Search results

This paper aims to depict the erosion performance of two HVOF-coated micron layers (Colmonoy-88 and Stellite-6) on pump impeller steel (SS-410) by using Taguchi's method. Taguchi's array (L16) was used to optimize the erosion wear (in terms of weight loss) by using four influencing parameters such as rotational speed, solid concentration, average particle size and time which were varied at four different levels.

The experiments were carried out by using a Ducom slurry tester with rotational speed in the range of 750-1,500 rpm, solid concentration of 35-65 per cent by weight, time period of 75-210 min and average particle sizes in the range of < 53 to 250 µm. Bottom Ash with a nominal size range of < 53 to 250 µm was used as erodent. The process parameters were optimized by using Taguchi's method. The ANOVA method was used to validate the results given by Taguchi's method.

The results revealed that the presence of both carbides and borides and the additional presence of Cr in Colmonoy-88 coating enhancing the slurry erosion resistance of Colmonoy-88 coating. Moreover, the chromium and tungsten carbide particles help in increasing the bond strength between the coating and the substrate material. Further, it was also found that the time was the most dominant factor as compared to other factors.

The very less work has been reported on optimization of erosion wear response of Colmonoy-88 and Stellite-6 coatings by using different design of experiment techniques. Further, the erosion wear mechanism of both coatings has been studied by using image j analysis software.

Prior to manufacturing, designing plays a vital role in the selection of materials and other design parameters. Therefore, during the deposition of materials, substrate materials provide support and affect the microstructure of the deposits, which may not be desirable in the manufactured product. Hence, the main purpose of the study is to analyse the behaviour of the microstructure at the interface of deposited material and substrate.

In this study, two blocks of Inconel 625 (IN625) and Stainless steel 304L (SS304L) metal powders were deposited on an SS304L substrate using laser directed energy deposition (DED) technique. Deposited blocks comprised 50% IN625 + 50% SS304L or 100% IN625. After deposition, microstructural behaviour at the interface of the deposits and substrates was analysed using different tests such as optical microscopy (OM), microhardness testing, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). An improvement in microstructure was proposed by performing heat treatment of the deposited sample.

Formation of martensite and precipitates at the interface of the deposit and substrate was observed. Formation of martensite and precipitates such as α, carbide and δ phases were observed in OM and SEM images. Due to the formation of these phases, interface regions showed a peak in the hardness graphs. Post-heat treatment of the samples was one of the solutions to resolve these issues.

This paper suggests the formation of a heat-affected zone (HAZ) at the interface of the deposit and substrate, which may negatively affect the overall utility of the deposited part. The properties of the HAZ were investigated. To suppress these detrimental effects, post-heat treatment of the deposited sample was performed, and the samples were further analysed. The post-heat-treated samples exhibited as reduction in HAZ thickness and had more uniform hardness throughout the cross-section compared with the untreated samples.