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,
- 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
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
--
To post to this group, send email to materials-welding@googlegroups.com
To unsubscribe from this group, send email to materials-welding-unsubscribe@googlegroups.com
For more options, visit this group's bolg at http://materials-welding.blogspot.com/
The views expressed/exchnaged in this group are members personel views and meant for educational purposes only, Users must take their own decisions w.r.t. applicable code/standard/contract documents.
THIS MESSAGE IS ONLY INTENDED FOR THE USE OF THE INTENDED RECIPIENT(S) AND MAY CONTAIN INFORMATION THAT IS PRIVILEGED, PROPRIETARY AND/OR CONFIDENTIAL. If you are not the intended recipient, you are hereby notified that any review, retransmission, dissemination, distribution, copying, conversion to hard copy or other use of this communication is strictly prohibited. If you are not the intended recipient and have received this message in error, please notify me by return e-mail and delete this message from your system. Ontario Power Generation Inc.
No comments:
Post a Comment