Process for diffusing titanium and nitride into a material having a generally compact, granular microstructure

#The present invention generally relates to a process for diffusing titanium and nitride into a base material. More specifically, a process is provided for diffusing titanium and nitride into a base material having a generally compact, granular microstructure (e.g., carbide).

#The present invention relates to a low temperature process for diffusing titanium and nitride into a base material having a generally compact, granular microstructure in the presence of electrolyzed titanium. A low temperature process is preferred in that it prevents or lessens warping and twisting of the material, two disadvantages of conventional surface treatment processes. Titanium is considered a generally inert, light-weight material which has very high tensile strength (or toughness) and excellent corrosion resistance. Accordingly, because of their inert nature, increased hardness, increased tensile strength and increased resistance to wear, products containing titanium may be used in various applications including industrial, biomedical, aerospace, automotive, defense, jewelry, tools, tool-making, gun-making applications and other such applications.

#Some materials having a generally compact, granular microstructure are known to be extremely hard and capable of withstanding high temperatures. Carbide is an example of one such material. Known carbides include, but are not limited to, boron carbide (B4C); chromium carbide (Cr3C2); iron carbide or cementite (Fe3C); niobium carbide (NbC or Nb2C); silicon carbide (SiC); tantalum carbide (TaC); titanium carbide (TiC); tungsten carbide (WC or W2C); vanadium carbide (VC); zirconium carbide (ZrC); ceramic carbide; any metal alloy containing carbide, and any other metal containing carbide. In one application of carbides, cutting tools containing such are generally used instead of high-speed steel or carbon steel tools to machine tough materials. In fact, cutting tools containing carbides may be used to machine carbon steel or other tough metals.

#Throughout this description, reference has been and will be made to the accompanying views of the drawing wherein like subject matter has like reference numerals, and wherein:

#FIG. 1 is a scanning electron micrograph cross-sectional view of a representative material having a generally compact, granular microstructure such as carbide;

#FIG. 2 is a scanning electron micrograph cross-sectional view of a representative steel having a generally amorphous structure;

#While the invention is susceptible of embodiment in many different forms and in various combinations, particular focus will be on the multiple embodiments of the invention described herein with the understanding that such embodiments are to be considered exemplifications of the principles of the invention and are not intended to limit the broad aspect of the invention. For example, the present invention is directed to any base material having a compact, granular microstructure. Although other suitable materials are contemplated, the base material may be a metal base material having a compact, granular microstructure. Carbides are also used herein to illustrate another suitable material having such a structure. Furthermore, in accordance with the teachings of the present invention, carbides include, but are not limited to, tungsten carbide (WC or W2C); boron carbide (B4C); chromium carbide (Cr3C2); iron carbide or cementite (Fe3C) niobium carbide (NbC or Nb2C); silicon carbide (SiC); tantalum carbide (TaC); titanium carbide (TiC); vanadium carbide (VC); zirconium carbide (ZrC); ceramic carbide; any metal alloy containing carbide, and any other metal containing carbide.

#In one embodiment of the present invention, a moderately heated non-electrolyzed salt bath is used which contains activated-electrolyzed metallic titanium. Sodium dioxide and a salt selected from the group consisting of sodium cyanate and potassium cyanate is present in the salt bath. Additionally, up to about 20 w/w % of NaCO2 or sodium chloride may further be added. To the bath is added from about 2 to about 20 micrograms of electrolyzed metallic titanium. A base material having a compact, granular microstructure is soaked in the bath for from about 10 minutes to 24 hours at from about 430° C. to about 670° C. The electrolyzed titanium catalyzes the diffusion of the titanium and nitride from the bath into about 20 to about 100 microns of the base material having a compact, granular microstructure.

#Through this process, titanium and nitride are diffused into the base material having a compact, granular structure. Surprisingly, it is not necessary for the base material to have an amorphous microstructure as disclosed in U.S. Pat. No. 6,645,566, wherein the larger voids and structure assist in the diffusion or titanium and nitride therethrough. In contrast and also surprisingly, through the above described process, the electrolyzed titanium catalyzes the diffusion of the titanium and nitride from the bath into about 20 to about 100 microns of the base material. More specifically, titanium and nitride from the bath diffuse into and fill the voids of the material's granular microstructure, despite its compact orientation. Accordingly, because carbide has a compact, granular structure, any material including such may be treated with the present invention process.