Sep 27, 2016

Wear Matters

Whether your company is an OEM or a Vendor, when a part fails your reputation is on the line.

Your failure analysis will usually identify one or two of the following conditions as root cause for failure:

1. Excessive surface wear

2. Fracture due to impact

3. Corrosion

Fatigue failures almost always begin at the surface of a material. The reasons are:

1. The most highly stressed fibers are located at the surface (Bending Fatigue)

2. The inter granular flaws which precipitate tension failure are more frequently found at the surface

As metallurgical wear specialists, Pazmac will work with you to provide effective solutions to prolong the life or your critical components. Using the latest in CNC Machining technology, Robotically applied Laser Cladding, Gas Nitriding, shot pene, burnishing and other wear specific processes, we have cost effective in house processes to enhance the reliability of your parts.

Perhaps your solution lies with improved impact resistance using different parent material, along with an application of customized laser cladding to improve surface wear. Perhaps better machined surface finishes coupled with gas nitriding is a potential solution. Or maybe it’s a combination of all of the above that solves the problem.

Please contact us with your wear issues and we’ll happily help you explore ways to improve part longevity, reduce costs and save your reputation!


About Laser Cladding

Laser cladding uses laser energy as a heat source to melt and weld a material that has different and beneficial metallurgical properties onto a component with the lowest chemical dilution possible for a welding process. This allows one to cost effectively customize the surface properties of less expensive substrate to provide greater resistance to corrosion, oxidation, wear and high temperature fatigue strength. Why spend a fortune on making components out of special materials when you only need a specialized surface? Pazmac’s laser cladding system has the ability to weld a very thin and smooth single pass layer of metal onto another metal substrate at high deposition rates, with little or no dilution.

Laser cladding techniques and equipment were developed to apply wear/corrosion resistant alloys on valve sealing surfaces. The techniques allow cladding on flat, cylindrical and contoured surfaces more economically than prior processes and techniques used. The advantages realized by using the laser cladding technique for production parts are: (1) less than 2% dilution of base metal, (2) improved surface wear and corrosion properties, (3) reduced cracking susceptibility, (4) minimal warpage and distortion of clad components, (5) high integrity metallurgical bond, (6) suitability for full automation, (7) considerable savings of expensive cladding materials due to the consistency and uniformity of applied cladding, (8) low heat input of laser cladding eliminates adverse effects on base metal properties.

About Gas Nitriding

Gas nitriding, one of the most important and common surface modification processes, is a thermochemical case hardening process used to increase wear resistance, improve surface hardness and fatigue life, and improve the surface corrosion resistance of steel parts by dissolution of nitrogen and hard nitride precipitations.

In the gas nitriding process, which was invented in the early 1900s, atomic nitrogen penetrates the steel surface and reacts with substrate atoms (predominantly iron) to produce nitrides. The metallic nitrides are hard and enhance the wear resistance of the surface. The hardness of the nitrided layer reaches up to 65 Rockwell Hardness (RC) while the substrate hardness is usually around 45 RC. The corrosion resistance of the nitrided layer is excellent in many environments.

Favoured for components that are subjected to heavy loading, nitriding imparts a high surface hardness which promotes high resistance to wear, scuffing, galling and seizure. Fatigue strength is increased mainly by the development of surface compressive stresses. The wide range of possible temperatures and case depths, which allow adjustment of different properties of the treated parts, give gas nitriding a broad field of applications.

Typical applications include gears, crankshafts, camshafts, cam followers, valve parts, springs, extrusion screws, die-cast tooling, forging dies, aluminium-extrusion dies, injectors and plastic-moulds.

Nitriding is most effective when applied to the range of steels containing nitride-forming elements such as chromium, molybdenum, vanadium and aluminium. The process is also applicable to tool steels such as hot-work, cold-work and mould steels. In general, all ferrous materials can be gas nitrided up to 5% chromium. For higher contents of alloying elements and for gas nitriding of stainless steel, plasma nitriding might be considered.

For optimum results, the material should be in a hardened and tempered condition prior to gas nitriding.

About Shot Peening

Shot peening is a cold working process used to produce a compressive residual stress layer and modify the mechanical properties of metals. It entails impacting a surface with shot (round metallic, glass, or ceramic particles) with a force sufficient to create plastic deformation. Peening a surface spreads it plastically, causing changes in the mechanical properties of the surface.

The main benefit of shot peening is the delay or prevention of cracks in highly tensile stressed alloy components. We can alter these undesirable manufacturing and operational tensile stresses to life enhancing residual compressive stresses therefore extending component life.

The process works by introducing the residual compressive stress in the surface of the component. The compressive stress helps to prevent crack initiation as cracks cannot propagate in the compressive environment generated by peening.

About Burnishing

Burnishing is the process of rubbing metal with a small hard tool, which can be either a ball type or roller type, to compact the surface. It is a very useful finishing technique which can increase the workpiece surface finish as well as adding micro hardness. Burnishing is also known by various other names such a super finishing process or ballizing process. The burnishing process is one of the more advanced finishing techniques in which no chips are produced and material is not removed from the surface of the workpiece. Plastic deformation or physical changes of a surface, due to sliding contact with another object, is achieved using this technique. The process of burnishing can be done using a sliding surface when the local contact stress exceeds the yield strength of the material.

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