Inquirer:-

Dear Sir, We have been told by our customer to control the Fe content up to 3% in Stellite 6 hardfacing on CF8M. Why ? How to control it ?

Reply:-

Dear Sir,

You have been told by your customer to control Fe content , mostly because your application is highly corrosive and Fe can oxidize and create FeO rust so you need to control Fe.

Fe can come to 6 Stellite ERCoCr-A weld overlay deposits from your base metal (Substrate CF8M), So, you need to control the dilution using welding process and with parameters like low heat input , so try to use the lowest practical welding current and voltage. Faster travel speeds can also help reduce dilution. Keep the lowest interpass temperature as much as possible. otherwise, you can increase nos. of layers as first layer will have more dilution but you will get proper 6 Stellite ERCoCr-A consumable chemistry on the top layer.

You can apply buffer layer of 309MoL Stainless Steel Electrodes but again SS electrodes contain Fe. But the only consumable without Fe or very least Fe with stellite series is like Stellite 1 or Stellite 12. These consumables still contain iron, but in much lower quantities compared to the stainless steel electrodes. But it is expensive option.

Otherwise, you can deposit ERNiCrMo-3 or pure Nickel based ERNi-1 which is completely Nickel based and Fe Free. But I think, using SS Electrode or ERNiCroMo-3 electrode and less H.I / IP you will be able to achieve Fe less than 3 chemistry in second or top layer itself.

Follow-up:- The inquirer has already been using ER309L as a buffer layer on carbon steel and SS and FCAW by robotic and GTAW by manual process.

In this connection, this is to add that FCAW is a high-productivity process that uses a consumable tubular electrode containing a flux. The heat input in FCAW is typically higher than in GTAW, which can lead to more base material melting and hence more dilution on the other hand, GTAW, being a precision welding process that uses a non-consumable tungsten electrode and an inert gas shield. GTAW usually operates at lower heat inputs than FCAW, which can limit the amount of base material that melts and mixes with the filler metal, resulting in less dilution.

I request you to run a PQR keeping low H.I (& IP) and use of SS Electrode or ERNiCroMo-3 in order to arrive at the filler metal chemistry at the top layer.

Hope this suggestion might help you,

Thanks