Wyniki 1-2 spośród 2 dla zapytania: authorDesc:"Dominika Panfil"

Laser heat treatment of gas-nitrided layer produced on 42CrMo4 steel DOI:10.15199/28.2015.5.21


  Gas nitriding, together with gas carburizing and gas carbonitriding, is the most commonly used thermochemical treatment. This process resulted in many advantageous properties: high hardness, enhanced corrosion resistance, and considerably improved wear resistance and fatigue strength. A wide range of steels, including special nitriding steels (41CrAlMo7, 33CrMoV12-9), low alloy steels, tool steels as well as austenitic steels, can be nitrided. Special attention requires the nitride layer at the surface that is mainly critical to such properties as corrosion resistance or resistance to friction wear. In this study, gas nitriding was carried out on 42CrMo4 steel resulting in ε + γ′ compound layer at the surface. Next, the nitrided layer was laser heat treated (LHT) using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as a single tracks and as multiple tracks with overlapping of about 86%. LHT caused the decomposition of continuous compound layer and an increase in hardness of previously nitrided layer, enlarging the hardened zone. The results showed an advantageous influence of laser heat treatment on the wear resistance. Key words: gas nitriding, laser heat treatment, microstructure, hardness, wear resistance. Laserowa obróbka cieplna warstwy azotowanej wytworzonej na stali 42CrMo4 Azotowanie gazowe, obok gazowych procesów nawęglania i azotonawęglania, jest najpowszechniej stosowaną obróbką cieplno-chemiczną. Proces ten skutkuje wieloma korzystnymi właściwościami: dużą twardością, poprawą odporności korozyjnej oraz znacznie zwiększoną odpornością na zużycie i wytrzymałością zmęczeniową. Proces jest szeroko stosowany w odniesieniu do stali, w tym specjalnych stali do azotowania (41CrAlMo7, 33CrMoV12-9), stali niskostopowych, narzędziowych, jak również stali austenitycznych. Szczególnej uwagi wymaga warstwa azotków przy powierzchni, która ma istotne znaczenie dla takich właściwości jak odporność na korozję czy na zuż[...]

Effect of laser heat treatment parameters on the microstructure and hardness of gas-nitrided layers DOI:10.15199/28.2016.6.9


  Nitriding is commonly used method of thermochemical treatment in order to produce surface layers of improved hardness and wear resistance. Using a gas nitriding with changeable nitriding potential, a nitrogen concentration at the surface could be controlled, influencing the phase composition and the growth kinetics of the layer. In this study, the hybrid surface treatment was applied. It consisted in gas nitriding and laser heat treatment (LHT) of 42CrMo4 steel. Two nitriding processes were carried out using changeable nitriding potential. Parameters on first process were as follows: temperature 570°C (843 K), time 4 h. The second process was performed at lower temperature 520°C (793 K) and longer duration 10 h. This resulted in various depths of the compound zone at the surface (20 and 8 μm, respectively). Next, the nitrided layers were laser heat-treated using TRUMPF TLF 2600 Turbo CO2 laser. Laser tracks were arranged as the single tracks with various scanning rates (vl = 2.88 m/min and vl = 3.84 m/min). The laser beam power (P) ranged from 0.26 to 0.91 kW. The effects of the depth of compound zone as well as LHT parameters on the microstructure, dimensions and microhardness of laser tracks were analysed. In the majority of the produced laser tracks, remelted (MZ) and heat-affected (HAZ) zones were easily identified. Different microstructure was visible at low laser beam power (0.26 kW). The dimensions of MZ were limited, whereas the HAZ was clearly observed. The compound zone was still visible at the surface. Only the porous ε nitrides were slightly melted. Hardness increased significantly after LHT with complete and partial remelting of compound zone. Laser beam power and scanning rate influenced the depth and width of MZ and HAZ, so the thickness of hardened zone. The greater laser beam power or the smaller scanning rate, the larger hardened zone was observed. Key words: gas nitriding, laser heat treatment, microstructure, hard[...]

 Strona 1