A study of the strengthening mechanisms in the novel precipitation hardening KEYLOS® 2001 Steel

KeyLos ® 2001 is a new precipitation-hardening steel especially developed for plastic moulds. In this study the precipitation stage of KeyLos ® 2001 steel has been investigated and compared to the results obtained with 17-4 PH steel. Precipitation-hardening has been carried out at three different temperatures and the stages of hardening and overageing have been studied in order to clarify the hardening mechanisms. It has been found that hardening and softening mechanism during the precipitation-hardening treatment occur at higher temperatures and in correspondence with more prolonged treatment times than those typical for the best known 17-4 PH steel; hardness is then expected to remain stable also for very extended mould lives. Microstructural investigations by means of Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) have also been carried out and the microstructural parameters responsible for the hardening and overageing have been pointed out

Effect of kolsterising treatment on surface properties of a duplex stainless steel

In recent years, attempts of engineering the surface of duplex stainless steels were made in order to enhance their hardness and tribological properties, without affecting their corrosion resistance. A possibility of improving these properties is provided by a family of processes developed by Prof. B.H. Kolster in the Netherlands in the late 1980’s. These processes (usually referred to as Kolsterising® treatments) consist in a low temperature surface carburizing, which involves the diffusion of large quantities of carbon atoms (up to 6-7 wt.%) into the steel at a diffusion temperature below 450 °C. In the present paper a characterization of the surface layer of Kolsterised duplex SAF 2205 stainless steel was carried out to study the effects of this treatment on surface properties. The characterization includes optical metallographic examination, microhardness tests and SEM-EDS investigation on the Kolsterised steel in the as treated condition and after annealing treatments at 200, 250, 300 350 and 400°C for 10 hours, to evaluate the stability of Kolsterised layer’s properties with a moderate increase in temperature. Moreover, complying with ASTM G48-03 Method E Standard, in order to evaluate the effect of the Kolsterising® treatment on steel pitting resistance, the critical pitting temperature was obtained for Kolsterised duplex SAF 2205 stainless steel compared with the base metal

On the crack path of rolling contact fatigue cracks in a railway wheel steel

The objective of the present paper is to give some preliminary results obtained in the frame of a more wide investigation on the rolling contact fatigue (RCF) behavior of a railway wheel steel. The effect of different test parameters on the RCF fatigue strength of the railway wheel steel was evaluated. RCF tests were conducted using two cylindrical contact specimens under different Po/k ratio (where Po is the maximum Hertzian pressure, k is the yield stress in shear of the material), under dry contact conditions or with water lubrication, and at varying slip ratio. In the present study crack initiation location and crack growth direction were carefully investigated; microscopic examination showed that the cracks were initiated at the surface, propagated obliquely in the depth direction and then occasionally branched into two directions. Usually multiple cracks are initiated, at the rolling contact surface, caused by the accumulation of shear deformation due to repeated rolling–sliding contact loading. Subsequent crack growth has been found to occur along specific sloped directions. The influence of Po/k ratio, dry or wet contact, and slip ratio on crack slope angle to the radial direction and the depths at which slope changes occur has been investigated. Observed crack slopes and slope change position have been discussed according to crack path prediction criteria in the literature

Study of the damage induced by thermomechanical load in ER7 tread braked railway wheels

Abstract This work aims to better understand the complex damage phenomena taking place at the wheel/brake block interface due to the thermomechanical load. An experimental procedure, articulated in three series of tests carried out with a bi-disc machine, was designed in order to experimentally simulate in controlled laboratory conditions the thermomechanical history of the real wheel during stop braking. The first series of tests was performed on ER7 wheel steel discs paired with cast iron shoe material discs, setting the sliding speed and the contact load in such a way to generate the heat flux needed to reproduce the typical tread temperature of a real wheel in stop braking. The second series was carried out by repeating the tests in the conditions of the first series and subsequently subjecting the tested wheel specimens to rolling/sliding contact with discs of 350HT rail steel. The third series was carried out by repeating the two phases of the second series and subsequently adding water to the contact interface of the wheel-rail specimens. Measurements of friction coefficient, surface temperature and weight changes were carried out during the tests. At the end, cross-sections of the specimens were observed with an optical microscope. The hardness along the depth was measured. It was observed that during the braking phase parts of the wheel specimen surface are coated by a discontinuous layer of cast iron that is transferred from the brake block specimens. During the braking phase and the subsequent phase of dry contact with the rail specimen, the transferred material is removed, promoting the nucleation of surface cracks; in addition, surface cracks are generated also by ratcheting due to high friction. During the subsequent wet contact phase, these cracks propagate in the wheel disc due to the pressurization of the fluid entrapped inside the cracks. The propagation of surface cracks in wet contact was assessed by a fracture mechanics approach, including the Finite Element simulation of a surface crack with entrapped fluid. The stress intensity factor range during a load pass was calculated and compared with the propagation threshold of the ER7 steel, determining this way the critical depth of surface cracks. This study is a step towards a damage tolerant approach for the designing and maintaining tread-braked wheels

An artificial diet for rearing three exotic longhorn beetles invasive to Europe

Anoplophora glabripennis, Anoplophora chinensis and Psacothea hilaris hilaris are three invasive exotic longhorn species (Coleoptera Cerambycidae) threatening native broadleaf trees in Europe and North America. Field studies on invasive species are somewhat difficult in the areas of introduction due to the application of eradication measures and the activation of quarantine protocols. Rearing these species in standard laboratory conditions would allow specific ecological and biological investigations to be conducted. In this paper, the rearing of these longhorn beetles has been tested on an artificial diet in laboratory conditions. The tested diet can be used to obtain viable healthy adults of each of the three studied species. P. h. hilaris had the best rearing performance with 74% of eggs producing new adults, while A. chinensis and A. glabripennis were poorer with 24.7% and 23.3%, respectively. The low percentage of emerging A. glabripennis and A. chinensis adults was due mainly to a high mortality of their first instar larvae not entering the diet. Moreover, A. chinensis and A. glabripennis had a mean development time, 60.06 and 37.29 weeks, respectively (including the chilling periods required for pupation), longer than P. h. hilaris (16.1 weeks). During development, larval moults varied according to species and within species ranging from 5-7 (P. h. hilaris), 6-11 (A. chinensis) and 7-8 (A. glabripennis) moults, respectively. Adults of A. glabripennis and P. h. hilaris reared on the diet were bigger than wild specimens collected from the same population, whereas A. chinensis adults were smaller. Adult survival was shorter in A. glabripennis (62.9 days) than in P. h. hilaris (119.3 days). According to the different performance of the three species, the rearing costs were about 2.0, 8.1 and 16.1 US dollars per adult beetle for P. h. hilaris, A. glabripennis and A. chinensis, respectively. A laboratory insect population has to be cost effective and self-sustainable over time, and the tested diet provided valuable results for the low-cost mass rearing of these invasive longhorn beetles

Improving the early detection of alien wood-boring beetles in ports and surrounding forests

International ports are generally considered the most likely points of entry for alien wood-boring beetles. A better understanding of the factors affecting their arrival and establishment at ports and their surrounding areas is of utmost importance to improve the efficacy and the cost-effectiveness of early detection programmes. Our work aimed at understanding how port size and the characteristics of the landscape surrounding the port, in terms of forest cover and forest composition, influence the occurrence of alien wood-boring beetles. From May to September 2012, 15 Italian international ports and the surrounding forests were monitored with multi-funnel traps baited with a multi-lure blend (\u3b1-pinene, ethanol, ipsdienol, ipsenol, methyl-butenol), three in each port and three in forests located 3\u20135 km away from the port. We identified both alien and native Scolytinae, Cerambycidae and Buprestidae beetles. Fourteen alien species, among which four are new to Italy, were trapped. Alien species richness was positively related to the amount of imported commodities at the port scale. Broadleaf forests surrounding ports received larger number of alien species than conifer forests. By contrast, total forest cover in the landscape surrounding ports was positively related to the occurrence of native but not alien species. The alien and native species richness was higher in the surrounding forests than in the ports. Synthesis and applications. The simultaneous use of traps in ports with large volume of imported commodities and in their surrounding broadleaf forests can strongly increase the probability of alien wood-boring beetle interceptions. The identification of sites where the arrival and establishment of alien species is more probable, combined with an efficient trapping protocol, can substantially improve the efficacy of early detection. Similar approaches may be used in other countries as early warning systems to implement timely measures to eradicate or contain alien invasions at the European scale

Composition and Elevation of Spruce Forests Affect Susceptibility to Bark Beetle Attacks: Implications for Forest Management

(6) spruce-broadleaf mixed forest

Prima segnalazione di Xylosandrus crassiusculus (Motschulsky, 1866) (Coleoptera Curculionidae Scolytinae) in Piemonte

Nel presente contributo gli autori segnalano per la prima volta la presenza del coleottero scolitide asiatico Xylosandrus crassiusculus in Piemonte, in tre località collinari e sub-montane della provincia di Cuneo. Nel contempo viene segnalato per la seconda volta, a livello europeo, lo sviluppo della specie a carico di impianti di castagno ibrido giapponese coltivati in coltura specializzata

New species and new records of exotic Scolytinae (Coleoptera, Curculionidae) in Europe

Background Bark and ambrosia beetles (Coleoptera, Scolytinae) are amongst the most important wood -boring insects introduced to Europe. During field investigations conducted between 2019 and 2021 in different countries and regions of Europe, many exotic species have been recorded providing new and relevant data. New information Dryoxylon onoharaense (Murayama, 1933) is recorded in Europe for the first time. Xyleborinus attenuatus (Blandford, 1894) is a species new to Italy, while Xylosandrus germanus (Blandford, 1894), Hypothenemus eruditus (Westwood, 1836) and Amasa sp. near A. truncata are new country records for Portugal. Cnestus mutilatus (Blandford, 1894), Phloeotribus liminaris (Harris, 1852) were collected in Italy and Amasa sp. near A. truncata was collected in France after the first discovery, confirming their establishment and their dispersal into new areas