Welding consumables
The welding consumables shall be of type Alloy 6 (Stellite 6 or equivalent). Alternative alloys (e.g. Triballoy 800, Ultimet or equivalent) is acceptable.

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.Componets shall also be heat treated as required in NACE MR0175.

Hardness
Hardness testing shall be carried out on the qualification test and shall include base material, heat affected zone (HAZ) and fused metal. Vickers hardness HV10 shall be used. The examination of HAZ shall be carried out with maximum 0.5 mm distance between the indentations from fusion line, through HAZ into the unaffected base material. The hardness for HAZ and unaffected base material shall not exceed the following values:

Carbon and low alloyed steel: 275 HV10 (22HRC)
22%Cr duplex stainless steel: 310 HV10 (28 HRC)
25%Cr duplex stainless steel: 330 HV10 (32 HRC)
6Mo type stainless steel: 340 HV10 (35 HRC)
Alloy 625: 320 HV 10 (35 HRC)
13Cr and 13Cr 4Ni type steel: According to NACE MR0175

Metallographic examination
Metallographic examination shall be carried out on the qualification testing for the following materials: 22%Cr duplex SS, 25%Cr duplex SS, 6Mo and Alloy 625. The testing methods and 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.

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.

Optional hardfacing
For non corrosive service and for oxygen free wellstream or produced water, overlay welded coatings may be replaced by a thermal sprayed coating.

Reference is made to EDS NHF2