Abrasive Wear Resistance of the Iron- and WC-based Hardfaced Coatings Evaluated with Scratch Test Method

Abrasive wear is one of the most common types of wear, which makesabrasive wear resistance very important in many industries. Thehard facing is considered as useful and economical way to improve theperformance of components submitted to severe abrasive wear conditions, with wide range of applicable filler materials. The abrasive wear resistance of the three different hardfaced coatings (two iron‐based and one WC‐based), which were intended to be used for reparation of the impact plates of the ventilation mill, was investigated and compared. Abrasive wear tests were carried‐out by using the scratch tester under the dry conditions. Three normal loads of 10, 50 and 100 N and the constant sliding speed of 4 mm/s were used. Scratch test was chosen as a relatively easy and quick test method. Wear mechanism analysis showed significant influence of the hardfaced coatings structure, which, along with hardness, has determined coatings abrasive wear resistance

The tribological performance of hardfaced/ thermal sprayed coatings for increasing the wear resistance of ventilation mill working parts

During the coal pulverizing, the working parts of the ventilation mill are being worn by the sand particles. For this reason, the working parts are usually protected with materials resistant to wear (hardfaced/thermal sprayed coatings). The aim of this study was to evaluate the tribological performance of four different types of coatings as candidates for wear protection of the mill’s working parts. The coatings were produced by using the filler materials with the following nominal chemical composition: NiFeBSi-WC, NiCrBSiC, FeCrCTiSi, and FeCrNiCSiBMn, and by using the plasma arc welding and flame and electric arc spraying processes. The results showed that Ni-based coatings exhibited higher wear resistance than Fe-based coatings. The highest wear resistance showed coating produced by using the NiFeBSi-WC filler material and plasma transferred arc welding deposition process. The hardness was not the only characteristic that affected the wear resistance. In this context, the wear rate of NiFeBSi-WC coating was not in correlation with its hardness, in contrast to other coatings. The different wear performance of NiFeBSi-WC coating was attributed to the different type and morphological features of the reinforcing particles (WC)

Alcoholism and Depression

Alcoholism and depression are entangled in many ways and appear in many combinations. In spite of this fact, to this problem is rarely given sufficient attention which results in poor diagnostic and inadequate therapeutic approach with all the consequences this engenders. The frequency of depression in alcoholics is investigated here with the object of finding out to what extent it can be successfully diagnosed and medically treated. The research was carried out in the Psychiatric Clinic of the Clinical Hospital »Split« and the sample of examinees included the patients treated in the stationary part of the Clinic and in the daily hospital

Effects of plastic deformation on the properties of W-Ni-Fe heavy alloys

The effects of reduction in area due to rotary forging on the structure, physical and mechanical properties of 92,5W-5Ni-2,5Fe heavy alloy rods have been presented in this paper. Sintered rods (20mm) were rotary forged with reduction ranging from 5 to 30. Tensile and toughness testing showed that intensive strengthening and rather moderate toughness lowering followed the reduction increase. After 30 deformation, the yield and tensile strength were increased from 729 to 1393 MPa (cca 90), and from 771 to 1400 MPa (cca 80) respectively. Toughness was reduced from 39 to 21 J. Hardening of the γ-interlayer (γ-phase) and spherical tungsten particle (W-phase) was monitored by microhardness measurements and changes in structure were analyzed as a function of achieved reductions. Fracture analysis has shown that, both in sintered and forged conditions, intercrystalline fracture prevails in the tungsten phase while transcrystalline fracture is rather typical for the γ-phase. Macro and microhradness variations with deformation were also modeled. .U radu su prikazani rezultati ispitivanja uticaja stepena hladne deformacije rotacionim kovanjem na strukturu, fizička i mehanička svojstva legura teških metala, nominalnog sastava 92,5W-5Ni-2,5Fe. Sinterovane šipke prečnika 20 mm rotaciono su kovane do stepena deformacije od 5 do 30. Ispitivanja zateznih svojstava i žilavosti pokazala su da sa porastom stepena deformacije čvrstoća intenzivno raste, a žilavost se smanjuje. Nakon deformacije od 30 granica razvlačenja i zatezna čvrstoća povećavaju se od 729 do 1393 MPa (cca 90) i od 771 do 1400 MPa (cca 80), respektivno. Žilavost legure menja se u znatno užem intervalu (39-21 J). Merenjem tvrdoće šipki po poprečnom preseku ustanovljena je izražena nehomogenost raspodele tvrdoće, kao posledica nehomogene deformacije. na osnovu merenja tvrdoće strukturnih mikrokonstituenata (W i γ-faza) praćen je intenzitet ojačavanja faza, i izvršena je analiza strukturnih promena u funkciji stepena deformacije. Analiza površine loma pokazala je da, kako u sinterovanom tako i u kovanom stanju, interkristalni lom preovladava kod volframove faze, a transkristalni kod γ-faze. Takođe, izvršeno je modelovanje promena makro- i mikrotvrdoće u zavisnosti od stepena hladne plastične deformacije.

The tribological performance of hardfaced/thermal sprayed coatings for increasing the wear resistance of ventilation mill working parts

During the coal pulverizing, the working parts of the ventilation mill are being worn by the sand particles. For this reason, the working parts are usually protected with materials resistant to wear (hardfaced/thermal sprayed coatings). The aim of this study was to evaluate the tribological performance of four different types of coatings as candidates for wear protection of the mill's working parts. The coatings were produced by using the filler materials with the following nominal chemical composition: NiFeBSi-WC, NiCrBSiC, FeCrCTiSi, and FeCrNiCSiBMn, and by using the plasma arc welding and flame and electric arc spraying processes. The results showed that Ni-based coatings exhibited higher wear resistance than Fe-based coatings. The highest wear resistance showed coating produced by using the NiFeBSi-WC filler material and plasma transferred arc welding deposition process. The hardness was not the only characteristic that affected the wear resistance. In this context, the wear rate of NiFeBSi-WC coating was not in correlation with its hardness, in contrast to other coatings. The different wear performance of NiFeBSi-WC coating was attributed to the different type and morphological features of the reinforcing particles (WC)

Some Applications of the Image Analysis in the Metal Material Science

In different areas of science such as medicine, biology and engineering the image analysis is widely used. Quantitative measuring by the image analysis has also found application in metal materials science, especially in metallographic microstructure analysis. The measuring of the linear and area dimensions of the microconstituents in the metal material structure performed by the image analysis is presented in the paper. The effects of the heat treatment temperature on the brittle phase content in the structure of the heat resistant Ni-Cr-Co-W alloy were analysed. Investigation of the influence of the alloying elements content in the Al alloys for automotive application, on dendrite arm spacing in the cast structure are also presented. Obtained results of the quantitative measured dimensions have shown direct impact of the process parameters on the analysed metals microstructure characteristics. All tests were performed by the light optical microscope with automatic image analyser. Presented experimental results are based on a large number of measurements. A statistical analysis was performed and a high correlation of the results was obtained. For each of the presented investigations and analyzed phenomenon, a statistical mathematical model is suggested with the boundary conditions defined by the investigated intervals of variables