MODUK DEF STAN 03-6: PART 2 PDF

INTRODUCTION

The purpose of this Defence Standard is to provide designers and users with advice on the application of flame sprayed coatings, principally for wearing surfaces. It includes cleaning, preparation of surfaces, design considerations, metals to be applied, quality control, inspection, and testing.

It is not intended to apply to aerospace parts and equipment.

This Defence Standard is divided into three parts:

Part 1, Unfused metal coatings

Part 2, Fused metal coatings

Part 3, Ceramic and cermet coatings.

Part 2, Fused metal coatings, covers the use and application of flame sprayed and subsequently fused coatings. These are applied to selected areas of engineering components to provide resistance to wear, abrasion, erosion, galling, and fretting, and to confer oxidation and corrosion resistance, particularly where these destructive influences accentuate wear. These coatings are used either to build up or repair components showing rapid destructive attack in service, or to provide specific desired service characteristics to new components by incorporating such coatings in the initial design, and applying them during manufacture.

By way of example, the following are typical applications:

(1) The sliding wear and hence dimensional variation of plug, ring, and snap gauges is minimized by coatings of fused nickel-chromium-boron alloys incorporating tungsten-carbide particles. Similar coatings are used to reduce the wear on press tools.

(2) Plug valves of cast iron and stainless steel handling abrasive and corrosive fluids under high pressure are subject to galling, abrasion, and corrosion. These can be overcome by hard-facing with fused coatings of nickel-chromim-boron alloys. Pump sleeves, shafts, and plungers can be similarly protected.

(3) Refinery hot oil gumps, sleeves, and shafts operating at high temperatures (345ºC) and high pressure (24.0 - 34.5 bar -/) and handling fluid-borne abrasive particles are protected against abrasive wear at high temperatures by cobalt-chromium-tungsten-boron alloys incorporating tungsten carbide.

(4) The heads of diesel engine pistons are protected against high temperature corrosion caused by diesel oil combustion residues by a fused nickel-chromium-boron coating.

Note: -/ 1 bar = 10⁵ N/m².

(5) To resist severe abrasive wear in bridge and core mandrels of brick making extruders, these are hard-faced by fused coatings of nickel-chromium-boron alloys. Shafts of cement mixers and conveyor screws are similariy treated.

(6) To resist high temperature oxidation, which discolours glassware, and to prevent wear of cast iron plungers in glass press and blow manufacture, the plungers are protected by fused machineable coatings of nickel-chromium-boron alloys.

This Standard must not be taken as approval to apply any flame sprayed coating to a component without the written consent of the purchaser or owner. This written consent may be in the form of a contract or order, or may be in the from of written permission from the Design/Approval Authority concerned.

If this Standard should be found unsuitable for a particular requirement, the Directos of Standardization shall be informed of the circumstances.