Method of making foodware with a tarnish-resistant ceramic coating

Abstract

A foodware article having a thermally stable color, tarnish-resistant ceramic coating that enables direct contact with a heat source, such as a gas flame or the heating element of an electric stove. The foodware article of the present invention includes a metal foodware article having an inner food-contacting surface and an outer heat source-contacting surface, a bonding layer deposited on a portion of the outer heat source-contacting surface, and a first ceramic layer deposited adjacent to a portion of the bonding layer, the first ceramic layer selected from (Ti,Al)N, (Ti,Al)CN, (Ti,Al,X)N, or (Ti,Al,X)CN. A top layer of TiCN can be deposited adjacent to the first ceramic layer. There may optionally be alternating layers of a third ceramic selected from (Ti,Al)N, (Ti,Al)CN, (Ti,Al,X)N, or (Ti,Al,X)CN and a fourth ceramic selected from TiN, TiCN, XN or XCN deposited adjacent to the bonding layer and below the first ceramic layer. The alternating layers can be repeated as many times as desired. A method of making such a foodware article is also disclosed.

1 . A method of making a foodware article having a thermally-stable color, tarnish-resistant, ceramic coating comprising: 
 providing a metal substrate having an inner food-contacting surface and an outer heat source-contacting surface;    depositing a bonding layer on a portion of the outer heat-source contacting surface;    depositing a first ceramic layer adjacent to a portion of the bonding layer, the first ceramic layer selected from (Ti,Al)N, (Ti,Al)CN, (Ti,Al,X)N, or (Ti,Al,X)CN; and    forming the metal substrate into the foodware article.    
     
     
         2 . The method of  claim 1  further comprising depositing a top ceramic layer of TiCN on a portion of the first ceramic layer.  
     
     
         3 . The method of  claim 1  further comprising depositing a second ceramic layer adjacent to the bonding layer and below the first ceramic layer, the second ceramic layer being selected from TiN, TiCN, XN, or XCN.  
     
     
         4 . The method of  claim 1  further comprising depositing alternating layers of a third ceramic selected from (Ti,Al)N, (Ti,Al)CN, (Ti,Al,X)N, or (Ti,Al,X)CN and a fourth ceramic selected from TiN, TiCN, XN, or XCN adjacent to the bonding layer and below the first ceramic layer.  
     
     
         5 . The method of  claim 4  wherein each of the alternating layers is in the range of about 0.1 to about 1.0 microns thick.  
     
     
         6 . The method of  claim 1  wherein the layers are deposited by a physical vapor deposition method.  
     
     
         7 . The method of  claim 1  wherein the layers are deposited by a cathodic arc deposition process.  
     
     
         8 . The method of  claim 1  wherein the metal substrate is formed into the foodware article before depositing the coating.  
     
     
         9 . The method of  claim 1  wherein the metal substrate is formed into the foodware article after depositing the coating.  
     
     
         10 . The method of  claim 1  wherein the metal foodware article is made of a material selected from steel, stainless steel, titanium, clad material, or alloys thereof.  
     
     
         11 . The method of  claim 1  wherein the bonding layer is a metal selected from titanium, chromium, zirconium, or alloys thereof.  
     
     
         12 . The method of  claim 1  wherein a total thickness of the coating is in the range of about 0.5 to about 20 microns.