OBRABOTKAMETALLOV TECHNOLOGY Vol. 24 No. 1 2022 Introduction Austenitic stainless chromium-nickel steels, due to high level of corrosion resistance, plasticity, heat resistance, manufacturability and biocompatibility [1-3], are widely applied in the oil and gas, chemical, nuclear, food and medical industries. For many critical applications, steels of 01Сr17Ni13Mo3 type (analog AISI 316L) are of particular interest. These steels retain corrosion resistance under mechanical infl uences due to its low tendency to martensitic deformation transformation [4], and are also prospective to be used in hydrogen economy as a hydrogen embrittlement-resistant material for hydrogen transportation and storage systems [5]. Dispersion-hardening steel of Cr16Ni15Mo3Ti1 type is additionally alloyed with ~1 wt.% titanium, which provides radiationstimulated release of the coherent γʹ-phase (Ni3Ti) and thereby multiplies the resistance to void (vacancy) swelling during irradiation with high-speed neutrons at temperatures of 480...500 °C [6-9]. Therefore, it is prospective as not only corrosion-resistant, but also radiation-resistant material, operable in the presence of aggressive environments. The microhardness of non-heat-treatable AISI 316L steel surface can be increased by ultrasonic treatment with a carbide spherical indenter (from 177 to 290 HV) [10] and balls in vacuum – by SMAT: surface mechanical attrition treatment (from 1.65 to 2.90 GPa) [11], by sandblasting (from 1.8 to 3.6 GPa) [12]. However, the surface layers formed during impact hardening treatments are characterized by high roughness Ra = 1.0...2.5 μm [11, 12]. Signifi cantly more effective hardening of 03Cr16Ni14Mo3Ti1 steel surface (from 270 to 580...720 HV 0.025) can be achieved by friction treatment with a sliding indenter made of synthetic diamond in an argon medium [13]. Such processing of austenitic chromium-nickel steels can also provide high quality of the formed surface with low roughness [14, 15]. Sliding burnishing of steels minimizes roughness and strengthens the surface layer. The surface quality and strength characteristics of the surface layer formed during burnishing are determined by the speed, feed and force of burnishing, the size of the contact area and multiplicity of loading [16-23]. The paper [16] shows the possibility of controlling surface layer smoothing and strengthening based on the evaluation of the integral parameter of the multiplicity of material loading during the burnishing process. When considering diamond burnishing of stainless 17-4 PH steel, the feed is determined by the most signifi cant parameter affecting surface roughness and hardness [17]. Under conditions of dry ball burnishing, the best roughness smoothing of the turned surface of 41Cr4 steel was provided by a small feed of 0.05 mm/rev, in contrast to 0.075 mm/rev and 0.1 mm/rev [18]. On the contrary, in [19], when studying the ball burnishing of AISI 1045 steel, it was found that the greatest infl uence on both the surface roughness and hardness is exerted by the burnishing force. The normal force is also a parameter determining a high level of compressive residual stresses (-1,100 MPa) being formed by ball burnishing on the 15-5PH martensitic stainless-steel surface [20]. The depth of spherical indenter penetration (determined by normal force, microhardness and roughness of the work surface), at which complete smoothing of the initial roughness is achieved, is proposed in [21] as a criterion for ensuring minimal roughness when burnishing hardened steels and is called stable indentation. An increase in the normal force and contact spot size, as well as a decrease in the feed to increase the multiplicity of loading and hardening of the material being treated, can cause micro-destruction of the work surface. In this regard, at diamond burnishing, there is a problem of the exact assignment of the normal force at a given feed. Maximov et al. in [22] noted that there is no data in the literature on the prospects of sliding indenter burnishing of AISI 316Ti (03Cr16Ni10Mo2Ti) austenitic steel, which is closest in chemical composition to the steel under study. However, the new results obtained in [22] do not allow establishing a connection between the normal force and surface microprofi les, both after turning and after burnishing. In addition, when choosing the burnishing force, it is important to assign it from the standpoint of material strengthening. 3D surface profi lometry during the transition from turning to diamond burnishing of disks made of AISI 304 metastable austenitic steel is considered in [23]. However, the assignment of the normal loading force of the surface layer during burnishing was not validated.
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