公开(公告)号：US4153453A

公开(公告)日：1979-05-08

申请号：US831471

申请日：1977-09-08

申请人： Anthony C. Hart ,  William R. Wearmouth

发明人： Anthony C. Hart ,  William R. Wearmouth

IPC分类号： C25D5/50 ,  C25D15/02 ,  C25D3/56 ,  C22C19/03 ,  C22C19/05 ,  C22C38/00

CPC分类号： C25D15/02 ,  C25D5/50

摘要： An alloy difficult to produce by conventional electrodeposition techniques is produced by electrodepositing at least one metal selected from the group comprising nickel, up to 50% cobalt, and iron with particles incorporating metal in chemically combined state. The particles contain a reactive element, such as carbon, nitrogen, and boron, and a metallic element, such as chromium, molybdenum, and tungsten. The electrodeposit of the particles in a metal matrix is treated in a reducing atmosphere so that the particles react, releasing at least some of their incorporated metal into the matrix to form the alloy while transferring the reactive element to the reducing atmosphere.This invention relates to a process for the production of an alloy.It is known to codeposit two or more metals on a substrate by electrodeposition either as permanent coatings or as coatings subsequently removed from the substrate, such as electroforms, to form an alloy with or without diffusion heat treatment. However, electrodeposition is subject to electrochemical restrictions which at best limit the alloy composition depositable or make it necessary to use commercially unsatisfactory process conditions and which at worst prevent certain alloys being produced as electroforms or even being produced at all by electrodeposition.For example, while attempts have been made to produce a nickel-chromium alloy electrodeposit by codepositing nickel and chromium metal, it has not proved possible in this way to produce commercially satisfactory nickel-chromium alloy electrodeposits containing useful amounts of chromium in the nickel matrix. Indeed the deposition processes used in these attempts have suffered from defects which have tended to make the processes themselves unsuitable for commercial usage.It is an object of the present invention to provide a process of making an electrodeposit of an alloy which is normally difficult to produce by conventional electrodeposition techniques.Generally speaking, the present invention is a process for producing an alloy comprising: coelectrodepositing a matrix of at least one metal selected from the group consisting of nickel, less than 50% by weight cobalt, and iron, with reactive particles incorporating metal in chemically combined state, said particles are compounds of at least one reactive element selected from the group consisting of carbon, nitrogen, and boron, and of at least one metallic element selected from the group consisting of chromium, molybdenum, and tungsten, thereby providing a composite electrodeposit; and heating said composite electrodeposit to temperatures of from about 1000.degree. C. to about 1400.degree. C. for at least 24 hours in a reducing gas atmosphere to release at least some of said metallic element of said particles from its chemically combined state into said matrix thereby forming said alloy while transferring at least some of said reactive element to said reducing gas atmosphere.While the process of the invention primarily is intended for the production of alloys which are difficult or even impossible to produce by conventional electrodeposition techniques, it is of course equally applicable to the production of alloys which can readily be produced by conventional electrodeposition techniques. Furthermore, the process of the invention can be used for the formation of alloy permanent coatings on a substrate or for the formation of coatings which are subsequently removed from the substrate, such as electroforms. References throughout this specification to "coatings" are to be taken to include electroforms which have been removed from the substrate upon which they were formed.The thermally decomposable reactive particles incorporating metal in chemically combined state may be codeposited in conjunction with particles which do not react under the conditions used to make the reactive particles react. In this way, an alloy may be produced containing particles which constitute, for example, a dispersion hardening dispersoid. The reactive particles incorporating metal in chemically combined state may alternatively or additionally to the foregoing non-reactive particles be codeposited with metal particles and/or with coated metal particles, for example, carbide coated metal particles.Although it has been proposed in the past to electrodeposit coatings made up of particles, incorporating metal in chemically combined state, in a metal matrix to improve the hardness and/or wear resistance of the matrix metal, such proposals have only resulted in the production of a composite coating of particles incorporating metal in chemically combined state in a metal matrix and not an alloy. Alloy production, it is thought, was precluded by the use of: (a) unreactive particles incorporating metal in chemically combined state, or (b) the wrong metal or metals, or (c) the use of process conditions or relative proportions of particles incorporating metal in chemically combined state, and matrix metal, which prevented reaction of the particles. For example, chromium carbide (Cr.sub.3 C.sub.2) and cobalt have been codeposited to form a Co--Cr.sub.3 C.sub.2 composite coating with improved initial hardness values, but have not been used to form an alloy.Preferably the process of the invention is used to codeposit nickel or nickel and up to 50% cobalt with chromium carbide particles to form an electrodeposited nickel-chromium or nickel-cobalt-chromium coating. Advantageously, sufficient chromium carbide particles should be utilized to give at least 13% chromium in the electrodeposited coating. However, when the electrodeposited coating contains both cobalt and chromium carbide particles, less than 50% by weight of the matrix should be cobalt, since more than this amount of cobalt leads to excessively high internal stress which precludes the use of such electrodeposites.The particles incorporating metal in chemically combined state can be reacted by heating in a reducing atmosphere such as hydrogen for at least 24 hours at temperatures of from about 1000.degree. C. to about 1400.degree. C. The degree of reaction of the particles incorporating metal in chemically combined state may be controlled, for example, by variation of the heat treatment temperature and/or time to allow different desired amounts of metal incorporated in the particles to be released. In this way, different properties may be achieved in the electrodeposited coatings. An advantageous heat treatment is to heat in hydrogen at 1000.degree. C. for 24 hours and air cool. It is preferred to transfer at least 50% of the reactive element from the electrodeposit to the reducing gas atmosphere.Deposits prepared according to the invention may be applied electrolytically, using any convenient electroplating solution such as a Watts bath or sulfamate solution which may be used for electroforming. Preferably an aqueous electroplating solution should be used, although a non-aqueous solution may be employed where suitable. Whether aqueous or non-aqueous, the solution used in the process according to the present invention may deteriorate with time, and it is recommended that such solutions be used while fresh and/or frequently discarded and replaced with fresh solutions. When an electroform is being prepared by the process according to the invention, the particles incorporating metal in chemically combined state should be reacted, for example, by heating, preferably after the electroform is stripped from the substrate upon which it was formed.Alloys made according to the invention may be harder or softer in the as-plated condition than an electrodeposited coating of the alloy matrix metal in the as-plated condition, depending upon the particular metal or metals being considered. However, no matter whether the alloy is harder or softer in the as-plated condition than an electrodeposited coating of the matrix metal alone in the as-plated condition, the alloy retains its hardness after or on heating, to a much greater extent than does the coating of the matrix metal alone. Furthermore, such hardness property improvements may be obtained with alloys made according to the invention, without unduly affecting the electroformability of the alloys.