hard facing question

Date 05-11-2015 19:57

The primary concerns for overlay qualification are running your test as cool as possible to minimize dilution while hot enough to provide adequate bonding to the substrate. This is why you see first layer concerns in the essential variables for overlays. For hardfacing the result you wish to achieve is a certain hardness level to be proven by testing.

By Mikeqc1 (****)

Date 05-11-2015 23:49

what would i use for a coupon?
Im thinking to treat it like a pipe seeing that the weld will be a circ.
So my base metal thk is 2.5?
weld deposit is .050. min.

By js55

Date 05-12-2015 12:36

Overall you can use either pipe or plate. Section IX has dimensions available for both.
In your case I would use pipe.

By Mikeqc1 (****)

Date 05-12-2015 00:00

here is what i read and would like to discuss. im mostly interested in the coupon i need, hardness specs and if the chem test is mandatory?

a PQR, As per ASME Sec IX , QW-453 following test are required for procedure qualification of hard face overlay
(3) The hard-facing surface shall be examined by the liquid penetrant method and shall meet the acceptance standards in QW-195.2 or as specified
in the WPS. Surface conditioning prior to liquid penetrant examination is permitted.
(7) After surface conditioning to the minimum thickness specified in the WPS, a minimum of three hardness readings shall be made on each of
the specimens from the locations shown in QW-462.5(b) or QW-462.5(e). All readings shall meet the requirements of the WPS.
(8) The base metal shall be sectioned transversely to the direction of the hard-facing overlay. The two faces of the hard-facing exposed by sectioning
shall be polished and etched with a suitable etchant and shall be visually examined with 5 magnification for cracks in the base metal or the
heat-affected zone, lack of fusion, or other linear defects. The overlay and the base metal shall meet the requirements specified in the WPS.
All exposed faces shall be examined. See QW-462.5(b) for pipe and QW-462.5(e) for plate.
(9) When a chemical composition is specified in the WPS, chemical analysis specimens shall be removed at locations specified in QW-462.5(b)
or QW-462.5(e).
The chemical analysis shall be performed in accordance with QW-462.5(a) and shall be within the range specified in the
WPS. This chemical analysis is not required when a chemical composition is not specified on the WPS.

By js55

Date 05-12-2015 12:50

Hardness is to be determined by customer specification.

By Mikeqc1 (****)

Date 05-12-2015 00:19

If the production part is solution anneal and tempered for 17-4 H1150m
will the coupon need same? I'm thinking yes

By js55

Date 05-12-2015 14:18

Yes.

By Mikeqc1 (****)

Date 05-12-2015 16:45

Sp, please help me understand this I would be very gratfull.
My product form is a round bar with a DIA of 8.493 it will have a min of .050 hard facing.
welded to that will be another round bar with a DIA of 2.623.
Both will have the .050 hard face.
Both will be solid when welded and drilled with a thru hole afterward.

My coupon base metal will have a compatible P number with the filler metal.
What sch and DiA pipe do I need and how do I find this out in the code.
Right now I can seem to grasp choosing the coupon size.
Any advise would help.

By js55

Date 05-12-2015 18:19 Edited 05-12-2015 18:22

Thickness per QW-403.23
Length per Table QW-453 Note 2.
Diameter per Table QW-453 Note 2
My best advice is to not 'think' like a circumferential qualification. 'Think' in terms of overlays. Don't try to fit a square peg into a round hole. What is it you are trying to accomplish? Once you do this the requirements will make more sense.

By Jovi Zhu (**)

Date 05-13-2015 04:53 Edited 05-13-2015 07:21

Mike,

IMHO the most important intents of ASME Sect. IX Safety Code for hard-facing overlay procedure qualification are to (1) achieve specified hardness and (2) guarantee pressure retaining base material integrity.

Table QW-453 Note 2 "Alternatively, the qualification may be performed on a test base metal coupon that represents the size of the production part." suits your specific case and you have an option to use your product round bars as test coupons.

When you use pipe coupons, be cautioned that your variables qualified on pipe coupons may not guarantee the same results on round bars. Some of the reasons I can come up with now are the different cooling rate, heat input and resultant dilution... Your overlay may be cooled too fast on a round bar to pass the PT and your bar HAZ may be cooled too fast to be free of cracks or, as Js55 indicated,too cold to be free of LOF.

Good luck!

JZ