WC-Co+NiCrBSi Applying on hydraulic piston rod

[Met.Eng.]

Hi,

Is anybody knows WC-Co+%30(NiCrBSi) corrosion resistance with hvof coating? We want to apply this powders on hydraulic piston rod for food industry

[Vadim Verlotski]

(05-07-2016 05:03 PM)Met.Eng. Wrote:  Hi,

Is anybody knows WC-Co+%30(NiCrBSi) corrosion resistance with hvof coating? We want to apply this powders on hydraulic piston rod for food industry

Hi Met.Eng.,
In salt spray tests hold on the best HVOF coatings of WC-Co-Cr or Cr3C2-NiCr more than 1000 hours before corrosion of substrate begin. This result is better than the for hard chrome. Nevertheless, the HVOF coatings provide no lasting protection from saltwater.
The molten layers of NiCrBSi (remelted after spraying on the steel substrate at 1050-1100°C) are absolutely resistant in salt water.
If you bring to melt a mixture of NiCrBSi and WC powder after flame spraying or HVOF spraying, you reach a corrosion resistant layer. However, 30% of NiCrBSi is not enough to melt the mixture tightly in air. Usually one takes a coarse-grained WC powder to about 50 mass.% in the mixture with NiCrBSi powder. When a vacuum heat treatment can also be fine-grained WC powder.
The agglomerated sintered WC-Co powders are not suitable for mixing with NiCrBSi Puver.

Regards
Vadim

[Arturas]

(05-07-2016 08:29 PM)Vadim Verlotski Wrote:  

(05-07-2016 05:03 PM)Met.Eng. Wrote:  Hi,

Is anybody knows WC-Co+%30(NiCrBSi) corrosion resistance with hvof coating? We want to apply this powders on hydraulic piston rod for food industry

Hi Met.Eng.,
In salt spray tests hold on the best HVOF coatings of WC-Co-Cr or Cr3C2-NiCr more than 1000 hours before corrosion of substrate begin. This result is better than the for hard chrome. Nevertheless, the HVOF coatings provide no lasting protection from saltwater.
The molten layers of NiCrBSi (remelted after spraying on the steel substrate at 1050-1100°C) are absolutely resistant in salt water.
If you bring to melt a mixture of NiCrBSi and WC powder after flame spraying or HVOF spraying, you reach a corrosion resistant layer. However, 30% of NiCrBSi is not enough to melt the mixture tightly in air. Usually one takes a coarse-grained WC powder to about 50 mass.% in the mixture with NiCrBSi powder. When a vacuum heat treatment can also be fine-grained WC powder.
The agglomerated sintered WC-Co powders are not suitable for mixing with NiCrBSi Puver.

Regards
Vadim

Hi,
I agree with Vadim it is not possible to fuse WC-Co+%30(NiCrBSi) correctly.
I suggest to use Gas Atomized Nickel Based HVOF NiCrBSi powders (alloy name like Deloro 60 ). You will have perfect free of pores coating after fusing hardness HRC about 60, it is easy to control fusing of this coating. If You will use NiCrBSi mixed with WC/Co (max 30%) I think there will be some defects in the coating as there will be oxidation of WC particles during fusing.

Arturas

[Met.Eng.]

But we dont fuse the coating, is this possible to spray with HVOF only cold system??? for this job or use WCCoCr or CrCNiCr only

[Vadim Verlotski]

(05-09-2016 04:27 PM)Met.Eng. Wrote:  But we dont fuse the coating, is this possible to spray with HVOF only cold system??? for this job or use WCCoCr or CrCNiCr only

Without fuse brings the addition of NiCrBSi to WC-Co no benefit as compared with pure WC-Co (WC-Co-Cr).