Chemical activation of self-passivating metals

A method for treating a workpiece made from a self-passivating metal and having a Beilby layer comprising:

• exposing the workpiece, at an exposing temperature below a temperature at which coarse nitride and/or coarse carbide precipitates form in the workpiece, to vapors produced by heating one or more non-polymeric N/C/H compounds to activate the workpiece for low temperature interstitial surface hardening, wherein the one or more N/C/H compounds:
• (a) is solid or liquid at 25° C. and atmospheric pressure;
• (b) has a molecular weight of ≤5,000 Daltons;
• and
• (c) can be either uncomplexed or complexed with a hydrohalide acid, and further wherein:
• (i) if the non-polymeric N/C/H compound is uncomplexed, any halogen atoms replace one or more labile hydrogen atoms of the non-polymeric N/C/H compound, and
• (ii) if the non-polymeric N/C/H compound is complexed, any halogen atoms form a part of the hydrohalide complexing acid.

A method for treating a workpiece made from self-passivating metal and having a Beilby layer comprising:

• exposing the workpiece to the vapors produced by heating a reagent having a guanidine [HNC(NH2)2] moiety and complexed with HCl to activate the workpiece for low temperature interstitial surface hardening;
• applying a heating protocol during the exposing that ramps from a lower to a higher temperature during the exposing to enhance decomposition of the reagent and/or surface harden the workpiece, wherein the heating profile is as follows:
• maintain a temperature of substantially 500° C. for approximately 15 minutes;
• ramp the temperature from approximately 500° C. to approximately 480° C.;
• maintain a temperature of 480° C. for approximately 15 minutes;
• ramp the temperature from approximately 480° C. to approximately 470° C.;
• and
• maintain a temperature of 470° C. for approximately 30 minutes.