EA033694B1 - Composition for thermal spraying of wear-resistant coatings - Google Patents

Abstract

The invention relates to the field of powder metallurgy, and more particularly to producing powder compositions which can be used for thermal spraying of wear-resistant coatings. The technical problem solved by the proposed invention is that a new composition for thermal spraying is created, which improves considerably the properties of obtained wear-resistant coating, where dense, easily polishable coatings solid at high temperatures, having good adhesion and resistance to thermal shocks are obtained. The set objective is achieved by the fact that the composition for thermal spraying of wear-resistant coatings including tungsten carbide powder with grain size of 10-50 μm and powder of PR-H18N9, PR-H18N10 or PR-H18N15 steel with grain size of 45-100 μm, contains additionally nickel-aluminum powder with grain size of 10-50 μm with the following component ratio, wt.%: nickel-aluminum powder - 20-30; tungsten carbide powder - 30; steel powder - 40-50.

Description

The invention relates to the field of powder metallurgy, in particular to the production of powder compositions that can be used for thermal spraying of wear-resistant coatings.

Known powder composition for thermal spraying of wear-resistant coatings based on self-fluxing powders [1], containing a powder of nickel alloy PG-10N-04 particle size distribution of 80-160 microns and diffusion-alloyed powder of steel PR-X18H9, PR-X18H10 or PRX18H15 particle size distribution 45- 100 microns in the following ratio of components, wt.%: Nickel alloy powder - 40-60; steel powder - 40-60.

The disadvantages of coatings obtained from such composite materials are low hardness and fading of alloying elements during spraying.

Known powder composition for thermal spraying of wear-resistant coatings based on self-fluxing powders PS-12NVK-01 [2], which is a mechanical mixture of self-fluxing powder of nickel alloy PG-10N-01 particle size 80-160 microns and tungsten carbide powder particle size 10-50 microns in the following ratios of components, wt.%: nickel alloy powder - 65; tungsten carbide powder - 35.

The disadvantages of coatings obtained from this powder composition are a high tendency to crack formation during surfacing, poor mechanical workability and a very high cost.

As a prototype, a composition was selected for thermal spraying of wear-resistant coatings [3], including tungsten carbide powder with a particle size distribution of 10-50 μm and steel powder PRX18H9, or PR-X18H10, or PR-X18H15 particle size distribution of 45-100 μm with the following ratios of components, wt .%: tungsten carbide powder - 30-40, steel powder - 60-70.

The disadvantages are rather high porosity and insufficient adhesion due to the high content of tungsten carbide powder, the complexity of subsequent machining and low heat resistance.

The technical problem that the invention solves is to create a new composition for thermal spraying, which significantly improves the properties of the resulting wear-resistant coating. The result is a solid at elevated temperatures, dense, easy to grind, having good adhesion strength and resistant to thermal shock coatings.

The problem is achieved in that the composition for thermal spraying of wear-resistant coatings, including tungsten carbide powder with a particle size distribution of 10-50 μm and steel powder PR-X18H9, PR-X18H10 or PR-X18H15 particle size distribution of 45-100 μm, additionally contains nickel-aluminum powder particle size distribution of 10-50 microns in the following ratio of components, wt.%: nickel-aluminum powder - 20-30, tungsten carbide powder - 30, steel powder - 40-50.

The invention consists in the following. An analysis of the processes for the preparation and use of self-fluxing powder materials allowed us to propose a fundamentally new concept for creating self-fluxing powders based on austenitic steel. The elements boron and silicon or only boron are introduced into the surface layer of each particle by diffusion to a certain depth, in certain quantities and with the condition of ensuring the required phase composition, due to which it must be ensured:

a) the implementation of the effect of contact eutectic melting between the boron-containing surface of the particle and the deposited product, between the surface of the particle and the core;

b) the exclusion of fumes of alloying elements upon receipt of the powder;

c) the resulting boride and carboboride phases should increase the tribotechnical characteristics of the deposited coatings.

High ductility and viscosity of the plasma coating is a significant factor in increasing wear resistance. The increase in hardness dramatically reduces ductility and toughness, leading to brittle fracture. The set of properties of the nickel-aluminum compound includes wear resistance at the level of tungsten carbide alloys, good adhesion strength and ductility at the level of nickel-chromium alloys with higher heat resistance, good mechanical workability. The introduction of nickel-aluminum powder into the composition for gas-thermal spraying increases the ductility and viscosity of the coating with a slight decrease in hardness, promotes the formation of a high adhesion strength on the coating interface, since it promotes plastic relaxation of stresses arising due to inconsistent changes in the volumes of the coating and base materials during heating and cooling. The properties of the powders are given in table. 1.

Table 1

Hardness, density and particle size distribution of powders

Powder grade Hardness HRC Bulk density, g / cm ³ Granulometric composition, microns Wolfram carbide 60-65 8.12 10-50 PR-X18N15 32-38 3.48 45-100 Nickel aluminum 26-30 2.79 10-50

- 1,033694

And so on the basis of the foregoing, we can conclude that the addition of carbide ceramics and self-fluxing powder to the powder mixture based on austenitic steels with a more fusible, ductile and heat-resistant nickel-aluminum component will significantly improve the properties of the resulting wear-resistant coating, increase abrasion resistance, reduce porosity and increase adhesion and heat resistance.

Example.

Coatings from a mixture of tungsten carbide, a self-fluxing powder based on austenitic steels and nickel-aluminum were obtained by flame spraying on a UPTR-86 installation on a carbon steel substrate 45. The powder flow rate was 4.5 kg / h, the pressure of acetylene, oxygen and compressed air was respectively 0.1; 0.9 and 0.16 MPa; their consumption is 1.8; 0.1 and 0.5 m ³ / h, spraying distance - 0.15 m. The percentage of powders in the mixture was selected on the basis of experiments (table. 2). Porosity studies were performed on an Epiguant automated structural analyzer. The porosity of the coatings was determined on etched thin sections with an increase of 200 times. The hardness of the coatings was measured by the Rockwell method on a TK2M instrument on a scale of C in accordance with the requirements of GOST 20017-74. The coatings were tested for abrasion by friction against fixed abrasive particles according to the standard method GOST 17367-71. The test results are given in table. 2.

table 2

Test results of powder compositions for thermal spraying

The composition of the mixture, mass% Hardness HRC Pori stost % Adhesion Strength, MPa Wear rate, μm / km, 70 PR-X18H15 - 30 WC (npoTOTHn) 57-64 2.0 65-70 0.013 60 PR-X18N15 - 30 WC-10NiAl 57-62 4,5 59-63 0.019 50 PR-X18H15 - 30 WC-20NiAl 55-60 1.5 69-73 0.012 40 PR-X18N15 - 30 WC-30NiAl 53-58 1,5 70-75 0.010 30 PR-X18N15 - 30 WC-40NiAl 45-49 2,5 60-65 0,023

Analyzing the test results shown in table. 2, we choose the following percentage in a mixture of powders - tungsten carbide powder (30 wt.%), Self-fluxing powder based on austenitic steels PR-X18H9; PR-X18H10; PR-X18H15 (40-50 wt.%), Nickel-aluminum powder (20-30 wt.%). At this percentage, the characteristics of the obtained wear-resistant coatings correspond or exceed the analogue.

Sources of information.

1. Patent of the Republic of Belarus No. 15833 C232C 4/06.

2. Volosenkov V.E., Kupriyanov I.L. Powders for thermal spray coating. - Mn .: Higher School, 1987. - 26 p. (p. 20).

3. Patent RB No. 19111 B22F 1/00, C23C 4/04.

Claims (1)

Composition for thermal spraying of wear-resistant coatings, including tungsten carbide powder of particle size 10-50 microns and powder of steel PR-X18H9, PR-X18H10 or PRX18H15 particle size 45-100 microns, characterized in that it additionally contains nickel-aluminum powder of particle size 10- 50 microns with the following ratios of components, wt.%: Nickel-aluminum powder - 20-30, tungsten carbide powder - 30, steel powder - 4050.