Stellite 6 overlay on SS with PTAW

By jon20013 (*****)

Date 01-06-2004 15:04

Okay, need some input from the great minds out there! :) My company will be getting back into placing Stellite 6 overlays on varying thicknesses of stainless steels (normally 304L) using the PTAW process. My predessesor's have tried with varying degree's of success using this process but have had cracking problems (discovered by PT). I KNOW this work can be done satisfactorily but have heard conflicting approaches....from cooling the stainless to heating the stainless. My personal experience with Stellite overlays using the PTAW process is very limited so I would like to hear from others who may have had success in this area. Cool the stainless, heat the stainless, heat the powder, etc.....

By MBSims

Date 01-06-2004 23:36

jon,

Have you thought about using Stellite 21 instead of Stellite 6? It is much more forgiving than 6 and can be welded on 300 series stainless base metals with no preheat.

Marty

By jon20013 (*****)

Date 01-07-2004 14:25

Marty, if it were up to me I would probably use GTAW too but my customer sets the requirements and they want to use Stellite 6 for their own reasons.

By jwright650 (*****)

Date 01-07-2004 15:34

jon, Marty,
Off subject question to help with my ignorance. PTAW is which, or is it both...[Plasma Tungsten Arc Welding] or [Plasma Transferred Arc Welding]?
jon was talking about powder so I was thinking it was Plasma Transferred Arc Welding, but with a brief search online I see PTAW called out as two methods and was wondering which is correct or is both correct.
John Wright

By Plasma Wizard Date 02-13-2004 13:13

I have done many st6/21 overlays, all tested and crack free. Metalurgically perfect.

Make sure you have a good quality powder-no knockoffs

A pre-heat is required, try 400 degree c

st 6 rules of thumb

St6 will not double layer, ruins impact resistance

if your gun has a 4mm electrode 3mm plasma tip hole and a 7-8mm powder hole, try the following

10mm weave width
it takes 25 seconds to complete 40 weaves
if your o.d. is say 120mm then your job feed speed is 120 seconds
10mm gun height ( easy for up to 4mm weld height )
55-65g/min
powder gas 6-10 (l/min) depending on hopper pressure
plasma flow 3 (l/min) bottle pressure 70psi
sheild flow 20 (l/min)
bead overlap 25%
amps 95
volts 31
electrode sharp point 30 degrees setback 4mm from plasma tip hole

hope it helps