AM Process Defects & Failure Modes

Comprehensive guide to understanding and preventing defects in additive manufacturing

Understanding AM Defects

Additive manufacturing processes, while revolutionary, are susceptible to various defects that can compromise part quality and performance. Each defect type has unique formation mechanisms, characteristics, and mitigation strategies.

This educational guide categorizes and explains the seven major defect types encountered in metal AM processes. Click on any defect card below to explore detailed information about its causes, characteristics, and prevention methods.

Lack-of-Fusion (LOF)

Insufficient energy input leaving unmolten particles

Severity: High

Key Characteristic:
Large, irregular voids along track boundaries

Main Causes:

  • Low laser power
  • Excessive scan speed
  • …and 2 more

Thermal Cracking

Cracks from rapid cooling and thermal stress

Severity: High

Key Characteristic:
Visible cracks, often intergranular

Main Causes:

  • High thermal gradients
  • Rapid cooling
  • …and 2 more

Recoater Errors

Mechanical failures in powder spreading system

Severity: High

Key Characteristic:
Visible streaks, gaps in powder bed, build crashes

Main Causes:

  • Blade damage/wear
  • Incorrect blade height
  • …and 2 more

Lack of Penetration (LOP)

Incomplete melting between layers

Severity: High

Key Characteristic:
Irregular, elongated voids between layers

Main Causes:

  • Insufficient overlap
  • Low energy density
  • …and 1 more

Powder Bed Irregularities

Non-uniform powder spreading

Severity: Medium

Key Characteristic:
Visible surface roughness, uneven layers

Main Causes:

  • Poor powder flowability
  • Powder contamination
  • …and 2 more

Gas Flow Management

Improper shielding gas flow patterns

Severity: Medium

Key Characteristic:
Oxidation patterns, spatter deposits, smoke plume issues

Main Causes:

  • Flow rate too high/low
  • Poor flow uniformity
  • …and 2 more

Oxidation & Contamination

Chemical reactions with environment

Severity: Medium

Key Characteristic:
Discoloration, brittle inclusions

Main Causes:

  • Inadequate shielding gas
  • Chamber leaks
  • …and 2 more

Keyhole Porosity

Vapor depression instability from excessive energy

Severity: Medium

Key Characteristic:
Round, smooth pores typically <100μm

Main Causes:

  • Excessive laser power
  • Slow scan speed
  • …and 1 more

Balling Defects

Molten metal forms spherical droplets

Severity: Medium

Key Characteristic:
Spherical droplets on surface

Main Causes:

  • Poor wetting
  • High surface tension
  • …and 2 more

Hot-Spot Formation

Localized overheating and irregular melting

Severity: Medium

Key Characteristic:
Localized surface irregularities

Main Causes:

  • Poor thermal management
  • Inadequate cooling time
  • …and 1 more

Gas Porosity

Trapped gas from powder or environment

Severity: Low

Key Characteristic:
Small, spherical, uniformly dispersed

Main Causes:

  • Powder contamination
  • Moisture in powder
  • …and 1 more

Defect Impact Summary

High Severity
4
Critical for structural integrity

Medium Severity
6
Affects quality and performance

Low Severity
1
Minor impact on properties