Bonding for Wire Flame Spray using Aluminum pure wire

[iwan-sedaryawan]

dear all,
please let me know if anyone have any experiences using Al pure for bonding instead of NiAl 80/20 , since the bonding strength Al pure is high enough, or Aluminum Bronze also can be used ?
Thanks in advance

[Gordon]

Hi Iwan

Flame sprayed aluminium and aluminium bronze will not make for a good bond coats on metal substrates (relatively poor bond strength, no "self-bonding"). You would probably be better off not having a bond coat. NiAl is hard to beat and really recommended where a bond coat to metal substrates is required.

The only exception may be for heat sensitive substrates (like plastics) where aluminium and other lower melting point materials could provide good base coats for higher melting point top coats. I would certainly not recommended NiAl for temperature sensitive substrates.

[loriolo]

Hi Iwan
I agree with Gordon, and I want to add some think else, aluminum arc spray coating can reach a coating bond strength at least 22 MPa, and with aluminum bronze you can obtain a bond strength higher than Ni/Al (about 56 MPa), but this only if you use arc spray system, I usually recommend to use bronze aluminum as bond coat for copper conductive coatings, bearings, I always obtained a good bond strenght, but i do not recomend to use aluminum wire as bond coat.

[MichiganMan]

As has been mentioned by the others bond wires are bond wires for a reason. You'll notice that the bond wires are composed of multiple metals. These compositions have been created to optimize reactivity between the constituents while spayed in order to manipulate the temperature and phase of the sprayed particles, thus creating the best possible bond.

That said, every project has its own variables, and if you can prove that using the aluminum does not take away from the performance of your coating, then it isn't a bad idea to ask the question. If you are going to try to make a change like this though, be sure that you have the understanding of the application and the laboratory tools that you will need to prove that it is a viable solution before you make a change. Usually higher bond strength is better, and the bond wires are going to give you a better bond.

Sometimes thinking outside of the box can lead to very interesting and very desirable outcomes. I once conviced a customer to change a specification from pure molybdenum to a far less expensive, easier to manipulate material, because I was able to prove comparable performance at dramatically reduced price. The result was exclusive approval to perform the new specification and a substantial influx in work.