Influence of nitriding on corrosion resistance of martensitic X17CrNi16‐2 stainless steel

Nitriding increases surface hardness and improves wear resistance of stainless steels. However, nitriding can sometimes reduce their corrosion resistance. In this paper, the influence of nitriding on the corrosion resistance of martensitic stainless steel was investigated. Plasma nitriding at 440 °C and 525 °C and salt bath nitrocarburizing were carried out on X17CrNi16‐2 stainless steel. Microhardness profiles of the obtained nitrided layers were examined. Phase composition analysis and quantitative depth profile analysis of the nitrided layers were preformed by X‐ray diffraction (XRD) and glow‐discharge optical emission spectrometry (GD‐OES), respectively. Corrosion behaviour was evaluated by immersion test in 1% HCl, salt spray test in 5% NaCl and electrochemical corrosion tests in 3.5% NaCl aqueous solution. Results show that salt bath nitrocarburizing, as well as plasma nitriding at low temperature, increased microhardness without significantly reducing corrosion resistance. Plasma nitriding at a higher temperature increased the corrosion tendency of the X17CrNi16‐2 steel.     

α‐Fe layer formation during metal dusting of iron in CO‐H2‐H2O gas mixtures

The formation of an α‐Fe layer between cementite and graphite was observed and investigated during metal dusting of iron in CO‐H₂‐H₂O gas mixtures at both 600°C and 700°C. The condition to form this phenomenon is determined by the gas composition which depends on temperature. The iron layer formation was observed for CO content less than 1 % at 600°C and less than 5 % at 700°C. With increasing CO contents, no α‐Fe layer was detected at the cementite/graphite interface by optical microscopy. In this case cementite directly contacts with the coke layer. The morphologies of the coke formed in the gas mixtures with low CO contents were also analysed. Three morphologies of graphite have been identified with 1 % CO at 600°C: filamentous carbon, bulk dense graphite with columnar structure, and graphite particle clusters with many fine iron containing particles embedded inside. At 700°C with 5 % CO the coke mainly consists of graphite particle clusters with some filamentous carbon at the early stage of reaction. Coke analysis by X‐ray diffraction shows that both α‐Fe and Fe₃C are present in the coke. The mechanism of α‐Fe accumulation between cementite and graphite is discussed in this paper.     

Residual stress measurement in AlSi alloys

In this work, the relaxation of residual stresses inside a sample made of the aluminum alloy AlSi7Mg0.3 after tempering is described. The comparison of stress evaluation by X‐ray diffraction and incremental hole drilling method combined with electronic speckle pattern interferometry strain determination gives the opportunity to evaluate micro stresses together with first order macro stresses. Compressive stresses within the surface of a cold worked sample are relaxed by tempering. The X‐ray diffraction evaluation is supported by the analysis of a stress‐free sample through incremental hole drilling method.     

Investigation of structural,electrical and tribological properties of duplex surface treated and aged Cu−Cr−Zr alloy

In this study, Cu−Cr−Zr alloy specimens were first subjected to aging heat treatment at 500 °C for two different durations (2 hours and 4 hours). Three different coating processes (silver, silver/copper duplex, and copper/silver duplex) were applied to the aged specimens using the physical vapor deposition method. Tensile test, microhardness measurement, wear test, electrical conductivity measurement and structural analysis (x-ray diffraction and scanning electron microscope) were applied to the specimens. After the aging processes, the highest hardness and strength values of the Cu−Cr−Zr alloy were obtained in the specimens that were aged at 500 °C for 4 hours. When the wear resistance and electrical conductivity of the coated specimens were examined, it was determined that the specimens with duplex surface treatment performed better.     

Nutzung von Werkstoffstrukturgrößen als Messnormale

Use of material structure sizes as measuring‐normal Lengths measurement is a comparison/evaluating of received measuring signals with a standard/calibration yardstick. The nano‐technology requires measuring accuracies from the submeter to the nanometer range, i.e. a range over 9 orders of magnitude. Strobes and possible measuringnormal are classified according to their requirements and analyzed on requirements, accuracy, stability, data sets and feasibility. For nano‐position‐ and nano‐measuring‐maschine are summarized suggestions for a feasibility.     

Charakterisierung von Randentkohlungsvorgängen bei der Austenitisierung des Wälzlagerstahls 100Cr6. Teil 1: Korrelation zwischen Randschichteigenschaften und Kohlenstoff‐Tiefenverlauf

Characterization of Decarburisation Processes During Austenitising of the Rolling Bearing Steel 100Cr6. Part 1: Correlation between Rim Zone Properties and Carbon Concentration Profile The influence of a decarburisation process during austenitising of the through‐hardenable rolling bearing steel 100Cr6 (SAE 52100) on the rim zone properties of the martensitic through‐hardened material was investigated by means of material analysis and diffusion calculations. For this purpose, two specimens were prepared under defined heat treatment conditions, and the near‐surface carbon distribution was determined micro‐chemically by using secondary ion mass spectrometry (SIMS). In part 1 of the present work, these concentration profiles are compared with the depth variation of the micro‐hardness and with the distance curves of the residual stresses and the line broadening ({211} α'‐Fe diffraction line) both measured by X‐ray diffraction (XRD). In addition, microstructure investigations were performed. In part 2, a refined kinetics model of a diffusion‐controlled reaction based on the finite element method (FEM) will be applied to the decarburisation process in order to describe the carbon distributions obtained.     

Eliminating the Extinction‐Induced Reflection Enlargement in the XRD Characterisations of Textured Films

This investigation throws additional light on the nature of secondary extinction (SE). A method is described for computing the correct integral breadth using the observed one, which is affected by SE. The method is applied for more precise measuring the integral breadths of reflections corresponding to the ideal directions of main texture components of electrodeposited silver films. Further, the effect of SE on the systematic error in integral breadth measurements is investigated in dependence on the reflectivity and pole density.     

Microstructure formation in electrochemically deposited Copper thin films

The influence of the electrochemical potential and deposition mode on the preferred orientation, morphology and microstructure of crystallites in electrochemically deposited (ECD) copper thin films was investigated using X‐ray diffraction (XRD), scanning electron microscopy (SEM) and the diffraction of back‐scattered electrons (EBSD). As a working electrode for the ECD process, thin gold layers were employed that were deposited on floating‐glass substrates in a vacuum evaporation process. With increasing negative electrochemical potential in the ECD process, the deposition mode changed from the charge transfer controlled one to the diffusion controlled one. At the highest electrochemical potentials, the copper deposition and the hydrogen release were running concurrently. The change of the deposition mode was accompanied by a change of the surface roughness of the thin films and by a change of the direction and degree of the preferred orientation of crystallites. The surface roughness of the deposited copper thin films increased with increasing electrochemical potential. Compact plate‐like crystallites with the preferred orientation {111} grew in the transport controlled deposition mode. Development of the {111} texture was supported by the {111} preferred orientation of the gold layers and by surface energy of copper, which is the lowest in the (111) plane. The diffusion controlled deposition mode was characterized by the growth of globular {110}‐oriented crystallites. The {110} texture resulted from the minimization of the anisotropic strain energy of copper via reduction of the structure defects in this deposition modus. For highest electrochemical potentials, the copper deposition run simultaneously with the development of hydrogen that resulted in growth of needle‐like crystallites with the {100} texture.     

Materialbeanspruchungsanalyse und ihre Anwendung auf Prüfstandsversuche zum Oberflächenausfall (Nierlich‐Schadensmodus) von Wälzlagern

Material Response Analysis and its Application to Rig Tests for the Surface Failure (Nierlich Damage Mode) of Rolling Bearings The material response analysis according to Nierlich using X‐ray diffraction represents an important physical examination technique for the evaluation of material stressing and the lifetime estimation of rolling bearings and other highly loaded machine parts. The method is presented and employed for the evaluation of automobile gearbox rig tests. The extensively described damage modes of the practically predominating surface and the classical sub‐surface failure of rolling bearings can be distinguished that way. In gearboxes, lubricating oil contaminated by metal abrasion of the cogwheels usually appears. Penetrating foreign particles produce indentations at the ring raceways and rolling elements of the rolling bearings, which promotes surface fatigue. The results of the X‐ray diffraction measurements confirm this damage mode. Evaluation of the occurred material stressing permits a more detailed characterization of the surface failure of rolling bearings.