Technical Data

Special Quality Welding Filler Metals for High Strength, Precipitation-Hardening, Stainless Engineering Steel Alloys


Advanced engineering construction industries have an increasing requirement for exceptional very high strength, corrosion-resistant, economical alloys that are formable and readily available. A range of noteworthy precipitation-hardening stainless engineering alloys, as a specialized metallurgical class, is able to develop a combination of superior tensile strength with corrosion and oxidation resistance.

fighterjet01These premium alloys offer the designer a unique combination of fabricability and challenging metallurgical characteristics not found in any other series of material. This combination of sought-after mechanical and chemical material attributes encourages the precipitation-hardening stainless steel alloys to be applied to military, nuclear, aerospace, transport and other advanced and critical applications for instance.

While designed originally for wrought applications in round sections, forgings and shapes, precipitation-hardening stainless steels now also find growing use in the flat rolled form. The precipitation-hardening stainless steel series is based upon iron- nickel- chromium and incorporates one or more extra elements such as copper, aluminium, molybdenum, niobium, carbon and titanium.

During a relatively straightforward ageing treatment of the fabricated components, separation from the matrix, of a second ultra-fine coherent copper-rich phase or a coherent nickel-aluminium phase provides the potent strengthening mechanism for some of this alloy series.

Filler Metals

U.S. Welding Corp. has been active in producing special MC-GRADE®, high purity welding filler metals for the range of precipitation- hardening stainless steel grades since their widespread inception in the mid 1970s for military use. In all the range of the precipitation hardening class of stainless engineering steels, USWC has successfully pioneered the appropriate matching and adjusted-chemistry filler metals for all types of applications to the benefit of the entire fabrication industry. USWC produces high quality filler metal, MC-GRADE® versions, of the martensitic precipitation-hardening grades of 17-4PH, FV520, PH13-8Mo and 15-5PH.

The aerospace quality grades of these filler metals, enhances ductility and toughness properties in high strength welded components that are aged to peak property levels. Large volumes of MC-GRADE® 17-4PH, AMS 5803 and AMS 5825 have been manufactured by USWC over a period of 35 years. MC-GRADE® filler wires are produced by roller die compression and are lubricant-free. There is control over subcutaneous processing contamination, which can be a feature of commercial wire drawn welding filler alloys. MC-GRADE® high purity filler metals are ideally suited for Wire + Arc Additive Manufacturing ( WAAM ) welding applications.

Classes of Precipitation-Hardening Stainless Steels

There are three classes of Precipitation-Hardening Stainless Steels based upon the ambient temperature matrix phase, which is further determined by the Martensite start and finish temperature, Ms & Mf, of each alloy and the as-quenched microstructure. During heat treatment of all three classes, the solution austenitisation heat cycle is the first step, followed by rapid cooling.

The classes of high-strength Precipitation-Hardening Stainless Steels are:

Individual Alloys and Welding Information

This martensitic precipitation-hardening stainless alloy is capable of high strength (exceeding 210,000psi UTS) and hardness along with good levels of resistance to general corrosion and stress corrosion cracking. It is uniquely strengthened by the uniform formation of very finely dispersed coherent NiAl intermetallic second phase. The exceptional mechanical properties of this alloy, even under severe environmental conditions, are obtained by the necessary tight control of the chemical composition and microstructure through specialized melting practice. In order to possess consistent through-thickness and isotropic properties, PH13-8Mo is produced with controlled low levels of residual and impurity elements.

aircraftcarrier01PH13-8Mo stainless has good fabrication characteristics and can be age-hardened by a single low temperature treatment. Cold work prior to aging increases the aging, especially for lower aging temperatures. PH13-8Mo stainless has been used for valve parts, fittings, cold-headed and machined fasteners, shafts, landing gear parts, pins, lock-washers, aircraft components, nuclear reactor components and petrochemical applications requiring resistance to stress-corrosion cracking. Generally, this alloy is considered where high strength, toughness, corrosion resistance, and resistance to stress-corrosion cracking are required in steel showing minimal directionality in properties. (minimum anisotropy)

PH13-8Mo, vacuum melted, MC-GRADE® high purity welding filler metal, produced to AMS5840, is widely acclaimed to be the most suitable welding alloy for use with the matching base alloy for demanding applications.

The perceptive application of MC-GRADE® processing of advanced engineering welding filler metals has enabled welding engineers to successfully fabricate many high grade materials. Underlying all of this work is the consistent control of trace elements and interstitial gases.