bronze powder coating

[attin]

Hi all,

are there anybody to help me on " bronze coated steel by powder spraying technique" ? We want to make the steel ( quality is 4140 ) surface coating by the bronze powder. this material is for hydraulic application parts, it used for hydraulic piston. Is it possible for the coating of this material? Currently, we use bronze wire for this application.

regards,

[derek]

There are several different ways to put brone powder on steel. You can use APS to spray powder on part, you also can use PTA to weld the powder on part. It depands on what kind of bond do you want.

[djewell]

We have had very good success spraying bronze powders with AC-HVAF. The coatings were extremely dense, and they were able to be machined to a smooth, bright finish. What are you hoping to achieve by switching to powder based spray? Do you need higher coating density, higher bond strength, better finishing capability, ... ?

[MichiganMan]

Why use powder when you have a system that works? The desired characteristics of the finished piece generally dictate materials and methods, and in many hydraulic applications wire would be the preferred, due to faster production and lower raw material costs. There are obviously cases where powder will be more suitable, but if this is a "typical" hydraulic application where the bronze is being used to act as bearing material (i.e. a cylinder that has some relatively minor side loading issues) then wire is probably the way to go.

Can you tell us more about what you are trying to accomplish?

[attin]

Thanks for your opinions,

I would like to achieve more strenght. tomorrow, i will show these parts pictures and give more informations to you. Another important point, wire that used for these applications we dont find regularly. wire composition is % 3 Ni + % 7 Sn + % 90 Cu. We want to change process and we want to increase bond strenght. Currently, this wire coating hardness is 100 HRB.

regards,

[loriolo]

Hi
If you want to increase bond, it is possible with plasma spray system, only if you use to spray it with Flame spray wire system, but if you use Arc spray system, you've just have a very good bonding, and with powder you are going to obtain a poorer bond, with plasma spray system you need to apply a Ni-Al Bond coat.

[attin]

Thanks loriolo and other friends,

I show bronze wire coated hydraulic parts. Firstly, we are melting wire parts surface about 6 mm after we are operating this overlay and decreased about 1-3 mm. I find very diificult to bronze wire that mentioned before and I think If we use bronze powder we can get more strenght and usability. Also, we can manufacturing this type of bronze powders, but we cant produce this type of bronze wires. In fact this is more important for us. Finally, How can we coating this steel parts ( 4140 quality )? What is the best process for this application? Is it suitable for us or let's continue to wire?

regards,

[djewell]

To get the highest density bronze coating, which you indicated was an important factor to you, you need to change to a high velocity process. It could be cold spray, HVOF, or HVAF. HVAF will give you a very fast deposition rate at a low operating cost. Oxide content and other coating properties will be comparable to the raw powder. The bronze will be strongly bonded to your 4140 steel, and you can apply thick coatings if necessary. Contact me off-line for specific information about HVAF.

[loriolo]

what kind of equipment do you use to do the coating, an spray equipment or you do it by welding?

[derek]

If you can put coating on part first and drill the hole later, PTA will be the best to do this job. Welding bond is the highest.
Or you can insert the holes first, PTA the part then drill the holes.

[attin]

Hi,

We use acetylene with oxygen flame for melting bronze wire on the surface. We put coating on part first after drill the hole in parts. Firstly, we melt wire on the surface.
If we will coating by the PTA, what will be the coating condition? and powder properties? Can you please tell somethings?

regards,

[derek]

Plasma transferred arc (PTA) is a versatile method of depositing high-quality metallurgically fused deposits on relatively low cost surfaces. Soft alloys, medium and high hardness materials, and carbide composites can be deposited on a variety of substrates to achieve diverse properties such as mechanical strength, wear and corrosion resistance, and creep. PTA has several significant advantages over traditional welding processes such as oxyfuel (OFW) and gas tungsten arc (GTAW) welding.

The PTA process:
PTA is easily automated, providing a high degree of reproducibility.


PTA allows precise metering of metallic powder feedstocks. As a result a lesser quantity of material is used when compared to other traditional welding processes.


PTA permits precise control of important weld parameters i.e. powder feed rates, gas flow rates, amperage, voltage, and heat input, ensuring a high degree of consistency from lot to lot. Controlled heat input ensures weld dilutions that can be controlled from 5-7% in most cases.


PTA produces deposits of a given alloy that are tougher and more corrosion resistant then counterparts laid down by GTAW or OFW processes. Weld deposits are characterized by very low levels of inclusions, oxides, and discontinuities.


PTA produces smooth deposits that significantly reduce the amount of post weld machining required.


PTA parameters can be adjusted to provide a variety of deposits in thicknesses from 1.2 to 2.5 mm (0.05 to 0.10 in.) or higher. These can be deposited by a single pass at a rate of 1 kg/h up to 13 kg/h depending upon the torch, powder and application.