Hydrogen and corrosion resistance of Ni-Co superalloys for gas turbine engines blades

Abstract

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.