Search results

Filters

  • Journals
  • Date

Search results

Number of results: 8
items per page: 25 50 75
Sort by:

Abstract

The sintered stainless steels of different microstructures (austenitic, ferritic and duplex) were laser surface alloyed with hard powders (SiC, Si3N4) and elemental alloying powders (Cr, FeCr, FeNi) to obtain a complex steel microstructure of improved properties. Laser surface alloying (LSA) involved different strategies of powder placing: the direct powder feeding to the molten metal pool and filling grooves machined on the sample surface by powder, and then laser surface melting. Obtained microstructures were characterised and summarised, basing on LOM, SEM and XRD analysis. The links between base material properties, like superficial hardness and microhardness, derived microstructures and erosion resistance was described. The LSA conditions and alloying powder placement strategies on erosion resistance was evaluated. The erosion wear is lower for Cr, FeCr, FeNi laser alloying, where powders were dissolved in the steel microstructure, and hard phases were not precipitated. Precipitations of hard phases (carbides, silicides, martensite formation) reduce erosion resistance of SiC alloyed stainless steel. The LSA with Si3N4 works better due to lack of precipitates and formation of a soft and ductile austenitic microstructure. The erosion wear at the impingement angle of 90° is high for hard and therefore brittle surface layers obtained as a result of alloying by hard particles (SiC, Si3N4). The softer and ductile austenitic stainless steel resist better than harder ferritic and duplex stainless steel material at studied erodent im pingement angle.
Go to article

Abstract

The paper presents the technology of manufacturing layered castings, consisting of grey cast iron (base part) and high-chromium stainless steel (working part/layer). The aim of researches was an attempt of integration of heat treatment of steel X46Cr13 grade with founding of grey cast iron in bimetallic system and determination of the influence of cooling rate of bimetallic system in classical sand mould with bentonite on microstructure and hardness of the working layer. The castings were manufactured using mould cavity preparation method, where steel plate was poured by grey cast iron using different pouring temperature and thickness of base part. Then, the quality of joint between cast iron and steel plate was estimated by using ultrasonic non-destructive testing. The efficiency of heat treatment process was analysed by measurement of hardness and in metallographic examination. Conducted studies showed, that self-hardening’s ability of steel X46Cr13 let obtain technologically usable layered casting characterized by hardness of working surface up to 35 HRC.
Go to article

Abstract

The machinability and the process parameter optimization of turning operation for 15-5 Precipitation Hardening (PH) stainless steel have been investigated based on the Taguchi based grey approach and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). An L27 orthogonal array was selected for planning the experiment. Cutting speed, depth of cut and feed rate were considered as input process parameters. Cutting force (Fz) and surface roughness (Ra) were considered as the performance measures. These performance measures were optimized for the improvement of machinability quality of product. A comparison is made between the multi-criteria decision making tools. Grey Relational Analysis (GRA) and TOPSIS are used to confirm and prove the similarity. To determine the influence of process parameters, Analysis of Variance (ANOVA) is employed. The end results of experimental investigation proved that the machining performance can be enhanced effectively with the assistance of the proposed approaches.
Go to article

Abstract

The automated laser welding process of 2.0 mm thick sheets of AISI 304 stainless steel was investigated. The disk laser with a beam spot diameter of 200 μm was used for bead-on-plate and next for autogenous butt joints welding. The influence of basic welding parameters such as laser power, welding speed, and focal spot position on fusion zone configuration, quality of joints, microstructure changes, and microhardness distribution across the joints were analysed and presented in this paper. The results have shown that stiffening of the 2.0 mm thick sheets is crucial for providing high quality and reproducibility of butt joint in a case of AISI 304 stainless steel due to relatively low thermal conductivity and simultaneously high thermal expansion. Relevant drop of microhardness in the weld zone was observed. The mean value of microhardness of the base metal was 230 HV0.1, while the microhardness in fusion zone of the test welds was ranged from 130 to 170 HV0.1. Additionally the microstructure changes in the weld metal and also in the heat affected zone of test joints is described.
Go to article

Abstract

The microstructure and corrosion properties of spark plasma sintered yttria dispersed and yttria free duplex and ferritic stainless samples were studied. Spark plasma sintering (SPS) was carried out at 1000°C by applying 50 MPa pressure with holding time of 5 minutes. Linear sweep voltammetry (LSV) tests were employed to evaluate pitting corrosion resistance of the samples. Corrosion studies were carried out in 0.5, 1 and 2 M concentration of NaCl and H2SO4 solutions at different quiet time of 2, 4, 6, 8 and 10 seconds. Yttria dispersed stainless steel samples show more resistance to corrosion than yttria free stainless steel samples. Pitting potential decreases with increase in reaction time from 2 to 10 seconds. Similarly, as concentration of NaCl and H2SO4 increases from 0.5 M to 2 M the corrosion resistance decrements due to the availability of more Cl¯ and SO4 2¯ ions at higher concentration.
Go to article

Abstract

The dry sliding wear behavior of heat-treated super duplex stainless steel AISI 2507 was examined by taking pin-on-disc type of wear-test rig. Independent parameters, namely applied load, sliding distance, and sliding speed, influence mainly the wear rate of super duplex stainless steel. The said material was heat treated to a temperature of 850°C for 1 hour followed by water quenching. The heat treatment was carried out to precipitate the secondary sigma phase formation. Experiments were conducted to study the influence of independent parameters set at three factor levels using the L27 orthogonal array of the Taguchi experimental design on the wear rate. Statistical significance of both individual and combined factor effects was determined for specific wear rate. Surface plots were drawn to explain the behavior of independent variables on the measured wear rate. Statistically, the models were validated using the analysis of variance test. Multiple non-linear regression equations were derived for wear rate expressed as non-linear functions of independent variables. Further, the prediction accuracy of the developed regression equation was tested with the actual experiments. The independent parameters responsible for the desired minimum wear rate were determined by using the desirability function approach. The worn-out surface characteristics obtained for the minimum wear rate was examined using the scanning electron microscope. The desired smooth surface was obtained for the determined optimal condition by desirability function approach.
Go to article

This page uses 'cookies'. Learn more