Влияние эксплуатационных и конструкционных факторов на скорость роста усталостных трещин в жаропрочном никелевом сплаве корпуса камеры сгорания авиационного ГТД

Abstract

 For scientific justification of operation of aviation gas-turbine engines on technical condition it is necessary to have information on the fatigue crack growth rate in material of details of engines from the initial cracks sizes to critical. This information, according to normative documents, is used at purpose of terms and volumes of carrying out scheduled tasks at maintenance of engines. Work purpose: the research fatigue crack growth rate in a high-temperature ni-base alloy of acombustion chamber casing of the aviation gas-turbine engine taking into account operational (temperatures) and constructional (a joint weld, product thickness) factors. Experimental procedure: the studies were performed on a flat specimens on tension (plate1.6 mmthickness) with a local cut by a standard ASTM E647 technique at temperatures of tests +550 °Cand +600 °C. Fatigue crack growth rate was investigated in the base metal, in a joint weld and in a zone of thermal influence apart23 mmfrom a joint weld. For this, a fatigue crack was initiated from a mechanically incised notch that was located in a corresponding place with respect to the welded seam: over the base metal, welded seam, and the zone of thermal influence. A linear portion of the fatigue crack growth diagrams is constructed and the coefficients of the Paris equation are obtained. Confidence intervals are also given, which illustrate the region where the results of the experiment hit the target with a probability of 95%. Conclusion: it is shown that taking into account statistical data interpretation on fatigue crack growth rate of the zone of thermal influence and the main metal differ slightly while fatigue crack growth rate in a joint weld increases in twothree times. Assessment of mechanical characteristics of studied alloy was performed, upon transition from the base metal through a zone of thermal influence to a joint weld. For this purpose were used measurements of hardness by Rockwell’s method. Results showed minor change of hardness that indirectly explains small difference (in borders of a statistical error) on the fatigue crack growth rate in the base metal and a zone of thermal influence. Исследована скорость роста трещин усталости в зоне термического влияния, в сварном шве и в основном металле жаропрочного никелевого сплава корпуса камеры сгорания авиационного газотурбинного двигателя при эксплуатационных температурах 550, 600 °С. Эксперименты выполнялись на плоских образцах на растяжение толщиной1,6 мм, что соответствует толщине корпуса камеры сгорания. Показано, что с учетом статистической обработки экспериментальных данных по кинетике роста трещин усталости зона термического влияния и основной металл отличаются незначительно, в то время как скорость роста трещин усталости в сварном шве увеличивается в два-три раза.