Oerlikon Carborod CrMo91 description: CARBOROD CrMo91 is an uncoated WCrMo91/ER90S-B9 type solid TIG welding rod for welding creep resisting steels of the type 9Cr 1Mo V Nb N. Suitable for use with Ar shielding gas. CARBOROD CrMo91 is especially designed for the ASTM steels T91/P91. Approved in long-term service at temperatures <650C. Improved creep strength is obtained by the addition of nitrogen, niobium and vanadium.