CLASSIFICATION

ísol-NCrCo7: The nominal composition (wt %) of this filler metal is 45 Ni, 25 Cr, 20 Co, 2 Nb, and 1 Ti. This is used for welding nickel-chromium-cobalt alloy (UNS N07740) for power boiler and coal ash applications to itself, to steels, and to weld overlay steels using the GTAW and GMAW processes. The weld metal will age harden on heat treatment. For specific information concerning age hardening, consult METAFIL. The alloy is resistant to oxidation, sulfidation, chlorination, and coal ash corrosion environments.

Welding Considerations

It can be used with any of a variety of welding processes. Most notable among them are gas tungsten arc welding (GTAW), gas metal arc welding (GMAW), submerged arc welding (SAW), electroslag strip cladding (ESW) and plasma arc welding (PAW). SAW, ESW, and PAW are quite specialized, and specialized consultation for recommendations concerning their use may be required. General suggestions are given below for the other two processes.

Before welding or heating any nickel-base alloy, the base metal must be clean. Oil, grease, paint, lubricants, marking pencils, temperature indicating materials, threading compounds, and other such materials frequently contain sulfur or lead that may cause cracking (embrittlement) of the base metal or the weld metal if present during welding or heating.

For GTAW, direct current-electrode negative (dcen) is used. Either argon or helium (or a combination of the two) are used as a shielding gas. For GMAW, direct current-electrode positive (dcep) is often employed. Argon shielding gas is often used, but mixtures of argon and helium are also commonly used.

Special Tests

It is recognized that supplementary tests may be required for certain applications. In such cases, tests to determine specific properties such as corrosion resistance, scaling resistance, or strength at elevated or cryogenic temperatures may be required.

Corrosion or Scaling Tests

Although welds made with electrodes and rods classified in this specification are commonly used in corrosion and heat-resisting applications, tests for those properties are not included in the specification. When required for a particular application, testing can be conducted on specimens taken from either a weld pad or a welded joint.

Specimens from a joint are suitable for qualifying the welding procedure (for a specific application involving corrosion or oxidation resistance), but not for qualifying the filler metal. Tests on specimens from a joint have the disadvantage of being a combined test of the properties of the weld metal, the heat-affected zone (HAZ), and the unaffected base metal. With such specimens, it is more difficult to obtain reproducible data (when a difference exists in the properties of the metal in the various parts of the specimen). Specimens taken from a joint do have the advantage of being able to duplicate the joint design and the welding sequence planned for fabrication.

Specimens for testing corrosion or oxidation resistance of the weld metal alone are prepared by following the procedure normally used for the preparation of pads for chemical analysis. The testing procedures should correspond to ASTM G4, Standard Guide for Conducting Corrosion Tests in Field Applications.

Test for Mechanical Properties

This filler metal is used with a variety of welding processes and procedures. For this reason, weld metal tests have not been included in the specification. The tensile properties, bend ductility, and soundness of welds produced with these filler metals are determined during qualification of the procedure.

Welding variables (current, voltage, and welding speed), the shielding medium (the specific gas mixture or the flux), the manual dexterity of the welder, and the composition of the base and filler metal may all influence the mechanical properties that can be obtained.

CHEMICAL COMPOSITION OF UNDILUTED WELD

Single values are maxima, except where otherwise specified. Rem = remainder. *Includes incidental cobalt. Patent application number US 2009/0257908, filed on October 15, 2009.

ALL-WELD-METAL MECHANICAL PROPERTIES

Tensile strength in the as-welded condition, unless otherwise specified. Age-hardened condition: Solution annealed at 1121°C for 1 hour, then water quenched and aged at 800°C for 4 hours then air cooled.

ELECTRODE SIZES: 0.80, 1.00, 1.20, 1.60, 2.00, 2.40, 3.20, 4.00, 4.80 (Available in GTAW, GMAW & SAW forms)

WARNING: Safety and health information is available from many sources, including, but not limited to Safety and Health Fact Sheets listed in A11.3, ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes published by the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166., and applicable federal and state regulations. The Safety and Health Fact Sheets are revised, and additional sheets added periodically.