372595884

COATINGS

JPRS-UMS-92-003 16 March 1992

the studies. Indcnter loads of 50 and 100 g were used. The starting particles of all five test powders were spherical porous formations consisting of evenly distrib-uted and sintered finely dispersed (particie size up to 10 pm) subparticles of titanium carbonitrides and metals constituting the binder-alloy. All of the starting compos-ites had a porosity of 40 to 55%. The technique of sputtering into water in a plasma stream was found to result in significant structural changes in each of the powders tested. The specific naturę of the changes depended on a number of factors, including composition of the metallic component of the powder composites, the wettability of the refractory inclusions formed by the melts, and the density of the sputtered powders. The naturę of the structure of the particles participating in the formation of the coatings was found to have a significant effect on the uniformity of the distribution of refractory inclusions in the field of the metal matrix of the composites, the ąuality of the boundary of fusion with the basie metal, and the porosity of the sputtered layers. Those coatings that were madę of composites characterized by complete wetting of the surface of the refractory particles by the metal binder melt and formation of fused composite particles with a heterodisperse structure proved to have the highest-quality structure. Coatings madę of powder 2 had the highest average microhardness (11.0 x 10³ MPa), whereas coatings of powder 5 had the lowest microhardness (7.30 x 10³MPa). Coatings of powders 1, 3, and 4 had average microhardness values of 8.40, 8.50, and 8.70 x 10³ MPa, respectively. In all cases, the microhardness of the center of the fused granules was much lower than that of the peripheral segments of the granules, thus indicating that the shells were filled primarily with refractory inclusions while the centers were filled primarily with binder-alloy. Figures 5, tables 3; references 3 (Russian).

Improving the Quality of Chemical Coatings of the System Ni-P on Tool Steels by Laser Irradiation

927D0049H Moscow FIZ1KA IKHIMIYA OBRABOTKIMATERIALOY in Russian No 3,

May-Jun 91 (manuscript received 11 Mar 90) pp 90-94

[Article by G.I. Brover, V.N. Varavka, Ye.A. Katsnelsov, V.T. Loginov, G.Ye. Trofimov, and V.D. Kritin, Ros-tov-na-Donu]

UDC 621.785:669.14.018.29

[Abstract] The authors of the study explored the possi-bility of using laser irradiation to improve the quality of Ni-P Chemical coatings on tool steels. Ni-P coatings were applied to the steels R6M5, R18, Crl2Vl, and 4Cr5W2VSi by the technique of Chemical deposition. A Kvant-16 laser unit was used at power-flow densities of 80 to 200 kW/cm². A Neophot-21 microscope was used for the metallographic analysis, a PMT-3 was used for the durability studies, and a DRON-0.5 difTractometer was used for the x-ray crystallographic analysis. The experiments performed revealed that the quality of the

Chemical coatings deposited on the study steels and then treated by laser irradiation depends above all on the thickness of the coating and the power-flow density of the radiation. The optimal coating thickness was found to be 10 to 30 pm. When coating thickness was inereased beyond 30 pm, the efficiency of the laser heat treatment process decreased. Power-flow densities above 100 kW/ cm² resulted in the formation of a crater-like zonę that was deepest in the central portion of the spot. Cracking of the coating throughout virtually the entire area of the defocusing spot was also observed. Neither of these effects was observed when the power-flow density was kept below 100 kW/cm². Laser treatment was found to produce a dendrite structure in the coated Steel spcci-mens, with the depth of the irradiated layer reaching 10-30 pm and the microhardness reaching 4-6 GPa (or cven 8-9 GPa when the specimens were subjected to tempering for 1 hour at 300°C). Laser irradiation also inereased the adhesion of the Ni-P coatings to the Steel substrates tested. The experiments performed thus dem-onstrated that laser treatment is an effective method of improving the quality of Ni-P Chemical coatings on tool steels. Figures 3; references 5 (Russian).

Laser-Stimulated Chemical Deposition of Nickel Films

927D0049G Moscow FIZIKA I KHIMIYA OBRABOTKI MATERIALOY in Russian No 3,

May-Jun 91 (manuscript recei\ed 12 Jan 90) pp 85-89

[Article by M.R. Bruk, Ye.A. Morozova, and G.A. Shafeyev, Moscow]

UDC 669.881:535.211

[Abstract] The authors of the study examined the laser-stimulated Chemical deposition of nickel films onto the following catalytically inactive substrates: Cu, GaAs, Si, A1₂0₃, and epoxy-resin glass-basc textolite. A Cu vapor laser (i, 0.51 pm; P 20 mW) and a YAG:Nd³* laser (X, 1.06 pm; Pa 10 W) served as radiation sources. Both were used in pulse and continuous-wave modes. The coatings were precipitated from a Chemical nickel plating solution. It main components were NiCl₂ and Na₂H₂P0₂. The Ni-P coatings studied were deposited by the technique of scanning a beam along the substrate. When the test substrate was irradiated by a laser, deposition of the coating began after some activation time t_a. Initially, the substrate temperaturę remained virtually unchanged. Then, at the moment t_a, there was an ava-lanche-likc incrcase in substrate temperaturę corre-sponding to the beginning of the deposition of the Ni onto the Cu. The deposition process was accompanied by the evolution of hydrogen gas. The time t_a decreased as the fraction of the colloidal solution of metallic Ni in the starting solution was inereased and was found to depend on the thickness of the solution over the target. A “running metallization” modę was detected in which the reaction was initiated at some arbitrary place on the coppcr path and then spread along the entire path of the