Fabrication of TiC/Fe–Ni cermet coatings by reactive thermal spraying of Fe–Ti–Ni–C composite powder

Abstract

A mixture of ferrotitanium, nickel powders and sucrose was heated with an intention of carbonising the sucrose. The tiny ferrotitanium, nickel particles are bound by the carbon obtained from pyrolysis of the sucrose to form a unique structure of Fe–Ti–Ni–C composite powder for reactive thermal spraying. The carbon is a reactive constituent as well as the binder in the composite powder. TiC/Fe–Ni cermet coating was prepared by reactive plasma spraying of this powder. A mass of TiC particles were in situ synthesised and uniformly distributed in the Fe–Ni alloy matrix without residuals of raw materials in the coating. The coating is consisted of two different areas: one is the composite area, where lots of spherical fine TiC particles (100–500 nm) are homogeneously distributed within the Fe–Ni alloy matrix; the other is a small fraction of TiC accumulation. The volume fraction of composite area is >87%.     

Properties of Ni–Cr–Al Alloys Obtained by a Powder Metallurgy Method

Alloys of practically 100% density were formed by hot pressing mixtures of nickel, chromium and aluminum powders. The principal phases formed are solid solutions based on chromium, on nickel, and also the intermetallic NiAl. These correspond to phases in the phase equilibrium diagram of theNi Cr Al system. The strength and wear resistance of the alloys are determined by the ratio of phase components.     

Structure of the molybdenum–carbon–copper composite coatings produced by electroexplosive spraying followed by electron-beam treatment

Electroexplosive Mo–C–Cu composite coatings are modified by a high-energy electron beam for the first time. Our studies demonstrate that the electron-beam treatment of the electroexplosive spraying layer that is performed under melting conditions leads to the formation of a structurally and concentration homogeneous surface layer.     

Processing of Cu–Al–Ni Alloy by Spray Atomization and Deposition Process

The present work describes a new route for the preparation of Cu–Al–Ni alloy strips via spray atomization and deposition route. The route consists of atomizing liquid Cu–Al–Ni alloy with a jet of argon gas in a closed chamber, at a pressure of 1 MPa. The semi-solid Cu–Al–Ni droplets are subsequently collected on the steel substrate placed vertically below the liquid metal stream in the atomization chamber to form a three-dimensional preform. The deposit produced on the substrate contains ~?5% porosity. The microstructural details of the spray deposited Cu–Al–Ni strips explains particularly the presence of porosity, formation of splats during the flight of spray casting and the associated microstructural evolution in Cu–Al–Ni spray deposit are explained.     

Properties of Electroless Ni–B and Ni–P/Ni–B Coatings Formed on Stainless Steel

In this study, Ni–P/Ni–B duplex coatings and Ni–B single layer were deposited on 410 stainless steel by the electroless process. The surface morphology and cross section observations were analyzed using scanning electron microscopy and optical microscopy. The results showed that by using the Ni–high P layer under the Ni–B deposit, the hardness value was increased. Also, the surface roughness of Ni–high P/Ni–B duplex coating was lower than the surface roughness of the Ni–B single layer. In addition, by using the Ni–high P layer as an intermediate layer prior to Ni–B coating, the surface morphology could be compressed. The mass loss diagram and the worn surfaces indicated that the Ni–high P/Ni–B duplex coating was the best wear resistant among the other coatings.     

Effect of Aging Time on Mechanical Properties and Wear Characteristics of Near Eutectic Al–Si–Cu–Mg–Ni Piston Alloy

Al–12Si–3Cu–1 Mg–1.78Ni alloy is widely used for piston parts in automobile industry. The present paper investigates the effect of aging time for 1–16 h at 180 °C after solution treatment of the alloy at 500 °C for 5 h, on alloys prepared by gravity casting and squeeze casting. The wear rate of the alloy shows a minimum at an intermediate aging time. The hardness and ultimate tensile strength showed a peak at intermediate aging time. Mechanical properties and wear resistance are found to be better in squeeze cast alloy. The result are explained based on the microstructure developed during casting process and on heat treatment for various durations.     

Crystallographic structure of Ni rich NiAl films prepared by co-evaporation

In order to understand the mechanisms controlling phase formation during vapour deposition we have co-evaporated Ni and Al (0–55 at% Al) on substrates held at temperatures between 360 and 790 K. Based on our observations we have constructed a thin film phase diagram. For temperatures above 500 K and Al concentrations less than 30 at.% the results agree with equilibrium data. For decreasing temperatures the solid solubility of Al in Ni increases and below 500 K no single phase α′ Ni₃Al is observed. In contrast to bulk alloys the lattice parameter increases linearly from 3.520 Å for pure Ni up to 3.560 Å at 25 at.%. For Al contents above 30 at.% free Al and α′ Ni₃Al co-exist with β′ NiAl whereas for bulk alloys β′ NiAl is the only phase above 40 at.% Al. The value of the lattice parameter shows that in our films β′ NiAl forms with its most stable composition of 52 at.% Al in films with 35 at.%. The phase formation may be explained in terms of the mobility and migration of the deposited atoms depending on temperature and composition.