Development of thermally-sprayed Al-Cu-Fe-Cr quasicrystal coating.

摘要

A class of quasicrystal alloys that has drawn a lot of attention is aluminum based quasicrystal alloys because they are hard, light weight, wear resistant, and have a non-stick property. Quasicrystalline materials in the form of coatings produced by thermal spray techniques have been developed to utilize their properties.; The goal of this research has been to develop the knowledge necessary to produce good thermally sprayed Al-Cu-Fe-Cr quasicrystal coatings. Boron has been found to improve ductility, reduce porosity and increase hardness when added to other thermally sprayed powders, therefore, as part of this research, quasicrystal coatings containing boron will also be produced and evaluated.; The first phase of this research utilized a fine QC-1 quasicrystal powder of {dollar}rm Alsb{lcub}70.5{rcub}Cusb{lcub}10.1{rcub}Fesb{lcub}8.8{rcub}Crsb{lcub}10.6{rcub}.{dollar} The addition of boron was done using mechanical mixing. The addition of boron in fused QC-1 powders shows that boron can reduce porosity and increase hardness. Due to difficulties with thermal spraying the fine QC-1 powder and evaporation of aluminum, a coarser QC-2 powder with similar composition to QC-1 powder was produced.; QC-2 and boron modified QC-2 coatings have similar hardness and levels of porosity, around 11%, although boron modified QC-2 coatings proved to be more wear resistant than plain QC-2 coatings. Both coatings demonstrated a weak coating-substrate interface bonding. Laser heat treatment was used to reduce the porosity and strengthen the coating-substrate interface bonding.; Laser treatment of QC-2 quasicrystal coatings resulted in harder and lower porosity coatings with better coating-substrate interface bonding. Unfortunately, hot-cracks in the coatings were also produced. Hot-cracks are undesireable because they decrease the coating's corrosion resistance.; Thermal spraying using High Velocity Oxygen Fuel (HVOF) technique was done. It was used on QC-2 powder and QC-3 powder of composition {dollar}rm Alsb{lcub}68.6{rcub}Cusb{lcub}10.8{rcub}Fesb{lcub}8.9{rcub}Crsb{lcub}9.7{rcub}Bsb{lcub}2.0{rcub}.{dollar} This spraying technology produced high quality quasicrystal coatings, with high hardness, low porosity, good coating-substrate interface bonding and good wear resistance. Heat treatments of QC-3 coatings at {dollar}600spcirc{dollar}C or above produce an even more wear resistant phase.