1. Well Tech Research Institute, China Offshore Services Limited, Langfang 065201, Hebei, China; 2. Collaborative Innovation Center of Steel Technology, University of Science and Technology Beijing, Beijing 100083, China
Abstract:The fracture failure reason of non-magnetic drill collar for drilling instrument was analyzed by means of optical microscope, scanning electron microscope, mechanical properties test and fretting wear test. The results show that fretting wear occurs on the logging while drilling (LWD) instrument drill collars during operation, and the annular wear groove is formed at the root of transition cone angle of workpiece. Annular wear not only reduces the effective diameter of drill collar drive shaft, but also causes strong stress concentration in the annular wear area under the complex load with bending, which eventually leads to the fracture of workpiece. Annular wear is caused by the assembly structure of workpiece, but because the driving shaft is taken within half of raw material forgings radius, where the grain is relatively coarser, hardness is lower, thus, the wear is relatively serious under the same working conditions.
Lee T H, Oh C S, Kim S J, et al. Deformation twinning in high-nitrogen austenitic stainless steel[J]. Acta materialia, 2007, 55(11): 3649.
[7]
SHI F, TIAN P, JIA N, et al. Improving intergranular corrosion resistance in a nickel-free and manganese-bearing high-nitrogen austenitic stainless steel through grain boundary character distribution optimization[J]. Corrosion Science, 2016, 107: 49.
Lee T H, Oh C S, Lee C G, et al. Precipitation of σ-phase in high-nitrogen austenitic 18Cr-18Mn-2Mo-0.9N stainless steel during isothermal aging[J]. Scripta Materialia, 2004, 50(10): 1325.
[11]
Zhou R, Northwood D O, Liu C. On nitrogen diffusion during solution treatment in a high nitrogen austenitic stainless steel[J]. Journal of Materials Research and Technology, 2020, 9(2): 2331.
HONG C, SHI J, SHENG L, et al. Effects of hot-working parameters on microstructural evolution of high nitrogen austenitic stainless steel[J]. Materials and Design, 2011, 32(7): 3711.
Akbari A, Mohammadzadeh R. Effect of grain refinement on the mechanical properties of a nickel-and manganese-free high nitrogen austenitic stainless steel[J]. Metallurgical Materials Transactions A, 2015, 46(4): 1570.
[28]
WANG Z, SUN S, WANG B, et al. Effect of grain size on dynamic recrystallization and hot-ductility behaviors in high-nitrogen CrMn austenitic stainless steel[J]. Metallurgical and Materials Transactions A, 2014, 45(8): 3631.