Preparation of W-Plated Diamond and Improvement of Thermal Conductivity of Diamond-WC-Cu Composite

The tungsten (W)-plated diamond process was explored and optimized. A dense and uniform tungsten coating with a thickness of 900 nm was successfully prepared by the powder covering sintering method. The Diamond-WC-Cu composite with high density and high thermal conductivity were successfully prepared by cyclic vacuum pressure infiltration. The microstructure and composition of the W-plated diamond particles were analyzed. The effect of tungsten coating on the microstructure and thermal conductivity of the Diamond-WC-Cu composite was investigated. After calculation, the interface thermal resistance of the composite forming the tungsten carbide transition layer is 2.11 × 10−8 m2∙K∙W−1. The thermal conductivity average value of the Diamond-WC-Cu composite with a diamond volume fraction of 60% reaches 874 W∙m−1∙K−1, which is close to the theoretical prediction value of Hasselman-Johnson (H-J) model and differential effective medium (DEM) model. Moreover, the Maxwell-Eucken (M-E) model, H-J model, and DEM model were used to evaluate the thermal conductivity of the Diamond-WC-Cu composite.

Characterization of vacuum plasma spray VPS - W coating deposited on stainless steel substrates

In this paper, studied was the melting of W powder particles in plasma, their behavior at oxidation as well as the mechanism of hardening on the surface of the substrate. Tungsten coating layers were deposited with vacuum plasma spray technology (VPS) on the test specimens of steel Č.4171 (X15Cr13 EN10027). VPS technology has advantages over the APS technology due to decreased oxidation of melted powder particles, by producing a coating with a controlled proportion of micro pores and greater uniformity of the deposited layers. Evaluation of mechanical characteristics of the layers was done by examining the microhardness using the HV0.3 method and tensile bond strength by tensile testing. The microstructures of the deposited layers were analyzed by means of optical microscopy (OM) and scanning electron microscopy (SEM). The results obtained showed that the tungsten coating consisted of well melted particles that interconnected and were overlapping, which shows a typical lamellar microstructure. Present in the microstructure are micro pores in very small proportion at the inter-lamellar boundaries. Tests have shown that layers of W coating deposited by plasma spray in inert gas shielding at low pressure have good mechanical properties and microstructure, which in the fully enables its use in exploitation.

Environment safety technology of creating coated powder of technical ceramics

Application of fuller materials for creation of the higt-strength coatings on part operating under abrasive wear is one of the promising ways of the resources increasing of road construction, emergency rescue and other types of equipment. However, in their creation process does not always comply with the environmental safety requirements, which leads to negative consequences for the natural environment and human health. The article presents the research work results of authors team created a coated powder by chemical vapor deposition of metal-organic compounds on the alumina particles surface and its applications for the wear-resistant coatings. A method of applying iron-tungsten coating on powder technical ceramics by thermal decomposition of vapors, containing iron pentacarbonyl and tungsten hexacarbonyl, is characterised by sequential application on powder particles of adhesion layer from mixture of iron pentacarbonyl and carbon monoxide in volume ratio of vapours1:5 at temperature of their thermal decomposition of 250 °С, and then surface layer from mixture of tungsten hexacarbonyl and carbon monoxide in volume ratio of vapours1:5 at temperature of their thermal decomposition of 800 °С. Metallization powder materials are carried out in a closed cycle, excluding contact workers with toxic substances and emissions of pollutants into the atmosphere, which ensures the safety of the production process. Plasma coatings obtained with the necessary physical and mechanical properties are obtained, which proves the effectiveness of the employed approach and promotes resource increase of the machines elements, subjected to abrasive wear.