Impact strength properties of nickel-based refractory superalloys at normal and elevated temperatures

This article is motivated by civil fire safety. Fire-prevention engineering demands a wide range of information about building materials including alternative cements, for instance CSA-cement. Because of exposure of the cement-base material to a high temperature, its strength properties deteriorate due to dehydration connected with phase and microstructure changes. Previous research indicated that the main endothermic reaction of CSA-based composite, dehydration of ettringite, might be used as a cooling system for a metal structure during fire-load. This article examines visual assessment, microstructure, density, as well as flexural and compressive strength parameters of CSA-based composite after isothermal heating at temperatures from 23 °C to 800 °C. The results of SEM/EDS investigations showed that the calcium sulfoaluminate paste may start partially re-sintering above 600 °C. Mechanical tests revealed significant reduction of strength parameters but residual compressive strength was maintained in the whole temperature range e.g., 8 MPa at 800 °C. Additionally, visual assessment of the specimens indicated that it might be possible to predict the material temperature heating based on the specific surface color. These findings add to the evidence of general knowledge about CSA hydrates.

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Research of the properties of rubber-cord composites in the presence of new adhesion promoters

Proceedings of the Voronezh State University of Engineering Technologies ◽

10.20914/2310-1202-2020-3-221-226 ◽

2020 ◽

Vol 82 (3) ◽

pp. 221-226

Author(s):

O. V. Karmanova ◽

S. G. Tikhomirov ◽

E. V. Lintsova ◽

L. V. Popova

Keyword(s):

Elevated Temperatures ◽

Tensile Elongation ◽

Physical And Mechanical Properties ◽

Cobalt Content ◽

Strength Properties ◽

Adhesion Promoters ◽

Serial Sample ◽

Rubber Compounds ◽

The Cost ◽

Processing Properties

Studies of experimental adhesion modifiers based on a mixture of fatty acids from the production of light vegetable oils. The properties of rubber compounds and their vulcanizates obtained using experimental adhesion promoters KK with cobalt content from 7.5 to 16.5% are investigated. The plastic-elastic and vulcanization properties of the properties of breaker rubber compounds based on polyisoprene, the physical and mechanical properties of breaker rubbers and the bond strength in the “rubber-brass-plated steel cord system” were studied. When testing belt rubbers containing experienced adhesion promoters or an imported analog of Manobond 680C, the following features were revealed. The plasticity of the prototypes was in the range of 0.2-0.4. This indicates satisfactory processing properties. The Mooney viscosity of the prototypes was lower than that of the production sample. The use of experienced adhesion promoters instead of the analogue (Manobond 680C) increases the resistance to scorching. On the basis of the analysis of elastic-strength properties, it was found that in terms of the conditional tensile strength, the prototypes were inferior to the serial ones. However, rubbers containing the KK-12, KK-13.5, KK-15 promoters met the control standards. The tensile elongation at break of the experimental rubbers is higher than that of the serial sample. This may indicate the formation of a more uniform cure network in the presence of the test products. When testing rubber-metal-hard composites, it was noted that, under normal conditions, the experienced adhesion promoters have advantages over Manobond 680C. However, at elevated temperatures, under conditions of salt and steam-air aging, they are slightly inferior to Manobond 680C. It has been established that the experimental adhesion promoters provide the required set of technical properties of belt rubbers with a CO2 + content of 12–16.5% wt. Thus, it is possible to recommend the adhesion promoters KK 12, KK-13.5, KK 15 for practical use in the composition of belt rubber compounds. This will allow replacing a foreign-made product and reducing the cost of production.

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