Mechanical part with a nanostructured tio2-cr2o3 ceramic coating and method for depositing a nanostructured tio2-cr2o3 ceramic coating on a substrate

Abstract

There is provided a method for depositing a TiO2—Cr2O3 ceramic coating on a substrate. The method includes mixing a powder of sprayable nanostructured titanium(IV) oxide (n-TiO2) and a powder of chromium(III) oxide (Cr2O3), thereby obtaining a n-TiO2—Cr2O3 powder blend. The method also includes thermal spraying particles of the n-TiO2—Cr2O3 powder blend on the substrate at an in-flight particle temperature of or greater than 2350° C. and a particle in-flight velocity of or greater than 350 m/s, thereby obtaining a coated substrate.

1 .- 20 . (canceled) 
     
     
         21 . A High-Pressure Acid Leach (HPAL) metal-seated ball valve, comprising a mechanical part subjected to wear due to friction with other parts of the valve during operation of the valve, the mechanical part being coated with a nanostructured titanium(IV) oxide (n-TiO 2 )-chromium (III) oxide (Cr 2 O 3 ) coating consisting of 50 wt % to 60 wt % n-TiO 2  and 40 wt % to 50 wt % Cr 2 O 3 , wherein the n-TiO 2 —Cr 2 O 3  coating has a microhardness of at least 1000 HV as measured under a 300 gf load. 
     
     
         22 . The HPAL metal-seated ball valve of  claim 21 , wherein the mechanical part is a ball or a seat. 
     
     
         23 . The HPAL metal-seated ball valve of  claim 21 , wherein the mechanical part is made of titanium. 
     
     
         24 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating comprises 53 wt % to 57 wt % of n-TiO 2  and 43 wt % to 47 wt % of Cr 2 O 3 . 
     
     
         25 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating comprises about 55 wt % of n-TiO 2  and about 45 wt % of Cr 2 O 3 . 
     
     
         26 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a microhardness of at least 1150 HV. 
     
     
         27 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a microhardness between 1150 and 1250 HV. 
     
     
         28 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a dry abrasion volume loss of less than 15 mm 3 . 
     
     
         29 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a dry abrasion volume loss of less than 8.4 mm 3 . 
     
     
         30 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a dry abrasion volume loss between 7 and 8.4 mm 3 . 
     
     
         31 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating is obtained from a powder blend consisting of n-TiO 2  and Cr 2 O 3 . 
     
     
         32 . The HPAL metal-seated ball valve of  claim 31 , wherein the powder blend is air plasma sprayed onto the mechanical part. 
     
     
         33 . The HPAL metal-seated ball valve of  claim 31 , wherein the n-TiO 2  comprises nanosized constituents agglomerated and/or sintered in microsized n-TiO 2  particles. 
     
     
         34 . The HPAL metal-seated ball valve of  claim 33 , wherein the nanosized constituents have a size ranging from 50 nm to 500 nm. 
     
     
         35 . The HPAL metal-seated ball valve of  claim 33 , wherein the microsized n-TiO 2  particles have a diameter distribution ranging from 4 μm to 100 μm. 
     
     
         36 . The HPAL metal-seated ball valve of  claim 30 , wherein the Cr 2 O 3  is a sintered and crushed Cr 2 O 3  powder. 
     
     
         37 . The HPAL metal-seated ball valve of  claim 21 , wherein the n-TiO 2 —Cr 2 O 3  coating has a microstructure comprising cracks, the cracks consisting of:
 cracks of a first type formed in particles of the n-TiO 2 —Cr 2 O 3  coating and at particle boundaries, due to quenching; and 
 cracks of a second type formed due to a coefficient of thermal expansion (CTE) mismatch between the mechanical part and the n-TiO 2 —Cr 2 O 3  coating and/or residual stresses within the n-TiO 2 —Cr 2 O 3  coating. 
 
     
     
         38 . The HPAL metal-seated ball valve of  claim 37 , wherein the cracks of the second type are larger than the cracks of the first type. 
     
     
         39 . A method for depositing a ceramic coating on a mechanical part of a High-Pressure Acid Leach (HPAL) metal-seated ball valve, the method comprising:
 providing a powder blend of sprayable nanostructured titanium(IV) oxide (n-TiO 2 )-chromium (III) oxide (Cr 2 O 3 ), wherein the powder blend consists of 50 wt % to 60 wt % of nTiO 2  and 40 wt % to 50 wt % of Cr 2 O 3 ; and   thermal spraying particles of the n-TiO 2 —Cr 2 O 3  powder blend onto a mechanical part of the valve, the mechanical part being subjected to wear due to friction with other parts of the valve during operation of the valve, by air plasma spraying (APS) at an average in-flight particle temperature between 2400° C. and 2800° C. and an average particle in-flight velocity of or greater than 350 m/s,   wherein the ceramic coating has a microhardness of at least 1000 HV as measured under a 300 gf load.   
     
     
         40 . The method of  claim 39 , wherein the ceramic coating has a microhardness between 1150 and 1250 HV.