Studies on laser surface melting of Al-11% Si alloy

In the present investigation the effect of laser surface melting on wear and corrosion resistance of Al-11 wt.% Si alloy has been investigated. Laser surface melting has been carried out using a 2 kW continuous wave CO2 laser at an applied power of 2.3 kW and scan speed ranging from 6 to 12 mm/min. Following the laser surface melting, a detailed investigation of the melted zone in terms of microstructure, composition and phases were undertaken. Mechanical properties of the melted zone were evaluated so far as the microhardness and wear resistance were concerned. The corro-sion behaviour of the as-received and the laser surface melted surface was evaluated in 1(M) H2SO4, 1(M) HNO3 and 3.56 wt.% NaCl solutions. The microstructure of the melt zone consists of grain refinedAl andAl-Si eutec-tic colonies which results in an improved microhardness from 87 VHN as compared to 55 VHN of the as-received Al-Si alloy. The wear resistance of the melt surface was improved significantly as compared to the as-received Al-Si alloy. A detailed corrosion study in various environments showed that corrosion resistance was marginally less in the 3.56 wt.% NaCl and 1 M H2SO4 solutions, but was better in the 1 M HNO3 solution

In-situ dispersion of titanium boride on copper by laser composite surfacing for improved wear resistance

The present study concerns the development of a hard in-situ titanium boride dispersed in a composite layer on a copper substrate with the objective of improving the wear resistance. Laser composite surfacing was carried out by melting the surface of a sand blasted commercially pure copper substrate using a continuous wave CO2 laser (with a beam diameter of 3.5 mm) and the simultaneous deposition of a mixture of K2TiF6 and KBF6 (in the weight ratio of 2:1) using an external feeder (at a feed rate of 4 g/min) and Ar as shroud. The process variables used in the present study were the laser power applied and the scan speed. Following the laser irradiation, a detailed characterisation of the composite layer was undertaken in terms of microstructure, composition and phases. Surface dependent mechanical properties such as micro-hardness and wear resistance were also evaluated in detail. Irradiation resulted in melting of the substrate, along with the delivered powder mixture, intermixing and rapid solidification. The microstructure of the composite layer consisted of uniformly dispersed titanium boride particles in a grain-refined copper matrix. The micro-hardness of the surface was improved threefold as compared to that of as-received copper substrate. There was a significant improvement in the wear resistance of the composite surfaced copper, as compared to that of the as-received copper. The mechanism of wear was investigated

Laser composite surfacing of a magnesium alloy with chromium carbide

The present study concerns improving the wear resistance of a Mg alloy (MEZ) by melting the surface with a high power laser and simultaneously injecting hard particles, of Cr2C3 +(25mm -40mm) into the surface. The laser processing was carried out using a continuous wave CO2 laser, Model: Rofin Sinar, RS 10000, with a beam diameter of 4 mm and a focal point 30 mm above the surface. Following laser processing, a detailed investigation of the microstructures, compositions and phases were undertaken and mechanical (wear resistance) and electrochemical (pitting corrosion resistance) properties of the surface layer were evaluated in details. The microstructure of the surface layer consists of uniformly dispersed Cr2C3 precipitates in grain-refined matrix. The micro-hardness and wear resistance of the surface layer were significantly improved as compared to the base metal

Laser surface cladding of EN19 steel with stellite 6 for improved wear resistance

The present study concerns the generation of a wear resistant Stellite 6 CO2 laser clad layer on the surface of an EN19 steel substrate by means of laser surface cladding. Laser surface cladding was carried out by melting the Stellite powder (particle size 10 to 40 μm) supplied through a pneumatically driven powder delivery system (using a 4 MP powder unit) with a 9 kW continuous wave (CW) CO2 laser with the wavelength 10.6 µm. The microstructure of the clad layer was found to consist of three zones: a clad layer comprised of dendrites of Stellite 6; an alloyed zone comprised of a cellular microstructure, which was a mixture of Fe and Co; and the heat affected zone (HAZ), which was a mixture of pearlite and martensite. Compared to the EN19 steel substrate, the micro-hardness of the clad layer represented a significant improvement, increasing to 1200 VHN

Laser surface treatment of Ti-6Al-4V for bio-implant application

The present study aims at enhancing the wear resistance of Ti-6Al-4V by laser surface melting and nitriding and subsequently, studying the influence of laser surface treatment on the corrosion resistance in a simulated body fluid and also the bio-compatibility. The laser surface treatment is carried out using a high power continuous wave diode laser with argon and nitrogen as shrouding gas. Laser surface melting leads to an increased volume fraction of acicular martensite and a decreased volume fraction of the β phase in the microstructure. Laser surface nitriding leads to the formation of titanium nitride dendrites. The micro-hardness could be improved up to a maximum of 450 Hv in laser surface melting and 900-950 Hv in the case of laser surface nitriding as compared to 260 Hv of the as-received substrate. Surface melting increases the corrosion potential (Ecorr) and primary potential for pit formation (Epp1) significantly as compared to the as-received Ti-6Al-4V. However, when processed under similar conditions, surface nitriding shifts Ecorr marginally in the more noble direction, and increased Epp1 as compared to Ti-6Al-4V. The biocompatibility behaviour shows a superior cell viability on surface nitriding and an inferior cell viability on surface melting as compared to the as-received Ti-6Al-4V

Effect of interlayer configurations on joint formation in TLP bonding of Ti-6Al-4V to Mg-AZ31

YesIn this research work, the transient liquid phase (TLP) bonding process was utilized to fabricate joints using thin (20μm) nickel and copper foils placed between two bonding surfaces to help facilitate joint formation. Two joint configurations were investigated, first, Ti- 6Al-4V/CuNi/Mg-AZ31 and second, Ti-6Al-4V/NiCu/Mg-AZ31. The effect of bonding time on microstructural developments across the joint and the changes in mechanical properties were studied as a function of bonding temperature and pressure. The bonded specimens were examined by metallographic analysis, scanning electron microscopy (SEM), and X-ray diffraction (XRD). In both cases, intermetallic phase of CuMg2 and Mg3AlNi2 was observed inside the joint region. The results show that joint shear strengths for the Ti-6Al-4V/CuNi/Mg- AZ31 setup produce joints with shear strength of 57 MPa compared to 27MPa for joints made using the Ti-6Al-4V/NiCu/Mg-AZ31 layer arrangement.NSERC (Canada

Evaluation of the possibility of using diatomite natural mineral as a composite agent in acrylic coating

WOS: 000427736200014In the present study the possibility of the commercially available acryl and diatomite earth (DE) mineral as a composite coating for corrosion protection of Mg alloys has been evaluated. The acrylic coating is used as a top coating in a wide field of applications like automotive, aerospace, medicine and electronics where it shows beneficial properties. Diatomite-dispersed acrylic paint was applied over the substrate by conventional spray technique with an air pressure of 3 kg cm(-2). Firstly the acryl was mixed with hardener and then the DE was added to the mixture. Four types of coating with 0, 2, 4, 8 g/L DE have been prepared. The results show that adding up to 4 g/L of the DE improved the corrosion resistance and produced a coating with acceptable surface roughness