IL42599A - Ion plating method and product therefrom - Google Patents

Description

PDian nsinm o¾ a ■ns*-*'? rra-w ION PLATING METHOD AND PRODUCT THEREFROM Γ0 ALL WHOM IT MAYsCONCER : , ' Be : it known that I, NIELS N. ENGEL, a citizen of the United States of America, residing at Atlanta, Fulton County, Georgia, lave invented -certain new and useful improvements in an .„.;:·. ION PLATING METHOD AND PRODUCT THEREFROM for which the, following is a specification.

ABSTRACT OF THE DISCLOSURE ^ · , ! : i ·.

An' ion plating method and product therefrom wherein ions of a metal; are implanted into or/and plated onto a substrate to increase the hardness of the surface. After plating, the product can be reacted with carbon, boron, nitrogen or another metal, thereby forming the carbide, boride, nitride or metal compound of the plating metal coating. Hardening of the product by quenching follows which produces a cutting tool of superior qualities.

BACKGROUND OF THE INVENTION This invention relates to an improved metalic deposition on a substrate and more particularly to an ion plating method and product therefrom.

The cutting power and edge life of knife blades depend . upon the presence of a matrix structure of slightly tempered martensite Of high hardness and the embedding of a sufficient number of finely, and uniformly distributed carbides in this matrix There are many procedures utilized in the formation of cutting tools to provide a cutting edge of great hardness and durability.- ' With stainless steel, for example, the carbon content of the steel substrate has been increased in order to increase the proportion of hard chromium carbides in the structure when used as cutting materials. Other carbide -forming alloying constituents, such as molybdenum, tungsten, vanadium, titanium and the like have also been added to the substrate. coat of the carbide, boride, nitride or metal compound to form an excellent cutting edge.

It is, therefore, a primary object of the present invention to provide a method of producing improved cutting edges and products therefrom.

Another object of the present invention is to provide a method of implanting ions of a metal into a steel or iron containing alloy substrate to form carbides of the metal within the martensite of the hardened substrate, thereby increasing the surface hardness of the substrate to produce an improved cutting tool Another object of the present invention is to provide a method of ion plating a metal onto the surface of a substrate.

A further object of the present invention is to provide a method of carburizing, boriding, nitriding or metallizing an ion plated substrate.

;A still further object of the present invention is to . provide cutting.and abrading tools which have superior cutting power, durability, strength and corrosion and wear resistance; Another object of the present invention is to provide a method of ion plating which is adaptable to substrates of steel or iron containing alloys.

'■■ An- object of the present invention is to provide an iron plated product which is very resistant to thermal shock.

Another object of the present invention is to provide an improved cutting edge which has a low coefficient of friction.

Still other objects and advantages of the present invention will become apparent , after reading the accompanying description of the selected illustrative embodiment.

DESCRIPTION OF THE FIGURES OF DRAWING Figure 1 is a : photomicrograph of plain carbon steel treated in accordance with the present invention; and Figure 2 is a photomicrograph of plain carbon steel which was given the same heat treatment but which has not been ion implanted.

. DESCRIPTION OF THE INVENTION Ion implanting in any metal will generally cause an increase in the hardness and strength of the metal. Ion implantation into a carbon containing steel combined with a hardening treatment leads to a superhard martensite independent of the implanted material. In ion implanting a steel substrate, the carbon content of the substrate should range from 0.31 to 1.8% b weight, with the optimum range being from 0.5% to 0.8% by weight. A substrate having a carbon content below 0.3% is called "mild" steel and is too soft for cutting tools and various wear resistant objects. Their coats will easily break down if the support or substrate is much softer" and weaker than the coating itself.

Therefore^ substrates should be hard, preferably hardened steel. There is actually no maximum limit of the carbon percentage within the. substrate; it depends on how brittle it is desired that the substrate be after it has been quenched as discussed below. The substrate used in the present invention can be any steel or iron containing alloy.

The ion implantation yields the advantage that the hardened matrix is harder than martensite obtained by normal hardening implanted matrix constitutes a method to obtai the hardest Coats on a super ard matrix, which cannot be obtained by any other method*. At the same time* the adherence between coat and matrix is better than can be obtained by any other method* Th fj&re step in the io plating process of the present inventio is to clean the substeate. The substrate is cleaned by any suitable method and then is quickly mounted on a metal holder with the edges to be ion plated exposed. The holder is trans erred to a vacuum chamber for ion Implantation and plating wherein the substrate forms the cathode* The chamber is pumped down to a vacuum of 2xlO"¾nmHg or better with frequent flushing with argon gas. Such a low pressure is necessary to support the plasma that is created therein as described below*' Argon gas is let into the chamber* An electrical potential is then applied to the cathode(substrate) and Is radualincreased until a pink argon plasma is formed. Argon is used as It will not react with the substrate or with the ion plating material and is heavy so as to increase the Impact force of the ions on the substrate whereby better cleaning action is achieved* The plasma forming starts in the range of 1KV and 50 mamps and can then be maintained to much lower potentials* The power setting can be varied according to the needs* The object to be Ion plated Is first ion cl eaned with the argon plasma* The argon sputters off any atomic impurities or dirt that are present on the substrate surface, and Inherently implants this inert gas into the surface of the substrate to produce a subsur ace containing the argon (an iner gas) as an element which is insoluble in the substrate* The ion plating material on a filament (such as a tungsten wire) or from a poo of melted meta heated by an electron gun forms the anode within the ohamber* By passing sufficient current through this filament while the argon plasma is holding,, the filament (anode) Is gradually heated until the material on the anode melts and, aided by the substantial vaouum within the 6a - chamber, then vaporizes. These ionized particles are attracted^ to the athode (object to be ion plated) due to the great potential .difference (which can vary from 500V to 50,000V), and thus , iom mplantation and/or plating is . accomplished .

Actually, the first ions that strike the substrate surface are implanted within the substrate and cause a gradual transition between the substrate and the surface. As the sub- strate becomes "saturated" by the ion implantation, the remainder of the ions are deposited on the substrate surface.

The "penetration depth" of the ion implantation into the substrate depends on the hardness of the substrate. Generally a substrate having a hardness of less than 50 Rockwell C is preferred. ' ■ ".

When the 'implanted ions react with the carbon present in the substrate , it , is not known at this time whether they form a precipitate or are in "solution" within the crystalline · lattice of the substrate. This is due to the fact that compounds formed b the implanted ions are too small to be observed by , present day methods .

■ /^..The time of ion plating can be varied from fractions of seconds to several minutes . During the ion plating process, the pressure in the chamber does drop somewhat, but should be maintained at the right level by adjusting the argon pressure of metal vaporization.

.Ob ects Ion Plated: The above ion plating procedure can be performed on a number of steel or iron containing alloys, such as Tazor blades , industrial blades,, band saws , files , nails, ; etc.■, as.''.well as other metals and shapes including meat chopper -Ion Plating Materials : A wide range o£ elements can be ion Dlated onto the substrate. These include all of the refractory elements (scandium, titanium, zirconium, hafnium, ; vanadium:j'rcolumbium, tantalum, chromium, molybdenum and tungsten) the rare-earth elements (lanthanum, cerium, praseodymium, neodymiu , promethium,. samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, yttrium, ytterbium, · and lutetium) the actinide series (actinium, thorium, protactinium, * uranium, neptunium, plutonium, americium, curium, berkelium, californium, einsteinium, fermium, mendelevium, nobelium, and lawrencium)',, iron , cobalt, nickel and boron. Some of these metals require a high powered vaporization unit, such as an electron gun, in order to evaporate the same. In industrial production, electron gun vaporization would be preferred.

.·; Carburizing, Boridin , Nitriding, and Metallizing: Wear resistant and corrosion resistant cutting edges are obtained with superhard materials which can be added to the ion implanted substrate surface . The hardest known materials are carbides, borides,; and nitrides and compounds of transistion elements with second period elements, for example TiC, ScN, VC, Cr^Cz, TiB, B4C, and BN. Additionally, any metal included in the above list of ion plating materials , other than the metal already plated on the substrate, tan be. added to the ion implanted substrate surface. These materials can be added to the substrate as compounds; however , they are very stable and difficult to evaporate. The best procedure . is to ion plate the pure metal (Ti , Cr, B, Sc, etc.) onto the substrate, and then convert the metal to the respective carbids boride or nitride . were carburized in a methane and hydrogen atmosphere and hardened by water quenching. It was found that there was a difference &ϊ nearly 300 points in the Knoop hardness between the two: '' '· ' ■ Annealed file 1120 Khn Unannealed file 825 Khn It is believed that this difference in hardness is caused by the ability of dislocations to penetrate into the material. The mechanism of creating superhard martensite is most probably that atoms impinging on the metal surface initiate a dislocation which moves to a certain depth into the material carrying the impinged atom with it. Soft materials are permeable to dislocations and can therefore absorb impinging atoms to penetrate below the surfac An. advantage of the present invention is that it. produces an adhesion between the coating and the substrate which is greater than the strength of the substrate. Glue was placed on a portion of the coated substrate. In an attempt to pull the coating away from the substrate surface, either the substrate or the glue broke under the tension. The "joint" or coating/substrate interface never did break.

The method of this invention produces a coating on a substrate which is very resistant to thermal shock. Extreme and sudden temperature changes do not effect either the coating or the inti This can be obtained by the selection of a coat with a smaller thermal expansion than the substrate. When cooled after plating at a somewhat elevated temperature, the coat will be under compressive stresses Also, the selection of a coat materiap. with a low coefficient of friction will prevent heating through rubbing such as with chopper plates in meai cutting. A titanium Figure Ids a photomicrograph of a sample A of plain carbon steel ion plated with titanium, carburized by a plasm .£s formed by a nitrogen-propane mixture and quenched in water.

/Figure 2 is a photomicrograph of a sample B of the same plain carbon steel carburized and quenched as sample A but without) ion plating. The test load for both samples A and B was 100 grams. The magnification of Figures 1 and 2 is 250X. As seen in the following Table I, the Knoop hardness values for the carburized sample (sample B) are fairly constant and are similar to that of a normal steel. However, for the ion implanted sample (sample A), the surface hardness is very much higher. rs Sample B 885 885 880 880 910 880 'Typical hardness values for samples under varying' experi' mental conditions of voltage, current, ion plating material and time of ion plating are presented in Table II. ater a on a ng me o age u Ion Material and Ion Plating (KV) (mamps) Medium Plated .Atmosphere (Minutes) 1. Plain Ti/Argon 100 C+H Carbon Steel 2. } Plain r Ti/Argon 2 100 C+H '·■ " Carbon Steel 3. Plain . Ti/Argon , 2 . 100 C+H Carbon Steel 4. ; Plain - Ti/Argon ½ 2 100 C+H Carbon Steel 5. Plain Ti/Argon 5 2 100 C+H. Carbon Steel 6 Plain Fe/Argon 2 2 100 C+H.

Carbon Steel ?V Plain Al/Argon 1 2 100 C+H. 3 Carbon Steel 8. Plain ·. ' Ti/Propane 2 2 100 Impulse Carbon Steel Hardene 9. Steel File - Ti/Argon 3 3 100 ¾+m Annealed 10. Steel File Ti/Argon 3 3 100· t+H. (Hardened) 11. Plain None -C,HR Carbon Steel 12. Plain None Impulse Carbon Steel Hardene VOTE:1--*'11 thf> " 1^ were nn cleaned for 2 minutes in argon except #2.

•C-cn^lmn-contair.inc caseous compounl. such as methane.

Claims (1)

1. Claims A method of producing a ooated bod comprising bombarding a substrate with a in ionic tio with such substrate is reactive and at a sufficient for the me a ions penetrate into said continuing the bombardment of said substrate with said meta a suffioient length of time to a coating of said metal over the surf ce of the implanted metal of said and reacting the coating on the sur with a substance which imparts greater hardness to the method according to Claim 1 wherein said hardening is accomplished by reacting the coating with a hardening chemica selected the group consisting of nitrogen and a seleoted one of the metals with which said substrate is reaotive othe than said bombarding A method according Claim 2 or 3 wherein said ning further includes heat treating said coated A method aooording to of Claims 1 to 3 including the step of leaning sur of said substrate prior to ste A method according to of 1 to including the steps of heat ng substrate to the austenite range of the substrate and cooling it with a supe A method according to 5 wherein said substrate is a carbon containing A method according to Claim 6 wherei said carbon containing substrate has a carbon content ging from to by A method according to Claim wherein the amount of carbon in said substrate ranges from to by A method according to any of Claims 1 to comprising the steps o bombarding a surface of the substrate with ions of a metal seleoted from the grou consisting of thulium actinium i e and boron to implant said ions to a preselected penetratio depth within continuing the bombardment until said substrate had become saturated with said ions within said lected further continuing said bombardmen to said ions to plate the surface of and reacting said io with element seleoted from the group consisting of nitrogen a seleoted of said metals other than the implanted so as to form the nitride or compound of the respective plated method of producing a ooated substantially hereinbefore coated whenever obtained by the according to any of Claims to coated product a iro an implanted subsur ace along sur ace of said said subsurface containing an element which is insoluble in aaid and coatin along said subsurface o a coating metal and a hardening substance reacted with said metal said substance with said coating a layer which is harder the coating itsel coated metal produc 12 wherein said insoluble is an inert gas and said coatin metal is the group consisting of soandium hafnium molybdenum s t thor mendelevium iron cobalt nickel A ooated metal product according to Claim 12 or wherein said hardening substance is selected group consisting of nitrogen and A coated metal product according to any of Claims 12 to 14 a knoop hardness in excess of insufficientOCRQuality