Abstract: The paper is a practical study, in which the authors have proposed to improve the reliability in operation of hot work tool steels, used for the manufacturing of seamless steel tubes.There were developed samples of hot work tool steel with different chemical compositions by micro-alloying with Mo. The samples were studied in order to investigate their structure and the relations between the microstructure and in-situ behavior.
Abstract: Idlers are machine elements which are subjected to friction solicitations. The geometry, dimensions and weight can’t be modified that is why we decided to modify the contact surface by coating. We have chosen the steel type OLC 45 and we coated it with CMoCuNiCrSiBO by thermal deposition. The selection of these materials was made after a detailed study of the literature. After we obtained the samples, we subjected them to qualitative analyses SEM and XRD and to Quantitative analysis – wearing – destructive test where we obtained the friction coefficient between two coated surfaces . We made the samples which we have analyzed by X-Ray Diffraction and we obtained the quality of the coating . The results showed that the new material has a better structure than the basic material, and we can estimate a high durability of the machine elements coated. On friction test we have determined friction coefficient value.
Abstract: In army industry are some of machine elements that are subjected to wear solicitations and must have a high wear resistance. The impact of their damage and also their maintenance costs are very high, that is why we proposed to improve their performances. Researches in surface engineering allow the obtaining of new systems of materials by coating the base material surface with other material having superior properties. In order to improve the machine elements durability, we proposed to obtain a new system of materials by thermal deposition. We have chosen the steel type OLC45 as base material and we coated it with CNiCrSiBO. We made the samples which we have analyzed by X-Ray Diffraction and we obtained the quality of the coating. The results showed that the new material has a better structure than the base material, and we can estimate a high durability of the machine elements coated.
Abstract: Graphenes have aroused great interest among the scientists lately, due to their special physical properties which are supposed to be transferred to composite materials [1,2,3,6]. Some polymers show low mechanical properties which can be improved by adding various types of materials [9,13]. Using nanoparticles, an enhancement of mechanical, thermal and electrical properties can be obtained, even for small contents of additives [10,11,12,14,15,16]. The evaluation of mechanical properties of polymer composites with graphene can be achieved relying on the three-point bending tests . This work presents a few conclusions resulting from the three points bending tests of the polyester composites with graphene and graphite [7,8].
Abstract: Gas oil is the fuel used in internal combustion engines with ignition through compression. This fuel contains various amounts of sulfur, an element that can contribute in the process of combustion to the forming of sulfuric acid on the internal walls of the cylinder. Sulfuric acid is a highly corrosive substance which can lead in time to the deterioration of the functional surface of the motor cylinder. For an accurate evaluation of the analyzed coatings a study was carried out on the resistance to sulfuric acid corrosion of the two coatings of Al2O3 30(Ni20Al) and NiAlSi. To this purpose a solution of sulfuric acid with a 30% concentration was used. The samples were immersed in sulfuric acid for 70 hours.
Abstract: This study presents the contact fatigue wear behavior of the cermet NiAlSi coating deposited by plasma spraying on alloyed steel. Wear is the failure cause for many component parts of the 4-stroke engine. For example the cylinders are subjected to wear caused by the sliding of the surfaces in EHD lubrication working conditions. Using the AMSLER test machine the rolls have been put to fatigue wear test for 5 hours in conditions of mixed friction. In order to make the results evident one carried out microscopic electronic scavenging analyses using the electronic microscope type QUANTA 200 3D DUAL BEAM.
Abstract: The paper presents the determination of the yield stress for copper, Cu_99.75, at standard ambient temperature, by means of upsetting of cilyndrical specimens, taking account the allowable degree of deformation of this material. The outcomes achieved can be used both plastic deformation processes and volumic deformation simulation of copper Cu_99.75.
Abstract: Chemical element silicon, placed in liquid iron behaves differently, through the influence they exert on the metallographic structure. The factors that define their influence are the melt temperature, melting bath temperature variation dynamics, the amount that is inserted into melting bath, chemical shape etc.Refining of metallographic structure was found when FeSi was used with 35% si 73% Si.
Abstract: After the formation of graphite in molten iron starts its dissolution phenomenon in the liquid metal matrix. The inoculants master alloys FeCaSiMg was mechanically mixed with aluminum, a superficial active element that concentrate on metal matrix - inoculant interface, increasing the graphite surface, which dissolves with greater speed in the liquid metal matrix. In the case of smaller cooling rates (parts with great wall thickness) the former compact – spheroidal graphite inclusions significantly reduces its degree of compactness, which results in the decrease of mechanical strength.