Cracks appeared at austenitic surfacing layer of BFP(boiler feed pump) casing.Finite element method was adopted to conduct thermal-stress coupling simulation on the assembly body.Moreover

the structure model was optimized to study the influence of uniform distributed radius of bolt hole R1 and the maximum outer radius of surfacing welding layer R2 on surfacing layer and casing mechanical properties.Furthermore

the aging behavior of austenitic surfacing layer was investigated by Larson-Miller parameters.The results showed that

the maximum stress at surfacing layer of original casing model occurred in surface with wrap angle of 0°

and the maximum stress value of P1 is much higher than that of P2 and P3

and the crack of bolt hole extended outward;the safety coefficient of casing structure was improved dramatically when 2×R1 and 2×R2 are equal to 685 mm and 605 mm respectively(namely when the screw thread was processed on the casing without interleaving with surfacing welding);the service life of casing with improved structure was prolonged by several times.