The paper deals with evaluation the corrosion characteristics of welded joints in two corrosion environments – SARS and 0.1 M NaCl solution. Welds were made by MAG technology using three protective gas mixtures - Ferroline He20C8, Ferroline C18 and Ferroline C6X1. There were realised chemical analysis of the base material and weld metal of all welded joints, Vickers hardness test of the base material, heat affected zones and weld metals, metallographic analysis of all areas of welds and measurement of base and weld metal corrosion rate in two corrosion environments. Hardness increases from the base material through the HAZ to the weld metal. The maximum difference between the hardness of the weld metal and the base material is 36 HV 0.1 - realised welds do not show a notch effect. The corrosion rate of the materials in SARS solution was higher than in the NaCl solution. The corrosion rate in weld metals of all welded joints was lower than the corrosion rate of the base material. The lowest corrosion rate in both corrosive environments showed a weld metal made using shielding gas Ferroline C18.
The paper focuses on assessment the resistance of hot-sprayed coatings applied by HVOF technology (WC–Co–Cr created using powder of two different grain sizes) against erosive wear by dry-pot wear test in a pin mill at two sample angles. As these coatings are designated for the environment with varying elevated temperatures and often are in contact with the abrasive, the coatings have been subjected to thermal cyclic loading and their erosive resistance has been determined in as-sprayed condition and after the 5th and 10th thermal cycles. The corrosion resistance of coatings was evaluated by linear polarization (Tafel analysis).
In this article, the attention is paid to the HVOF (High Velocity Oxygen Fuel) thermal spraying method by which the progressive coatings are applied on basic material C15E (STN 412020). These coatings are based on C-17CO, WC-CO-Cr and Cr3C2-25NiCr. There was made determination of the chemical composition of the coatings and assessment of coatings quality - adhesion, microhardness, porosity and wear resistance at room temperature (21°C) and also at operational elevated temperature (900°C). Results of adhesive wear showed high quality of all evaluated coatings and their suitability to extreme tribological conditions.
The paper presents results of research of the essential characteristics of two kinds of advanced coatings applied by HVOF technology. One studied coating: WB-WC-Co (60-30-10%) contains two types of hard particles (WC and WB), the second coating is eco-friendly alternative to the previously used WC-based coatings, called “green carbides” with the composition WC-FeCrAl (85-15%). In green carbides coating the heavy metals (Co, Ni, NiCr) forming the binding matrix in conventional wear-resistant coatings are replaced by more environmentally friendly matrix based on FeCrAl alloy. On the coatings was carried out: metallographic analysis, measurement of thickness, micro-hardness, adhesion, resistance to thermal cyclic loading and adhesive wear resistance (pin-on-disk test). One thermal cycle consisted of heating the coatings to 600°C, dwell for 10 minutes, and subsequently cooling on the still air. The number of thermal cycles: 10. The base material was stainless steel AISI 316L, pretreatment prior to application of the coating: blasting with white corundum, application device JP-5000.