The effect of long-term thermal exposure on the carbide evolution in a Ni-16Mo-7Cr base superalloy was investigated. The results show that M12C carbides are mainly precipitated on the grain boundaries during thermal exposure, and the primary massive M₆C carbides can be completely transformed to M12C carbides in situ at temperatures above 750 °C for long-term thermal exposure. The transformation...

κ-carbide hardening in a ferrite-austenite duplex low-density FeMnAlC steel has been investigated as a function of annealing processing within the temperature range 500−900 o C. Below 600 o C, a high hardness can be attained by the fine microstructures, e.g. the thin lamellar κ-carbides in austenite and dispersed nanosized particulate κ-carbides in ferrite. After further annealing, the alloy so...

We have studied the transformation of carbides in AISI M42 high-speed steels in the temperature window used for forging. The annealing was found to result in the partial transformation of the large, metastable M2C carbides into small, more stable grains of M6C, with an associated change in the crystal orientation. In addition, MC carbides form during the transformation of M2C to M6C. From the h...

It is a long-standing controversy whether metal carbide clusters do exist during the nucleation and growth process of single-walled carbon nanotubes (SWCNTs). In the current work, we are trying to elucidate the carbon nucleation on nickel carbides during the initial stages based on density functional theory calculated formation energy and chemical potential for a series of Ni55Cn carbides (n is...

Crack initiation and growth behaviour of an austempered ductile iron (ADI) austenitised at 800C and austempered at 260C has been assessed under three point bend fatigue conditions. Initiation sites have been identified as carbides remaining from the as cast ductile iron due to insufficient austenisation. The number of carbides cracking on loading to stresses greater than 275 MPa is critical in ...

Studies of 4Cr5MoSiV1 die steel suggest that under appropriate conditions, additions of rare earth (RE) can enhance tensile property. This improvement is apparently due to the more uniform distribution of carbides and the enhancement of precipitation strengthening after RE additions. In this present work, the effect of the RE addition on the carbides evolution and tensile property of 4Cr5MoSiV1...

Many steels contain substitutional solutes which have a strong affinity for carbon or nitrogen. Such steels can be hardened by heat treatment which induces the precipitation of fine alloy carbides. Examples of such carbides include MX, 2 73 , 6 and 236 , where M stands for a mixture of iron and substitutional solute atoms and X stands for interstitial solute atoms. In practice, the heat treatme...

A screening study of the steam reforming reaction on clean and oxygen covered early transitionmetal carbides surfaces is performed by means of density-functional theory calculations. It is found that carbides provide a wide spectrum of reactivities, from too reactive via suitable to too inert. Several molybdenum-based systems are identified as possible steam reforming catalysts. The findings su...

The 25Cr-35Ni heat resistant steel has been widely used when resistance to oxidation and creep rapture at elevated temperatures is required. In this paper, the microstructural effect on the weldability of this alloy is investigated. The results of this study indicate that this steel has a perfect weldability in the as cast condition but does not possess good weldability in the aged condition. T...

Tungsten carbides with surface areas ranging from 4 to 39 m2/g were prepared by the temperatureprogrammed carburization of tungsten oxide and nitride powders with pure C H 4 o r a 48.9% CH4 in H 2 mixture. Oxygen uptakes on the carbides were low most likely because of the presence of graphitic carbon at the surface. Nevertheless, the carbides were active and selective for the dehydrogenation of...