SU749933A1 - Paste for borochrome-plating of steel parts - Google Patents

Description

The invention relates to the chemical and heat treatment of metals and alloys and can be used to increase the wear resistance, reliability and durability of a wide range of machine parts, for example, connecting rods and pistons of hydraulic machines, piston pins and distribute the shaft of autotractor engines, etc. In many cases, it will allow to replace expensive scarce steels with the cheapest ones, which, combined with increasing the resources of the machines, will have a significant economic effect. Known compositions of pastes for diffusion saturation of steel during induction heating with high frequency iron, for example, paste for boroalytirirovanii steel containing boron amorphous and aluminum powder in an amount of 2-10% by weight of the total JJL mixtures , to carry out the process of chromium plating of steel by the method of aluminothermy (2, the saturating mixture consists of chromium oxide, aluminum, fluorine agaomin and alumina with the following percentage ratios: 10 O% 25-5 OA 2Oe + 5O-75% (80% Cn, 0 + + 20% AE) + 3-5%. A disadvantage of the known powder saturation mixture is that the coatings obtained from diffusive saturation from this mixture have increased fragility ( due to the formation of chromium carbides), insufficient HbUvOi antifriction and extreme pressure properties, the result is increased wear of the counterbody; insufficient activity of the mixture, resulting in a longer process time (8-10 hours and toxicity of the activators used (aluminum fluoride). The purpose of the invention is to create such a composition that would allow KanenKW to increase its wear resistance and improve their anti-seizing properties during processing. This is achieved by carrying out a diffusion process from a paste of the following composition by weight: Chrome oxide 28-34 Boron amorphous 28-34 Chromium 10-14 ALUMINUM1O -14 Calki fluoroborate 3-10 Sodium chloride 0.5-7 Sodium fluoride. 0.5-7-7 Chromium oxide and chromium chloride from suppliers of atomic chromium in the surface metal layer ,. With a decrease in the content and mixture of the indicated components below 28 wt.% And 10 wt.% (Respectively), the impoverishment of chromium in the iron occurs, which reduces the hardness and wear resistance of the surface. An increase in the content of chromium oxide and chromium to more than 34% by weight and 14% by weight (respectively) does not lead to an improvement in the operational properties of the coating. Boron amorphous and potassium fluoroborate are the suppliers of boron to the surface layer of the metal, and potassium fluoroborate is also an activator of the process named stalemate. Reducing the boron content in the paste below 28% is not advisable, since it does not significantly improve the performance properties of the coatings; an increase in the content of more than 34 wt.% leads to a significant increase in hardness, which increases the wear of the counterbody. 35

Ingredients weight%

Table 1 Aluminum is a reducing agent for chromium from its oxide, reducing its amount below 10 wt.%, Leads to the fact that the reduction reaction is not completely. An excessive amount of aluminum (over 14 wt.%) Leads to the diffusion of aluminum into the metal, which reduces the hardness and wear resistance of the coatings. Sodium chloride and fluoride are process activators and, together with potassium fluoroborate, provide a qualitative substitute for toxic aluminum fluoride (in the prototype). Reducing the amount of sodium chloride and fluoride to less than 0.5 wt.% And potassium fluoroborate less than 0.3 IHC,% leads to a deterioration in the process of diffusion saturation} an increase of more than 7 wt.% Chloride and sodium fluoride and 10 V9C.% Potassium fluoroborate will worsen surface cleanliness (corroded). PRI me R. Strengthened areas of parts, for example, ball bearings of the connecting rod of a hydraulic machine 210.32, material - ZOHZMFA, paired with the same, material-nitrated steel 38KHMUA, put paste, the composition of which is shown in Table 1. Paste is put dipping to thickness, 2-3 mm. in several stages with drying each layer at a temperature of 80-100 ° C for 1015 minutes. The solution is nitrocellulose in acetone. The compositions of pastes for surface doping of connecting rods are given in Table. one.

311212

31

14

14

34

34

Induction heating of high frequency conduct

about.-, -.

up to the temperature of НО 0-1130 С at isothermal elevation of the ЗО-50 s. When the temperature reaches 5OO-550 C

eight

3

0.5

0.5

Those are rapidly developing and proceeding: an isothermal reduction of chromium from chromium oxide, as a result of which the heating rate of the part increases dramatically.

After the heating is turned off and, sharpening up to 900-850 C, quenching is carried out while cooling with water using a sprayer. Studies of diffusion layers (m & talographically and X-ray diffraction) allowed us to establish that. they are achlg t from an l-solid solution of chromium in iron doped with boron and boride; (geSp, the depth and microhardness of diffusion layers from the steel of kohsmf are given in table 2

7499336

Table

Microhardness and depth of the layer depending on the composition of the paste. The results of comparative tests of wear resistance on the SMC-.2 friction machine after treatment in the known and proposed compositions are given in Table. 3, T a b l and c a B

Claims (1)

SUMMARY OF THE INVENTION Paste for borochroming of steel parts containing chromium oxide and aluminum, characterized in that, in order to increase the wear resistance of products and improve extreme pressure properties, it additionally contains chromium, amorphous boron 55, sodium chloride, sodium fluoride, TsNIIIPI Order 4560/20 28-34 28-34 10-14 10-14 3-10 0.5 - 7 0.5 -7 potassium fluoroborate in the following ratio of components, wt.%: Chromium oxide Aluminum Chromium Amorphous boron Sodium Chloride Sodium Fluoride Potassium fluoroborate