H. J. Shin, S. Y. Lee, K. H. Ko, Ajou University, Suwon, South Korea; H. J. Lee, Ajou University, SUWON, South Korea; Y. H. Yu, S. H. Jung, S. H. Ahn, J. J. Lee, Solmics Co., Ltd, Pyungtak, South Korea
Multi-layers of Al, Ni, and Ti were prepared by cold gas dynamic spray process (CDSP) and characteristics of intermetallic compound formation during post-annealing were examined. The powder particles were accelerated by highly pressurized air through a standard De Laval type nozzle with the pressure of 8 to 25 MPa (prior to enter). The multi-layered coatings were annealed at 500~630°C in the air or Ar atmosphere. At relatively low acceleration pressure (< 8 MPa), the intermetallic compound layers in Al/Ni coatings were the Al3Ni and Al3Ni2 which formed initially at the original interface and moved toward Ni side owing to the faster diffusion of Al than Ni atoms(Kirkendall effects). At high pressure conditions (> 10 MPa), the diffusion of Al was further facilitated by more abundant defects formed by higher velocity impaction and shifting of composition to Al-richer compound was prevail. In the case of Al coating/Ti substrate, there was a little difference between high and low pressure conditions, presumably due to high hardness and low deformability of Ti. Conclusively, the massive defects in the cold sprayed layer originated from the adiabatic plastic deformation of incoming particle can be manipulated by process parameters and utilized in post-treatment such as compound formation and/or sintering, etc.
Summary: Multi-layers of Al, Ni, and Ti were prepared by cold gas dynamic spray process and characteristics of intermetallic compound formation during post-annealing were examined. The powder particles were accelerated by highly pressurized air with the pressure of 8 to 25 MPa .The multi-layered coatings were annealed at 500~630 oC in the air or Ar atmosphere. At relatively low acceleration pressure , the intermetallic compound layers in Al/Ni coatings were the Al3Ni and Al3Ni2 which formed initially at the original interface and moved toward Ni side owing to the faster diffusion of Al than Ni atoms. At high pressure conditions , the diffusion of Al was further facilitated by more abundant defects formed by higher velocity impaction and shifting of composition to Al-richer compound was prevail. In the case of Al coating/Ti substrate, there was a little difference between high and low pressure conditions, presumably due to high hardness and low deformability of Ti.Conclusively, the massive defects in the cold sprayed layer originated from the adiabatic plastic deformation of incoming particle can be manipulated by process parameters and utilized in post-treatment such as compound formation and/or sintering, etc.
