Gray Cast Research Articles

Tribological behaviour of yttria-stabilised zirconia under dry sliding conditions when tested against itself and grey automotive cast iron

In this study the wear mechanisms of ceramic/cast iron and ceramic/ceramic couples and the relationship of these mechanisms with the tested materials' microstructure were analysed. Wear mechanisms were identified in this particular type of testing and a correlation between material testing parameters and its wear behaviour was established. The interaction between the various wear mechanisms of wear particle generation is also discussed. Transformation toughening controls the major wear mechanisms of 3Y-TZP ceramic material. Models were developed by statistical analysis of the data and the results show close agreement with the experimental results. The wear rate was found by the analysis to be more sensitive to load than to the number of revolutions per minute (rotating speed) or number of cycles (the length of the wear track). These parameters would be expected to have a stronger fundamental influence on wear. In general, ceramic/cast iron couples displayed lower friction than ceramic/ceramic sliding couples under the test conditions.

Growth retardation and cysteine deficiency in gamma-glutamyl transpeptidase-deficient mice.

gamma-Glutamyl transpeptidase (GGT) is an ectoenzyme that catalyzes the first step in the cleavage of glutathione (GSH) and plays an essential role in the metabolism of GSH and GSH conjugates of carcinogens, toxins, and eicosanoids. To learn more about the role of GGT in metabolism in vivo, we used embryonic stem cell technology to generate GGT-deficient (GGTm1/GGTm1) mice. GGT-deficient mice appear normal at birth but grow slowly and by 6 weeks are about half the weight of wild-type mice. They are sexually immature, develop cataracts, and have coats with a gray cast. Most die between 10 and 18 weeks. Plasma and urine GSH levels in the GGTm1/GGTm1 mice are elevated 6-fold and 2500-fold, respectively, compared with wild-type mice. Tissue GSH levels are markedly reduced in eye, liver, and pancreas. Plasma cyst(e)ine levels in GGTm1/GGTm1 mice are reduced to approximately 20% of wild-type mice. Oral administration of N-acetylcysteine to GGTm1/GGTm1 mice results in normal growth rates and partially restores the normal agouti coat color. These findings demonstrate the importance of GGT and the gamma-glutamyl cycle in cysteine and GSH homeostasis.

NI-ROD 55 WELDING ELECTRODE

Abstract NI-ROD 55 Welding Electrode is used for shielded-metal-arc welding of gray, ductile, malleable, and Ni-Resist cast irons. It is also used for welding cast irons to various wrought materials, including carbon steels, low-alloy steels, and nickel alloys. The electrode is especially useful for welding heavy sections and high-phosphorus irons. NI-ROD 55 Welding Electrode can be operated in all welding positions. Power supply: direct current, electrode positive is preferred although alternating current can be used. This datasheet provides information on composition and tensile properties. It also includes information on joining. Filing Code: Ni-499. Producer or source: Inco Alloys International Inc.

Ni-ROD WE

Abstract NI-ROD Welding Electrode is used for shielded-metal-arc welding of gray, ductile, and malleable cast irons. It is also used for joints between cast irons and carbon steel or low-alloy steel. The electrode is particularly useful for thin sections and for joints to be machined. NI-ROD welding electrode can be operated in all welding positions. Power supply: direct current, electrode positive is preferred although alternating current can be used. This datasheet provides information on composition and tensile properties. It also includes information on joining. Filing Code: Ni-490. Producer or source: Inco Alloys International Inc.

Wear Behavior of Laser Surface-Hardened Gray and Ductile Cast Irons. Part 2—Erosive Wear

A 1.2-kW, continuous wave, CO2-gas laser was used to transformation harden or melt the surface of gray and ductile cast irons. Effects of surface-hardened layers on solid particle erosion showed that the erosion rate decreased with an increase in surface hardness and case depth. The order of matrix microstructures that increased the erosion rate were ledeburite, tempered martensite, and pearlite. These results were opposite to those observed in bulk-hardened alloys. Erosion mechanisms of brittle, gray iron included micromachining in the untreated condition and grain boundary cracking in the laser-treated condition. In contrast, erosion modes of ductile iron were plastic flow followed by cracking in the untreated condition and platelet formation and fatigue in the laser-treated conditions. The beneficial effects of surface hardening on erosion were examined and discussed.

Fatigue Characteristics of Laser Surface-Hardened Cast Irons

Contrary to expectations, laser surface heat treatment has a deleterious effect on the fatigue performance of pearlitic gray and ductile cast irons. A 1.2 kW, continuous wave, CO2 gas laser, operating in square beam mode, was employed to heat-treat the surfaces of standard fatigue specimens. Rotational-bending fatigue tests were then conducted on untreated (as-cast) and laser treated specimens. Results indicated that the effect on fatigue behavior of case depth, microstructure and hardness of laser-hardened surface layers were opposite to that observed in carbon and low alloy steels. A fracture model based on the presence of graphite, residual stresses, and strain-induced transformation is postulated to explain the adverse effect of laser hardening of cast irons.

Laser Heat Treatment of Cast Irons—Optimization of Process Variables: Part I

A 1.2 kw CO2-CW laser operating in ring and Gaussian beam modes was used to surface harden gray and ductile cast irons. The microstructure, case depth, hardness, surface integrity, and distortion were studied as functions of process variables (i.e., laser power, focusing optics, beam size, scan rate and thickness of the specimen). The results indicate that the ring mode is preferred over Gaussian whereas ductile iron response to laser heat treatment is better than gray iron. The maximum case depth achieved with minimum melting was 0.38 mm, and the maximum coverage rate obtained was 322.58 mm2/s.

Computer Simulation of the Structure Formed During Solidification of Cast Iron

ABSTRACTBy combining heat extraction laws with kinetic growth laws, the solidification process of nodular, grey and white cast iron have been calculated. The risk for formation of white structure during solidification of grey and nodular cast iron was calculated. The calculations was done for different thickness of the casting as well as, as a function of the number of growing units. The fraction of white structure was also calculated.

Effects of the structural state on the failure of magnesium-modified cast iron

1. The structure of a fracture surface is affected by the shape, size, and distribution of the graphite grains. The failure rate is also controlled by the graphite inclusions. 2. The path of a crack is uniquely determined by the graphite inclusions and is independent of the form of loading for the pearlitic and bainite forms of matrix in grey and alloyed cast irons, and it is also independent of the failure conditions. 3. The total failure time is governed not only by the deformation characteristics but also by the relaxation ones. 4. The failure rate in the matrix is constant in these materials and is governed by the stress concentration around the graphite inclusions. 5. Mechanical hardening up to a critical value on the whole does not reduce the tendency to brittle failure but does reduce the relaxation time around the graphite inclusions.

CENTRI-CAST GRAY IRON 45

Abstract CENTRI-CAST GRAY IRON 45 has a nominal tensile strength of 45,000 psi. It is gray iron cast centrifugally in the form of tubing which has a wide range of uses for applications where freedom form pattern cost is an important consideration and where size and shape are of paramount importance. Its many applications include automotive equipment, farm machinery, bushings and machine tools. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and compressive and shear strength as well as fatigue. It also includes information on casting, heat treating, machining, joining, and surface treatment. Filing Code: CI-50. Producer or source: Federal Bronze Products Inc..

Characteristics of the fracture surface of gray magnesium cast irons after dynamic fracture

Modification of gray test iron with as much as 0.08% Mg leads to globularization of graphite and greatly changes the average rate of fracture. The fracture of the pearlitic matrix is brittle in character. The fracture of the pearlitic matrix is brittle in character. Thus, the discrete pattern of crack propagation observed is due mainly to the presence of graphite inclusions, which are areas of scattering of the elastic energy of the crack — relaxation areas. Comparison of the electron fractographs of cast and heat-treated samples (alloy with 0.08% Mg) revealed new elements of brittle fracture in the latter. Crack propagation in the ferritic cast iron is a ccompanied by intensive twinning (Fig. 3g, positive replica). It should be noted that ferritizing annealing has a negligible effect on the average rate of crack propagation (∼350 m/sec).

Effect of surface hardening on the kinetics of fracture of gray alloy cast iron

Effect of surface hardening on the kinetics of fracture of gray alloy cast iron