≤0.5Mo)cracked and failed af- ter serveed for 2 years and nine months at ≤980 ℃.The analysis results showed that the g phase precipitation which led to brittleness of materials was main cause for cracking of radiant tubes
the served temperature at cracking region was higher than that at non-cracking region
in cracking region the precipitated g phase was coarse
the amount of σ phase increased
and the plasticity and toughness of this region obviously decreased led to cracking and failure.