Boiler tube coating and method for applying the same
AssigneeEutectic Corporation
InventorFrederick T. Jaeger
Life of this patent
Estimating the term…
Abstract
A boiler tube coating and method are disclosed in which industrial steel tubes or pipes, for example, steel boiler tubes and/or integrated panels of steel boiler tubes, are provided with a fused overlay of a corrosion and erosion resistant coating comprised of a refractory hard component, e.g. tungsten carbide, dispersed through a corrosion resistant matrix alloy.
Claims8
A method of extending the life of a boiler tube subject in use to corrosion, oxidation and erosion which comprises:
- cleaning said boiler tube by grit blasting the surface thereof,
- preheating said cleaned boiler tube preparatory to receiving an alloy coating thereon, spray coating an overlay on said boiler tube of a coating composition in the form of a powder mixture consisting essentially of 10% to 70% by weight of a refractory hard powder component selected from the group consisting of carbides of W, Si, V, Ti, B, Cr and Mo;
- nitrides of Si, B and Ti;
- borides of Cr. W, Mo, Ta and V;
- and silicides of B, Mo and Cb blended with 90% to 30% by weight of a self-fluxing matrix alloy powder selected from the group consisting of nickel-base, nickel-copper base, iron-base and cobalt-base alloys containing by weight at least one element from the group consisting of 0.5% to 6% silicon and 0.5% to 5% boron, and thereafter fusing said overlay to the surface of said boiler tube to provide a relatively void-free bonded coating characterized by improved resistance to corrosion, oxidation and erosion.
A method for extending the life of a boiler tube comprising the steps of:
- cleaning said boiler tube by grit blasting the surface thereof,
- preheating said cleaned boiler tube preparatory to receiving an alloy coating thereon,
- spray coating an overlay on said boiler tube of an alloy composition in the form of a powder mixture consisting essentially of about 10% to 70% by weight of a refractory hard powder component selected from the group consisting of carbides of W, Si, V, Ti, B, Cr and Mo;
- nitrides of Si, B and Ti;
- borides of Cr, W, Mo, Ta and V;
- and silicides of B, Mo and Cb blended with 90% to 30% by weight of a self-fluxing matrix alloy powder selected from the group consisting of:
- a. 0.5 to 1.1% C, 3% to 6% Si, 3% to 4% B, 6% to 28% Cr, up to 5% Fe and the balance essentially nickel;
- b. 0.01% to 0.1% C, 2% to 5% Si, 1% to 3% B, up to 2% Fe and the balance essentially nickel;
- c. up to 0.2% C, 2% to 6% Si, 0.5 to 2% B, up to 1% Cr, up to 1.5% Fe, 10% to 40% Cu and the balance essentially nickel;
- and
- d. 0.6% to 3% C, 0.3% to 2% Si, up to 3% B, 20% to 35% Cr, 4% to 14% W, up to 3% Fe, up to 5% Ni and the balance essentially cobalt,
- and thereafter fusing said overlay to the surface of said boiler tube to provide a relatively void-free bonded coating characterized by improved resistance to corrosion, oxidation and erosion.
As an article of manufacture, a composite steel boiler tube comprising a fused protective overlay of a heat, corrosion and erosion resistant alloy consisting essentially of:
- 10% to 70% by weight of powder refractory hard component selected from the group consisting of carbides of W, Si, V, Ti, B, Cr, and Mo;
- nitrides of Si, B and Ti;
- borides of Cr, W, Mo, Ta and V;
- and silicides of B, Mo and Cb dispersed through 90% to 30% by weight of a matrix alloy selected from the group consisting of
- a. 0.5 to 1.1% C, 3% to 6% Si, 3% to 4% B, 6% to 28% Cr, up to 5% Fe and the balance essentially nickel;
- b. 0.01% to 0.1% C, 2% to 5% Si, 1% to 3% B, up to 2% Fe and the balance essentially nickel;
- c. up to 0.2% C, 2% to 6% Si, 0.5% to 2% B, up to 1% Cr, up to 1.5% Fe, 20% to 40% Cu and the balance essentially nickel;
- and
- d. 0.6% to 3% C, 0.3% to 2% Si, up to 3% B, 20% to 35% Cr, 4% to 14% W, up to 3% Fe, up to 5% Ni and the balance essentially cobalt;
- said protective overlay being dense and relatively void-free.
As an article of manufacture, a composite steel boiler tube panel comprising an array of steel boiler tubes welded together in side-by-side relationship to provide an integrated panel of steel boiler tubes, said panel having fused to the surface thereof a protective overlay of heat, corrosion and erosion resistant alloy consisting essentially of:
- 10% to 70% by weight of powder refractory hard component selected from the group consisting of carbides of W, Si, V, Ti, B, Cr and Mo;
- nitrides of Si, B and Ti;
- borides of Cr, W, Mo, Ta and V;
- and silicides of B, Mo and Cb dispersed through 90% to 30% by weight of a matrix alloy selected from the group consisting of
- a. 0.5 to 1.1% C, 3% to 6% Si, 3% to 4% B, 6% to 28% Cr, up to 5% Fe and the balance essentially nickel;
- b. 0.01% to 0.1% C, 2% to 5% Si, 1% to 3% B, up to 2% Fe and the balance essentially nickel;
- c. up to 0.2% C, 2% to 6% Si, 0.5 to 2% B, up to 1% Cr, up to 1.5% Fe, 20% to 40% Cu and the balance essentially nickel;
- and
- d. 0.6% to 3% C, 0.3% to 2% Si, up to 3% B, 20% to 35% Cr, 4% to 14% W, up to 3% Fe, up to 5% Ni and the balance essentially cobalt;
- said protective overlay being dense and relatively void-free.
As an article of manufacture, a composite steel boiler tube comprising a fused protective overlay of a heat, corrosion and erosion resistant alloy consisting essentially of:
- 10% to 70% by weight of powder refractory hard component selected from the group consisting of carbides of W, Si, V, Ti, B, Cr and Mo;
- nitrides of Si, B and Ti;
- borides of Cr, W, Mo, Ta and V;
- and silicides of B, Mo and Cb dispersed through 90% to 30% by weight of a matrix alloy selected from the group consisting of nickel-base, nickel-copper base, iron-base and cobalt-base alloys containing by weight at least one element from the group consisting of 0.5% to 6% silicon and 0.5% to 5% boron,
- said protective overlay being dense and relatively void-free.
Dependencies are inferred from the claim text.