Hardfacing by overlay welding should be avoided. If not possible to find other solutions by design or material selection hard facing may be used provided the rerquirement in this EDS is fulfilled.

Welding consumables
The welding consumables may be of type Ultimet (trade name) , Triballoy 800 (trade name) or equivalent.

Manufacture
The hard facing shall be made by overlay welding using PTAW (plasma transferred arc) or GTAW(gas tungsten inert gas).

Heat Treatment
Heat treatment after hardfacing shall be carried out, as necessary, to meet specified properties.

Hardness

The hardness of the hard facing overlay weld shall be minimum 22HRC for Ultimet (trade name) and minimum 35HRC for Triballoy 800 (trade name),

Metallographic examination
Metallographic examination shall be carried out on the qualification testing and the acceptance criteria shall be as stated on the MDS for the material in question.

Macrosection
The macrosection for the qualification shall show no cracking and complete fusion between base material and hardfacing.

Corrosion testing
Corrosion testing shall be carried out on the qualification testing for 6Mo, 25%Cr duplex and Alloy 625. The sample shall include the cross section from hardface into the unaffected base material. The test conditions and acceptance criteria shall be as stated on the MDS in question.

Impact testing
The qualification testing shall include Charpy V-notch impact testing for materials require impact testing by the applicable ASTM standard or MDS. The test conditions and acceptance criteria shall be as stated in the standard or MDS. One set of impact testing shall be carried out with specimens located in the base material 2 mm below the fusion line between the hardfacing and base material. The notch shall be perpendicular to the hard faced surface.

Thickness
The thickness of final hardfacing shall be minimum 1.6 mm after final machining. The deposit thickness shall be measured.

Welding
The hardfacing shall be carried out according to qualified procedures according to ASME IX modified as follows:

· Size and geometry of test plates shall be representative of the actual components which shall be welded. This is especially important for small components.
· The qualification shall be carried out on base material of same grade as used in production.
· The testing shall be carried out according to ASME IX and the requirements in this EDS.

Welding technique
Preferably a string technique shall be used. If weaving is used the width shall be limited taking into consideration risk for overheating of the material and cracking.

NDT
All deposited surfaces shall, after final machining, be 100% PT examined in accordance with ASME VIII, div. 1, app. 8. The acceptance criteria are: No defects on sealing surfaces.