustrated as an affirmative best practice.
2:40 PM
Metallographic Study of Corroded Music Wire Springs: Roxana Ruxanda1; Richard Obara1; 1Emerson Climate Technologies
A thick combination of “white residue” and “red residue” was found on the surface of springs placed inside pressure regulator valves used in a commercial refrigeration circuit/system. The residues were identified by using EDS and X-Ray fluorescence methods as zinc oxide and iron oxide/ hydroxide. Metallographic analysis, performed after the residues were collected and the springs cleaned out, showed various levels of corrosion of the material, local decarburization of the microstructure and extensive damage to the protective zinc layer. The progression of the corrosion into the microstructure was documented. Superficial decarburization and small areas with lack of zinc coating, and therefore protection, where observed between tightly spaced coils in new springs. It was determined that the most probable cause of corrosion is the presence of moisture inside the valves.
3:00 PM Cancelled
Failure Investigation of Hydrogen Production Reformer Tube: K. Ravindranath1; S. Al-Dhafiri2; K. L. Reddy2; B. Hussain1; N. Tanoli1; 1Kuwait Institute for Scientific Research; 2Kuwait National Petroleum Company
Centrifugally cast reformer tubes have been widely used in the petroleum refining and petrochemical industries to produce hydrogen at high temperatures. However, the reformer tube materials undergo microstructural degradation and failure during service. The paper deals with an investigation carried out on a failed reformer tube to understand the root cause of the failure. The failed reformer tube, HP-Mod, was in service for 23 years. The reformer tube was subjected to optical and scanning electron microscopy to characterize the microstructure and to understand the failure mode. The microscopic study revealed the precipitation of secondary phases and presence of creep voids and fissures in the material. Chromium and niobium rich carbides and intermetallics, the secondary phases found commonly in similar materials, were precipitated in the tube material. The creep voids were found to initiate predominantly at the carbide/matrix boundary. The failure of the tube was due to coalescence of creep voids.
3:20 PM Break
3:40 PM
Sigma Phase Embrittlement of a Boiler Tube Lug: Adrian Hruszkewycz1; 1Applied Technical Services
Metallurgical failure analysis performed on a boiler tube support lug from a power plant revealed evidence of sigma-phase embrittlement. Improper welding of the lug was initially suspected by the customer, but microstructural and fractographic results were consistent with material embrittled during service. The lug was made of 310 stainless steel, a high temperature alloy designed for use in temperatures exceeding 1800 °F. This alloy is known to precipitate a brittle iron-chromium phase (i.e. sigma phase) in the range of 1400-1600 °F, which dissolves in temperatures above 1800 °F. Boilers commonly operate at 1800-2100 °F, but the boiler in question was of a newer, lower-temperature design intended for operation at 1500-1700 °F. These relatively low service temperatures placed the lug in the temperature range for sigma-phase precipitation. This study illustrates the need for careful material selection, especially for high temperature applications.
4:00 PM
Butterfly Martensite in Rolling Bearings: Dorota Szczesniak1; 1General Electric
Jet engine mainshafts are commonly supported by ball and roller bearings manufactured from high quality tool steels which operate at high speeds. The primary purpose of roller and ball bearings is to reduce rotational friction and support radial (rolling bearings) and radial and axial (ball bearings) loads. Higher loaded bearings can result in the formation of local regions of sub-surface untempered martensite commonly referred to as “butterfly” indications that can commonly form near the sub-surface max-Hertz stress location within the bearing components. Formation of “butterfly” indications has been local shear heating attributed to differences in elastic modulus between carbides and matrix. Evaluation of several roller bearings exhibiting “butterfly” will be discussed.
4:20 PM
Embrittlement of Forging Brass Components Due to Microstructural Defects: Burak Akyuz1; 1ATS, Inc.
Metallurgical failure analysis was performed on multiple forging brass components. The components mainly fractured during the installation under normal stresses. Fractography and microstructural analysis indicated the failures were due to lead migration to grain boundaries. The material was C37700 forging brass. This study illustrates the need for careful material selection, especially for high temperature applications. Embrittlement of the components was caused by lead migration to the grain boundaries during the hot forging process due to a over heated die.
4:40 PM
A Metallography-Based Examination of Inadvertent Diffusion Bonding During Heat Treatment: Tom Ackerson1; Brett Miller1; James Zellers1; Jennifer Breetz1; 1IMR Metallurgical Services
Inadvertent diffusion bonding of workpieces during heat treatment is a relatively well understood but troublesome phenomenon. Metallurgical failure analysts are often called upon to investigate material damage due to heat treatment damage, including unintentional bonding. This talk provides an introduction to the diffusion bonding process and a discussion of three metallography-based case studies of inadvertent diffusion bonding.