GB1120299A - Improved flame spray powder - Google Patents

Abstract

In making a flame-spray powder, which may be used to coat steel, nickel-based alloys or aluminium, particles of metal or other heat resistant material are rendered resistant to corrosion or abrasion by bonding a fluxing ceramic oxide (or mixed oxide) to the surface of the particles, and submitting the powder to a flame spray process, e.g. using a plasma powder flame-spray gun, whereby a non-porous coating is formed on the particles. The proportion of fluxing ceramic oxide is such that it comprises 1 to 50%, preferably 5 to 25%, by volume with respect to the powder. The fluxing ceramic must have the ability to wet the surface of the nucleus particles at the spraying temperature; and lithium cobaltite, or lithium manganite, is preferably utilized. Other fluxing ceramics which may be used are: -lithium -zirconate, -titanate, -aluminate and -silicate, soda lime glass, borosilicate glasses, alumino borosilicates, and high silica content glasses. The substrate particles are mixed with a bonding agent such as chlorinated rubber, a polyester, a cellulose plastic, or a phenolic or epoxy resin; and the fluxing ceramic oxide particles, suspended in an organic liquid, are then added. The mixture is then dried, and submitted to the flame-spray process. The particulate substrate may comprise particles of metals or alloys such as stainless steels, carbon steels, iron, nickel-chromium alloys, nickel-copper alloys, chromium, nickel, cobalt, nickel clad aluminium, tungsten, molybdenum, tantalum, niobium, refractory metal alloys, platinum, silver, hafnium, silicon, titanium, zirconium (and hydrides of these latter two) "self fluxing alloys", aluminium, copper, brass, bronze, beryllium, vanadium; ceramics such as zirconia, titania, magnesia, ceria, rare earth oxides, hafnia, nickel oxide, thoria, beryllia, alumina, stabilized zirconia and chromia; combinations of oxides including: alumina containing titania, zirconium silicate magnesium silicate, calcium silicate, magnesia alumina spinel, beryllium titanate, yttrium zirconate, aluminium silicate, mullite; cermets such as cobalt clad or bonded zirconia, nickel clad or bonded alumina; carbides such as zirconium carbide tantalum carbide, hafnium carbide, niobium carbide, boron carbide, tungsten carbide, chromium carbide and titanium carbide; combined carbides including tantalum carbide with zirconium or hafnium carbide. Any of the above listed carbides may be crystalline, i.e. "pure" carbides or bonded carbides, as for example tungsten carbide bonded with 5-20% cobalt, titanium carbide bonded with 5-20% nickel, chromium carbide bonded with 5-20% nickel or nickel-chrome alloy. The carbides may also be clad for example with nickel, cobalt or nickel-chrome alloy. The particulate substrate may also be a boride such as a boride of zirconium, hafnium, titanium, silicon or chromium, or may be a silicide such as a silicide of molybdenum or chromium or a nitride e.g. titanium nitride. Mixtures of these may also be used.ALSO:Particles of metal or other heat-resistant material are rendered resistant to corrosion or abrasion by bonding a fluxing ceramic oxide (or mixed oxide) to the surface of the particles, and submitting the powder to a flame spray process, e.g. using a plasma powder flame spray gun, whereby a non-porous coating is formed on the particles. The proportion of fluxing ceramic oxide is such that it comprises 1 to 50% preferably 5 to 25% by volume with respect to the powder. The fluxing ceramic must have the ability to wet the surface of the substrate particle at the spraying temperature; and lithium cobaltite, or lithium manganite, is preferably utilized. Other fluxing ceramics which may be used are: lithium-zirconate, -titanate, -aluminate and -silicate, soda lime glass, borosilicate glasses, alumino borosilicates and high silica content glasses. The particulate substrate may comprise particles of metals or alloys such as stainless steels, carbon steels, iron, nickel-chromium alloys, nickel-copper alloys, chromium, nickel, cobalt, nickel clad aluminium, tungsten, molybdenum, tantalum, niobium, refractory metal alloys, platinum, silver, hafnium, silicon, titanium, zirconium (and hydrides of these latter two) "self-fluxing alloys," aluminium, copper, brass, bronze, beryllium, vanadium, ceramics such as zirconia, titania, magnesia, ceria, rare earth oxides, hafnia, nickel oxide, thoria, beryllia, alumina, stabilized zirconia and chromia; combinations of oxides including: alumina containing titania, zirconium silicate, magnesium silicate, calcium silicate, magnesia alumina spinel, beryllium titanate, yttrium zirconate, aluminium silicate, mullite; cermets such as cobalt clad or bonded zirconia, nickel clad or bonded alumina; carbides such as zirconium carbide, tantalum carbide, hafnium carbide, niobium carbide, boron carbide, tungsten carbide, chromium carbide and titanium carbide; combined carbides including tantalum carbide with zirconium or hafnium carbide. Any of the above listed carbides may be crystalline, i.e. "pure" carbides or bonded carbides, as for example tungsten carbide bonded with 5-20% cobalt, titanium carbide bonded with 5-20% nickel, chromium carbide bonded with 5-20% nickel or nickel-chrome alloy. The carbides may also be clad for example with nickel, cobalt or nickel-chrome alloy. The particulate substrate may also be a boride such as a boride of zirconium, hafnium, titanium, silicon or chromium, or may be a silicide such as a silicide of molybdenum or chromium or a nitride, e.g. titanium nitride. Mixtures of these may also be used.ALSO:Particles of metal or other heat-resistant material are rendered resistant to corrosion or abrasion by bonding a fluxing ceramic oxide (or mixed oxide) to the surface of the particles, and submitting the powder to a flame spray process, e.g. using a plasma powder flame spray gun, whereby a non-porous coating is formed on the particles. The proportion of fluxing ceramic oxide is such that it comprises 1 to 50% preferably 5 to 25%, by volume with respect to the powder. The fluxing ceramic oxide must have the ability to wet the surface of the substrate particle at the spraying temperature; and lithium cobaltite, or lithium manganite, is preferably utilized. Other fluxing ceramics which may be used are:-lithium-zirconate, -titanate, -aluminate, and -silicate, soda lime glass, borosilicate glasses, alumino borosilicates, and high silica content glasses. The substrate particles are mixed with a bonding agent such as chlorinated rubber, a polyester, a cellulose plastic, or a phenolic or epoxy resin; and the fluxing ceramic oxide particles, suspended in an organic liquid, are then added. The mixture is then dried, and submitted to the flame spray process. The particulate substrate may comprise particles of metals or alloys such as stainless steels, carbon steels, iron, nickel-chromium alloys, nickel-copper alloys, chromium, nickel, cobalt, nickel clad aluminium, tungsten, molybdenum, tantalum, niobium, refactory metal alloys, platinum, silver, hafnium, silicon, titanium, zirconium, (and hydrides of these latter two) "self fluxing alloys", aluminium, copper, brass, bronze, beryllium, vanadium; ceramics such as zirconia, titania, magnesia, ceria, rare earth oxides, hafnia, nickel oxide, thoria, beryllia, alumina, stabilised zirconia and chromia; combinations of oxides including: alumina containing titania, zirconium silicate magnesium silicate, calcium silicate, magnesia alumina spinel, beryllium titanate, yttrium zirconate, aluminium silicate, mullite; cermets such as cobalt clad or bonded zirconia, nickel clad or bonded alumina; carbides such as zirconium carbide, tantalum carbide, hafnium carbide, niobium carbide, boron carbide, tungsten carbide, chromium carbide and titanium carbide; combined carbides including tantalum carbide with zirconium or hafnium carbide. Any of the above listed carbides may be crystalline, i.e. "pure" carbides or bonded carbides, as for example tungsten carbide bonded with 5-20% cobalt, titanium carbide bonded with 5-20% nickel, chromium carbide bonded with 5-20% nickel or nickel-chrome alloy. The carbides may also be clad for example with nickel, cobalt or nickel-chrome alloy. The particulate substrate may also be a boride such as a boride of zirconium, hafnium, titanium, silicon or chromium, or may be a silicide such as a silicide of molybdenum or chromium or a nitride e.g. titanium nitride. Mixtures of these may also be used.