CS251119B1 - Electrolyte for the elimination of nickel-phosphorus-graphite alloys - Google Patents

Abstract

The electrolyte for the deposition of nickel-phosphorus-graphite alloy contains, per 1,000 parts by weight of water, 500 to 1,000 parts by weight of water-soluble nickel salts, such as nickel chloride, nickel fluoroborate, nickel perchlorate or nickel amidosulfonate, 0.1 to 10 parts by weight of a vinyl-based polymeric organic substance, 1 to 500 parts by weight of graphite, 1 to 50 parts by weight of substances containing monovalent or trivalent phosphorus, such as sodium phosphate, ammonium phosphate, sodium phosphate, ammonium phosphate, nickel phosphate and phosphorous acid, and 0.1 to 100 parts by weight of a carboxylic acid or its salts with 1 to 6 carbon atoms, preferably dicarboxylic and hydroxycarboxylic acids, for example lactic, succinic or tartaric acids, or sodium lactate.

Description

The invention relates to an electrolyte for cathodic deposition of a nickel-phosphorus graphite alloy from an aqueous solution.

Electrolytically deposited nickel alloys with phosphorus and graphite are characterized by very good slip properties and high heat hardness after heat treatment. The coatings combine these two characteristics, making them ideal for use in extreme sliding conditions.

A number of electrolytes are described in the literature which allow the nickel-phosphorus-graphite alloy to be deposited. In most cases, the alloy is precipitated electrolessly at a temperature of 90 to 95 ° C. The coatings comprise 1 to 2% by weight of graphite and 6 to 10% by weight of phosphorus. The drawbacks of these electrolytes are low deposition rate, poor electrolyte stability and considerable sensitivity to electrolyte contamination by metal salts. Electrolytes for depositing an alloy coating electrolytically eliminate coatings with high internal stress and uneven distribution of graphite.

The above-mentioned drawbacks are eliminated by the electrolyte for the precipitation of the nickel-phosphorus-graphite alloy according to the invention, which consists in that per 1000 wt. parts of water contains 500 to 1000 wt. % by weight of water-soluble nickel salts, such as nickel chloride, nickel perchlorate, nickel fluoroborate or nickel amidosulfonate; 1 to 500 wt. parts of graphite, 1 to 50 wt. parts by weight of mono- or trivalent phosphorus-containing substances such as sodium hypophosphite, ammonium hypophosphite, nickel hypophosphite and phosphorous acid; parts of a carboxylic acid or a salt thereof having a carbon number of 1 to 6, preferably dicarboxylic and hydroxycarboxylic acids, for example lactic, succinic or tartaric acid, or sodium lactate.

The advantage of the electrolyte according to the invention is by 50 to 60% higher elimination rate compared to known electrolytes used for the same purpose. During electrolysis, the electrolyte is stable and not sensitive to iron salts.

The invention is illustrated by the following examples.

Example 1

Electrolyte containing 600 wt. parts by weight of nickel chloride, 10 wt. parts by weight of lactic acid, 0.1 wt. parts by weight of polyvinylpyrrolidane, 10 wt. 100 parts by weight of sodium hypophosphite; parts of graphite and 1000 wt., parts of water are heated to 50 ° C.

At a cathode current density of 1 to 5 A / dm and mechanical stirring, a coating of 4 wt. % graphite, 6 wt. % phosphorus and 90 wt. nickel.

The microhardness of the deposited coating is 650 to 700 HVm. After heat treatment at 200 ° C, the hardness increases to 950-1000 HVm.

Example 2

Eletrolyt containing 800 wt. parts by weight of nickel fluoroborate, 15 wt. 0.5 parts by weight of succinic acid; parts of polyvinyl alcohol, 30 wt. parts of nickel hypophosphite,

200 wt., Parts of graphite per 1000 wt. parts of water are heated to 50 ° C.

At a cathode current density of 1 to 10 A / dm, the deposited coating composition is 5.5% by weight of graphite, 8.5% by weight. % phosphorus and 86 wt. nickel.

The microhardness of the deposited coating is 400 to 450 HVm. After heat treatment at 200 ° C the hardness increases to 700 HVm.

Example 3

Electrolyte containing 600 wt. parts by weight of nickel amidosulfonate, 5 wt. 0.2 parts by weight of citric acid; parts of polyvinyl alcohol, 10 wt. parts by weight of ammonium hypophosphite; parts of graphite per 1000 wt. parts of water are heated to 40 to 60 ° C.

At a cathode current density of 1 to 10 A / dm and mixing by the pump, the composition of the deposited coating is as follows: 1.5 wt. % graphite, 5 wt. % phosphorus, 93.5 wt. nickel. The microhardness of the deposited coating is 350 to 450 HVm.

Example 4

Electrolyte containing 700 wt. parts by weight of nickel perchlorate, 10 wt. 0.1 parts by weight of phosphorous acid; parts by weight of polyvinyl alcohol, 20 wt. parts of lactic acid and 100 wt. parts of graphite per 1000 parts by weight of water are heated to 40-60 ° C.

At a cathode current density of 1 to 10 A / dm, the deposited alloy contains 3.5 wt. graphite, 7 wt. % phosphorus and 89.5 wt. nickel.

The microhardness of the deposited coating is 450 to 500 HVm.

The heat treatment at 200 ° C increases to 750 to 900 HVm.

Example 5

Electrolyte containing 600 wt. parts by weight of nickel chloride, 10 wt. parts by weight of ammonium hypophosphite, 50 wt. parts of graphite, 0.2 wt. parts by weight of polyvinyl alcohol, 50 wt. parts of sodium lactate per 1000 wt. parts of water are heated to 20 to 60 ° C.

At a cathode current density of 1 to 10 A / dm, the composition of the deposited coating is 0.8% by weight. % graphite, 6.2 wt. % phosphorus and 93 wt. nickel. The microhardness of the deposited coating is 450 to 500 HVm.

Example 6

Electrolyte containing 700 wt. parts by weight of nickel chloride, 30 wt. parts by weight of nickel hypophosphite, 150 wt. parts of graphite, 30 wt. parts of magnesium lactate, 0.1 wt. parts by weight of polyvinyl alcohol per 1000 wt. parts of water are heated to 40 to 60 ° C.

At a cathode current density of 1 to 8 A / dm, the composition of the deposited coating is as follows: 1.8 wt. % graphite, 2.8 wt. % phosphorus and 95.4 wt. nickel.

The microhardness of the deposited coating is 560 to 600 HVm.

Claims (1)

An electrolyte for the precipitation of a nickel-phosphorus-graphite alloy from an aqueous solution based on nickel salts, phosphorus-containing substances and graphite, characterized in that it contains from 500 to 1000 wt. % by weight of water-soluble nickel salts, such as nickel chloride, nickel perchlorate, nickel fluoroborate or nickel amidosulfonate; 1 to 500 wt. parts of graphite, 1 to 50 wt. parts by weight of monovalent or trivalent phosphorus-containing substances such as sodium hypophosphite, ammonium hypophosphite, nickel hypophosphite and phosphorous acid; parts of a carboxylic acid or a salt thereof having a carbon number of 1 to 6, preferably dicarboxylic and hydroxycarboxylic acids, for example lactic, succinic or tartaric acids or sodium lactate.