Bimodal and multimodal dense boride cermets with superior erosion performance

A bimodal cermet composition comprising:

• a) a TiB2 phase with a bimodal distribution of non-spherical shaped particles;
• b) a M2B phase wherein M is selected from the group consisting of Cr, Fe, Ni, Ti and combinations thereof;
• c) an impurity phase selected from the group consisting of TiO2, TiC, TiN, Ti(C,N), and combinations thereof;
• and
• d) a metal binder phase comprising at least one first element selected from the group consisting of Fe, Ni, Co, Mn and mixtures thereof and at least one second element selected from the group consisting of Cr, Al, Si and Y, and Ti,
• wherein said metal binder phase comprises about 5 to 40 vol. % of the volume of said bimodal cermet composition,
• wherein said bimodal distribution of non-spherical shaped particles comprises fine grit particles in the size range of about 3 to 60 microns and coarse grit particles in the size range of about 106 to 800 microns,
• wherein said coarse grit particles comprise at least 50 vol. % of the of the TiB2 phase, and
• wherein the normalized erosion resistance HEAT index of the bimodal cermet composition ranges from 7 to 11.

A method for protecting a metal surface subject to erosion at temperatures up to 1000° C., the method comprising the step of providing a metal surface with a bimodal cermet composition, wherein said composition comprises:

• a) a ceramic phase, and b) a metal binder phase,
• wherein said ceramic phase is a metal boride with a bimodal distribution of non-spherical shaped particles, wherein at least one metal is selected from the group consisting of Group IV, Group V, Group VI elements of the Long Form of The Periodic Table of Elements and mixtures thereof,
• wherein said metal binder phase comprises at least one first element selected from the group consisting of Fe, Ni, Co, Mn and mixtures thereof, and at least one second element selected from the group consisting of Cr, Al, Si and Y, and Ti,
• wherein said metal binder phase comprises about 5 to 40 vol. % of the volume of said bimodal cermet composition,
• wherein said bimodal distribution of non-spherical shaped particles comprises fine grit particles in the size range of about 3 to 60 microns and coarse grit particles in the size range of about 106 to 800 microns,
• wherein said coarse grit particles comprise at least 50 vol. % of the of the ceramic phase, and
• wherein the normalized erosion resistance HEAT index of the bimodal cermet composition ranges from 7 to 11.

A method for protecting a metal surface subject to erosion at temperatures up to 1000° C. with a bimodal boride cermet composition, the method comprising the following steps:

• a) providing a bimodal boride cermet composition, wherein said composition comprises:
• i) a TiB2 phase with a bimodal distribution of non-spherical shaped particles;
• ii) a M2B phase wherein M is selected from the group consisting of Cr, Fe, Ni, Ti and combinations thereof;
• iii) an impurity phase selected from the group consisting of TiO2, TiC, TiN, Ti(C,N), and combinations thereat and
• iv) a metal binder phase comprising at least one first element selected from the group consisting of Fe, Ni, Co, Mn and mixtures thereof, and at least one second element selected from the group consisting of Cr, Al, Si and Y, and Ti,
• wherein said metal binder phase comprises about 5 to 40 vol. % of the volume of said bimodal cermet composition,
• wherein said bimodal distribution of non-spherical shaped particles comprises fine grit particles in the size range of about 3 to 60 microns and coarse grit particles in the size range of about 106 to 800 microns,
• wherein said coarse grit particles comprise at least 50 vol. % of the of the TiB2 phase, and
• wherein the normalized erosion resistance HEAT index of the bimodal cermet composition ranges from 7 to 11,
• b) mixing said ceramic phase and said metal binder phase in the presence of an organic liquid and a paraffin wax to form a flowable powder mix,
• c) placing said flowable powder mix into a die set,
• d) uniaxially pressing said die set containing said flowable powder mix at a pressure from about 40 to about 80 tons to form uniaxially pressed green bodies,
• e) heating said uniaxially pressed green bodies through a time-temperature profile to effectuate burn out of said paraffin wax and liquid phase sintering of said uniaxially pressed green bodies to form a sintered bimodal boride cermet composition,
• f) cooling said sintered bimodal boride cermet composition at a cooling rate of about 5° C./minute to form a bimodal boride cermet composition tile, and
• g) affixing said bimodal boride cermet composition tile to said metal surface to be protected.