PTA cracking problem

[Arturas]

Hello,
We are trying to rebuild roll surface which is constantly suffering rolling contact fatigue using PTA process but our expierence/knowlidges here is insufficient . Please explain why we have cracks in first welded seam after we are trying to put second seam near first one. We cant preaheat the roll over 100C. The material is NiCrBSi (HRC 60).
Best regards
Arturas

[derek]

Using NiGrBSi 60 powder to PTA a roller, you have to pre-heat the part to 600 C to avoid the crack. THere is no choice. Or you can change the powder to NiGrBSi 30. I bet you don't want to do it.

[Arturas]

(01-26-2010 10:48 PM)derek Wrote:  Using NiGrBSi 60 powder to PTA a roller, you have to pre-heat the part to 600 C to avoid the crack. THere is no choice. Or you can change the powder to NiGrBSi 30. I bet you don't want to do it.

Helo ,
This roller can not be preheated to such temperature, there is other surfaces which are very precise with tolerances 0.005mm. Of course I can weld buffer layer NiBSi and then top layer NiCrBSI(HRC60) ? Hardness must be on this surface .

Arturas

[derek]

You can thermal spray to get hard face coating.

[Arturas]

(01-27-2010 02:47 PM)derek Wrote:  You can thermal spray to get hard face coating.

Hello,
Once I tried on this roll to spray WC12Co (thickness 0.2-0.3mm) but the coating delaminated after one working week so .... I am afraid .
Best regards
Arturas

[djewell]

(01-27-2010 07:55 PM)Arturas Wrote:  

(01-27-2010 02:47 PM)derek Wrote:  You can thermal spray to get hard face coating.

Hello,
Once I tried on this roll to spray WC12Co (thickness 0.2-0.3mm) but the coating delaminated after one working week so .... I am afraid .
Best regards
Arturas

Which thermal spray process (equipment) did you use to apply the WC12Co? That should not happen with a quality coating application with a good spray system.