Purpose: This paper is devoted to the investigation of gaseous hydrogen and ash
gas turbine fuel influence on the mass loss in long-term corrosion and mechanical
properties of cast heat-resistant blade materials. It has been established that the level of
corrosion resistance of the investigated alloys (Ni59Cr21Co10W4Ti3Al3MoLa (SM-104-VI);
Ni57Cr16Co12W6Ti4Al3Mo2Hf (SM-90-VI); Ni57Cr16Co11W6Ti4Al4Mo2Hf (SM-88U-VI))
correlated with the chromium content and is the highest among similar materials. The
advantage of SM-104-VI alloy increases with the increasing of time base and temperature.
Design/methodology/approach: This work presents research results concerning
corrosion and hydrogen resistance of a investigated alloys examined at a standart
mechanical tests under short-term static tension was determined on smooth cylindrical
five-time samples with a diameter of the working part 5 mm at speed 1 mm/min. The
destructed areas were examined by optical and electron microscopes with computer image
analysis.
Findings: It has been found that the level of resistance of the investigated alloys high-
temperature sulfide and oxide corrosion in the ash of the gas turbine fuel is correlated with
the criterion alloying and is the highest among the known materials of the blades. The value
of specific mass loss decreases in the order of SM-88U-VI, SM-90-VI, SM-104-VI. Moreover,
its advantage over alloys of SM-90-VI and SM-88U-VI as bigger as the time the corrosive
environment.
Research limitations/implications: An essential problem is the verification of the
results obtained using the standart mechanical tests, computer-based image analysis and
other methods.
Practical implications: The observed phenomena can be regarded as the basic
explanation of reduces the plasticity characteristics of the alloys for gas turbine blades.
Originality/value: The value of this work is that increasing temperature reduces the
negative influence of hydrogen, however, even at 900°C, the values of elongation and
transverse contraction in hydrogen is lower than in the air. For a short stretch in the
temperature interval 20-900°C the least sensitive to the action of hydrogen at a pressure of
30 MPa is a single crystal SM-90-VI alloy.
One of the most promising structural materials in gas turbine engineering is the alloys based on an intermetallide, the type of Ni 3 Al, with an equiaxial and directional columnar structure. These materials make it possible to increase the working temperature of blades to 1,220 °C. The blades are made by the method of precise casting in a vacuum; in this case, it is necessary to technologically join the nozzle blades into blocks, to fix the signal holes in cooled blades, to correct casting defects.
Welding by melting intermetallide materials, as well as other cast heat-resistant nickel alloys (HNA), does not yield positive results. Therefore, various brazing techniques are used such as TLP-Bonding (Transient Liquid Phase Bonding). Filler metals' melting point is lower than that of the main metal. The key issue related to the technology of brazing HNA, including the design of appropriate filler metals, is the improvement of the physical-mechanical and operational properties of brazed joints. This paper reports the established rational doping of a filler metal base, as well as depressants, the critical temperatures and surface properties of filler metals, their chemical composition, the structure and properties of brazed joints, the mode parameters, and brazing technology.To improve the stability of the structure and the high-temperature strength of the brazed joints, the filler metal was alloyed with rhenium and tantalum. Mechanical tests of brazed joints at 900 °C were conducted in Ukraine; at a temperature of 1,100 °C -in the People's Republic of China. The test results showed that the short-term strength of alloy compounds with an equiaxial structure based on the Ni 3 Al-type intermetallide at 1,100 °C is 0.98 of the strength of the main metal. The long-lasting strength at the same temperature meets the requirements for the strength of the main metal
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