Special features of boronizing iron and steel using a continuous-wave CO2 laser

Abstract

In some cases saturation of a surface by alloying elements with the use of laser treatment provides unique structures with a novel set of properties. Processes of laser alloying after which the heat treatment of the parts is unnecessary present a special interest. Laser boronizing is one such process.The use of pulse and continuous-wave low-power lasers for boronizing the surface of iron-carbon alloys can provide molten alloyed layers that contain boride phases 0.15-0.2 mm thick and up to 2 mm wide [1,2]. It has been shown in [3] that after boronizing iron and steels with the help of a continuous CO 2 laser with a power of up to 3 kW the thickness of the boronized layers increases to 0.4 mm and the width increases to 6 mm. A unique structure is formed in the molten layer that consists of a boride eutectic and a solid solution or a boride.The aim of the present work consisted in studying the microstructure and properties of iron-carbon alloys boronized by radiation of a continuous-wave CO 2 laser.The boronizing was conducted by laser treatment of the surface resulting in melting of the surface of specimens 20 x 20 x 50 mm in size from technical iron and from steels 40Kh, 14Kh2N3MA, 20Kh13, and 13Khl 1N2V2MF (Table 1). The surface of the specimens was coated by a mixture of a powder of amorphous boron and a BF2 adhesive with an acetone additive. The thickness of the coat was controlled by the method of weighing and using a magnetic thickness gage MT-41NTs. The Spectra Physics 973 laser had a radiation power P = 1 -3 kW, the specimen was displaced under the laser beam at a speed v = 2.5 -13.75 mm/sec, the diameter N. I~. Bauman Moscow State Engineering University, Moscow, Russia.of the processed spot d s = 2 -6 mm, and the thickness of the coat 5 = 20 -140 lam. The microstructure and the thickness of the boronized layers were studied using a light microscope and a scanning electron microscope, and the phase composition was determined using a DRON-3 diffractometer. The wear tests of the specimens were conducted on a MM295 bench under a specific pressure of 100 N/cm 2 at a speed of 0.06 m/sec for a test time of 30 min. The standard was carburized steel 14Kh2N3MA (60 HRC). The abrasion strength of the specimens under rolling friction with 10% sliding was determined using machines of MI type in a clay suspension with addition of sand. The counterbodies were plates from steel ShKhl5 (61 -62 HRC). The wear of the specimens was determined by weighing them on an analytical balance with an accuracy of 1 x 10 -4 g before and after the test. Figure 1 presents the dependences of the sizes of the boronized zones and the Vickers hardness on the spot diameter in laser treatment of the specimens conducted in air. Since the microrelief of the surface of the boronized zones was uneven, we determined the effective thickness hef t equal to the distance from the dimple on the surface to the maximum melting level. The quantity her r characterizes the maximum depth of boronizing after grinding the surface. It can be seen from Fig. 1 that ...

Special features of electron-beam boronizing of steels

“…2c and d). It should be noted that in laser boronizing the boride crystals tbrmed have similar shapes [9]. In the formation of the layer from the daubing containing amorphous boron the crystals of iron boride inherit the shape of the elementary cell.…”

Influence of Laser Cladding Parameters on Microstructure, Microhardness, Chemical Composition, Wear and Corrosion Resistance of Fe–B Composite Coatings Reinforced with B4C and Si Particles

“…A number of important properties may be changed or improved, for example microhardness, corrosion resistance and wear resistance [5,10,[14][15][16]. Compounds in the form of high-melting phases such as carbides or borides [3,5,[7][8][9][10], as well as high-melting elements like chromium or boron [4,[15][16][17][18][19], have an important role in the coating microstructure. Boron contributes to improving properties such as microhardness and wear resistance in the case of coatings produced on steel.…”

“…Boron contributes to improving properties such as microhardness and wear resistance in the case of coatings produced on steel. Research on the influence of this element has been is described in many publications [15][16][17][18][19]. Safonov's works are widely known among researchers interested in this area.…”

“…Safonov's works are widely known among researchers interested in this area. Safonov [17,18] concluded that the addition of a low amount of boron into the melt, which occurs with a small thickness of the coating or in deep melting, leads to the formation of a hypoeutectic microstructure consisting of α eutectic. This eutectic consists of primary dendrites and lamellar boride eutectic.…”

Microstructure and selected properties of Monel 400 alloy after laser heat treatment and laser boriding using diode laser

“…Moreover, it was found that addition of copper which is the second main element of Monel 400, to boron layer, reduces brittleness and enhances wear resistance of the surface [5,18]. Borided layers are mostly produced in diffusion processes but in the last two decades of intensive laser techniques progress, there was a much increase in using lasers for obtaining boron-alloyed metal surfaces [14,16,17,[19][20][21][22][23][24] and others [25][26][27][28][29][30][31][32][33][34][35][36].…”