Search Results for environmentally induced cracking

This article discusses the fundamental aspects of environmentally induced cracking. It provides a theoretical basis for the evaluation, testing, and methods of protection against the cracking. The article describes the mechanisms of corrosion that produce cracking of metals and intermetallic compounds as a result of exposure to their environment.

Metal-induced embrittlement is a phenomenon in which the ductility or the fracture stress of a solid metal is reduced by surface contact with another metal in either the liquid or solid form. This article summarizes some of the characteristics of liquid-metal- and solid-metal-induced embrittlement. This phenomenon shares many of these characteristics with other modes of environmentally induced cracking, such as hydrogen embrittlement and stress-corrosion cracking. The discussion covers the occurrence, failure analysis, and service failures of the embrittlement. The article also briefly reviews some commercial alloy systems in which liquid-metal-induced embrittlement or solid-metal-induced embrittlement has been documented and describes some examples of cracking due to these phenomena, either in manufacturing or in service.

Stress-corrosion cracking (SCC) is a form of corrosion and produces wastage in that the stress-corrosion cracks penetrate the cross-sectional thickness of a component over time and deteriorate its mechanical strength. Although there are factors common among the different forms of environmentally induced cracking, this article deals only with SCC of metallic components. It begins by presenting terminology and background of SCC. Then, the general characteristics of SCC and the development of conditions for SCC as well as the stages of SCC are covered. The article provides a brief overview of proposed SCC propagation mechanisms. It discusses the processes involved in diagnosing SCC and the prevention and mitigation of SCC. Several engineering alloys are discussed with respect to their susceptibility to SCC. This includes a description of some of the environmental and metallurgical conditions commonly associated with the development of SCC, although not all, and numerous case studies.

Corrosion of metals is defined as deterioration caused by chemical or electrochemical reaction of the metal with its environment. This article provides information on corrosion of iron and steel by aqueous and nonaqueous media. It discusses the corrosive environments of carbon and alloy steels, namely atmospheric corrosion, soil corrosion, corrosion in fresh water and seawater. The article describes the corrosion process in concrete, which tends to create conditions that increase the rate of attack. The focus is on the stress-corrosion cracking of steels; an environmentally induced crack propagation that results from the combined interaction of mechanical stress and corrosion reactions. The article tabulates a guide on corrosion prevention for carbon steels in various environments. It also discusses protection methods of steel from corrosion, including coatings, such as temporary protection, cleaning, hot dip coating, electroplating, thermal spray coatings, conversion coatings, thin organic coatings, and inhibitors.

Corrosion is classified into two categories: corrosion that is not influenced by any other process and corrosion that is influenced by another process such as the presence of stresses or erosion. This article discusses uniform corrosion, localized corrosion, metallurgically influenced corrosion, and microbiologically influenced corrosion, which fit under the classification of corrosion that is not influenced by any outside process. It also explains mechanically assisted degradation and environmentally induced cracking, which fit under the classification of corrosion that is influenced by an outside process.

This article describes the fatigue mechanism and behavior of environmentally induced fatigue and cyclic fatigue. It discusses three basic strength test methods, namely, static, dynamic, and cyclic, along with their analytical relations for determining the fatigue parameters and behavior of ceramics and glasses. The article explains the double torsion and double-cantilever beam fracture mechanics methods, which employ test specimens with relatively large, induced cracks. Crack growth data are typically determined directly by the observation of the crack or by devices that monitor test specimen compliance, such as clip gages and strain gages.

This article reviews the corrosion behavior in various environments for seven important nickel alloy families: commercially pure nickel, Ni-Cu, Ni-Mo, Ni-Cr, Ni-Cr-Mo, Ni-Cr-Fe, and Ni-Fe-Cr. It examines the behavior of nickel alloys in corrosive media found in industrial settings. The corrosive media include: hydrochloric acid, sulfuric acid, phosphoric acid, hydrofluoric acid, hydrobromic acid, nitric acid, organic acids, salts, seawater, and alkalis. The modes of high-temperature corrosion include oxidation, carburization, metal dusting, sulfidation, nitridation, corrosion by halogens, and corrosion by molten salts. Applications where the corrosion properties of nickel alloys are important factors in materials selection include the petroleum, chemical, and electrical power industries. Most nickel alloys are much more resistant than the stainless steels to reducing acids, such as hydrochloric, and some are extremely resistant to the chloride-induced phenomena of pitting, crevice attack, and stress-corrosion cracking (to which the stainless steels are susceptible). Nickel alloys are also among the few metallic materials able to cope with hot hydrofluoric acid. The conditions where nickel alloys suffer environmentally assisted cracking are highly specific and therefore avoidable by proper design of the industrial components.

This article describes the types, mechanism, and typical test methods along with their configurations for the evaluation of hydrogen embrittlement, stress-corrosion cracking, and corrosion fatigue with an emphasis on fracture mechanics methodologies for metals. An overview on the environmentally assisted crack growth of polymers is also included. The article details the evaluation of nanoscale environmental effects and indentation-induced cohesive cracking. It also provides information on scanning probe microscopy.

Stress-corrosion cracking (SCC) is a phenomenon in which time-dependent crack growth occurs when the necessary electrochemical, mechanical, and metallurgical conditions exist. This article provides an overview of the environmental phenomenon, mechanisms, and controlling parameters of SCC. It describes the phenomenological and mechanistic aspects of the initiation and propagation of SCC. The article includes a phenomenological description of crack initiation and propagation that describes well-established experimental evidence and observations of stress corrosion. Discussions on mechanisms describe the physical process involved in crack initiation and propagation. The article also includes information on dissolution models and mechanical fracture models.

Overload failures refer to the ductile or brittle fracture of a material when stresses exceed the load-bearing capacity of a material. This article reviews some mechanistic aspects of ductile and brittle crack propagation, including a discussion on mixed-mode cracking, which may also occur when an overload failure is caused by a combination of ductile and brittle cracking mechanisms. It describes the general aspects of fracture modes and mechanisms. The article discusses some of the material, mechanical, and environmental factors that may be involved in determining the root cause of an overload failure. It also presents examples of thermally and environmentally induced embrittlement effects that can alter the overload fracture behavior of metals.

This article describes measurement techniques for the three basic types of adhesion: fundamental adhesion, thermodynamic adhesion, and practical adhesion. It discusses common measurement methods for each type of adhesion with the main focus on practical adhesion testing of coatings and thin films. The article provides an insight into the mechanisms of environmentally induced interfacial degradation by discussing the fundamental aspects of adhesion between two dissimilar materials. It examines the use of adhesion tests in the evaluation of stress-corrosion cracking within bimaterial interfaces. Testing techniques for <i>in situ</i> environmental testing of thin-film adhesion are also reviewed.

Metal-induced embrittlement is a phenomenon in which the ductility or fracture stress of a solid metal is reduced by surface contact with another metal in either liquid or solid form. This article summarizes the characteristics of solid metal induced embrittlement (SMIE) and liquid metal induced embrittlement (LMIE). It describes the unique features that assist in arriving at a clear conclusion whether SMIE or LMIE is the most probable cause of the problem. The article briefly reviews some commercial alloy systems where LMIE or SMIE has been documented. It also provides some examples of cracking due to these phenomena, either in manufacturing or in service.

With any polymeric material, chemical exposure may have one or more different effects. Some chemicals act as plasticizers, changing the polymer from one that is hard, stiff, and brittle to one which is softer, more flexible, and sometimes tougher. Often these chemicals can dissolve the polymer if they are present in large enough quantity and if the polymer is not crosslinked. Other chemicals can induce environmental stress cracking (ESC), an effect in which brittle fracture of a polymer will occur at a level of stress well below that required to cause failure in the absence of the ESC reagent. Finally, there are some chemicals that cause actual degradation of the polymer, breaking the macromolecular chains, reducing molecular weight, and diminishing polymer properties as a result. This article examines each of these effects. The discussion also covers the effects of surface embrittlement and temperature on polymer performance.

This article illustrates the three techniques for producing glassy metals, namely, liquid phase quenching, atomic or molecular deposition, and external action technique. Devitrification of an amorphous alloy can proceed by several routes, including primary crystallization, eutectoid crystallization, and polymorphous crystallization. The article demonstrates a free-energy versus composition diagram that summarizes many of the devitrification routes. It provides a historical review of the corrosion behavior of fully amorphous and partially devitrified metallic glasses. The article describes the general corrosion behavior and localized corrosion behavior of transition metal-metal binary alloys, transition metal-metalloid alloys, and amorphous simple metal-transition metal-rare earth metal alloys. It concludes with a discussion on the environmentally induced fracture of glassy alloys, including hydrogen embrittlement and stress-corrosion cracking.