SU1014981A1 - Pulverulent composition for chromium casehardening - Google Patents

Abstract

POWDERED COMPOSITION FOR DIFFUSION CHROMINATION, containing chrome oxide ,. alumina, aluminum powder and ammonium chloride, 1 distinguished by the fact that, with a multiple use chain mixture, it additionally contains magnesium oxide and potassium tetrafluoroborate at the following ratio of components, wt.%: 32.5-36.5 Aluminum oxide 12 -18 Aluminum powder 1-3 ammonium chloride 2-3 magnesium oxide 0.5-1.5 potassium tetrafluoroborate Rest chromium oxide

Description

4 WITH

00 The invention relates to the chemical and heat treatment of metals and alloys in powder saturating media, in the course of bone diffusion chrome plating, and can be used in machine-building, instrument-making and metallurgical industries for surface hardening of machine parts, tools and tooling. Known diffusion chromium plating in powder fluids and the use of electrolytic powders of chromium atoms in the suppliers as a source of active chromium; chromium, chromium carbide, ferrochrome, as well as a mixture of chromium powder with alumina 11. So, for example, the use of the composition for chromium plating, including, wt.%: 70 CV, 29, 1 K NdSe allows to obtain a carbide layer of O, O1O, 03 mm thickness on high carbon steel 12 hours). The diffusion layer consists of (C), f e) and (C, pe) 7Ccc with a microhardness of 16000-17000 MPa. A disadvantage of the known constituents on the basis of powders of pure elements is their deficiency, as well as the laborious operation of turning lumpy chromium or ferrochrome into powder. The closest in technical terms to the proposed invention is a composition containing, wt%: Alumina, 27, Chromium oxide52 Aluminum powder 18 Ammonium chloride 3 Using this composition allows to obtain diffusion layers with a thickness of 0.02-0.025 mm (saturation temperature 1050 ° C, saturation time 6 h) The chrome-plated layer consists on the surface of carbides (Cl, e) C (у к (CY-, e) -jC with a microhardness of 160001700 O MPa. The cost of the mixture based on oxides of pinning elements is not very high, which manner and foresees the widespread use of However, the use of an aluminothermic mixture based on chromium oxide more than 2–3 times is not possible, since the subsequent use of the mixture leads to a sharp decrease in the thickness of the diffusion layer to 10–15 μm and lower. This necessitates the regeneration of the mixture, and subsequently its complete replacement. The purpose of the inventions is to reuse the mixture. To achieve this goal, a powder, a diffusible chromium compound, containing chromium oxide, aluminum oxide, aluminum powder and ammonium chloride It additionally contains magnesium oxide and potassium tetrafluoroborate in the following ratio of ingredients, wt.%: Aluminum oxide 32.5-36.5 Aluminum powder 12-18 Ammonium chloride 1-3 Mg oxide 2-3 Potassium tetrafluoroborate 0.5-1.5 Chromium OxideEverything Else. The introduction of magnesium oxide into the graded mixture increases the adsorbing capacity of the mixture, while potassium tetrafluoroborate ensures complete completion of the reaction to form active chromium atoms. Chrome plating with the use of the proposed composition is carried out in containers with fusible closures at 10OO-1050С for 6-8 hours. Comparative data on the strength of the known and proposed compositions are given in the table. The expansion was carried out at 1050 C. for 6 h on samples of high carbon steel U8. From the above data, it follows that the use of the proposed composition allows to increase the multiplicity of use of the mixture up to 5-6 times without a noticeable decrease in the thickness of the forming diff. zion carbide layer. Thus, the proposed composition is 2-3 times more effective than the known composition. Approximately, the proposed composition can be used on 10 enterprises with an effect of 379 thousand rubles.

Famous

27AC2 Oj-b52Cr O + 18Ae + 3l4H j Ce 20-25 15-22 12-20 12-18 1O-12 8-10 Offered

36, .48CbxO3 + 12Ae +

 .Ge + 0,5KBF.20-25 20-25 18-22 18-22 15-20 15-20

34.5AR2rz + 45СГ2 0э + 15Аеч + 2, 5MgO 2NH CE + lKBF4.20-25 2O-25 18-22 18-22 15-2O 15-20

32.5Ae2.Oz + 42СГ2р + 18AE +

+ 3M | gD + 3NH C +1.5 KBrd2O-25 20-25 18-22 18-22 15-20 15-20

Jt- figure - packing density 0.6 cm / g (packing density - quantity, mixture, g, optionally: | sodimo for strengthening the surface unit of the product) in cm second figure - packing density 0.2.

Claims (1)

2. Borisenok G.V. et al. Sat, Metallurgy *, no. 8, Minsk, 1976, p. 26-29. 'POWDER COMPOSITION FOR DIFFUSION CHROMIATION, * containing chromium oxide, alumina, aluminum powder and ammonium chloride, characterized in that, with reusable mixture,) it additionally contains magnesium oxide and potassium tetrafluoroborate in the following "ratio of components, weight .%:. Alumina 32.5-36.5 Aluminum powder 12-18 Ammonium chloride 1-3 Magnesium oxide 2-3 Potassium Tetrafluoroborate 0.5-1.5 Chromium oxide