Is WC based hard coating is repairable?

[dibyendudhara]

Hello Forum,

I'm facing a new problem.
If some portion of WC coating is damaged is it repairable?
For hydro turbine application(pelton bucket), if some portion of the coating is damaged can we repair that portion or we have to remove full coating and coat in again?
How would be the performance in high silt and cavitative environment?
Is it comparable with new one?
What is the removal procedure of the coating?

Please help me.

With warm regards

Dibyendu*

[Gordon]

Hi Dibyendu

Patch repairs are possible, but carry significant risk.

You will have to consider all the pros and cons.

If you are trying to just extend the life of the original coating for a short while say up to the next major overhaul, then it may be worth considering. A patch repair is never going to be as good as a complete removal and re-coating. Selective removal of some of the damage coating by chiselling and grinding may be possible followed by grit blasting. The main problem starts here, preparing the surface so that you can blend in the new. The quality of the interface between the old coating edge, exposed substrate and new coating is critical. One problem is feathering the old coating down the the exposed substrate without inducing edge flaws. I've seen this a few times where people start a patch repair on a tiny area of damage coating, finding that during grit blasting they end up chasing the old coating/exposed substrate edge to find a sound area. Realising that they have been wasting their time as the repair area becomes so large they would have been better off with a complete repair in the first place

I would remove all and start again unless premature failure is an acceptable risk worth taking for the cheaper repair.

[hvofhamid]

hello all
I often repair pieces for bop ,when damage is too small that we can see it only with non destuctif control ,you can use poretanche.but if it s bigger,it s hasardous ta take risk to coat only the damaged place .cracks can be noticed around