SSC test on welding between ASTM F65 and SMLS 450

[Giuseppe76]

Hello,

I have a question regarding test result on welding root between ASTM F65 and SMLS 450.
Indeed, on 12 coupons tested in accordance with NACE TM177 two coupons were presented cracks of 0.7mm depth. To understand the problem we performed microhardenss test beside the cracks and we discovered value between 290 HV10 and 320 HV10 that can give the reason of the cracks.
My question is:
Due to difference in terms of hardness between the coupons with and without the cracks, can the hardness be the explanaition of this cracking?
In case of positive answer, can this material be accepted in terms of SSC test if hardness will be inspected and reported less than 250 HV10 even if we have these two coupons with cracks?

Thanks
Giuseppe

 

[SJones]

The high microhardness values are more than likely to have contributed to the cracking, but how are you testing the weld, since TM0177 does not have an appropriate weld test? Normally, when the pieces crack, they fall apart. What is the stipulated acceptance criterion for the test: is it 'no cracking?' If yes, then it will be hard for somebody to pass it off as acceptable.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.

 

[Giuseppe76]

We tested the weld as per same methodology of base material indicated in NACE TM0177 and Client critiria in No SSC Cracks. Yes it is difficult to accept this welding. So our though is to cover the surface with clad to avoid SSC corrosion (inconel 625 overlay).

Thanks for your answer

Giuseppe

 

[SJones]

For the weld, a four point bend test would be required. TM0177 does not cover this type of test. You may be making a materials selection decision on the basis of an inappropriate test.

Steve Jones
Materials & Corrosion Engineer

http://www.linkedin.com/pub/8/83b/b04

All answers are personal opinions only and are in no way connected with any employer.