Wear resistant inner coating for pipes and pipe fittings

1. A petroleum refinery pipe for use in processes for cracking petroleum feedstocks comprising:

a pipe body substrate selected from among carbon steels, alloy steels, and stainless steels; and

a Co-based metallic coating on an internal surface of the pipe body wherein the coating has a thickness between about 0.25 and 2.5 mm thick;

wherein the coating composition comprises between 31 and 34 wt % Cr, between 16 and 19 wt % Mo, between 2.1 and 2.5 wt % C, between 0.5 and 1.5 wt % Si, up to 1 wt % B, and between 42 and 50 wt % Co;

wherein the coating has a hypereutectic microstructure characterized by carbides in a cobalt matrix and an average carbide grain size of less than 50 microns;

wherein the Co-based metallic composition overlays the pipe internal surface at an interface which is free of heat-affected zone and which has a diffusion zone which is less than 0.002 inches thick.

2. A petroleum refinery pipe for use in processes for cracking petroleum feedstocks comprising:

a pipe body substrate selected from among carbon steels, alloy steels, and stainless steels, wherein the pipe body substrate has a pipe bend of at least 90 degrees; and

a Co-based metallic coating on the internal surface wherein said coating encompasses an outer arc of the at least 90-degree pipe bend, wherein the coating has a thickness between about 0.25 and 2.5 mm thick;

wherein the coating composition comprises between 31 and 34 wt % Cr, between 16 and 19 wt % Mo, between 2.1 and 2.5 wt % C, between 0.5 and 1.5 wt % Si, up to 1wt % B, and between 42 and 50 wt % Co;

wherein the coating has a hypereutectic microstructure characterized by carbides in a cobalt matrix and an average carbide grain size of less than 50 microns;

wherein the Co-based metallic composition overlays the pipe internal surface at the interface which is free of heat-affected zone and which has a diffusion zone which is less than 0.002 inches thick.

3. The petroleum refinery pipe of claim 2 wherein the coating composition consists essentially of between 31 and 34 wt % Cr, between 16 and 19 wt % Mo, between 2.1 and 2.5 wt % C, between 0.5 and 1.5 wt % Si, up to 1 wt % B, and between 42 and 50 wt % Co.

4. The petroleum refinery pipe of claim 2 wherein the at least 90-degree bend is a U-bend.

5. The petroleum refinery pipe of claim 3 wherein the at least 90-degree bend is a U-bend.

6. A method of imparting high-temperature wear and erosion resistance to an internal surface of a pipe comprising:

applying a metal slurry comprising metallic powder to an internal surface of a pipe substrate selected from among carbon steels, alloy steels, and stainless steels;

and sintering the Co-based metallic composition to form a substantially continuous Co-based alloy coating between about 0.25 and 2.5 mm thick;

wherein the metallic powder has an average size less than 45 microns and is pre-alloyed Co-based alloy powder comprising between 31 and 34 wt % Cr, between 16 and 19 wt % Mo, between 2.1 and 2.5 wt % C, between 0.5 and 1.5 wt % Si, up to 1 wt % B, and between 42 and 50 wt % Co;

wherein the sintered continuous Co-based metallic composition has a microstructure characterized by carbides in a cobalt matrix and an average carbide grain size of less than about 50 microns;

wherein the Co-based metallic composition overlays the pipe internal surface at an interface which is free of heat-affected zone and which has a diffusion zone which is less than 0.002 inches thick.

7. The method of claim 6 wherein the pipe has a bend of at least 90 degrees and the coating is formed on a segment of the pipe internal surface which encompasses an outer arc of the bend.

8. The method of claim 7 wherein the pre-alloyed Co-based alloy powder consists essentially of between 31 and 34 wt % Cr, between 16 and 19 wt % Mo, between 2.1 and 2.5 wt % C, between 0.5 and 1.5 wt % Si, B in a concentration up to 1 wt %, and between 42 and 50 wt % Co.

9. The method of claim 7 wherein the at least 90-degree bend is a U-bend.

10. The method of claim 8 wherein the at least 90-degree bend is a U-bend.