SU1676751A1 - Method of depositing nickel coats on powdered materials - Google Patents

Abstract

The invention relates to powder metallurgy. The purpose of the invention is to reduce the cost of production, reduce the energy intensity of the process, increase its productivity while ensuring a given degree of metallization. The method of applying a nickel coating on powdered materials involves treating the powder with heating and stirring and a chemical precipitation solution containing nickel chloride and additives. As an additive, take ammonium acetate, sodium salt of higher fatty acids or sodium tripolyphosphate and aqueous ammonia with the following content of components, g / l: nickel chloride 30-300; ammonium acetate 15-150; Additive 5-10, aqueous ammonia to pH 7.5-8.5. The process is carried out at 80-98 ° C, first adding sodium or potassium hypophosphite at a rate of 0.2-0.5 mash. for 1 mch. of nickel-plated powder, and then hydrazine hydrate is added in the amount of 0.95-1.2 wt.h. on 1 ma.ch. nickel 2 tablets w

Description

The invention relates to powder metallurgy, in particular to a method for applying a nickel coating on powdered materials.

The purpose of the invention is to reduce production costs, reduce the energy intensity of the process, increase productivity.

The method is carried out as follows.

Nickel-plated material powder is suspended in a calculated volume of an aqueous solution containing, g / l:

Nickel Dichloride (6-water) 30-300

Ammonium acetate 15-150

Sodium salt of higher fatty acid 5-10

Aqueous ammoniaDo pH 7.5-8.5

After the solution is heated to 80-98 ° C, sodium or potassium hypophosphite is added to the suspension with stirring at the rate of 0.2-0.5 parts by weight. on 1 ma.ch. nickel powder At the end of the reaction (cessation of foaming), hydrazine hydrate is added dropwise or in doses of 5-7% of the total amount with an interval of 8-10 minutes from the calculation of 0.95-1.2 wt. on 1 ma.ch. recoverable nickel. The total time of addition of hydrazine hydrate is 2.5-3.5 hours. The obtained metallized powder is filtered, washed with distilled water and suO h |

Och

Vi ate

Shat at 98 ° C. The used solution is suitable for re-use (further) after additional addition of nickel chloride and ammonia solution to it to the desired pH value (7.5-8.5).

The finished product — nickel-plated powder — is well applied to the surface of the parts by thermal spray coating (nickel successfully performs both functions: protects the powder from burnout and helps fix it on the (part surface). Determining the degree and quality of powder metallization is carried out by chemical and metallographic analyzes.

The nickel content of the powder is determined as follows. A portion of the powder is boiled in nitric acid until the nickel layer is completely dissolved. The solution is filtered, the nickel in the solution is determined by the gravimetric method in the form of nickel dimethylglyoxime according to the generally accepted method.

The continuity and uniformity of the coating thickness is determined by the metallographic method. To do this, make thin sections of the powder filled with pro-acrylic resin and determine the continuity and thickness uniformity around the cut perimeter of the particles of metallized powder on an MIM-8 microscope with an increase of 300 times.

Example: In a three liter glass reactor with a capacity of 10 liters, equipped with a stirrer, a thermometer, a reflux condenser and an addition funnel, 1.6 kg of nickel dichloride (6-water), 0.8 kg of ammonium acetate, 2.5 l of distilled water and water are charged. ammonia solution to pH 8 ± 0.5. The reactor is heated in a sand bath to 80-98 ° C. With stirring, 100 g of graphite, 50 g of higher fatty acid sodium salt (sodium stearic acid) and 50 g of sodium hypophosphite are loaded into the reactor. Starting foaming is a sign of the start of nickel plating. To maintain the normal course of the reaction, the pH of the medium is periodically determined and, if necessary, an ammonia solution is added. At the end of foaming (a sign of the reaction of reduction under the action of sodium hypophosphite) 0.48 kg of another reducing agent, hydrazine hydrate, is added from the dropping funnel.

Hydrazine hydrate is added dropwise (1-2 drops per 1 s) until the solution is completely discolored, i.e. until complete recovery of nickel ions. Then the contents of the reactor are cooled to room temperature, the powder is filtered off, washed three times with distilled water and dried at 98 ° C. The coating is solid, uniform. The nickel content here is 79.6% (Example 1 in Table 1).

Table 1 provides examples illustrating the effect of the parameters of the method for achieving the goal.

When the concentration of nickel chloride and ammonium acetate is lower than the claimed interval to achieve 80% content

Nickel powder requires large volumes of nickel plating solution. The process takes from 8 to 10 hours. Therefore, it is impractical to conduct the process with such concentrations. At a pH of 7 (below

claimed interval) nickel plating does not go. At pH above the claimed range, as well as in cases of excessive amounts of sodium hypophosphite, excess sodium salt of higher fatty acids, or

sodium tripolyphosphate and solution overheating, abundant foaming is observed, which prevents the process from operating in the indicated reactor volumes.

When the temperature of the solution is lower than the claimed interval, as well as insufficient quantities of hypophosphite, sodium salt of higher fatty acids, or sodium tripolyphosphate, the nickel plating process proceeds extremely slowly. At contents

nickel chloride and ammonium acetate in excess of the stated intervals, the excess amounts of these salts are suspended in the reactor and the mixing and the whole process is difficult.

With a lack of hydrazine hydrate, the required degree of powder metallization is not achieved, nickel ions remain in solution, and an excess of hydrazine hydrate does not affect the process, it is an irrational waste of this reagent.

When implementing the method in the claimed parameter ranges, the nickel time does not exceed 6 hours, the nickel coating of the powder surface is continuous and

uniform, the amount of metal deposited on the powder corresponds to the calculated one.

Table 2 presents data on productivity, energy intensity and cost of nickel-plated product.

Productivity is calculated from the expression

M

PNI r-V

0)

where M - performance;

PNI is the amount of reduced nickel on the powder (filler);

t is nickel deposition time;

V is the volume of the reactor, necessary and sufficient for nickel plating. The cost is calculated by the formula

C Ј Ci + Ce + St,

(2)

where C is the cost; Ci - the cost of raw materials; Ce - the cost of energy consumption; Art - the cost of labor. Energy intensity is calculated using the formula for N g,

e -RIG- (3)

where e is the energy intensity;

N is the power of drives and electric heaters;

PNI is the mass of precipitated nickel.

As follows from table 1 and 2, the proposed method provides a reduction in the cost of production, reducing energy intensity, improving the performance of the process.

Claims (1)

Invention Formula The method of applying a nickel coating on powdered materials, includes five 0 Processing the powder with heating and stirring in a solution of chemical precipitation containing nickel chloride and additives, characterized in that, in order to reduce the cost of production and reduce the energy intensity of the process, increase productivity, use ammonium acetate, sodium salt of higher fatty acids or tripolyphosphate as additives sodium and aqueous ammonia in the following ratio of components, g / l: Nickel Dichloride 30-300 Ammonium Acetate15-150 Sodium salt of higher fatty acids or sodium tripolyphosphate 5-10 Aqueous ammoniaDo pH 7.5-8.5 and the treatment of the powder is carried out at 80-98 ° C and adding sodium or potassium hypophosphite to the precipitation solution first in an amount of 0.2-0.4 wt.h. on 1 ma.ch. powder, and then hydrazine hydrate in the amount of 0.95-1.2 wt.h. on 1 wt.h. nickel Table I table 2