Other

Cime Bocuze

Guy Nicolas

Pascal Mahot

Marc Voltz

Laurent Brunisholz

Tungsten-based alloy material sintered at a high sintering power that may contain additive elements soluble in the nickel and selected from the group constituted, for example, by rhenium, molybdenum, tantalum, niobium, vanadium or a mixture of these, wherein, after sintering in liquid phase at a temperature of around 1500&#xb0; C., it has:

High-powder tungsten-based sintered alloy

The invention relates to a process for the production of a heavy tungsten-nickel-iron alloy with high mechanical characteristics comprising the steps of using powders of each of the elements of a FISHER diameter between 1 and 15 .mu.m, mixing the powders in proportions corresponding to the composition of the desired alloy, compressing the powders in the form of compacted items, sintering the compacted items at a temperature of between 1490 and 1650.degree. C. for 2 to 5 hours, treating the sintered compacted items under vacuum at between 1000.degree. and 1300.degree. C., and subjecting the compacted items after treatment under vacuum to at least three cycles of operation, each cycle comprising a working step followed by a heat treatment.

Heavy tungsten-nickel-iron alloys with very high mechanical

The invention relates to heavy tungsten-nickel-iron alloys with high mechanical characteristics and a specific gravity between 15.6 and 18. The alloys include a tungsten .alpha.-phase in the shape of butterfly wings with dislocation cells of dimensions between 0.1 and 1 .mu.m, and a nickel-iron bonding .gamma.-phase having a mean free path of less than 15 .mu.m and an Ni/Fe ratio greater than or equal to 2.

A process for reducing disparities of mechanical properties in tungsten-nickel-iron alloys containing in % by weight 85 to 99% of tunsten, 1 to 10% of iron, the alloys being obtained from tungsten, nickel and iron powders which have the same or different grain diameter, shape and size distribution, which entails simultaneously adding an effective amount of each of cobalt and manganese powders to tungsten powder or to a mixture of tungsten, nickel and iron powders.

Process for reducing the disparities in mechanical values of

The invention concerns an abrasion resistent coating for steel and a method which makes it possible to obtain such a coating. The coating comprises two surface layers. The first surface layer, the outer layer, is formed of the phase (Cr, Fe).sub.2 B and possibly the phase M.sub.23 C.sub.6, while the second surface layer, the inner one, is formed of the phase (Fe, Cr).sub.2 B. In order to obtain this coating, a boriding is effected on steels at a temperature less than or equal to 950.degree. C. for a period of time greater than or equal to four hours, followed by a chromizing at a temperature less than or equal to 950.degree. C. for a period of time greater than or equal to 10 hours. Application to all steels in order to increase their resistance to wear is possible.

Chromium-base coating for wear-resistant steel and method of preparing

An object of the present invention is a method for the anti-wear treatment of the surface of steel parts having a carbon content of at least 0.15% and the coating obtained thereby. The method is characterized by the fact that an addition of sulfur, by depositing of a metal sulfide for example, and a vapor-phase chromizing are carried out in sucession on the surface to be treated. The coating obtained is characterized by the presence of a layer of chromium sulfide on the surface and by the partial recrystallization of the underlying M.sub.7 C.sub.3 chromium carbide layer. The invention can be applied to any moving mechanical system which is subject to abrasion. The invention has importance because it increases the resistance to wear and the life of the system treated while limiting the wear of the untreated opposing part as a result of friction.

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Bonneville, France

Guy Nicolas