SU1618552A1 - Method of laser-plasma alloying - Google Patents

Abstract

The invention relates to a laser surface treatment and can be used to strengthen metals and alloys. The aim of the invention is to increase the wear resistance and hardness of the surface layer of the metal. The method involves the preparation of a saturated solution of carbamide in water or organic and organometallic solvents, which is blown with a hot stream of pelvis containing carbon, nitrogen, oxygen or hydrogen, after which the gas mixture is ionized in the plasma torch and sent to the surface of the metal melted by a laser beam to simultaneously alloy ions N, C +, 0 +, N. 4 hp ff. 2 Il.

Description

The invention relates to the field of laser surface treatment.

The aim of the invention is to increase the wear resistance and hardness of the surface layer of metals to a predetermined depth.

In the proposed method, carbamide is used as a source of alloying elements, which is previously dissolved, for example, in organic, organometallic solvents, water to saturation, and then blown with a hot gas stream containing nitrogen, carbon, oxygen, hydrogen and the resulting gas mixture. through the plasma torch, is directed to the surface of the molten liquid bath.

When flushing with a stream of hot gas containing nitrogen, carbon, oxygen, hydrogen, a saturated solution of urea (NHaCONhto), a vapor-gas mixture is formed, which is directed to the plasma torch. Mixture

subjected to high temperature in the plasma torch (5000 - 7000 ° C, depending on its mode of operation), resulting in its dissociation and ionization. The resulting plasma jet containing such alloying elements as nitrogen, carbon, hydrogen, oxygen, is blown into the liquid bath of a metal melted by a laser beam. Some of the ions are dissolved in the liquid metal, while others are bound to chemical compounds — nitrides, carbides, hydrides, oxides. After crystallization, the structure of the melted layer consists of a solid solution of alloying elements and their chemical compounds, which leads to an increase in the wear resistance and hardness of the surface layer of the metal to a predetermined depth,

Example. Samples of steel 25HGSNMA 1.3 mm thick were processed on a laser HEBR-1A. Laser power 00

ate

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1.3 kW; the speed of movement of the part relative to the laser beam is 25 mm / s; beam diameter at focus 0.4 mm; lens focal length 107 mm; the focus was buried under the surface by 3 mm; carbon dioxide was used as the working gas. He also, preheating in a tubular furnace to 100 ° C, blows a saturated solution of urea in water under a pressure of 2 atm. In the second case, nitrogen was used for these purposes, and urea was dissolved in acetone. The resulting vapor-gas mixture was sent to the plasma torch for its dissociation and ionization under the influence of a temperature in the arc of 5000–7000 ° C and further to the surface of the molten bath. The plasma torch operated in direct polarity (minus was applied to the hafnium electrode), voltage 21 V, current 50 A, power was supplied from a line source VDC-504.

Figure 1 shows a graph of the microhardness distribution over the depth of the melting zone of the surface of a part made of steel 25HGSMA; Fig. 2 is a graph of the microhardness distribution across the width of the table of contents at a distance of 1 mm from the surface.

The measurements were carried out on a PMT-3 device with a load of 100 g. Curves 1 and 2 show two variants of the proposed method, curves 3 are the basic method described in the prototype.

As follows from figures 1 and 2, the microhardness of the melted zone of the proposed method, on average, 30% more than the prototype.

Wear tests were conducted on. machine 77MT-1. Contact scheme: finger - plane. Tests were conducted under dry friction conditions. The degree of wear was determined by reducing the weight of the finger. As a sample, a cylinder with a diameter of 8 mm from steel 25HGSMA was used.

The treated end of the cylinder under pressure of 0.8 MPa slid over the response body - a disk made of ShKh15 steel. The degree of wear is determined after 3-15 disk speeds

decrease the weight of the finger. When processed according to the technology chosen for the prototype, the average wear per three trials was 28.1 mg. When processing by the proposed method, the wear was in the first embodiment

9.3-11.2 mg; in the second 10.1 -12.2 mg. Weighing was performed on a VLA-200 scale. Thus, the increase in wear resistance is in relation to the prototype: pu 2.5-3 times during the treatment according to the first embodiment.

the proposed method and 2.3-2.8 times in the processing according to the second variant.

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Claims (2)

Invention Formula 1. A method of laser-plasma doping, including melting a metal with a laser beam, feeding a doping substance, ionizing it and doping a melting zone, characterized in that in order to increase the wear resistance and hardness of the surface layer to a given depth, a saturated solution is used as the doping substance carbamide, through which a stream of hot gas is passed, and ionization is carried out in a plasmatron ,. 2. A process according to claim 1, characterized in that the urea is dissolved in water. 3. A process according to claim 1, characterized in that the urea is dissolved in organic solvents. A. The method according to PP. 1 and 3, that is, tol and h.and y and y, so that the urea is dissolved in metal-organic solvents. 5. The method according to nil, characterized by the fact that as the gas used gas selected from the group containing carbon dioxide, nitrogen, oxygen and hydrogen. fffoj.  a J s O 0.4 0.2 S, 2 16 Z & 2 2 & 4 Rig. /