B元素迁移对耐热钢高温持久性能的影响

Influences of Boron Migration on High-temperature Endurance Performance of Heat Resistant Steel

对某新型含有3%Co、3%W和微量B的12%Cr系耐热钢进行调质处理后,常温力学性能及金相组织能满足规范要求,但高温短时持久性能多次出现不合格,对此进行了研究。结果表明,如果B元素大量向晶内迁移,将形成含B量极高的第二相质点,对抑制M23C6和Laves相的粗化,促进MX的细化,稳定析出物,抑制板条状马氏体组织回复的作用明显减弱,晶界强化作用将明显削弱,造成高温短时持久性能下降,其蠕变断裂方式为延性断裂。

A new type of 12%Cr heat-resistant steel with 3%Co, 3%W and trace B was quenched and tempered by vacuum heat treatment furnace, whose room temperature mechanical properties and metaUographic structure supplied the specific requirements. However, the high-temperature short-time lasting performance was unqualified repeatedly. This problem was studied. The results show that a large number of Boron migration will form the second phase particles of high B contents. The effects significantly decrease including the suppression of M23C6 and Laves phase coarsening, the promotion of MX refinement, the stability of precipitates and the suppression of lath martensite response. Therefore the grain boundary strengthening effect will be significantly weakened, resulting in the decline of high-temperature short-lasting performance and the creep fracture mode is ductile fracture.