This applies in particular to moulding, casting and activities like baking and curing in which a product is held against the component surface for an extended time. The issue is not usually one of wear; instead, the main requirement is that the product can be separated from the surface without adhesion or damage to either surface. However, in many cases, the product must first flow into the mould and, if pressure is applied during processing, the product may also creep across the surface as it cures or sets. Both these can cause wear.

Before continuing with the analysis, you should go to the "Problem Solver" and read the sections on friction and adhesion.

The base material

In many food applications the substrate will be stainless steel or aluminium alloy. Dies and moulds for plastic moulding are most likely to be made in alloy steel or, more rarely, aluminium, brass or copper. Die casting of aluminium or zinc products will generally use H-Series tool steels; glass moulding uses similar steels as well as cast irons.

Applications

A) Food baking and moulding.

For bread, cakes, confectionery, biscuits, etc, try:

1. Fluorinated Polymer Coatings; FEP provides the best release. PFA gives release and wear resistance. PTFE provides best low friction
2. Electroless Nickel + PTFE will provide both low friction and good release properties, but not high wear resistance
3. Anodising + PTFE seal for non-stick with aluminium alloy parts
4. Electro-Ceramic Coating, with added polymer for non-stick with aluminium and magnesium alloys

B) Plastic injection and moulding.

For windows frames, plastic cutlery, plastic toys (e.g. bricks), etc, try:

1. Nitriding or Nitrocarburising for alloy steel parts when the plastic is filled and expected to be abrasive
2. Hard Cr Plate for steel, brass or copper parts when abrasion is expected
3. Ion-Implantation for improved wear resistance of alloy steel and chrome plated parts
4. Anodising + PTFE seal for non-stick and wear resistance with aluminium alloy parts
5. Electro-Ceramic Coating, with added polymer for non-stick and wear resistance with aluminium and magnesium alloys

C) Die Casting.

1. Nitriding for H-Series tool steels
2. PVD Coatings, e.g. CrN or TiAlN

D) Die Casting.

1. Chromising for hot erosion-corrosion resistance
2. Thermochemically formed chromium oxide-based ceramic coatings for glass moulds
3. Hard Chrome Plating, best is the crack-free variety

Poeton Industries Ltd. Head Office, Eastern Avenue, Gloucester GL4 3DN, England, UK   Tel: 01452 300500  Fax: 01452 500400
Production facilities in Cardiff & Gloucester and in Wisconsin. USA.