Effect of alloying and heat treatment on the structure and tribological properties of nitrogen-bearing stainless austenitic steels under abrasive and adhesive wear

The effect of nitrogen, silicon, and aging modes on the structure, resistance to abrasive and adhesive wear, friction factor, and mechanical properties of nitrogen-bearing (0.27–0.83% N) chromium-manganese austenitic steels is studied. It is shown that it is possible to ensure a favorable combination of mechanical and tribological properties in such steels by choosing the appropriate chemical composition and aging mode. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 9–18, May, 2007.     

Microstructure and Properties of Oil and Gas Range Pipe Steel Subjected to Improvement

Metallurgist - The effect of alloying on the properties of highly tempered steels used for production of a range of petroleum pipes is studied. It is shown that an increase in molybdenum content...     

Formation and sublimation of the intermediate products of the reduction of silicon from its dioxide

The products of the partial reduction of silicon from its dioxide are studied experimentally. Different ratios of silicon to oxygen ions are revealed on the surface of the initial phase and in the condensate of the reduction products having sublimated from this surface. The quenched condensate particles have a block structure with different atomic-packing densities and contain elemental silicon, silicon monoxide, and some undetected crystalline oxides, which are intermediate reduction products. A mechanism is proposed for the formation and sublimation of the products of incomplete silicon reduction.     

Study of Low-Carbon Pipe Steel Strain Ageing

Metallurgist - Strain aging of pipe steels 06G2FB and 07G2MFB with ferrite-pearlite and ferrite-bainite structures is investigated. It is established that a ferrite-bainite structure is more...     

Strain aging and the Bauschinger effect in low-carbon pipe steel

Strain aging and the Bauschinger effect in low-carbon ferrite–pearlite and ferrite–bainite pipe steel are studied. Steel with ferrite–bainite structure is more susceptible to strain aging and the Bauschinger effect. After alternating loading, strain aging develops, with increase in the yield point. After alternating loading of already aged steel, the Bauschinger effect appears; it is comparable with the effect in unaged steel.     

Role of the silicate phase of an enclosing rock in the prereduction of disseminated chromium ores

The composition and distribution of the products of solid-phase metal reduction from disseminated chromium ores are studied. Reduction is shown to occur in these ores despite the presence of isolating layers, which are made from the silicate phase of the enclosing ore, between a reducer and an ore grain. The channels of rapid reduction propagation inside ore grains are cracks filled with silicates. The propagation of reduction through the silicate phases is caused by favorable (as compared to chromospinellides) conditions for the motion of charged oxygen vacancies and oxygen, since these phases are in a glass state at the reduction temperature. The absence of boundaries and lattice defects in the glass state decreases the concentration of dislocation barriers. The low concentration of reducible cations in the silicates causes their motion to vacancy sinks, where reduced metals are accumulated.     

Structural transformations and tribological properties of amorphous alloys upon wear at room and cryogenic temperatures

The abrasive wear resistance of the Fe₆₄Co₃₀Si₃B₃, Co_86.5Cr₄Si₇B_2.5, Fe_73.5Nb₃Cu₁Si_13.5B₉, and Fe_82.6Nb₅Cu₃Si₈B_1.4 commercial amorphous alloys (ribbon 0.03 mm thick and 12 mm wide) has been investigated under the conditions of abrasive and adhesive wear upon sliding friction. The character of fracture of the surface and structural transformations that occur in these materials upon wear have been studied by the metallographic and electron-microscopic methods. It has been shown that at room and cryogenic (−196°C) temperatures of tests the abrasive wear resistance of the amorphous alloys is two-three times lower than that of tool steels Kh12M and U8. A comparatively small abrasive wear resistance of the amorphous alloys is explained by local softening of these materials in the process of wear. Under the conditions of adhesive wear of like friction pairs at room temperature in air and argon, the amorphous alloys are characterized by the rate of wear that is smaller approximately by an order of magnitude than in steels 12Kh13 and 12Kh18N9. It has been established that upon wear the deformed surface layer of the alloys under study retains a predominantly amorphous state but in local sections of this layer nanocrystalline structures that consist of crystals of bcc and fcc phases and borides are formed. The possible effects of this partial crystallization on the microhardness, friction coefficient, and wear resistance of these alloys have been considered.