Copper based alloy as a bonding layer in Flame / arc spray.

[iwan-sedaryawan]

Dear all,
Does anyone has any experience to use coper based alloy for bonding layer in both : flame or arc spray processes ? how about the bonding strength compare with Nickel based alloys, since Ni alloys price is very expensive for the time being.
Thanks in advnance

[Vijay Deshpande]

Dear You can use Al Bronze as Bond coat provided you have a very effective fume exhaust system. Other wise your operators will fall sick as fumes are very poisonous. Also Ni-Al is always preffered considering criticality of the job
iwan-sedaryawan

[Gordon]

Hi iwan-sedaryawan

Aluminium bronze when arc sprayed (flame spray not good as bond coat) produces a good bond and can be used as a bond coat for some special applications. I would not recommend it as a general replacement for NiAl though, as bond strength are around 1/3 - 1/2 of NiAl and there is a much higher potential for corrosion problems on steel substrates.

You can use Al Bronze as Bond coat provided you have a very effective fume exhaust system. Other wise your operators will fall sick as fumes are very poisonous.

True, but please don't read this as NiAl or any other thermal spray material as not requiring effective fume extraction or personal protective equipment. For instance spraying nickel alloys may not give such chronic metal fume fever, but may have very serious implications with longer term health (carcinogenic) . So treat all fume and dust as harmful and be safe .

[iwan-sedaryawan]

Hi iwan-sedaryawan

Aluminium bronze when arc sprayed (flame spray not good as bond coat) produces a good bond and can be used as a bond coat for some special applications. I would not recommend it as a general replacement for NiAl though, as bond strength are around 1/3 - 1/2 of NiAl and there is a much higher potential for corrosion problems on steel substrates.

You can use Al Bronze as Bond coat provided you have a very effective fume exhaust system. Other wise your operators will fall sick as fumes are very poisonous.

True, but please don't read this as NiAl or any other thermal spray material as not requiring effective fume extraction or personal protective equipment. For instance spraying nickel alloys may not give such chronic metal fume fever, but may have very serious implications with longer term health (carcinogenic) . So treat all fume and dust as harmful and be safe .

Appreciated to your explanation & how about pure-copper alloy or bronze that most common available material in the market ? also only 1/2 - 1/3 of bonding strength compare with NiAl ?

[Gordon]

Hi iwan-sedaryawan

Generally copper and most of it alloys do not make for good bond coat coatings. Arc spray aluminium bronze being the exception.

We need to consider what properties are wanted from a bond coat and whether in fact we need one. The idea is to improve a coating system and not merely to make more expensive

*Primarily, an inherent high bond strength to the substrate, usually one that's capable of bonding well to a ground/polished surface.

*Produces a surface on which the top coat will bond strongly. Little point choosing a bond coat that bonds to the substrate with greater say than 12000 psi only to have the top coat bonding to the bond coat at say 2000 psi. I did a comparison between a traditional NiCrFe arc wire bond coat wire and a new (at the time) NiMoAl cored arc wire which was claimed to be the "best bond coat ever" Well, tests showed that bonding to polished steel substrates was very much in favour of the new material with a bond strengths >8000 psi compared to around 3000 - 4000 psi. But on testing with a full coating system, grit blast/bond coat and around 1 mm 13Cr steel top coat, the tradition NiCrFe wire coating system was shown to be best at ~7000 psi while the cored wire system could only manage ~5000 psi. All failures occurring between bond and top coat. You need to look for the weakest in the chain and that's not all ways the substrate/coating interface.

*Other factors need consideration, such as effect on corrosion resistance of the coating system and how the bond coat redistributes residual stresses between substrate and coating.

I stop rambling now. What reliable, proven and commercially available bond coats do we have in wire form - NiAl, Mo, some special cored wires and NiCrFe (arc only). Titanium and aluminium bronze and no doubt a few others could be considered for special applications.

[iwan-sedaryawan]

Hi iwan-sedaryawan

Generally copper and most of it alloys do not make for good bond coat coatings. Arc spray aluminium bronze being the exception.

We need to consider what properties are wanted from a bond coat and whether in fact we need one. The idea is to improve a coating system and not merely to make more expensive

*Primarily, an inherent high bond strength to the substrate, usually one that's capable of bonding well to a ground/polished surface.

*Produces a surface on which the top coat will bond strongly. Little point choosing a bond coat that bonds to the substrate with greater say than 12000 psi only to have the top coat bonding to the bond coat at say 2000 psi. I did a comparison between a traditional NiCrFe arc wire bond coat wire and a new (at the time) NiMoAl cored arc wire which was claimed to be the "best bond coat ever" Well, tests showed that bonding to polished steel substrates was very much in favour of the new material with a bond strengths >8000 psi compared to around 3000 - 4000 psi. But on testing with a full coating system, grit blast/bond coat and around 1 mm 13Cr steel top coat, the tradition NiCrFe wire coating system was shown to be best at ~7000 psi while the cored wire system could only manage ~5000 psi. All failures occurring between bond and top coat. You need to look for the weakest in the chain and that's not all ways the substrate/coating interface.

*Other factors need consideration, such as effect on corrosion resistance of the coating system and how the bond coat redistributes residual stresses between substrate and coating.

I stop rambling now. What reliable, proven and commercially available bond coats do we have in wire form - NiAl, Mo, some special cored wires and NiCrFe (arc only). Titanium and aluminium bronze and no doubt a few others could be considered for special applications.

Dear Gordon,
Okay well noted with thanks..