The purpose of this investigation was to identify the distribution of ultrafine particles in a steel matrix introduced through a conventional melting and casting method, and above all to determine the methodology and analysing techniques suitable for the analysis and identification of ultrafine particles incorporated into the steel matrix. In the frame of this work, steels dispersed with Al2O3 ultrafine particles were produced by a conventional casting method and their microstructure investigated with light microscopy (LM), scanning electron microscopy (SEM) and auger electron spectroscopy (AES). Microstructural analyses show that the distribution of the Al2O3 ultrafine particles is non-uniform and has a high degree of agglomeration. Furthermore, for a detailed analysis of the nanoparticles a specific preparation and characterization using advanced microscopic techniques is required. Keywords: particle distribution, microscopic characterization, steel matrix Namen raziskave je bil ugotoviti porazdelitev ultrafinih delcev v jekleni matrici, ki je bila proizvedena s konvencionalnim postopkom litja, predvsem pa dolo~iti metodologijo in analizne tehnike, primerne za analizo in identifikacijo ultrafinih delcev, ki so bili vklju~eni v jekleno matrico. Delci Al2O3 so bili dodani med procesom konvencionalnega litja in so bili analizirani s pomo~jo razli~nih analiznih tehnik, in sicer: z uporabo opti~nega mikroskopa (LM), vrsti~nega elektronskega mikroskopa (SEM) in spekroskopije Augerjevih elektronov (AES). Analiza mikrostrukture je pokazala neenakomerno porazdelitev in aglomeracijo Al2O3 delcev. Za podrobno analizo je potrebna karakterizacija mikrostrukture s pomo~jo naprednih mikroskopskih tehnik. Klju~ne besede: porazdelitev delcev, mikroskopska karakterizacija, jeklena matrica

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Austenitic stainless-steel specimens reinforced with aluminium oxide (Al2O3) nanoparticles added in (0.5, 1.0 and 2.5) w/% concentrations were produced by a conventional casting route. The produced composite specimens were analysed in terms of microstructural properties and wear resistance. The pin-on-disc testing method was used to study the wear behaviour of the composite at room temperature, including steady-state coefficient of friction, the running-in behaviour and wear resistance. A hardened stainless-steel ball (X47Cr14) with a diameter of 10 mm and hardness of 490 HV1 was used as a loading counter-body, sliding against an investigated disk specimen. Microstructure observations revealed that the concentration and size of the particles have an impact on the distribution of the reinforcement within the matrix as well as on the wear behaviour. The Al2O3 particles increased the hardness and consequently led to improved tribological properties of the composites.

The aim of the study was to assess the influence of adding Al2O3 nano-particles of 0.5 wt. % with the mean particle size of 500 nm on the mechanical properties and wear behaviour of the austenitic stainless steel matrix reinforced with nano-particles produced by conventional ingot casting. The focus was on the methods and possibilities of homogeneous and uniform distribution of the particles within the steel matrix using conventional casting routes. The main drawback of the casting method used is the agglomeration of the particles and poor interface between the particles and the metal matrix. The results show that through a proper insertion method, nano-particles can be successfully introduced into the metal matrix. The Al2O3 nano-particles were successfully incorporated into the steel matrix with no signs of clustering and intermetallic reactions taking place between the nano-particles and the steel matrix. This led to improved mechanical properties as well as the wear behaviour of the stainless steel, achieved by using conventional casting routes.