Microstructures of Laser Processed Fe-Cr Surface Alloys

In recent years, the effects of chromium on the transformation characteristics of pure iron and the structures produced thereby have been extensively studied as a function of cooling rate. In this paper, we present TEM observations made on specimens of Fe-10% Cr and Fe-20% Cr alloys produced through laser surface alloying process with an estimated cooling rate of 8.8 x 104°C/sec. These two chromium levels were selected in order to study their phase transformation characteristics which are dissimilar in the two cases as predicted by the constitution diagram. Pure iron (C<0.01%, Si<0.01%, Mn<0.01%, S=0.003%, P=0.008%) was electrodeposited with chromium to the thicknesses of 40 and 70μm and then vacuum degassed at 400°F to remove the hydrogen formed during electroplating. Laser surface alloying of chromium into the iron substrate was then performed employing a continuous wave CO2 laser operated at an incident power of 1200 watts. The laser beam, defocussed to a spot diameter of 0.25mm, scanned the material surface at a rate of 30mm/sec, (70 ipm).

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TiC/Ti Composite Layers Fabricated by Laser Surface Alloying

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.336-338.1148 ◽

2007 ◽

Vol 336-338 ◽

pp. 1148-1150

Author(s):

Jian Bin Zhang ◽

Ding Fan ◽

Jing Jie Dai ◽

Yao Ning Sun

Keyword(s):

Continuous Wave ◽

Composite Layer ◽

Pure Titanium ◽

Surface Hardness ◽

Laser Surface ◽

Commercially Pure Titanium ◽

Surface Alloying ◽

Micro Hardness ◽

Laser Surface Alloying ◽

Commercially Pure

Laser surface alloying is an attractive processing to improve surface hardness, wear and corrosion resistance. In this paper, a continuous wave CO2 laser was used to irradiate commercially pure titanium surface with pre-placed active carbon powders in argon atmosphere. A compact, well-adherent, and crack-free TiC/Ti composite layer was obtained. The microstructure and phase constitution of the alloyed layers were determined and analyzed, and the micro-hardness was measured. The result of X ray diffraction (XRD) analysis shows that the alloyed layers contain TiC and Ti (martensite). The scanning electron microscopy (SEM) observation shows TiC growth morphologies have a well-developed dendrite, cellular dendrite, globular microstructure and cross-petal microstructure. The mechanism of the formation of titanium carbides is discussed. Micro-hardness of the laser surface alloyed layer was improved to 420 Hv as compared to 200 Hv of the as-received commercially pure titanium.

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Process Characterization of 40Cr Steel Roller by Laser Surface Alloying with Rare Earths Oxide Y2O3

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.295-297.520 ◽

2011 ◽

Vol 295-297 ◽

pp. 520-526

Author(s):

An Qi Wu ◽

Qi Bin Liu ◽

Shui Jie Qin

Keyword(s):

Mechanical Properties ◽

Continuous Wave ◽

Laser Surface ◽

Surface Alloying ◽

Laser Surface Alloying ◽

Steel Roller ◽

Process Characterization ◽

40Cr Steel ◽

Microhardness Tester

To increase the mechanical properties of the metal rollers, Mo and Mo+Y2O3alloy powders were designed. And a kind of coating fabricated by a continuous wave CO2laser surface alloying(LSA) on 40Cr steel roller was obtained. The effect of Mo and Mo+Y2O3on microstructure, hardness and wearing resistance of alloying coating were studied by OM, SEM, XRD, microhardness tester and wearing tester. The experimental results indicate that the grain size in alloying coating is obviously fined, and the grain boundary is strengthened. The uniformity and density of microstructure are improved. The microhardness and wear resistance of alloying coating are significantly increased.

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