Effect Of Heat Treatment Process On Microstructure And Properties Of Ta15X Titanium Alloy Drill Pipe

Titanium alloy drill pipe has the advantages of low density,good toughness,good fatigue resistance and good corrosion resistance,etc.It is a hot spot in the current oil and gas industry research.In this paper,the mechanical properties test,OM,SEM,XRD,TEM and other characterization methods were used to study the effect of heat treatment process on the structure and performance of TA15X titanium alloy drill pipe,and the physical objects were evaluated.The results show that the TA15X titanium alloy drill pipe material has a lamellar structure in the as-cast state,a dual-state structure in the forged state,a lamellar structure in the extruded state,and T_?/?phase transition temperature of 970°C.Under the action of compressive external force below the phase transition point,the dislocation density of the lamellar structure increases to form sub-grain boundaries and thermal grooves,and the?phase cuts into the?phase to make the lamellar structure spheroidize.?1?As the annealing temperature increases,the strength increases and the elongation decreases;after air cooling,the volume fraction of the?phase layer decreases,the size becomes shorter,and the volume fraction of the needle-shaped martensite??transformed into?phase after water cooling increases,and the size becomes slender,the original Widmannstatten structure is transformed into a near-net basket structure.When the annealing temperature is 900?,the strength increases by at least 100MPa,and the lower elongation after air cooling can reach 13%,and the overall performance is better.After double annealing,the strength increases and the toughness decreases.?2?As the solution temperature increases,the lamellar?phase transforms into?phase,and the lamellar?phase width becomes wider,the strength decreases,the plasticity increases,and the dislocation cluster?phase slips to?/?at the interface,the strength is increased.?3?After aging treatment,the?grain size of TA15X titanium alloy drill pipe material increases,the grain boundary is clear,the?phase colony phenomenon disappears,the grain boundary?phase disappears,and the size of the initial lamellar?phase becomes larger and larger.The secondary?phase content gradually increases,the strength increases,and the elongation decreases.?4?As the aging temperature increases,the strength increases first and then decreases,and the plasticity decreases.When the heat treatment process is 930?/1h/WQ+500?/6h/AC,R_m=1236MPa,an increase of 27%,R_0.2=1146MPa,an increase of 29.5%,A=9.5%,with excellent performance Matching:With the extension of the aging time,the strength gradually decreases,and the plasticity gradually increases.When the ageing process is 930?/1h/WQ+600?/6h/AC,the elongation reaches the highest A=11.5%.?5?After aging treatment,a large number of dislocation pileup are found at the?/?phase interface,thereby improving the strength of the alloy.The greater the number of secondary?phases precipitated,the finer the smaller,the more significant the strengthening effect.The anti-torque,anti-extrusion,and tensile properties of the actual TA15X titanium alloy drill pipe meet the mechanical properties of 105ksi steel drill pipe.The high temperature performance is good.As the temperature increases,the strength decreases and the plasticity increases.Under the 200°C environment,the material still has good mechanical properties.R_m=847MPa,R_0.2=737MPa,A=14%,at this time it is still meet the mechanical properties of105ksi steel drill pipe;the friction and wear resistance is worse than that of the same steel grade steel drill pipe.