1. Introduction

Tungsten carbide/cobalt (“WC/Co”) is widely used for cutting tools, metal forming tools, mining tools, and wear resistance surfaces, with wide range of applications, ranging from aerospace, automobile, to home appliances. For these applications, the mechanical properties of interest are hardness, toughness, compressive strength, transverse rupture strength, and wear resistance. The first patents on WC/Co were issued to the Germany company “Osram Studiengesellschaft” in 1923, with the first marketable hardmetal of WC/6w.t.%Co, was produced in 1926 under the name of “Widia.”

Over the past century, researches in WC/Co hardmetal were focused on improving the manufacturing process, so that the as-produced WC/Co has maximized hardness while maintaining a reasonable toughness. All these activities are constrained in the frame of micrometer structured carbide material. In the late 70s and early 80s, ultrafine or submicron WC materials are then introduced, thus greatly extended the application of WC into new emerging applications in the area of microelectronics and telecommunications. Today several companies are producing submicrometer WC materials, including OMG, Tokyo Tungsten, and Sandvick. These companies are capable of producing tonnage quantities of WC powder and bulk materials with carbide size >100 nm and <1 micron.

The concept of making nanograined WC powder was first introduced by Kear et al at Exxon. The manufacturing process was later developed by Nanodyne in collaboration with Rutgers University. Kear’s process uses a wet chemical process, where W and Co are uniformly mixed at the molecular level, intermediate pre-carbide form was then produced via a spray dry process, and the final carbide formation process was accomplished via a fluidized bed reactor. In the late 90s, Nanodyne was capable of producing up to few hundred quantities in batch operation mode. The Nanodyne process was bought by Union Muniere (a Belgium company), with the intention of full commercialization. In the last years, Union Muniere had tried very hard to convert Kear’s batch process into a commercial quantities production via a fluidized bed reactor. Due to the intrinsic limitation of the Kear process, commercialization of nanostructured WC eventually failure, and Union Muniere had shutdown the nanostructured WC/Co activity in 2001.

Learned from Nanodyne’s hard process lessons, Inframat Corporation (“IMC”) had taken rather a different approach to manufacturing superfine WC/Co material. IMC’s process utilized the low cost and scalable wet chemical synthesis technique, yet its operation uses a continuous production mode, so that the process can be precisely controlled and stable at different stage of carburization process. To date, large quantities of superfine WC powders with a superfine particle size WC, have been produced in continuous operation mode. Thus, we anticipate no commercialization barrier to this technology.

2. Technology Description

Powder production -- IMC’s nanostructured WC materials are produced via a wet chemical process, where precursors of W and C are mixed at the molecular level in an aqueous media. A low temperature conversion of the liquid precursor produces a preceramic intermediate product. Further chemical process of this preceramic powder using IMC’s a proprietary continuous heat treatment schedule at controlled stages resulted in superfine structured WC material. The as-synthesized WC powder has average grain size of ~ 40 nm. These nanograined WC particles are agglomerated with average agglomerate size of 0.2 to 0.4 micron.

The next step in IMC’s synthesis process is to add a cobalt source into the WC materials to produce a superfine WC/Co composite. Thus, the final powder can be sold to venders as either WC powders or ready-to-press WC/Co composite powders. Under appropriate processing procedures, they can be engineered to either submicrometer particle sized or nanograin sized powders.

WC/Co Hardmetal Development -- IMC is developing a variety of leading edge technologies in the area of hardmetals (tungsten carbide/cobalt and its alloys) that enable exceptional hardness in end products comprised of these materials without concomitant loss in fracture toughness. This performance edge is achieved by an important innovation in the alloying of proprietary grain growth inhibitors with tungsten carbide/cobalt powders, both for nanostructured WC/Co and superfine WC/Co. IMC is now developing industrial scale pilot plant capability to manufacture and sell these nanoscale and superfine alloyed powders under the trade names Nanalloy® and InfralloyTM. These proprietary tungsten carbide products can be sold as is for the thermal sprayed coatings industry or in bulk consolidated (sintered) form for the cutting tools and related industries.

IMC’s technology is based on a chemical process for the synthesis of WC and WC/Co powders, in which the individual W, C, and/or Co precursors are intimately mixed at the molecular level, yielding a uniquely homogeneous product with exceptional high performance. IMC has developed exceptionally hard bulk consolidated composite materials, with hardness measured up to 2300 VHN. These sintered materials exhibit unparalleled fracture toughness at this level of hardness. These materials are compression sintered in inert gas or vacuum furnaces to form highly homogeneous monoliths. The hardness of the sintered products is found to be a function of cobalt content. Typically, cutting tool applications force the minimum Co content level to be above 6%, below which the material cannot be sintered.

Superfine ceramic-Metal (”Cermet”) bulk materials have been shown to exhibit improved wear resistance. The key advantage of superfine cermet is in the greatly improved toughness and hardness, wear resistance. In conventional materials, hardness and toughness are mutually exclusive attributes. Generally, very hard materials lack toughness, and vice versa. Fig. 1 shows that this inverse proportionality is shifted upward and outward in the case of superfine cermets, and effectively, these materials exhibit excellent values for both hardness and toughness. This unusual marriage of properties is anticipated to enable applications where both properties are required. Tooling is a common example of this dual requirement.

Fig. 2 shows a typical abrasive wear behavior of the sintered WC/Co Nanalloy Ingot, performed by ABB under simulated deep sea mining application. As a comparison, Sandvick’s superfine WC/Co was also used as a base line. The data suggested that IMC’s WC/Co composite is advantages to the current best superfine Sandivk’s WC/Co ingot for deep-sea petroleum applications. This improved wear behavior is benefited from a combination of increased hardness and toughness.

Fig. 3 shows a typical cavitation behavior of the sintered WC/Co Nanolloy Ingot, performed by Hydro-Qubet for hydropower plant applications. As a comparison, Conventional WC/Co was also used as a base line. The data suggested that IMC’s WC/Co composite is at least 4X better than the current used WC/Co material.

3. Commercialization Status

IMC had completed all the scientific experimental research work in making superfine sized WC/Co powders and hardmetal ingots. IMC had completed pilot plant production of this unique WC powder, and is in the processing commercializing this material at US with tonnage quantities. Inframat is currently forming a joint venture with a WC manufacturer for large-scale production of this material.

Inframat Corporation
Tel: 860.553.6154 | Fax: 860.553.6645 | sales@advancedmaterials.us

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