Effect of laser treatment on the wear resistance of steels

Abstract

It is known that laser hardening increases the wear resistance of friction parts quite substantially. At the same time, many problems connected with the effect of the treatment process and the special features of laser hardening on the characteristics of wear resistance require detailed consideration. The present paper is devoted to the development of recommendations on choosing the optimum location and proportion of the areas of the hardened and unhardened regions of the surface of structural steels after their treatment with radiation of a continuous CO2 laser.Cylindrical specimens of steel 40KhlOS2M and fiat specimens of steels 45, 40Kh, and 38KhMYuA were treated with radiation of a continuous CO 2 laser with fusing the surface. The radiation power P, the rate of treatment v, and the diameter of the spot d s are presented in Table 1 (the regimes of laser treatment for steels 45 and 38KhMYuA are similar to that for steel 40Kh). The choice of laser treatment with fusing of the surface is connected with the fact that in this case the wear resistance of structural steels under conditions of boundary friction is increased considerably [1,2]. Specimens of steels 40KhlOS2M and 38KhMYuA were heat treated before the laser action, and specimens of steels 45 and 40Kh were normalized.In the course of the laser treatment a series of hardened strips 2 mm wide located a certain distance apart and inclined at an angle of 45 ~ to the generatrix of the cylinder were formed on the cylindrical surface of steel 40KhlOS2M. The area of the hardened strips amounted to 33, 50, and 75% of the total area of the specimens, which corresponded to a filling factor Kf equal to 0.33, 0.5, and 0.75, respectively. Some of the specimens were subjected to laser hardening over the entire cylindrical surface by creating annular strips overlapping 30% (Kf = 1.0). Hardened strips 2 mm wide were deposited on the surface of fiat specimens of steels 45, 40Kh, and 38KhMYuA at an angle of 45 ~ to the direction of motion in the wear resistance tests by analogy with the pattern of [3].After the laser treatment the functional surface of the specimens was polished to R a = 0.28 -0.34 pm. The microhardness of the polished surfaces of the hardened and unhardened regions was measured by means ofa PMT-3 device (at least 50 measurements on each region). The average microhardness H of the surface of the steel after the laser treamaent and its standard deviation S are presented in Table 1. 399Comparative tests for wear resistance were conducted under conditions of boundary friction by the standard methods (GOST 23224-86). Tests of round specimens were conducted on an SMTs-2 friction machine by the "disk-block" method with feeding of AS-8 oil into the friction zone at a rate of 20 -25 drops per minute. The immobile block of steel R6M5 had a hardness of 60 -62 HRC. The specific load in the tests was q = 2.5 and 5 MPa, the sliding rate was 1.05 m/sec, and the test base was N = 1.2 x 105 and 3.6 x 105 cycles, respectively. The specknens were preliminarily run in for 3 -...

Archives of Metallurgy and Materials

“…Additionally the B 0.7 Fe 3 C 0.3 complex phase was detected. The results of this study were in an excellent agreement with the results obtained by Author of paper [21]. The cited paper focused on produced a boronized layer on the specimens, with precoat of amorphous boron paste underwent laser modification.…”

“…Modification methods of boronized layers include production of single-phase Fe 2 B layers [3], or complex combinations of well-known processes such as nitriding and boronizing [10], nickelizing with boronizing [4], whether, for example chromizing with boronizing [5,13]. Laser modification of surface layers is becoming increasingly popular and widely used [3,4,7,8,[19][20][21][22][23][24][25][26][27][28][29][30][31][32][33]. By using the high energy of laser beam can be modified the diffusion boronized layer, and this way the mild microhardness gradient can be obtained.…”

Corrosion Resistance of Coatings Produced by Spraying Powders Under a Laser Beam in a Saline Environment NaCl 3% by the Electrochemical Method

“…In order to ensure protection against corrosion and abrasion, nickel and cobalt alloys are widely used in industry for the coating of machine parts working at very high temperatures [6], [7]. Surface treatments carried out under high energy beams by powder injection offers the possibility to apply a broad variety of metallurgical coatings on the surface of materials, and they can be effective and economical solutions [4].…”

Study of Powder Particle Size Effect on Microstructural and Geometrical Features of Laser Claddings Using Response Surface Methodology RSM

“…The laser cladding obtained by powder injection offers the possibility to apply a broad variety of metallurgical and ceramic coatings on the surface of materials. The Ni-Cr alloys are widely used in the glassware industry for coating parts working at high temperature in order to ensure a protection against corrosion and abrasion [4,5]. However, the quality of the coatings with regard to microstructural defects (cracking and porosity), mechanical properties (microhardness and wear resistance) and residual stresses state depends on many parameters such as laser power, powder feed rate and beam focus relative to the substrate surface and usually, no systematic study of the combined influence of these parameters was carried out.…”