Effect of Structure and Composition on the Hardness of Sintered Composites Based on Stainless Steels

A phenomenological model is constructed to describe the hardness of a composite material based on stainless steels. The effect of the structure and the content of dispersed inclusions on the hardness of such composites is studied. The adequacy of the model is checked on test specimens made of stainless steel Kh18N15 containing 0.6% carbon and 10-30% dispersed inclusions of chromium carbide. The model makes it possible to not only evaluate the reinforcing effect of fine inclusions, but also to optimize that effect.

     

Economically Alloyed Manganese-Containing Powder Structural Steels. Composition, Preparation Conditions, and Properties

The possibility of replacing nickel by manganese in Cu - Ni steels is studied. The physicomechanical properties, composition, and production conditions for manganese-containing steels sintered in hydrogen and converted gas are determined. It is established that they may replace standard steel grade PK40N2D2.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 25–31, March–April, 2005.     

Wettability and contact interaction in the systems complex titanium-chromium carbide-iron and cast iron melts

Because of their high hardness, complex titanium-chromium carbides are of considerable interest for the creation of tungsten-free hard alloys and carbide steels. According to data in the literature, which is analyzed in [1], the solubility of Cr₃C₂ in titanium carbide varies from 40 wt.% at 1600°C to 51 wt.% at 1725°C. It is notable that it drops sharply with decreasing temperature, and is ～4 wt.% at 1300°C. It was established in [2] that the microhardness of titanium carbide containing 30 wt.% Cr₃C₂ in solid solution is 40 GPa.     

Cointegration between oil spot and future prices of the same and different grades in the presence of structural change

The purpose of this study is to examine whether crude oil spot and futures prices of the same and different grades are cointegrated using a residual-based cointegration test that allows for one structural break in the cointegrating vector and high-frequency data. We choose the US WTI and the UK Brent as the representative crudes for this analysis since these two crudes have well-established spot and futures markets. We find that spot and future prices of the same grade as well as spot and futures prices of different grades are cointegrated. We examine potential causes of structural change as revealed by the cointegration test in terms of events that have impacted on world oil markets as well as discuss the implications of the results for hedge managers, investors and regulators.     

Electric-spark alloying of steels with chromium carbide base alloys

Conclusions It is shown that, of the Cr₃C₂-Fe cermets investigated, KKhZh-50 alloy is the best alloying electrode material. Alloying should be performed under soft conditions (E_pulse ^–2 J). The quality of the reinforced layer depends on the pulse energy and the base and electrode materials. The continuity of the layer increases and its surface roughness and thickness decrease with increasing pulse energy. Anode erosion and alloyed layer formation are affected by the secondary structure on the electron surface. For KKhZh-50 alloy its formation decreases anode erosion and the cathode weight gain, while for KKhNF-15 alloy, by contrast, it increases them. It is proposed that, to increase the corrosion resistance of such coatings (by about two orders), 65G steel should be alloyed in two stages, first with KKhZh-50 cermet and then with nickel.Translated from Poroshkovaya Metallurgiya, No, 4(304), pp. 1–6, April, 1988.     

Layered Powder Metallurgy Wear- and Corrosion-Resistant Materials for Tool and Tribological Applications. Structure and Properties

Three-layered non-tungsten hard alloys for tool applications of the type KKhNFT5 KKhNFT25 KKhNFT5 and layered powder metallurgy materials for tribological applications with a working layer of composites based on stainless steels were investigated. Basic requirements for the creation of wear- and corrosion-resistant powder metallurgy materials for tool and tribological applications were formulated. These mainly concern their composition and structure.     

New Weldable High-Strength Wear-Resistant Steel with a Minimum Tensile Strength of 1050 N/mm2

The Severstal’ Metallurgical Combine has successfully introduced the production of rolled steel plates having mechanical properties commensurate with those of the best comparable foreign products. The new wear-resistant high-strength steel should find wide use in new technologies, especially within the mining industry. The steel, with the grade designation 18KhGNMFR, has been awarded Russian Patent No. 2223343.Translated from Metallurg, No. 1, pp. 36–37, January, 2005.     

Cobalt-Chromium Powder Alloys and Retention Coatings Made from Them for Orthopaedic Stomatology

An alloy of Co-Ni-Mo-Cr is prepared by diffusion impregnation with chromium from point sources of cobalt-nickel-molybdenum alloy powder synthesized by combined reduction. Optimum regimes are determined for preparing alloy powder by combined reduction of cobalt, nickel, and molybdenum oxides (reduction temperature 1325 K, isothermal soaking time 3 h) and diffusion impregnation with chromium (temperature 1373 K, isothermal soaking time 4 h). The adhesive strength of a facing coating with material of a dental prosthesis manufactured using the alloy developed is studied. It is shown that with application of retention layers the adhesive strength increases by a factor of three to five compared with using cast spheres (beads). __________ Translated from Poroshkovaya Metallurgiya, Nos. 5–6(443), pp. 3–7, May–June, 2005.     

Sintered metals and alloys

The paper examines the production of a composite material that is double hardened by adding titanium carbides and borides to the steel and by quenching the metal matrix and letting it to age. Samples containing 30 wt.% TiC or TiB₂ are produced by liquid phase sintering, hot pressing, and hot forging. The effect of thermal treatment on the mechanical properties and structural state of the material is investigated. The material quenched and aged is established to be twice as durable and hard as the sintered one. Hence, it can be mechanically treated after sintering and then thermally treated. The highest possible strength of the material produced is 1400 to 1500 MPa and hardness 60 to 65 HRC. Strengthening worn reinforcing-wire knives with plates of the composite material prolonged their life by 50 to 100% compared with the standard knife. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 7–8 (456), pp. 28–34, 2007.