This article presents fractographs that show evidence of overload and fatigue in gray cast irons. The overload failure section illustrates a fractured motor housing, valve body, and bracket with microvoid coalescence (dimpled rupture) in the metal matrix between graphite flakes. The fractographs of fatigue failures illustrate a gearbox housing with fatigue striations and pearlitic microstructure.

This article presents fractographs of overload fractures in a ductile cast iron piston, tensile test bar, differential case, brake caliper, compressor crankshaft, and pivot arm. SEM images show such features as dimpled rupture at the thin metallic matrix ligatures between the graphite nodules, bull's-eye ferrite and pearlite microstructure, loose graphite nodules and dimpled rupture morphology transitioning to cleavage, cleavage morphology with river lines, and ratchet marks and beach marks.

This article presents fractographs that show evidence of overload in white cast irons. Images illustrate brittle fracture with cleavage facets and fracture at carbide boundaries, as well as cracks caused by shear stress and the tensile stress due to rebounding.

This article presents fractographs that show evidence of overload in a ferritic malleable cast iron. The images illustrate crack initiation and propagation, as well as regions of dimpled rupture.

The cast iron family includes several different groups, including gray iron, ductile iron, compacted graphite iron, malleable iron, white iron, and many different grades within each of these alloy groups. This article addresses issues specific to gray iron, but in many instances the discussion can be related to the other cast iron groups and the various grades within those groups. It discusses the usage of techniques and procedures in cast iron fractography. The article presents a list of common defects that can initiate failure.

Hardening and depth of hardening of steel is a critically important material and process design parameter. This article presents a selective overview of experimental and predictive procedures to determine steel hardenability. It also covers the breadth of steel hardenability, ranging from shallow, to very difficult to harden, to air-hardening steels.

The information provided in this article is intended for those individuals who want to determine why a casting component failed to perform its intended purpose. It is also intended to provide insights for potential casting applications so that the likelihood of failure to perform the intended function is decreased. The article addresses factors that may cause failures in castings for each metal type, starting with gray iron and progressing to ductile iron, steel, aluminum, and copper-base alloys. It describes the general root causes of failure attributed to the casting material, production method, and/or design. The article also addresses conditions related to the casting process but not specific to any metal group, including misruns, pour shorts, broken cores, and foundry expertise. The discussion in each casting metal group includes factors concerning defects that can occur specific to the metal group and progress from melting to solidification, casting processing, and finally how the removal of the mold material can affect performance.

This article focuses on friction and wear of automotive and aircraft brakes. It provides a comparison of friction and wear behaviors, frictional characteristics, and frictional performance of the friction materials. The article describes the components of brake friction materials and the classifications of brake lining materials. It discusses the effect of formulation compositions and manufacturing processes and the effect of braking operation conditions. The article provides information on aircraft brake linings, which operate under a wide range of kinetic energy conditions. The morphology effect of graphite on automotive brake drum and disk is explained. The article also describes the characteristics of specific wear rates for both normal and local cast iron in automotive brake drums and disk rotors. It provides information on noises, vibrations, and harshness caused by brake pads. The article concludes with information on physical and chemical testing of brakes and toxicity of brake formulation and regulations.

Cast irons have been widely used by engineers in applications that require low cost, excellent castability, good damping capacity, ease of machining, and wear resistance. This article discusses the classification of wear for cast irons: adhesive wear, abrasive wear, and erosive wear. Typical wear applications for a variety of cast iron grades are listed in a table. The article reviews the general wear characteristics of gray irons, compacted graphite (CG) irons, and ductile irons. It discusses the typical compositions and properties of white and chilled iron castings. Gray cast iron is the dominant material for both brake drums and disk brake rotors. The article reviews brake lining chemistry effects, graphite morphology effects, and external abrasive effects on brake drums. It concludes with information on cast iron grinding balls.

Austempered ductile iron (ADI) results from a specialty heat treatment of ductile cast iron. This article discusses the production of austempered ductile iron by heat treatment. The austempered ductile iron grades, according to ISO 17804 and EN 1564, are presented in a table. For economic reasons, or to avoid metallurgical problems, combinations of alloys are often used to achieve the desired hardenability in austempered ductile iron. The article provides information on the alloy combinations for austempered ductile iron. The mechanical properties, fracture toughness, fatigue, and abrasion resistance of the austempered ductile iron are discussed. The article concludes with information on the applications for austempered ductile iron.

Malleable iron is a type of cast iron that has most of its carbon in the form of irregularly shaped graphite nodules instead of flakes, as in gray iron, or small graphite spherulites, as in ductile iron. This article discusses the production of malleable iron based on the metallurgical criteria: to produce solidified white iron throughout the section thickness; and to produce the desired graphite distribution (nodule count) upon annealing. It describes the induction heating and quenching or flame heating and quenching for surface hardening of fully pearlitic malleable iron. Laser and electron beam techniques also have been used for hardening selected areas on the surface of pearlitic and ferritic malleable iron castings that are free from decarburization.

The transformation of austenite of cast irons represents a more complex and less studied subject. This article discusses the general features of the decomposition of austenite into bainite. It describes the heat treatment cycles of austempered cast iron microstructure. The article reviews several factors, such as presence of graphite and austenite grain size, which affect the transformation rate of austenite during austempering of free-graphite cast irons.

Thermal analysis is used to analyze solidification processes by recording the temperature as a function of time during cooling or heating of a metal or alloy to or from a temperature above its melting point. This article describes the use of cooling curves for analyzing a solidification process, such as the solidification temperature, structure analysis, fraction of phases and heat of fusion with focus on solidification of cast iron, and the use of cooling curves to control and adjust the casting conditions. It discusses deviations from equilibrium that occur due to kinetic effects during solidification. The article also illustrates the evaluation of fraction of solid formed during the precipitation of austenite from heat balance.

Foundry practices critical to the production of cast irons include melting, alloying, molten metal treatment, pouring, and the design of feeding systems (gating and risering) to allow proper filling of the casting mold. This article reviews these production stages of iron foundry casting, with particular emphasis on the melting practices, molten metal treatment, and feeding of molten metal into sand molds. It discusses the castability factors, such as fluidity, shrinkage, and resistance, of gray iron. Typical cupola charge compositions and the final analyses for class 30 and class 40 gray iron castings are presented in a table. The article describes the induction melting and arc furnace melting used in gray iron foundries. It also reviews the inoculation methods such as stream inoculation and mold inoculation, of gray iron.

The microstructure that develops during the solidification stage of cast iron largely influences the subsequent solid-state transformations and mechanical properties of the cast components. This article provides a brief introduction of methods that can be used for simulating the solidification microstructure of cast iron. Analytical as well as numerical models describing solidification phenomena at both macroscopic and microscopic scales are presented. The article introduces macroscopic transport equations and presents analytical microscopic models for solidification. These models include the dendrite growth models and the cooperative eutectic growth models. The article provides some solutions using numerical models to simulate the kinetics of microstructure formation in cast iron. It concludes with a discussion on cellular automaton (CA) technique that can handle complex topology changes and reproduce most of the solidification microstructure features observed experimentally.

Unlike gray iron, which contains graphite flakes, ductile iron has an as-cast structure containing graphite particles in the form of small, rounded, spheroidal nodules in a ductile metallic matrix. This article discusses the raw materials that are used for ductile iron production and outlines the most common and important requirements for controlling the composition of ductile iron. Treatment to produce ductile iron involves the addition of magnesium to change the form of the graphite, followed by or combined with inoculation of a silicon-containing material to ensure a graphitic structure with freedom from carbides. The article describes the methods of magnesium treatment, control of magnesium content, and inoculation. It concludes with a discussion on the metallurgical controls of ductile iron production.

This article discusses the stable and metastable three-phase fields in the binary Fe-C phase diagram. It schematically illustrates that austenite decomposition requires accounting for nucleation and growth of ferrite and then nucleation and growth of pearlite in the remaining untransformed volume. The article describes the austenite decomposition to ferrite and pearlite in spheroidal graphite irons and lamellar graphite irons. It provides a discussion on modeling austenite decomposition to ferrite and pearlite.

This article describes different methods by which the composition of cast iron can be analyzed. It provides particular emphasis on the methods for evaluating the graphitization potential of a melt with prescribed limits on carbon, silicon, and alloying elements. The article discusses the effect of cooling rate on the graphitization of a given composition by chill and wedge tests. Thermal analysis of cooling curves gives excellent information about the solidification and subsequent cooling of cast iron alloys. The article presents some applications of the cooling curve analysis and explains the evaluation of carbon-silicon contents, graphite shape, graphite nucleation, and contraction-expansion balance. It illustrates the use of an immersion steel sampling device for compacted graphite iron production and provides information on the ferrite-pearlite ratio in ductile iron.

This article discusses the production process, testing methods, quality control, and common defects found in heavy-section ductile iron (DI) castings, along with analyses of industrial examples. The common defects include shrinkage defects, graphite-particle-related defects, and chunk graphite defects. The recommended chemical compositions for certain section thicknesses in ductile iron grades are presented in a table. The article illustrates the relationship between microstructure and mechanical properties of DI by using either industrial examples or castings produced under laboratory conditions.