单晶高温合金的中温Ⅰ阶蠕变--涡轮叶片伸长的重要因素

单晶镍基高温合金已广泛用于制造先进燃气涡轮叶片,但这种合金至今仍被忽视的薄弱环节是它的中温Ⅰ阶蠕变伸长量远高于高温蠕变,而且与高温蠕变相比,中温Ⅰ阶蠕变对取向偏离、合金成分和热处理组织的变化更为敏感.虽然预蠕变引进较高的位错密度能有效抑制中温蠕变,但在实用上仍有困难.在选用单晶合金作为涡轮叶片时,应考虑到先进的二代和三代单晶在中温下的抗变形能力不如一代单晶,同时中温大应力状态下的叶片根部可能过度伸长.

Primary creep of single crystal superalloys at intermediate temperature --An important factor of turbine blade extension

The single crystal Ni-base superalloys were widely used for manufacturing advance gas turbine blades, but the ignored weakness of these alloys to date is that the extent of primary creep at intermediate temperature is much higher than that at high temperature. Moreover, compared with high temperature creep, the primary creep strain at intermediate temperature is extraordinary sensitive to changes in the orientated deviation, composition and the heat-treated microstructure. Although the high-density dislocations introduced by pre-creep treatment can restrict the intermediate temperature creep, it is difficult for application in practice. As single crystal alloys are selected as manufacturing turbine blades, it is considered that the resistance to deformation of the second or the third generation single crystal superalloys at intermediate temperature is inferior to first generation alloys and the excessive extension of blade root could take place at the service environment of intermediate temperature and high stress.