Re: [MW:25912] Hard-facing overlay versus Corrosion resistant overlay

Dear Sir,

What will be the qualification range, when a PQR is made by hardfacing weld(ER CoCr-A) of 2.5mm and chemical & Hardness checked at top surface of the weld.

Thanks

Subrata 

On Saturday, 3 July 2010 09:09:43 UTC+5:30, pgoswami wrote:

 

Hi Fernando,

 

A per ASM-Metals Handbook, and AWS welding handbook  the differences between  hardfacing and corrosion resistant overlays are as  follows:

 

1)      Hardfacing is the application of a hard, wear-resistant material to the surface of a component by welding, thermal spraying, or allied welding processes to reduce wear or loss of material by abrasion, impact, erosion, galling, and cavitation . Processes using  heat treatment or surface modification processes such as flame hardening, nitriding, or ion implantation are not considered to be hardfacing  processes. Hardfacing, as compared to corrosion resistant overlay normally would produce thinner surface coating. Hardfacing generally is based on carbide alloys. It could involve  application  a number of hard wear resistant carbides (metallurgical bonding:- through arc welding process) or application of wear resistant restraint  carbides (mechanical bonding:-through thermal spray).Nominal Hardness levels for hardfacing—typically from HRC-30-60.

 

2)      Corrosion Resistant Overlay or Weld Cladding :- usually denotes the application of a relatively thick layer (3 mm, or 1/8 in.) of weld metal for the purpose of providing a corrosion-resistant surface. It could be predominantly of austenitic type , free from any carbides (otherwise corrosion resistance would be  minimized. Ferrite No typically applies to corrosion resistant overlays. Typical hardness values for  weld overalys-22-35 HRC max.

 

Essentially for Hard-facing overlay versus Corrosion resistant overlay- the difference  is the  service and application media. If the service media calls for wear resistance they the technique to be adopted is  hardfacing , if for corrosion resistance then weld overlay.

 

Valve industry needs both type of alloys depending on the service. Example Stellite-6 or 12 on Moderators Valves (Nuclear services)require galling resistances, high temperature piping require high temperature erosion resistance, while austenitic  alloys would be required for corrosion resistance in oil, gas or chemical environments. Some type of Stellite alloys used in the oil and gas offshore production industries would require both. See the attached  link to the relevant document on hardfacing alloys for  your  information.

 

Hope this clarifies your query.

 

Thanks

 

 

 

Pradip Goswami,P.Eng.

Welding & Metallurgical Engineer/Specialist

Ontario Power Generation Inc.

Email-pgoswami@sympatico.ca,

pgoswami@quickclic.net

 

• http://www.stellite.com/Portals/0/Microsoft%20PowerPoint%20-%20Deloro%20Stellite%20Advances%20in%20Wear%20Resistant%20Alloys%20and%20Products.pdf

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Fernando Gameiro
Sent: Friday, July 02, 2010 4:24 AM
To: materials-welding@googlegroups.com
Subject: RE: [MW:5825] Hard-facing overlay versus Corrosion resistent overlay

Thank you,

 

Is that "thinking" well and clear defined on any code, with real figures like hardness or  ferrit number or what else?

 

Regards

Fernando Gameiro

 

From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com] On Behalf Of Harish Kannepalli
Sent: 02-Julho-2010 08:20
To: materials-welding@googlegroups.com
Subject: Re: [MW:5823] Hard-facing overlay versus Corrosion resistent overlay

 

Dear Fernando,

                     Hard facing overlay is for wear resistance applications, where continuous rupture of the part is involved. Incase of ,corrosion resistant overlays, its purely for acidic or alkali resistance applications. At times some overlays are hard facing as well as corrosion resistant.

            In hard facing overlays, hardness is an important feature. In corrosion resistant overlays, bonding of base metal, chemistry of layers are some of the important features.

regards,

Harish.

2010/7/1 Fernando Gameiro <fgameiro@velan.pt>

Dear All,

 

According to ASME IX the difference between Hard-facing overlay and Corrosion resistant overlay is limited to the type of tests that is required on PQR and WPS ?

 

According to ASME, how to define if certain overlay is a Corrosion resistant or a Hard-face?

 

Thanks

 

Fernando Gameiro

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