A new composite matrix was developed for a cutting tool based on tungsten carbide ligated with cobalt (WC-Co) using sintering technique. The admixtures of niobium carbide, tantalum carbide, and ...titanium carbide with the WC-Co matrix aim to inhibit the grain growth of WC and to promote covalent bonding at the interface. The modified WC-Co tools were coated with titanium nitride and titanium carbonitride layers by CAE-PVD technique. To substantiate the performances of the new coating-substrate systems, we have performed X-ray diffraction, atomic force microscopy, and scratch test measurements to estimate: phase content, average crystallite size, average texture coefficient, residual stress level, coating thickness, average roughness, square mean root, fractal dimension, cohesive adhesion, and adhesive adhesion. The results enable the in-depth understanding of the coating growth mechanisms and provide an objective evaluation of the coatings adhesion to the new cutting tools matrix. The results provide evidence to support the potential of TiN and TiCN coatings to enhance the working performances of the composite WC-Co cutting tools and to differentiate their properties. TiCN coating is shown to be superior to TiN coating in terms of adhesion and thus represents a better alternative for coating the modified WC-Co composite matrix.
•A new composite WC–Co cutting tool was coated with TiN, TiCN, TiAlN by CAE-PVD.•Corrosion resistance in 3.5% NaCl solution of TiN, TiCN, TiAlN coatings were measured.•Structural changes induced by ...corrosion test upon TiN, TiCN, TiAlN were investigated.•Corrosion resistance of TiN, TiCN, TiAlN was ranked based on Eoc, icorr, P parameters.•TiN coating is the best solution for new tool designed to work in marine environment.
A new advanced sintered composite cutting tool has been developed based on tungsten carbide matrix ligated with cobalt (WC–Co) additivated with tantalum carbide (TaC), titanium carbide (TiC) and niobium carbide (NbC) as grain growth inhibitors. Titanium nitride (TiN), titanium carbonitride (TiCN) and titanium aluminium nitride (TiAlN) coatings were deposited on these tools by CAE-PVD technique to find out the best solution to improve the corrosion resistance of this tool in marine environment. The electrochemical behaviours of the specimens in 3.5% NaCl water solution were estimated by potentiodynamic polarization measurements i.e. the open circuit potential (Eoc), corrosion potential (Ecorr) and corrosion current density (icorr). Wide angle X-ray diffraction (WAXD), optical microscopy (OM) and atomic force microscopy (AFM) investigations have been carried on tested and untested specimens to substantiate the corrosion resistance of the tested specimens. Based on the open circuit potential (Eoc) and corrosion potential (Ecorr) results, the tested specimens were ranked as TiN, TiAlN, TiCN and WC–Co while on corrosion current density (icorr) and protective efficiency (P) values they have been ranked as TiN, TiAlN, WC–Co and TiCN. The WAXD, MO and AFM results unambiguously show that the corrosion resistance depends on the nature and morphology of the coating.
The aim of the research is to improve the exactness of the measurement of the surface tension of the molten SnAgCu soldering alloy at different temperatures. The method used for surface tension ...measurement of molten alloys is of pendant drop type. The weak point of this method is the exactness of the curvature radius measurement, but mostly the exactness of the first order derivative of the droplet profile function depending on the droplet height measured from its apex. The authors propose a modeling approach of the droplet profile by analytical function of the class C2. Based on the analytical profile function were calculated the curvature of the droplet and subsequently the surface tension. The paper will present the main data and results obtained during the first part of the researches regarding implementation the method for temperature in the range of soldering process. There were measured the surface tension of a SnAgCu 305 alloy obtained in a laboratory of UPB at temperature ranging from 225 to 265°C. The expanded measurement uncertainty of the results, with 95% degree of confidence, was estimated based on multi-convolutional approach of uniform probability density functions. The main result of the paper consists in finding of a simple way of simulating of the symetric shape profile with analytical function. Based on the first and second order derivatives of the simulated profile function were calculated the surface tension. An other important result consists in improving the quality of the test results based on measurement uncertainty estimation.
The paper addresses mainly an advanced way of statistical data processing applied to a Round Robin spectrochemical laboratory scheme. This may be applied with adequate modification to the proficiency ...testing scheme or to other interlaboratories comparisons. BIOMAT and ICEM organized a six laboratories Round Robin scheme designed to demonstrate the competence of the three laboratories that candidate to RENAR accreditation to perform OES-SDAR analysis. The other accredited ones are interested in this scheme to demonstrate that their spectrochemical analysis proficiency is improved or are at the level they were accredited. There were analyzed two MRCs (medium alloyed steel and Al-Cu-Zn alloy) and were dozed simultaneously 10 and 8 elements, respectively. Because of the different Z scores obtained by the laboratories for the same sample it is quite impossible to classify the laboratories competence. In this regard, the authors introduced a new way of classification of the laboratorypsilas analytical competence based on the mean Z score and its associated dispersion.
