Effect of sample geometry on regression rate of the melting interface for carbon steel burned in oxygen

Promoted-ignition testing on carbon steel rods of varying cross-sectional area and shape was performed in high pressure oxygen to assess the effect of sample geometry on the regression rate of the melting interface. Cylindrical and rectangular geometries and three different cross sections were tested and the regression rates of the cylinders were compared to the regression rates of the rectangular samples at test pressures around 6.9 MPa. Tests were recorded and video analysis used to determine the regression rate of the melting interface by a new method based on a drop cycle which was found to provide a good basis for statistical analysis and provide excellent agreement to the standard averaging methods used. Both geometries tested showed the typical trend of decreasing regression rate of the melting interface with increasing cross-sectional area; however, it was shown that the effect of geometry is more significant as the sample's cross sections become larger. Discussion is provided regarding the use of 3.2-mm square rods rather than 3.2-mm cylindrical rods within the standard ASTM test and any effect this may have on the observed regression rate of the melting interface.

Electrodeposition of composite copper/liquid-containing microcapsule coatings

This paper presents results on the preparation of microcapsules containing liquid organosilica, and their co-deposition with copper in an acidic copper electrolyte onto a carbon steel cathode to form a copper/microcapsule composite coating. Microscopic analyses of the surface and the cross-section of the coating confirm the incorporation of the liquid-containing microcapsules in the coating layer. The influence of microcapsules in the electrolyte on the cathode polarization, as well as that of process conditions on the microcapsule inclusion, is also discussed. (C) 2004 Kluwer Academic Publishers.

Microstructure and grain boundary microanalysis of X70 pipeline steel

Grain boundaries (GBs), particularly ferrite: ferrite GBs, of X70 pipeline steel were characterized using analytical electron microscopy (AEM) in order to understand its intergranular stress corrosion cracking (IGSCC) mechanism(s). The microstructure consisted of ferrite (alpha), carbides at ferrite GBs, some pearlite and some small precipitates inside the ferrite grains. The precipitates containing Ti, Nb, V and N were identified as complex carbo-nitrides and designated as (Ti, Nb, WC, N). The GB carbides occurred (1) as carbides along ferrite GBs, (2) at triple points, and (3) at triple points and extending along the three ferrite GBs. The GB carbides were Mn rich, were sometimes also Si rich, contained no micro-alloying elements (Ti, Nb, V) and also contained no N. It was not possible to measure the GB carbon concentration due to surface hydrocarbon contamination despite plasma cleaning and glove bag transfer from the plasma cleaner to the electron microscope. Furthermore, there may not be enough X-ray signal from the small amount of carbon at the GBs to enable measurement using AEM. However, the microstructure does indicate that carbon does segregate to alpha : alpha GBs during microstructure development. This is particularly significant in relation to the strong evidence in the literature linking the segregation of carbon at GBs to IGSCC. It was possible to measure all other elements of interest. There was no segregation at alpha : alpha GBs, in particular no S, P and N, and also no segregation of the micro-alloying elements, Ti, Nb and V. (C) 2003 Kluwer Academic Publishers.

The effect of resin type on the sintering of freeformed maraging steel

The role of the resin type on the sintering of maraging steel with boron additions has been investigated. Two different resins were added to the steel mixture and their subsequent debinding was evaluated and sintering responses compared with that of a resin-free alloy. The two resins used, nylon and a mixture of phenolic resin and synthetic wax, possessed different debinding behaviour, with the latter causing significant carbon contamination of the parts. This caused the formation of a Ti-Mo carbide, depleting the matrix of these elements. Consequently, the microstructure consisted of the equilibrium Fe-Fe2B eutectic, as well as a Mo-rich boride. The liquid phase also appeared to contain significant amounts of carbon, which lowered the temperature at which the liquid formed, resulting in high density occurring at a much lower temperature. When nylon was used as the binder, a similar sintering response to the resin-free alloy was observed. (C) 2002 Published by Elsevier Science B.V.

Sintering of maraging steel with phosphorous additions

The aim Of this study was to develop a steel powder system for rapid tooling applications. The properties required are rapid densification, dimensional precision. high mechanical strength and corrosion resistance. To this end. the densification and microstructural development of a loose packed 200 grade maraging steel powder sintered with ferrophosphorous additions was examined. Liquid initially formed from a reaction of the Fe3P and carbon, which was a residue of the polymeric binder used to shape the powder compact. This liquid caused a burst of sintering which ceased as the liquid dissipated. On further heating, a phosphorous rich supersolidus liquid appeared at triple points and grain boundaries leading to rapid densification and a sintered density of 98%.

Atom probe field ion microscope measurements of carbon segregation at an a:a grain boundary and service failures by intergranular stress corrosion cracking

This work reports on a critical measurement to understand the intergranular stress corrosion cracking (IGSCC) of pipeline steels: the atom probe field ion microscope (APFIM) measurement of the carbon concentration at a grain boundary (GB). The APFIM measurement was related to the microstructure and to IGSCC observations. The APFIM indicated that the GB carbon concentration of X70 was similar to 10 at% or less, which correlated with a high resistance to IGSCC for X70. (C) 2005 Elsevier Ltd. All rights reserved.

Crystallography of carbide-free bainite in a hard bainitic steel

The convergent beam Kikuchi line diffraction technique has been used to accurately determine the orientation relationships between bainitic ferrite and retained austenite in a hard bainitic steel. A reproducible orientation relationship has been uniquely observed for both the upper and lower bainite. It is [GRAPHICS] However, the habit plane of upper bainite is different from that of lower bainite. The former has habit plane that is either within 5 degrees of (221)(A) or of (259)(A). The latter only corresponds with a habit plane that is within 5 degrees of (259)(A). The determined orientation relationship is completely consistent with reported results determined using the same technique with an accuracy of +/- 0.5 degrees in lath martensite in an Fe-20 wt.% Ni-6 wt.% Mn alloy and in a low carbon low alloy steel. It also agrees well with the orientation relationship between granular bainite and austenite in an Fe-19 wt.% Ni-3.5 wt.% Mn-0.15 wt.% C steel. Hence it is believed that, at least from a crystallographic point view, the bainite transformation has the characteristics of martensitic transformation. (c) 2006 Elsevier B.V. All rights reserved.