CHAPTER 12
METAL BUILDUP
CHAPTER LEARNING OBJECTIVES
Upon completing this chapter, you should be able to do the following:
Explain the thermal spray system.
Explain contact electroplating.
spray. All four generally perform the same basic
Metal buildup is a rapid and effective method that
function: they heat the wire or powder to its melting
can be used to apply almost any metal to a base material.
point, atomize the molten material with either
It is used to restore worn mechanical equipment, to
high-velocity gas or air, and propel it onto a previously
salvage mismachined or otherwise defective parts, and
prepared surface. In this chapter we will discuss the
to protect metals against corrosion. Compared to
wire-oxygen-fuel and powder-oxygen-fuel spray
original component replacement costs, metal buildup is
The rapid rate at which metal coatings can be
As you advance in the MR rating you must know
sprayed and the portability of the equipment have
how to prepare a surface for metal buildup and to set up
increased the use of thermal spray processes. Metal
and operate the equipment used in the thermal spray
coatings are especially useful to (1) rebuild worn shafts
systems and the contact electroplating process. In this
and other machine parts not subject to tensile stress,
chapter, we will briefly discuss the thermal spray
(2) apply hard surfacing that must resist wear and
systems and contact electroplating. We will not cover
erosion, and (3) protect metal surfaces against heat and
the actual spraying or plating processes; you will learn
corrosion. Navy repair facilities use thermal spray
them in classes you need to attend before you can be a
processes to coat metallic and nonmetallic surfaces with
qualified sprayer or plater.
practically any metal, metal alloy, ceramic, or cermet
Additional information on metalizing is in
that can be made in wire or powder form. (Cermet is a
MIL-STD-1687A(SH), Thermal Spray Processes for
strong alloy of a heat-resistant compound, a metal used
Naval Ship Machinery Applications.
especially on turbine blades.)
Additional information on electroplating is in
MIL-STD-2197(SH), Brush Electroplating on Marine
APPLICATIONS
Machinery.
As with any shop equipment, you must observe all
Thermal spray coatings have been approved by
posted safety precautions. Review your equipment
NAVSEA for several applications. Case-by-case
operators manual for safety precautions and any
approval is not needed for the folllowing applications,
chapters of Navy Occupational Safety and Health
but the procedures used for these applications are
(NAVOSH) Program Manual for Forces Afloat,
limited to those approved by NAVSEA:
OPNAV Instruction 5100.19B, that apply to the equip-
Repair of static fit areas to restore original
ment. Also, read the sections in MIL-STD-1687A(SH)
dimensions, finish, and alignment
and MIL-STD-2197(SH) that cover safety.
Repair of seal (including packing areas) to
restore original dimensions and finish
THERMAL SPRAY SYSTEMS
There are four different thermal spray processes:
Repair of fit areas on shafts to restore original
dimensions and finish (except for motor
wire-oxygen-fuel spray, wire-consumable electrode
spray, plasma-arc spray, and powder-oxygen-fuel
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