Method of making a tungsten carbide body

Claim 1

The method of preparing a very dense tungsten carbide body, consisting essentially of the steps of: (a) preparing a mixture of carbon precursor and finely powdered tungsten, wherein the precursor is a vinylidene chloride based polymeric material, and wherein the ratio of the carbon component of the precursor and the metallic tungsten is substantially stoichiometric; (b) blending the mixture to obtain an intimate and uniform mixture of the carbon precursor and powdered metal; (c) removing moisture, if any, which has accumulated upon particles of the mixture; (d) compressing the mixture to form a self-supporting green body of a desired shape; (e) heating the green body to a temperature at which significant dehydrohalogenation beings; (f) subsequently heating the green body at a uniform and slow rate to accomplish significant dehydrohalogenation without polymeric material melting or puffing, until a weight loss of about 20% of the polymeric material has occurred; (g) further heating the green body in order to remove such metal oxides as are present, with removal being accomplished by the formation of sublimable metal oxychlorides and chlorides, with said heating being sufficiently gradual that the temperature differential within the body is held to no more than 5° C., until a weight loss of approximately 50% has been achieved; (h) further heating the body at an average rate no greater than about 50° C. per hour to a temperature within the range of about 800°-1300° C.; and (i) subsequently densifying the body by heating the body at about 2000° C. for at least 10 minutes in an inert or evacuated environment.

Claim 2

The method of preparing a very dense tungsten carbide body, consisting essentially of the steps of: (a) preparing a mixture of carbon precursor and finely powdered tungsten, wherein the precursor is a vinylidene chloride based polymeric material, and wherein the ratio of the carbon component of the precursor and the metallic tungsten is substantially stoichiometric; (b) blending the mixture to obtain an intimate and uniform mixture of the carbon precursor and powdered metal; (c) removing moisture, if any, which has accumulated upon particles of the mixture; (d) compressing the mixture to form a self-supporting green body of a desired shape; (e) heating the green body to a temperature at which significant dehydrohalogenation beings; (f) subsequently heating the green body at a uniform and slow rate to accomplish significant dehydrohalogenation without polymeric material melting or puffing, until a weight loss of about 20% of the polymeric material has occurred; (g) further heating the green body in order to remove such metal oxides as are present, with removal being accomplished by the formation of sublimable metal oxychlorides and chlorides, with said heating being sufficiently gradual that the temperature differential within the body is held to no more than 5° C., until a weight loss of approximately 50% has been achieved; (h) further heating the body at an average rate no greater than about 50° C. per hour to a temperature within the range of about 800°-1300° C.; and (i) subsequently densifying the body by heating the body at about 2000° C. for at least 10 minutes in an inert or evacuated environment.

Claim 13

The method of preparing a very dense tungsten carbide body, including the steps of: (a) preparing a green body from mixture of a carbon precursor and finely powdered tungsten, wherein the precursor is a vinylidene chloride based polymeric material, the ratio of carbon precursor to metallic tungsten falling within the range from one in which the carbon compnent of the carbon precursor is in essentially stoichiometric relation to the metallic tungsten to one in which there is a deficiency of one atomic percent of the carbon component as compared with an essentially stoichiometric mixture; (b) removing moisture, if any, which has accumulated upon particles of the mixture; (c) initially heating the green body at a controlled rate to effect partial decomposition of the polymer so as to evolve HCl gas to cleanse the powdered tungsten of surface contamination; (d) subsquently heating the green body to an intermediate temperature to effect complete decomposition of the polymeric material and to drive off all volatile oxychlorides and chlorides; (e) subsequently baking the green body at an elevated temperature near 1000° C. for converting all of the powdered metal to a stable but relatively low density carbide; and (f) subsequently heating the carbide body at a temperature of about 2000° C. in an inert or evacuated environment to convert the relatively low density carbide into relatively high density carbide.

Claim 14

The method of preparing a very dense tungsten carbide body, including the steps of: (a) preparing a green body from mixture of a carbon precursor and finely powdered tungsten, wherein the precursor is a vinylidene chloride based polymeric material, the ratio of carbon precursor to metallic tungsten falling within the range from one in which the carbon compnent of the carbon precursor is in essentially stoichiometric relation to the metallic tungsten to one in which there is a deficiency of one atomic percent of the carbon component as compared with an essentially stoichiometric mixture; (b) removing moisture, if any, which has accumulated upon particles of the mixture; (c) initially heating the green body at a controlled rate to effect partial decomposition of the polymer so as to evolve HCl gas to cleanse the powdered tungsten of surface contamination; (d) subsquently heating the green body to an intermediate temperature to effect complete decomposition of the polymeric material and to drive off all volatile oxychlorides and chlorides; (e) subsequently baking the green body at an elevated temperature near 1000° C. for converting all of the powdered metal to a stable but relatively low density carbide; and (f) subsequently heating the carbide body at a temperature of about 2000° C. in an inert or evacuated environment to convert the relatively low density carbide into relatively high density carbide.

Claim 20

The method of preparing a very dense tungsten carbide body, consisting essentially of the steps of: (a) preparing a stoichiometric mixture of a carbon precursor and finely powdered tungsten, wherein the carbon precursor is a vinylidene chloride-based polymeric material, the carbon precursor being a precursor of a quantity of carbon which is in substantially stoichiometric ratio to the metallic tungsten; (b) blending the mixture to obtain an intimate and uniform mixture of the carbon precursor and powdered metal; (c) removing moisture, if any, which has accumulated upon particles of the mixture; (d) compressing the mixture to form a self-supporting green body of a desired shape; (e) heating the green body to a temperature at which significant dehydrohalogenation begins; (f) subsequently heating the green body at a uniform and slow rate to accomplish significant dehydrohalogenation without polymeric material melting or puffing, until at least 20% of the polymeric material has decomposed; (g) further heating the green body in order to remove such metal oxides as are present, with removal being accomplished by the formation of volatile tungsten oxychlorides and chlorides, with said heating being gradual enough such that the temperature differential within the body is held to no more than 5° C., until a weight loss of approximately 50% of the polymeric material has been achieved; (h) further heating the body at an average rate no greater than about 50° C. per hour to a temperature within the range of about 800°-1050° C.; and (i) subsequently densifying the body by heating the body at about 2,000° C. for about 10 minutes in an inert or evacuated environment.

Claim 21

The method of preparing a very dense tungsten carbide body, consisting essentially of the steps of: (a) preparing a stoichiometric mixture of a carbon precursor and finely powdered tungsten, wherein the carbon precursor is a vinylidene chloride-based polymeric material, the carbon precursor being a precursor of a quantity of carbon which is in substantially stoichiometric ratio to the metallic tungsten; (b) blending the mixture to obtain an intimate and uniform mixture of the carbon precursor and powdered metal; (c) removing moisture, if any, which has accumulated upon particles of the mixture; (d) compressing the mixture to form a self-supporting green body of a desired shape; (e) heating the green body to a temperature at which significant dehydrohalogenation begins; (f) subsequently heating the green body at a uniform and slow rate to accomplish significant dehydrohalogenation without polymeric material melting or puffing, until at least 20% of the polymeric material has decomposed; (g) further heating the green body in order to remove such metal oxides as are present, with removal being accomplished by the formation of volatile tungsten oxychlorides and chlorides, with said heating being gradual enough such that the temperature differential within the body is held to no more than 5° C., until a weight loss of approximately 50% of the polymeric material has been achieved; (h) further heating the body at an average rate no greater than about 50° C. per hour to a temperature within the range of about 800°-1050° C.; and (i) subsequently densifying the body by heating the body at about 2,000° C. for about 10 minutes in an inert or evacuated environment.