材料期刊网

<正> 热喷涂技术广泛用于修复磨损件,并可提高工件的耐磨、耐蚀及耐热性能。有些工件除经受摩擦、腐蚀外还承受动载作用,因而人们关心经表面喷涂后材料的疲劳行为。以前的工作指出,等离子喷涂或火焰喷涂都降低材料的疲劳强度。本工作采用二次重熔的火焰喷焊工艺以改善喷涂件的疲劳性能、并研究了喷涂后的腐蚀疲劳行为.

Flame sprayed welding with secondary remelting was adopted to improve the fatigue property of steel 45.The effect of the plasma sprayed Ni/Al coating on fatigue strength of steel 45 in air and in corrosive medium were compared with that of the flame sprayed welding Ni60.It was demonstrated that all the coatings reduced the fatigue limit in air,the plasma spraying (P.S)gave a reduction of 12% and the flame sprayed welding(F.S.W), 7%.On the contrary,thermal coating shows an advantageous effect on corrosion fatigue strength in 3.5%NaCl solution.F.S.W can increase over 70% in corrosion fatigue strength at 10~7 cycles and P.S can only increase 29%.It can be seen by fractographic analysis that fatigue cracks initiated at such places of coating which contain more defects,and the cracks grew more rapidly in cleavage or mixed mode through the Ni/Al or Ni60 coating. Occasionally,the interface between coating Ni/Al and matrix may be separated.It is found that coating Ni60 consisting of Ni-Cr solid solution and borides can decrease the passive current density.Obviously the micros- tructure and strength of the coating and bonding strength are related to the lifetimes of fatigue crack initiation.