The paper presents recent developments concerning the formation of surface layer in austempered ductile iron castings. It was found that the traditional methods used to change the properties of the surface layer, i.e. the effect of protective atmosphere during austenitising or shot peening, are not fully satisfactory to meet the demands of commercial applications. Therefore, new ways to shape the surface layer and the surface properties of austempered ductile iron castings are searched for, to mention only detonation spraying, carbonitriding, CVD methods, etc.

In this study, a preliminary evaluation was made of the applicability ofthe signalsof the cutting forces, vibration and acoustic emission in

diagnosis of the hardness and microstructure of ausferritic ductile iron and tool edge wear rate during its machining. Tests were performed

on pearlitic-ferritic ductile iron and on three types of ausferritic ductile iron obtained by austempering at 400, 370 and 320⁰C for 180

minutes. Signals of the cutting forces (F), vibration (V) and acoustic emission (AE) were registered while milling each type of the cast iron

with a milling cutter at different degrees of wear. Based on individual signals from all the sensors, numerous measures were determined

such as e.g. the average or maximum signal value. It was found that different measures from all the sensors tested depended on the

microstructure and hardness of the examined material, and on the tool condition. Knowing hardness of the material and the cutting tool

edge condition, it is possible to determine the structure of the material .Simultaneous diagnosis of microstructure, hardness, and the tool

condition is probably feasible, but it would require the application of a diagnostic strategy based on the integration of numerous measures,

e.g. using neural networks.

The article presents the results of a comparative analysis of the metal substructure for dental prosthesis made from a Co-Cr-Mo-W alloy by

two techniques, i.e. precision investment casting and selective laser melting (SLM). It was found that the roughness of the raw surface of

the SLM sinter is higher than the roughness of the cast surface, which is compensated by the process of blast cleaning during metal

preparation for the application of a layer of porcelain. Castings have a dendritic structure, while SLM sinters are characterized by a

compact, fine-grain microstructure of the hardness higher by about 100 HV units. High performance and high costs of implementation the

SLM technology are the cause to use it for the purpose of many dental manufacturers under outsourcing rules. The result is a reduction in

manufacturing costs of the product associated with dental work time necessary to scan, designing and treatment of sinter compared with

the time needed to develop a substructure in wax, absorption in the refractory mass, casting, sand blasting and finishing. As a result of

market competition and low cost of materials, sinter costs decrease which brings the total costs related to the construction unit making

using the traditional method of casting, at far less commitment of time and greater predictability and consistent sinter quality.

The paper discusses possible applications of the percolation theory in analysis of the microstructure images of polycrystalline materials.

Until now, practical use of this theory in metallographic studies has been an almost unprecedented practice. Observation of structures so

intricate with the help of this tool is far from the current field of its application. Due to the complexity of the problem itself, modern

computer programmes related with the image processing and analysis have been used. To enable practical implementation of the task

previously established, an original software has been created. Based on cluster analysis, it is used for the determination of percolation

phenomena in the examined materials. For comparative testing, two two-phase materials composed of phases of the same type (ADI

matrix and duplex stainless steel) were chosen. Both materials have an austenitic - ferritic structure. The result of metallographic image

analysis using a proprietary PERKOLACJA.EXE computer programme was the determination of the content of individual phases within

the examined area and of the number of clusters formed by these phases. The outcome of the study is statistical information, which

explains and helps in better understanding of the planar images and real spatial arrangement of the examined material structure. The results

obtained are expected to assist future determination of the effect that the internal structure of two-phase materials may have on a

relationship between the spatial structure and mechanical properties.

The paper attempts to analyze distortions of cast iron and cast steel rings, after heat treatment cycles. The factors influencing distortion are: chemical composition of material, sample geometry, manufacturing process, hardenability, temperature and heat treatment method. Standard distortion tests are performed on C-ring samples. We selected a ring-model, which approximate the actual part, so that findings apply to gear rings. Because distortion depends on so many variables, this study followed strictly defined procedures. The research was started by specifying the appropriate geometry of the samples. Then, the heat treatment was conducted and samples were measured again. The obtained results allow to determine the value of the resulting distortion and their admissibility. The research will be used to evaluate the possibility of using the material to produce parts of equipment operated under extreme load conditions.

The paper presents the effect of pre-heat treatment on the mechanical properties of ductile cast iron with elevated content of Cu and Mo elements. Austempered Ductile Iron is a material with non-standard properties, combining high tensile strength and abrasion resistance with very good plasticity. In addition, it is prone to strain hardening and have good machining abilities. The study was conducted for five designed heat treatment cycles. The variables were the time and temperature of the pre-heat treatment, followed by one of two standard heat treatments for ADI cast iron. The aim of the authors was fragmentation of the grains of perlite during the initial heat treatment. It is presumed, that subsequent heat treatment will cause further refinement of the microstructure than would be the case without initial heat treatment. Diffusion is much faster than in case of ferritic matrix of cast iron. The results will be used to evaluate material for the production of parts of equipment that must operate under extreme load conditions.