Femtosecond laser processing of advanced technical materials

Ultra-short pulsed laser ablation may be used for high-precision machining with very low thermal influence on the processed materials. Due to this reason, lasers are increasingly used for processing of advanced materials, such as titanium alloys, nickel-based alloys or steel, every year. In this study, four advanced technical materials were analysed and compared under femtosecond laser irradiation with three different wavelengths. The main laser-material interaction parameters were identified, namely the ablation threshold and removal efficiency parameters. Higher removal rates were found for Ti6Al4V alloy with all three harmonic wavelengths. To increase process productivity, a method of increasing the repetition rate and scanning speed was presented. With the maximum repetition rate, the productivity increased five-fold with a similar removed depth and surface quality. Finally, the suitability of the identified parameters with regard to quality and productivity was demonstrated for fabrication of two complex structures – honeycomb and dot – which has the potential to improve friction properties of advanced materials

Integrita povrchové vrstvy broušených ploch

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta strojn

Vliv procesní kapaliny při broušení

Řezné prostředí, tvořené většinou procesní kapalinou, je důležitým parametrem, který ovlivňuje významně přesnost a jakost obráběných ploch. Vzhledem ke své funkci zastává roli právě u povrchů vytvářených s cílem dosažení vysoké přesnosti a jakosti. Řezné prostředí ovlivňuje množství tepla přecházejícího do obrobku, nástroje, třísky a množství tepla odváděné vlastní procesní kapalinou. To znamená, že prostředí ovlivňuje tzv. tepelnou bilanci obrábění. Při broušení ploch je význam zvýšen odlišnostmi procesu v porovnání s běžným obráběním

Advanced technology for grinding of aluminium alloys parts

In the presents the aluminium and its alloys is doing high advanced technical materials whose proprieties use in the automotive and aerospace industry. In the production of products is effort of producer to production of parts quality and machine with acceptable price. The machining is making important portion by production of the machine parts of automotive industry. The long-terms opinions on the grinding of aluminium alloys in relation to lost of cutting power (glued up of wheel and impaction of pores) important terms there are not so use for aluminium alloys grinding and surface quality. The competition of grinding to advanced production method e.g. forming and turning with advanced tools do not threat dominance of these methods. The use of grinding we are finding in the minor series of production where the use of CNC and forming machines is not suitable in view point of price. The customer requirement of quality (roughness and geometrical accuracy) by grinding of aluminium alloys is guaranteed and correspond with normal and precision grinding e.g. for steels and hardened steels

Vliv vlastností konstrukčního vrubu na jeho chování

Strojní součásti, které jsou opatřeny konstrukčními vruby, mohou být zatěžovány řadou možných zatížení. V první řadě se jedná o statické zatížení, dale o stálé dynamické zatížení a nakonec o cyklické dynamické zatížení, které klade nejvyšší nároky na strojní součásti i jejich jednotlivé prvky a tedy i vruby.Projevy cyklicky se měnícího zatížení lze sledovat při různých kombinacích, například střídavý tah – tlak, míjivé tahové zatížení a podobně. V praxi se nejčastěji vyskytují zatížení ohybu za rotace, cyklického krutu a především komplexní zatížení součástí, což lze však velmi obtížně simulovat. Dokončovací technologie má významný vliv na okolí vrubu a samotný vrub. To se při chodu zařízení projevuje dobou životnosti a velikostí únosnosti součásti při určitém zatížení. Dokončování má výrazný vliv na vlastnosti součástí zařízení, které pracujív dynamickém režimu při proměnlivé velikosti zatížení

Mechanical and Microstructural Anisotropy of Laser Powder Bed Fusion 316L Stainless Steel

This paper aims at an in-depth and comprehensive analysis of mechanical and microstructural properties of AISI 316L austenitic stainless steel (W. Nr. 1.4404, CL20ES) produced by laser powder bed fusion (LPBF) additive manufacturing (AM) technology. The experiment in its first part includes an extensive study of the anisotropy of mechanical and microstructural properties in relation to the built orientation and the direction of loading, which showed significant differences in tensile properties among samples. The second part of the experiment is devoted to the influence of the process parameter focus level (FL) on mechanical properties, where a 48% increase in notched toughness was recorded when the level of laser focus was identical to the level of melting. The FL parameter is not normally considered a process parameter; however, it can be intentionally changed in the service settings of the machine or by incorrect machine repair and maintenance. Evaluation of mechanical and microstructural properties was performed using the tensile test, Charpy impact test, Brinell hardness measurement, microhardness matrix measurement, porosity analysis, scanning electron microscopy (SEM), and optical microscopy. Across the whole spectrum of samples, performed analysis confirmed the high quality of LPBF additive manufactured material, which can be compared with conventionally produced material. A very low level of porosity in the range of 0.036 to 0.103% was found. Microstructural investigation of solution annealed (1070 °C) tensile test samples showed an outstanding tendency to recrystallization, grain polygonization, annealing twins formation, and even distribution of carbides in solid solution

Investigation of Multiparameter Laser Stripping of AlTiN and DLC C Coatings

The lifetime and properties of cutting tools and forming moulds can be prolonged and enhanced by the deposition of hard, thin coatings. After a certain period of usage, the coating will deteriorate. Any remaining coating must be removed prior to successful recoating. Laser stripping is a fast and environmentally friendly coating removal method. In this paper, we present laser removal of two types of coatings deposited on a 1.2379 tool steel substrate, namely, an AlTiN coating with high hardness and a DLC C coating with a small coefficient of friction (COF). A powerful nanosecond laser was employed to remove the coating from the substrate with high efficiency, along with suitable residual surface roughness. Measurements were taken of surface roughness, removed depth, and working time on a stripped area of 1 cm2. The samples were evaluated under a microscope, with a 3D profilometer, and by EDS chemical analysis. Successful removal of the coating was confirmed by optical analysis, but detailed chemical characterisation showed that about 30% of the coating element may remain on the surface. Moreover, a working time of less than 7.5 s per cm2 was obtained in this study. In addition, it was shown that the application of a second low energy, high frequency laser beam pass leads to remelting of the peaks of the material and reduced surface roughness