WEAR-RESISTANT, HIGH-TEMPERATURE, REDUCED-COBALT ALLOYS FOR WELDING AND OTHER APPLICATIONS

Abstract

An iron-based welding and forging alloy with a complex chemistry produces a dense, homogenous weld deposit that is resistant to hardness loss at elevated temperatures with less reliance on cobalt content. Such an alloy may comprise, in approximate percentages by weight: cobalt: 5-25; chromium: 7-14; tungsten: 2.5-10; molybdenum: 2-9; nickel: 1-6; carbon: 0.01-5; manganese: 0.01-3; with iron and residual elements comprising the balance. The residual elements may include one or more of the following: silicon, vanadium, phosphorus, and sulfur. The amounts of the residual elements may be up to 1% by weight. The inventive alloys may be provided in any suitable form for welding purposes, including metal-core TIG (GTAW), coated electrode (SMAW) and metal-core-wire (MCAW). The inventive alloy combinations may be fabricated as welding filler, providing resistance to high temperature softening, facilitating use in applications that previously dictated a specific cobalt-based material.

Claims

1. A high temperature, wear-resistant, low-cobalt alloy for high-temperature applications comprising, in approximate percentages by weight: cobalt: 9.5-11.0; chromium: 9.3-10.0; tungsten: 4.2-5.3; molybdenum: 4.2-5.3; nickel: 2.4-3.0; carbon: 0.10; manganese: 0.50 and iron and other elements: balance.

2. The alloy of claim 1, wherein the other elements include one or more of the following: silicon, vanadium, phosphorus, and sulphur.

3. The alloy of claim 2, wherein the amount of silicon is up to 1% by weight.

4. The alloy of claim 2, wherein the amount of vanadium is up to 1% by weight.

5. The alloy of claim 2, wherein the amount of phosphorous is up to 1% by weight.

6. The alloy of claim 2, wherein the amount of sulphur is up to 1% by weight.

7.-11. (canceled)

12. A welding electrode including the alloy of claim 1.

13. (canceled)

14. A tool including the alloy of claim 1.

15. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] FIG. 1 is a cross section illustrating the use of the invention as a cored wire electrode; and

[0011] FIG. 2 is a cross section illustrating the use of the invention in a shielded metal arc welding electrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] This invention resides in a high-temperature, low-wear welding alloy with reduced reliance on cobalt content. Due to the unique chemistry, the alloy may nevertheless be used where certain cobalt-based alloys, including Stellite alloys, are traditionally used. When used as designed, the alloy may produce a homogenous weld deposit, developing an as-welded hardness of 42-60 on the Rockwell “C” scale, depending upon the precise mixture of the alloy constituents.

[0013] The properties of the invention are provided by the chemistry shown in TABLE II, below:

TABLE-US-00002 TABLE II ELEMENT % WEIGHT Cobalt  5-25 Chromium  7-14 Tungsten 2.5-10  Molybdenum 2-9 Nickel 1-6 Carbon 0.01-5   Manganese 0.01-3   Silicon <1 Vanadium <1 Phosphorus <1 Sulphur <1 Iron balance

[0014] The alloy broadly contains, by weight, carbon between 0.01-5.0%; cobalt between 5.0 and 25.0%; and a molybdenum addition of between 2-9%. Lending to this invention's performance is the inclusion of not an insignificant amount of tungsten, with a weight percentage of 2.5-10. Work hardenability is the result of a volume of nickel (1-6%), with an addition of manganese that amounts to 0.01-3%. The strength of the alloy is aided by the addition of chromium in the 7-14% range, silicon and vanadium at a weight of less than 1% each. Silicon, vanadium, phosphorus and sulphur may be provided in trace amounts, with the balance being iron.

[0015] A more specific preferred chemistry range is set forth in TABLE III, below:

TABLE-US-00003 TABLE III ELEMENT % WEIGHT Cobalt 9.5-11  Chromium  9.3-10.0 Tungsten 4.2-5.3 Molybdenum 4.2-5.3 Nickel 2.4-3.0 Carbon 0.10 Manganese 0.50 Silicon 0.30 Vanadium 0.40 Phosphorus 0.03 Sulphur 0.03 Iron balance

[0016] As evident from TABLES II, III the inventive alloy compositions disclosed herein contain substantially less cobalt, leading to reduced cost, but with excellent wear resistance and high-temperature performance comparable to Stellite. The electrode composition contains at least some of the elements of the material being targeted for replacement, but in considerably reduced volumes. Working in concert with a unique compliment of supporting elements allows the weld deposit to perform at the same level in some applications as a cobalt-based alloy. Indeed, alloys according to the invention contain less than half the cobalt of Stellite, and in some cases less than one-tenth the amount, by weight, as shown in TABLES II, III, above.

[0017] The invention provides a lower cost, more readily available high-performance, high-temperature alloy for use in difficult application environments, including the field of welding. The inventive alloys may be fabricated as welding filler providing resistance to high temperature softening, permitting their use in applications that previously dictated a specific cobalt-based material. The fabricated welding filler may be provided at a greatly reduced cost to the consumer, and the nature of the fabrication process translates into significantly improved lead times and ready availability.

[0018] The inventive alloys may be provided in any suitable form for welding purposes, including metal-core TIG (GTAW), coated electrode (SMAW) and metal-core-wire (MCAW). FIG. 1 is a cross section illustrating the use of the invention as a cored wire electrode 102, wherein the inventive alloy is provided as a fine, highly mixed powder (with arc stabilizers and de-oxidizers) 104, surrounded by an outer steel sheath 106. The cored wire may be fabricated with any known suitable method, including the process described in U.S. Pat. No. 7,950,126, incorporated herein by reference. FIG. 2 is a cross section illustrating the use of the invention in a shielded metal arc welding electrode 202. In this application, the cored wire 204 is surrounded or encased in an extruded alloy flux coating 206 with arc stabilizers and de-oxidizers. The flux coating may be a water-or silicate-based mixture that is dried or hardened around the core 204.

[0019] Note that, depending upon the final product configuration, some of the trace elements listed in TABLES II, III may be derived from sheath material. For example, assuming the sheath is steel, some or all contributions of carbon, manganese and silicon may be provided by the sheath. If such materials are sufficient or unintentional, additional amounts may not be added per the TABLES above. Again, while examples of welding electrodes are described, the invention may be used in any application requiring durable, wear-resistant elements or alloys, including tools and tool edges associated with drills, blades, pads and other implements for cutting, grinding, sanding, polishing, drilling, etc.